Guidelines for the implementation of practical work. With what safety factor are slings made? Safety factor for steel chains
Answer. Must be at least 5 for machine drive and at least 3 for manual drive (clause 3.4.7.3).
Question 132. In what way is chain splicing allowed?
Answer. Allowed by electric or forge welding of new inserted links or by using special connecting links. After splicing, the chain is inspected and tested by load in accordance with the documentation (clause 3.4.7.6).
Question 133. What is the use of hemp ropes for?
Answer. It is allowed to use for the manufacture of slings. In this case, the safety factor must be at least 8 (clause 3.4.8.1).
Question 134
Answer. The inventory number, permissible carrying capacity and the date of the next test must be indicated (clause 3.4.8.3).
Question 136. What should be paid attention to when inspecting ropes?
Answer. It is necessary to pay attention to the absence of rot, burning, mold, knots, fraying, dents, tears, cuts and other defects. Each turn of the rope should be clearly distinguished, the twist should be uniform. Hemp ropes used for guying should not have frayed or macerated strands (clause 3.4.8.9).
Question 137. During what periods should ropes and cords be inspected during operation?
Answer. Should be inspected every 10 days (clause 3.4.8.11).
Question 138
Answer. Designed to work on wooden and wooden poles with reinforced concrete stepchildren of power transmission and communication lines, on reinforced concrete supports overhead lines power transmission lines (VL) 0.4-10 and 35 kV, as well as on cylindrical reinforced concrete poles with a diameter of 250 mm VL 10 kV (clause 3.5.1).
Question 139
Answer. Service life 5 years (p. 3.5.12).
Question 140. When are claws and manholes subjected to static tests?
Answer. They are tested at least once every 6 months (clause 3.5.16).
Question 141. What should be the mass of the belt?
Answer. Should be no more than 2.1 kg (clause 4.1.7).
Question 142. What dynamic load should the belt withstand?
Answer. Must withstand the load arising from the fall of a load weighing 100 kg from a height equal to two lengths of the sling (halyard) (clause 4.1.9).
Question 143
Answer. Should it be made of steel rope or chain?
Question 144
Answer. They are used to ensure the safety of an employee when ascending and descending along vertical and inclined (more than 75 ° to the horizon) planes (clause 4.3.1).
Question 145. What is the principle of operation of the catcher and the system as a whole?
Answer. When the worker falls under his weight through the belt-sling system, the body of the safety device rotates, and the safety rope is pinched between the movable and stationary cams, locking the safety device on the safety rope and keeping the worker from moving down (clause 4.3.3).
Question 146. For what purposes should helmets be used?
Answer. They should be used to protect the worker's head from mechanical damage from objects falling from above or from collisions with structural and other elements, to protect against water, electrical shock, such when working at height on construction, installation, dismantling, repair, adjustment and other work. 4.5.1).
Question 147. What should helmets provide?
Answer. Should provide the maximum transmitted force at a nominal impact energy of 50 J, not more than 5 kN (500 kgf) - for helmets of the first quality category and not more than 4.5 kN (450 kgf) - for helmets of the highest quality category (clause 4.5.3).
Question 148. What colors are the helmet casings produced in?
Answer. Available in four colors:
white - for management staff, heads of workshops, sections, employees of the labor protection service, state inspectors of supervisory and control bodies;
red - for foremen, foremen, engineering and technical workers, chief mechanics and chief power engineers;
yellow and orange - for workers and junior service personnel (clause 4.5.6).
Question 149. What marking does each helmet have?
Answer. Has the following markings:
in the middle of the upper part of the visor of the helmet, the name of the helmet - "Builder" should be applied by casting;
on the inside of the visor or body by casting or molding should be applied: the trademark of the manufacturer, the designation of the standard, the size of the helmet, the date of issue (month, year) (clause 4.5.16).
Question 150. What is the warranty period for storage and operation of helmets?
Answer. The warranty period is 2 years from the date of manufacture (clause 4.5.21).
Question 151. What safety devices should have mechanisms and equipment with a mechanical drive?
Answer. Must have automatic start interlocks that are easily accessible and clearly recognizable to the operator by emergency stop devices. Hazardous moving parts must be guarded (clause 5.1.4).
Question 152. What are the requirements for wrenches?
Answer. Yawns wrenches must correspond to the dimensions of the nuts or bolt heads and not have cracks, nicks. It is not allowed to increase the levers of wrenches that are not designed to work with an increased leverage (clause 5.2.10).
Question 153
Answer. They must be provided with gloves with anti-vibration padding on the side of the palm (clause 5.3.6).
Question 154. What voltage should an electrified hand tool be used for?
Answer. It should be used, as a rule, for a voltage not exceeding 42 V. The body of a class I electrified hand tool (at a voltage above 42 V, not having double insulation) must be grounded (zeroed) (clause 5.4.1).
Question 155. Who is allowed to work with a hand-held electrified tool?
Answer. Persons at least 18 years of age who have undergone special training, have passed the appropriate exam and have an entry about this in their labor protection certificate (clause 5.4.6) are allowed.
Question 156. What should a hand pyrotechnic instrument have?
Answer. Must have:
protective device or shield;
a device that protects against an accidental shot;
a device that prevents a shot if the nozzle of the pistol is not resting on the working surface (clause 5.5.2).
Question 157. Who is allowed to work with the use of hand pyrotechnic tools?
Answer. Workers trained in its safe use are allowed (clause 5.5.7).
Question 158 independent work with a hand-held pyrotechnic piston-type instrument?
Answer. Allowed employees are at least 18 years of age, who have worked in the organization for at least 1 year, have a qualification of at least the third category, have completed a training course according to an approved program, have passed the exams of the qualification commission and received a certificate for the right to work with a manual piston-type pyrotechnic tool (clause 5.5. 10).
Question 159. Who should have a certificate for the right to manage work with a manual pyrotechnic tool?
Answer. Must have foremen, foremen, mechanics and other specialists associated with the operation of this tool, who must take a course in the program for specialists and receive a certificate for the right to manage these works (clause 5.5.11).
Question 160
Answer. Should get:
work permit for the right to perform work;
pyrotechnic tool;
cartridges (no more than the established norm);
personal protective equipment (hard hat, earmuffs, protective shield, leather gloves or mittens) (clause 5.5.12).
Ropes, chains, lifting devices, lifting devices and containers
What are crane ropes used for?
Ropes on hoisting cranes serve to transfer traction forces from winches to executive working bodies and set them in motion.
According to the "Rules for the Construction and Safe Operation of Hoisting Cranes", steel ropes used as cargo, boom, byte, load-bearing traction and slings must comply with the current state standards and have a certificate (certificate) or a copy of the certificate of the rope manufacturer about their testing in accordance with GOST 3241-66. Upon receipt of ropes without a certificate, they must be tested in accordance with the specified standard.
Ropes that do not have a certificate of their testing are not allowed to be used.
What types of steel ropes are subdivided into according to the type of contact of the wires in the strands?
According to the nature of the touch of the wires in the strands, steel ropes are mainly divided into three types: ropes with a point touch (TK), consisting of wires of the same diameter; ropes with linear touch (LC), consisting of wires of different diameters, and ropes with point and linear touch of wires in strands (TLK). Moreover, if the rope has wires in separate strands of the same diameter, then the letter O is added to the designations LK and TLC, for example, LK-O, TLC-O. If individual strands consist of two wires of different diameters, then the letter P is added to the designations, for example, LK-R, TLC-R. If individual strands consist of wires of different and identical diameters, then RO is added to the designations, for example, LK-RO, TLC-RO.
To characterize steel ropes, including their basic data, it is accepted symbol, where the diameter of the rope is indicated in the first place, its purpose is in the second, the mechanical properties of the wire are in the third, the operating conditions are in the fourth, the direction of laying the rope elements is in the fifth, the laying method is in the sixth, and the marking group by time is in the last place wire breaking resistance. At the end, the GOST number is indicated, in accordance with which the rope is made.
For example, a rope with a diameter of 24 mm, for cargo purposes (G) made of light wire (grade B), for light working conditions (LS), non-untwisting (N) with a marking group for a tensile strength of 160 kg / cm2 is designated as follows: 24-G- V-LS-N-160 GOST 3077 - 69. How are steel ropes subdivided according to the direction of laying wires and strands in a rope?
According to the lay direction of the wires and strands in the rope, steel ropes are divided into one-sided lay ropes and cross lay ropes.
If the wires in the strands and the strands in the rope are twisted in the same direction, for example, to the right or to the left, then such a rope is called a one-sided lay rope.
If the wires in the strands are twisted in one direction, for example to the right, and the strands are twisted in the other direction, for example to the left, then such a rope is called a cross lay rope. Although it has less flexibility than a one-sided lay rope, it is less prone to untwisting and flattening when bending around blocks.
How is the lay pitch determined?
The rope lay pitch is determined as follows: a mark is applied to the surface of a strand, from which as many strands are counted along the central axis of the rope as there are in the rope section (usually six), and the second mark is placed on the next strand after the count. The distance between the marks will be the lay step.
What design are steel ropes?
Steel ropes are different designs, new ropes of construction 6X19+1 are mainly used; 6X37+1; 6X61 + 1. Moreover, these figures indicate that all the listed rope designs are six-strand, and in each strand in the first case there are 19 wires plus one core, in the second case 37 wires plus one core and in the third case 61 wires plus one core, which in all ropes is in the center of the rope, and the strands are wound around it. In order for the rope to be lubricated during operation, the core is impregnated with a special lubricant before being put into the rope.
What design ropes are used on cranes?
Ropes of construction 6X19 + 1 are recommended to be used for braces and guys, i.e. in cases where they are not subjected to repeated bending, ropes 6X37 + 1 - for chain hoists of the load lifting mechanism, boom and as a traction rope, since they are more elastic than cananbX 19+1.
What methods are used to fasten the ends of the rope?
On cranes, the following methods of end fastening of ropes are mainly used: wedge clamp; casting the end of the rope with fusible metal in a steel forged, stamped or cast conical bushing; loops on clips (fastening with clips); loops with the help of a gossip and clamping strips.
It is forbidden to use cast-iron or steel welded bushings when fastening the end of the rope with a wedge clamp or low-melting metal.
How is the end of the rope secured with a wedge clamp?
The end of the steel rope is fastened with a wedge clamp as follows: from the narrow side of the steel conical body, the end of the rope is passed in such a way that the free end of the rope and the working branch come out of the narrow side of the cone hole, forming a loop behind the broadened end of the body.
Next, a steel wedge is laid in the loop, which has grooves on the side surfaces for a better fit of the rope. After that, the rope with the wedge is pulled into the body, clamping the ends of the rope between internal surfaces taper hole and wedge.
It should be remembered that the free end of the rope with such fastening should be released beyond the edge of the conical hole to a length equal to 10-12 rope diameters.
How is the end of the rope attached by pouring it with fusible metal?
The fastening of the end of the steel rope by pouring low-melting metal is carried out as follows: the end of the rope is passed through the narrow side of the steel cone body over the wide side. Then this end is untwisted into separate wires, a hemp core is cut out, the wires and the inner side of the conical sleeve are etched with hydrochloric acid, and the untwisted end is pulled inside the sleeve. After that, the formed brush of steel wires inside the conical sleeve is filled with solder or other low-melting metal.
How many clamps should be installed when attaching the rope with clamps?
The number of clamps when fastening the rope with clamps is determined during the design, but must be at least three.
The pitch of the clamps (distance between the clamps) and the length of the free end of the rope from the last clamp must be at least six rope diameters.
All clamp nuts must be located on the side of the working branch of the loop, and the tightening density of the two ends of the rope is considered normal if the diameter of the rope after tightening the nuts is 0.6 of the original diameter.
Should the hinge and its fastening be checked after tightening the clamp nuts?
Should. The rope is kept under load, and then the nuts of the clamps are tightened again to the specified limit. To prevent the free end of the rope from touching anything during operation, it is wrapped with soft wire.
Should thimbles be installed when attaching the end of the rope with clamps?
When attaching the end of a steel rope, both with the help of clamps and with the help of a braid, a thimble must be placed in the loop, as it protects the rope from sharp bending and premature wear.
How many rope punctures should each strand have when braiding the end of the rope?
The number of rope punctures by each strand during braiding should be at least 4 - with a rope diameter of up to 15 mm, at least 5 - with a rope diameter of 15 to 28 mm and at least 6 - with a rope diameter of 28 to 60 mm. When braiding the end of the rope, the end is untwisted into strands, a hemp core is cut out and
the non-braided * part is tightly applied to the carousel>k” groove of the thimble. Then the untwisted strands are woven into the working branch of the rope, piercing it with a special tool. The last puncture is allowed to be made with half the number of rope strands, and the braid must fit tightly to the end.
How is the rope attached to the rope drum?
The fastening of the rope to the rope drum must be reliable, allowing the possibility of its replacement. If clamping bars are used, their number must be at least two. The length of the free end of the rope from the last clamp on the drum must be at least twice the diameter of the rope. It is not allowed to bend the free end of the rope under the clamping bar or near it.
Should the rope be checked for strength before placing it on a crane?
When the total breaking force is given in the certificate or test certificate of the rope, the value of P is determined by multiplying the total breaking force by 0.83 or by the coefficient determined in accordance with GOST for the rope of the selected design.
What is the Rope Safety Factor?
The safety factor of a rope is the ratio of the breaking force of the rope as a whole to the highest working load.
What is the safety factor of steel ropes installed on cranes?
The smallest allowable safety factors for steel ropes installed on cranes are shown in the table.
To reduce the wear of the ropes of jib, gantry and overhead cranes, they are lubricated with rope ointment heated to about 60 ° C every month of operation.
Before lubrication, the rope is carefully checked and dirt and old grease are removed from its surface with a rag soaked in kerosene. It is forbidden to clean dirt from the surface of the rope with a metal brush, as this removes galvanizing from the surface of the wires, and this leads to rusting of the rope.
In what cases are steel ropes rejected?
Steel ropes are rejected in the following cases: if even one strand is broken; if the number of broken wires at the lay step is more than the norm (see table on p. 244); if the surface wear or corrosion of the rope wires is 40% or more; if creases have formed on the rope; if the rope is severely deformed (flattened).
Does the rate of rejection of the number of wires of the rope decrease if they have surface wear or corrosion?
Decreases, since in this case the strength of the rope is reduced. Moreover, with a decrease in the diameter of the wires as a result of surface wear or corrosion by 10, 15, 20 25 and 30%, the number of breaks per lay step should be reduced by 15, 25, 30, 40 and 50%, respectively.
When the diameter of the wires is reduced by 40% or more, the rope is rejected.
How is the surface wear or corrosion of the rope (wires) determined?
Surface wear or corrosion of wire rope is determined as follows. At the site of the greatest wear or corrosion of the rope lay, the end of the broken wire is bent, cleaned of dirt and rust, and the diameter is measured with a micrometer or other instrument that provides sufficient accuracy. If, for example, the initial diameter of the wires was 1 mm, and the measurement showed 0.5 mm, then wear or corrosion in this case will be 50%. Such a rope, of course, is rejected.
What should be paid special attention to when using ropes?
Since the ropes of jib, gantry and overhead cranes are particularly critical parts of them, they should be constantly supervised and ensure timely proper care. There are frequent cases when, due to the lack of supervision, timely proper care and untimely replacement of worn ropes, major accidents occurred.
That's why:
under no circumstances should worn or rejected ropes be used;
it is necessary to systematically carefully check and tighten the fastening of the ends of the rope on the rope drum and in other places where the ropes are terminated;
do not allow the number of turns of the rope on the drum to be less than 1.5;
lubricate the rope in a timely manner, since its service life largely depends on timely and proper lubrication;
do not allow blocks with chipped flanges to be used, since a chipped flange causes the rope to come off the block or drum, and sometimes cuts the rope;
if broken wires are found in an amount less than that at which the rope is rejected, they should be cut with wire cutters to avoid damage to adjacent wires;
do not allow the rope to touch the elements of the crane structure.
What chains are used on lifting machines?
Lamellar chains are used on lifting machines - GOST 191-63, welded and stamped - GOST 2319-70. The latter are used as cargo and for slings.
In addition to these chains, chains according to GOST 6348-65 can be used for the manufacture of slings. All chains used on cranes, as well as chains from which slings are made, must have a manufacturer's certificate of testing. If there is no test certificate, a sample of the chain must be tested to determine the breaking load and check for compliance with the dimensions of the State Standard.
What is the safety factor of chains in relation to the breaking load?
The safety factor of welded and stamped cargo chains and sling chains in relation to the breaking load should not be less than:
cargo, working on a smooth drum with a manual drive - 3, with a machine drive - 6;
cargo, working on an asterisk (calibrated) with a manual drive - 3, with a machine drive - 8;
for slings with a manual drive - 5, with a machine drive - 5.
The safety factor of leaf chains used in hoisting machines must be at least 5 with a machine drive, and at least 3 with a manual drive.
Is chain splicing allowed?
Splicing of chains is permitted by forge-forge or electric welding of newly inserted links, or by using special connecting links. After splicing, the chain shall be inspected and tested with a load equal to 1.25 times its carrying capacity. Inspection and testing should be carried out at the plant where the chains were repaired.
In what cases are chains rejected?
Chains are rejected if the link is broken, if the wear of the welded or stamped chain link is more than 10% of the original diameter (caliber) plus a minus tolerance for chain manufacture, if cracks are found in the chain links.
How are the blocks used on cranes divided?
The blocks used on load-lifting cranes are divided into working and equalizing.
Working blocks, in turn, are divided into movable and fixed. If the block during the operation of the crane does not rise and does not fall relative to the ground level, then such a block is called stationary, although it rotates on its axis. If, when lifting or lowering the load, the block moves with it, then such a block is called movable.
Both movable and fixed blocks are made of cast iron and steel. Moreover, cast iron blocks are used to work under small loads, and steel blocks are used to work under large and heavy loads.
Which blocks are subject to the most wear?
High-speed blocks are subjected to the greatest wear. In order for the wear of the blocks to be uniform, they should be interchanged in multiblock chain hoists when repairing a crane.
How can uneven block wear be eliminated?
Uneven wear of the block can be eliminated by turning the profile of the stream, and the reduction in the initial diameter is allowed by no more than 3 mm for blocks with a diameter of 300 mm and no more than 5 mm for blocks with a diameter of up to 500 mm.
Is it possible to operate a block with a chipped flange?
It is strictly forbidden to operate a block with a broken flange, since a chipped flange causes the rope to come off the block, and sometimes it can cut the rope, which threatens with a serious accident.
It should be remembered that the blocks of cranes must be constantly monitored, since the failure of the block can lead to an accident.
The equalizing block, which aligns the ropes of the left and right sides of the chain hoist, does not rotate during the operation of the mechanism, and sometimes they do not pay attention to it - they do not lubricate its axis, do not inspect the axle mount. The crane operator needs to remember that a break in the equalizing block axle or its falling out of the supports will lead to a severe accident - the load with the hook will fall to the ground.
What is called a polyspast?
A lifting device consisting of fixed and movable block clips, through the blocks of which a rope or chain is passed, is called a chain hoist. Moreover, the more blocks in the movable and fixed clips of the chain hoist, the more branches of the rope or chain, and therefore, the greater the gain in strength or speed.
Why is there a gain in strength in chain hoists?
The gain in strength in chain hoists occurs because the mass of the load lifted by the chain hoist is distributed between all branches of its rope. Therefore, the more blocks in the chain hoist, the more branches of the rope are involved in lifting the load and the less effort falls on each branch of the rope. Thanks to this, a smaller diameter rope can be used, and a lifting or boom lifting winch can be used with less traction.
What multiplicity chain hoists are used on cranes?
On load-lifting cranes, chain hoists with a multiplicity of 2, 3, 4, 6, etc. are used. A chain hoist with a multiplicity of 2 consists of one fixed block and one movable one. In this case, the cargo rope, fixed on the boom, first goes around the movable block located on the hook clip, and then the stationary one and goes to the winch drum.
The chain hoist with a multiplicity of 3 consists of two fixed blocks mounted on the boom and one movable block placed in the hook holder. The chain hoist with a multiplicity of 4 consists of two movable and two fixed blocks.
The multiplicity of the chain hoist is its most important characteristic, since the greater the multiplicity, the less effort must be expended to lift the load.
What applies to interchangeable load-handling devices?
Interchangeable lifting devices include a hook, a grab, a lifting electromagnet, etc.
How are lifting hooks made?
Hooks for lifting machines - forged and stamped - must be manufactured in accordance with GOST 2105-64.
After manufacturing, they must be marked in accordance with GOST 2105-64.
Hooks with loads over 3 tons must be made rotating on closed ball bearings, with the exception of crane hooks for special purposes.
What should crane hooks be equipped with?
Hooks of load-lifting cranes must be equipped with a safety device that prevents spontaneous loss of a removable load-handling device from the mouth of the hook.
Rice. 3. Single block hook block:
1 - locking trunks; 2 - casing; 3 - cheek; 4 and 8 - ball bearings; 5 - axis; 6 - block; 7 - hook nut; 9 - traverse; /0 - hook; 11 - hook latch
Such a device may not be provided with hooks of portal cranes operating in seaports, and1 hooks of cranes transporting liquid slag or! molten metal.
Is hook wear allowed?
Hook wear is allowed, but very slight. The maximum wear in the throat should not exceed 10% of the initial height of its section.
In what cases is the hook rejected?
The hook is rejected in the following cases: if it does not rotate in the traverse; if the hook horn is bent;
if the wear of the hook in the throat exceeds 10% of the initial section height;
if there is no OTK stamp on the hook; if there are cracks on the hook.
What are the parts of the hook block?
The hook clip (Fig. 3) consists of two side cheeks made of grade 3 steel, a stop, blocks, a traverse and a hook. The cheeks are interconnected by spacer tubes and tightened with tie bolts. The clip blocks are installed on the axis, which is fixedly fixed in the side cheeks with the help of crossbars. The hook traverse is also installed in the side cheeks and is secured from axial movement with two locking bars; since the traverse pins have grooves in a circle, the traverse can freely rotate in the holes of the side cheeks, due to which, in addition to rotating around the shank axis, the hook can also swing along with the traverse, which greatly facilitates slinging loads.
What is the hook block stop used for?
The stop of the hook clip serves to protect the clip block from a possible impact in cases of the hook approaching to the extreme upper position.
What should maintenance personnel pay attention to when using hooks and hook blocks?
The hook frame of jib, gantry and overhead cranes is a very important unit, therefore crane operators and slingers must constantly monitor the condition of the hook frame during crane operation. At each inspection, it is imperative to check the serviceability of the side cheeks, blocks, traverse, hook, nut securing the hook, fastening the axles and stop. During operation of the crane, defects may appear in the hook: bending of the hook horn, nicks on the hook body, wear or contamination of the support bearing, breakage of the hook fastening nut lock, abrasion of the surface of the hook mouth, cracks that can lead to serious consequences. The crane operator and slinger must notice each of these defects in time. The crane operator must also ensure that the hook block blocks and hook thrust bearing are lubricated, as lack of lubrication will prematurely disable these parts. What are the requirements for grabbers?
Grabs are subject to the following requirements:
the grab must have a plate indicating the manufacturer, the number of the grab, its own weight, the type of material for which the grab is intended to be handled, the maximum allowable weight scooped up material; in the absence of a nameplate, the latter must be restored by the owner of the grapple;
by its design, the grab must exclude the possibility of spontaneous opening;
grabs made separately from the crane must have (in addition to the plate) a passport in which all the data about the grab provided by the type passport of the crane must be recorded.
The crane operator must remember that the crane, in which the grapple is the lifting device, can only be allowed to work after weighing the scooped material during trial scooping; the weight of the grab with scooped material should not exceed the lifting capacity of the crane.
For cranes with variable lifting capacity depending on the reach of the boom, the weight of the grab must not exceed the lifting capacity corresponding to the reach at which the crane is operating with the grab. Trial scooping should be carried out from a horizontal surface of freshly filled soil.
Removable lifting devices and containers
What devices are removable load-handling devices?
Removable lifting devices include those devices that are hung on the hook of a lifting machine (for example, slings, pliers, traverses, etc.).
What are the slings?
Slings are universal, lightweight and multi-branch. A sling in the form of a closed loop is called a universal sling, as it is used for slinging various loads.
A sling consisting of one branch with hooks and rings fixed at the ends is called lightweight (Fig. 4).
Rice. 4. Slings: a - universal; b - lightweight
Rice. 5. Multi-branch sling
A multi-branched is such a sling, which consists of several branches assembled on a ring, having hooks or grips at the ends (Fig. 5).
How are the hooks, rings and loops attached to the ends of the lines?
Hooks, rings and loops at the ends of the slings are fixed using a thimble, by braiding the free end of the sling or by setting clamps. When braiding, the end of the sling (rope) is untwisted into strands, then these strands are woven into the body of the rope, followed by braiding the junctions with wire.
How many strands of rope should be punched during braiding?
The number of piercings of the sling rope with strands during braiding should be at least four with a rope diameter of up to 15 mm, at least five with a rope diameter of 15 to 28 mm and at least six with a rope diameter of 28 to 60 mm.
How many clamps should be placed on the end of the sling rope?
When fixing hooks, rings and loops at the end of the sling rope by setting clamps, their number is determined during design, but must be at least three; the pitch of the clamps and the length of the free end of the rope from the last clamp must be equal to at least six rope diameters. It is forbidden to put clips on slings by blacksmithing or any other hot method.
What material are hooks and rings for lightweight and multi-branch slings made of?
Hooks and rings for slings should be made of grade 20 steel or grade 3 calm open-hearth steel, and the hooks should have devices that prevent the hook from spontaneous falling out of the mounting loops or from the container hangers.
Who has the right to manufacture slings, tongs and traverses?
Slings, tongs, traverses and other lifting devices have the right to be manufactured by an enterprise or construction site, but their manufacture must be organized centrally and produced according to standards, technological maps or individual drawings. In addition, when welding is used, the documentation for the manufacture of slings, tongs, traverses, etc., must contain instructions for its implementation and quality control.
Information about the manufacture of slings, pincers, traverses, etc. must be entered in their register. This journal should contain: name of removable load-handling devices, load capacity, normal number ( technological map, drawing), numbers of certificates for the material used, results of welding quality checks, test results of a removable lifting device. Are slings, tongs and traverses subjected to technical examination after their manufacture?
After the manufacture of slings, tongs, traverses and other lifting devices must be subject to technical examination at the enterprise or construction site where they were manufactured; however, they must be examined and tested with a load of 1.25 times their rated capacity.
After the test, these removable load-handling devices shall be provided with a metal tag or brand, on which the number, load capacity and date of the test shall be stamped. Moreover, the carrying capacity of general-purpose slings is indicated at an angle between branches of 90 °, and the carrying capacity of special-purpose slings designed to lift a certain load is indicated at an angle between branches taken in the calculation. Slings, tongs, traverses and other removable load-handling devices manufactured for third-party organizations, in addition to stamps or tags, must be supplied with a passport.
Who should carry out the technical examination of slings, tongs, traverses and containers?
Technical examination of slings, tongs, traverses and containers must be carried out by a supervisor or another person specially appointed by order for the enterprise or construction site.
Should slings, pliers and traverses be checked periodically during their operation?
Slings, tongs and traverses during their operation must be periodically checked by a thorough inspection within the time limits established by the administration of the enterprise or construction site, but not less than: slings - every ten days, pliers - after one month, traverses - after six months.
Inspection must be carried out by a person responsible for the good condition of removable load-handling devices; the results of the inspection should be recorded in the log of their inspection.
Should slings, pliers and traverses be checked daily (every shift)?
Slings, tongs and traverses must be checked daily (every shift) before starting work. They should be checked by slingers, crane operators and persons responsible for the safe movement of goods.
At what maximum angles between the branches of the slings is it allowed to moor the cargo?
The maximum angle between the branches of the slings when mooring the cargo should be no more than 90°. An increase in this angle to 120° can be allowed only in exceptional cases by calculation.
Why is it impossible to allow the angle between the branches of the slings to be more than 90 ° when lifting the load?
Because with an increase in the angle between the branches of the slings, the tension on the branches will increase greatly, which can lead to rupture of the slings themselves, hooks or mounting loops of reinforced concrete or concrete products. So, at an angle between the branches of the lines equal to 60°, the tension on the branches of the lines will increase by 15%, at an angle of 90° the tension will increase by 42%, and at an angle of 120° the tension on the branches of the lines will increase by 2 times.
In what cases are slings rejected?
Slings are rejected in the following cases: if the number of broken wires per lay pitch in the ropes of the slings is more than the norm (see the table on p. 244), if the hooks of the slings are cracked, if the mouth of the hook of the sling has wear of more than 10% of its original height of its section, if the rope the sling has a broken strand if the sling rope has surface wear or corrosion of 40% or more, if the thimbles have fallen out, if the sling rings have cracks or wear is more than acceptable, if the sling rope is severely deformed (flattened).
Who has the right to make containers?
An enterprise or construction site has the right to manufacture containers, but it must be manufactured centrally and produced according to standards, technological maps and individual drawings.
After manufacturing, the container must be subjected to technical examination by inspection, since testing the container by the load is not necessary. Inspection of containers should be carried out according to the instructions approved by the management of the enterprise or construction site, which determines the procedure and methods for inspection, as well as the elimination of detected defects.
Information about the manufacture and examination of containers must be entered in the register of removable load-handling devices and containers. This journal should contain: the name of the container, its own weight of the container, its carrying capacity, the purpose of the container, the number of the normal (technological map, drawing), the numbers of certificates for the material used, the results of checking the quality of welding, the results of the inspection of the container.
What information should be applied to the container after its technical examination?
After the technical examination, the tare shall be marked with the following information: the tare number, the dead weight of the tare, the maximum weight of the cargo for which it is intended to be transported, and the purpose of the tare.
Should containers be inspected periodically?
Containers should be inspected periodically (monthly) and the results of the inspection recorded in the log of inspection of load-handling devices and containers. Inspection of the container should be carried out by the person responsible for the good condition of the container. In addition, slingers, crane operators and a person responsible for the safe operation of cranes should inspect the containers daily (every shift) before starting work.
In what cases is the container rejected?
Crane operators and slingers must remember that removable load-handling devices and containers that have not passed a technical examination, do not have tags (brands) and are faulty are not allowed to work and they should not be located in the places of work.
TO Category: - Crane operators and slingers
Tasks 81-90
Calculate a vertical bucket elevator with a capacity of Q, intended for transportation of bulk density material r, medium size AWith to the height H. The elevator is installed in an open area.
Select the initial data for solving the problem from Table 5.
Table 5
task number | Q, t/h | r, t/m3 | AWith, mm | Conveyed material |
|
clay dry |
|||||
Pyrite flotation |
|||||
Lump sulfur |
|||||
Sand dry |
|||||
Limestone |
|||||
Chalk crushed |
|||||
Dry ash |
|||||
Bauxite crushed |
Guidelines:, p.216 ... 218, example 12.
Guidelines for the implementation of practical work
Practical work No. 1
Selection of steel ropes and chains, pulleys, sprockets and drums.
1. Selection of steel ropes and chains .
The exact calculation of ropes, welded and plate chains, due to the uneven distribution of stresses, is very difficult. Therefore, their calculation is carried out according to the norms of Gosgortekhnadzor.
Ropes and chains are selected according to GOST in accordance with the ratio:
FR£ FR.m
Where FR.m- breaking force of the rope (chain), taken according to the tables
relevant GOSTs for ropes (chains);
FR- estimated breaking force of the rope (chain), determined by
Fp =FmOh· n,
Where n- safety factor, taken according to Pra-
forks of Gosgortekhnadzor, depending on the purpose of the rope and
mode of operation of the mechanism. Its meaning for nk ropes and chains
nц are given in Table P1 and P2.
FmOh- maximum working force of the rope branch (chain):
Fmax =G/zhn, kN,
Here G- cargo weight, kN;
z- the number of branches of the rope (chain) on which the load is suspended;
hn- Efficiency of the chain hoist (Table P3).
The number of branches of the rope on which the load is suspended is:
z = u · A ,
Where A- the number of branches wound on the drum. For simple (one
narny) chain hoist A= 1, and for the double A = 2;
u- polyspast multiplicity.
According to the value of the breaking force FR from the condition FR£ FR.m
according to the GOST tables, we select the dimensions of the rope (chain).
Example 1 Choose a rope for the lifting mechanism of an overhead crane with a lifting capacity G= 200 kN. Lifting height H= 8m. Mode of operation - easy (PV = 15%). Polyspast double multiplicity u= 4.
Initial data:
G= 200 kN - the weight of the lifted load;
H\u003d 8m - the height of the load;
Mode of operation - easy (PV = 15%);
A= 2 - the number of branches wound on the drum;
u\u003d 4 - the multiplicity of the chain hoist.
Maximum working force of one branch of the rope:
Fmax =G/zhn= 200/ 8 0.97 = 25.8 kN,
Where z=u· A= 4 2 = 8 - the number of branches on which the load is suspended;
hn- efficiency of the chain hoist, according to the table. P3 at u= 4 for pulley block with bearing
nick rolling hn= 0.97 Estimated breaking force: Fp =FmOh· nTo= 5 25.8 = 129 kN,
Where nTo– rope safety factor, for a crane with a machine
drive for light duty nTo= 5 (Table A1).
According to GOST 2688-80 (Table P5), we select a rope of the LK type - R 6x19 + 1 o. With. with breaking force FR.m. = 130 kN at ultimate strength GV= 1470 MPa, rope diameter dTo= 16.5 mm. Actual Rope Safety Factor:
nf =FR.m. · z· hn/G= 130 8 0.97/200 = 5.04 > nTo = 5,
Therefore, the selected rope is suitable.
Example 2 Choose a welded calibrated chain for manual hoist carrying capacity G= 25 kN. Polyspast multiplicity u= 2 (polyspast simple).
Initial data:
G= 25 kN - lifting capacity of the hoist;
u\u003d 2 - the multiplicity of the chain hoist;
A= 1 - simple chain hoist.
Fmax =G/zhb= 25/2 0.96 = 13 kN,
Where z=u· A= 2 1 = 2 - the number of branches on which the load is suspended;
hb\u003d 0.96 - efficiency of the chain block. Estimated breaking force: Fp =FmOh· nc= 3 13 = 39 kN,
Where nc- chain safety factor, for welded calibrated
chains with manual drive nc= 3 (Table A2).
According to table P6, we select a welded calibrated chain with a breaking force FR.m. = 40 kN, in which the diameter of the bar dc= 10 mm, internal length (pitch) of the chain t= 28 mm, link width IN= 34 mm.
Actual margin of safety:
nf =FR.m. · z· hn/G= 40 2 0.96/25 = 3.1 > nc= 3.
The selected chain is suitable.
Example 3 Select a load leaf chain for a machine-driven hoist with a lifting capacity of G= 30 kN. The load is suspended on two branches ( z = 2).
Initial data:
G= 30 kN - the weight of the lifted load;
z= 2 - the number of branches on which the load is suspended.
Maximum working force of one branch of the chain:
Fmah =G/zhsv= 30/2 0.96 = 15.6 kN,
Where hsv\u003d 0.96 - sprocket efficiency.
Estimated breaking force: Fp =FmOh· nc= 5 15.6 = 78 kN,
Where nc- safety factor of the chain, for a lamellar chain with
machine driven nc= 5 (Table A2).
According to table P7, we accept a chain with a breaking force FR.m. = 80 kN, which has a step t= 40 mm, plate thickness S= 3 mm, plate width h= 60 mm, number of plates in one chain link n= 4, diameter of the middle part of the roller d= 14 mm, roll neck diameter d1 = 11 mm, roller length V= 59 mm.
Actual margin of safety:
nf =FR.m. · z· hn/G= 80 2 0.96/30 = 5.12 > nc= 5.
The selected chain is suitable.
2. Calculation of blocks, stars and drums.
The minimum allowable diameter of the block (drum) along the bottom of the stream (groove) is determined according to the norms of Gosgortekhnadzor:
Db³ (e - 1)dTo, mm
Where e- coefficient depending on the type of mechanism and mode of operation, you
taken according to the normative data of the Rules of Gosgortekhnadzor
(Table A4);
dTo- rope diameter, mm.
Block sizes are normalized.
The diameter of the block (drum) for welded non-calibrated chains is determined by the ratios:
for manual mechanisms Db³ 20 dc;
for machine-driven mechanisms Db³ 30 dc;
Where dc- the diameter of the steel bar from which the chain is made.
The diameter of the starting circle of the sprocket for a welded calibrated chain (the diameter along the axis of the bar from which the chain is made) is determined by the formula:
Dn. O. = t/sin 90° /z, mm
Where t- internal length of the chain link (chain pitch), mm;
z- the number of sockets on the sprocket, accept z³ 6.
The diameter of the starting circle of the sprocket for the leaf chain is determined
are calculated according to the formula:
Dn. O. = t/sin 180° /z, mm
Where t- chain pitch, mm;
z- number of sprocket teeth, take z³ 6.
Rope drums are used with a single-layer and multi-layer winding, with a smooth surface and with a screw thread on the surface of the shell, with one-sided and two-sided winding of the rope.
The diameter of the drum, as well as the diameter of the block, is determined according to the Rules of Gosgortekhnadzor:
Db³ (e - 1)dTo, mm.
The length of the drum with double-sided winding of the rope is determined by the formula:
and with one-sided winding:
https://pandia.ru/text/78/506/images/image005_7.png" width="124" height="32 src=">,
Where z- the number of working turns of the rope;
https://pandia.ru/text/78/506/images/image007_5.png" width="18" height="23 src=">,
Where b- the distance between the axes of the streams of the extreme blocks, is taken according to table P8;
hmin- the distance between the axes of the drum and the axis of the blocks in the uppermost position;
Permissible angle of deviation of the rope branch running onto the drum from the vertical position, = 4 ... 6 °.
The wall thickness of the drums can be determined from the condition of compressive strength:
https://pandia.ru/text/78/506/images/image009_4.png" width="48" height="29"> - allowable compressive stress, Pa, when calculating take:
80MPa for cast iron C4 15-32;
100MPa for steels 25L and 35L;
110MPa for steels St3 and St5.
For cast drums, the wall thickness can be determined by empirical formulas:
for cast iron drums https://pandia.ru/text/78/506/images/image010_1.png" width="26" height="25 src=">= 0.01 dB+3 mm, and then perform a compression test. Should be:
https://pandia.ru/text/78/506/images/image012_2.png" width="204" height="72"> mm
Where t\u003d 28 mm - internal link length (pitch) of the chain;
z 6 - the number of nests on the block (asterisk), we accept z=10.
Example 5 According to example 3, determine the diameter of the initial circle of the sprocket.
Sprocket Pitch Circle Diameter
mm,
Where t\u003d 40 mm - chain pitch;
z 6 - the number of teeth of the sprocket, we accept z=10.
Example 6 Determine the main dimensions of the cast iron drum according to the example 1..png" width="156 height=44" height="44">, mm
Where dk= 16.5 mm - rope diameter;
e- coefficient depending on the type of mechanism and operating mode, for cranes with a machine drive in light duty e=20 (Table A4)
dB\u003d (20-1) ∙ 16.5 \u003d 313.5 mm, we take the value of the drum diameter from the normal series dB\u003d 320 mm (Table A8).
Determine the length of the drum. Drum with double-sided cutting. The working length of one half of the drum is determined by the formula:
mm
Where t- pitch of turns, for a drum with grooves
t=dk+(2…3)=16.5+(2…3)=(18.5…19.5) mm, accept t= 19 mm;
zo\u003d 1.5 ... 2 - the number of spare turns of the rope, we accept zo=2 turns;
zp- the number of working turns of the rope
https://pandia.ru/text/78/506/images/image019_0.png" width="210 height=36" height="36"> mm
Full drum length:
Lb=2(lp+l3)+lo, mm,
Where l3- the length of the drum required for fastening the rope;
https://pandia.ru/text/78/506/images/image022_0.png" width="16" height="15">=4-6° - the permissible angle of deviation of the rope branch running onto the drum from the vertical position, we accept = 6°.
l0=200-2∙4/80∙tg6°=99.1mm
accept l0=100 mm.
Thus, the total length of the drum
lb\u003d 2 (608 + 60) + 100 \u003d 1436 mm, we accept
lb=1440 mm = 1.44 m
The wall thickness of the drum is determined by the formula:
https://pandia.ru/text/78/506/images/image024_0.png" width="47 height=19" height="19">mm.
The wall thickness of the cast drum must be at least 12 mm.
Practical work No. 2
Calculation of winches and lifting mechanisms of hoists with manual and electric drives according to specified conditions.
1. Calculation of winches with manual drive
sequence of calculation of a winch with a manual drive.
1) Select a load suspension scheme (without a chain hoist or with a chain hoist).
2) According to the given load capacity, select a rope.
3) Determine the main dimensions of the drum and blocks.
4) Determine the moment of resistance on the drum shaft from the weight of the load Ts and the moment on the shaft of the handle, created by the force of the worker Tr.
Moment of resistance from the weight of the load
N∙ m,
Where Fmax- maximum working force in the rope branch, N; dB- diameter of the drum, m.
The moment on the shaft of the handle:
N∙m,
Where pp- the effort of one worker, is accepted
pp=100…300 N
n– Number of workers;
https://pandia.ru/text/78/506/images/image001_21.png" width="15" height="17 src=">.png" width="80 height=48" height="48">
Where η – winch efficiency.
6) Calculate open gears and shafts (the method of their calculation was studied in the section "Machine parts" of the subject "Technical mechanics").
7) Determine the main dimensions of the handle. The handle rod diameter is determined from the bending strength condition:
m,
Where l1- the length of the handle rod, is taken l1=200…250 mm for one worker and l1=400…500 mm for two workers;
https://pandia.ru/text/78/506/images/image029_1.png" width="29" height="23 src=">=(60…80) MPa=(60…80)∙106Pa.
The thickness of the handle in the dangerous section is calculated on the combined action of bending and torsion:
 | ||
The width of the handle is taken equal to
Where G- lifting capacity of the winch, kN;
Vr- the circumferential speed of the drive handle is usually taken
Vr=50...60 m/min.
Example 7 Calculate the lifting mechanism of a hand winch designed to lift a load with a weight G= 15 kN per height H= 30m. Number of workers n=2. winch efficiency h=0.8. The drum surface is smooth, the number of layers of rope winding on the drum m=2. Polyspast multiplicity u=2. Polyspast simple ( A=1).
Initial data:
G\u003d 15kN - weight of the lifted load;
H\u003d 10m - the height of the load;
n=2 - the number of workers;
h\u003d 0.8 - winch efficiency;
m=2 - the number of layers of rope winding on the drum;
drum surface is smooth;
u\u003d 2 - multiplicity of the chain hoist;
A=1 - the number of branches wound on the drum.
Rope selection.
Maximum working force in one rope strand:
Fmax= 15/2×0.99=7.6 kN,
Where z=u×a= 2 - the number of branches on which the load hangs;
The efficiency of the chain hoist according to the table. P3 for chain hoist with multiplicity u=2 on rolling bearings 0.99.
Estimated breaking force:
fp=nk× Fmax\u003d 5.5 × 7.6 \u003d 41.8 kN,
Where nTo- safety factor of the rope, for a cargo winch with a manual drive nTo=5.5 (Table P1).
According to GOST 26.88-80 (Table P5), we select a rope of the LK-R type 6x19 + 1 o. With. with breaking force fp.m.= 45.45 kN at tensile strength 1764 MPa, rope diameter dTo=9.1 mm.
Actual Rope Safety Factor:
nf =Fr.m. ·z hn/G = 45.45 2 0.99/15 = 6 > nTo = 5,5.
Determination of the main dimensions of the drum.
Minimum allowable drum diameter:
dB ³ ( e– 1)dk, mm
Where e- coefficient depending on the type of mechanism and mode of operation, for
manual cargo winches e=12 (Table A4);
dk- rope diameter, mm, then
dB³ (12 – 1)9.1=100.1mm
We accept from the normal range dB=160mm (Table P8).
The working length of the drum with multi-layer winding of the rope is determined by the formula:
Where t – winding pitch, for a smooth drum ; t= dk=9.81 mm ;
Lk – rope length excluding spare turns
Lk=H∙u=30∙2=60m
Full length of the drum with one-sided winding
lb= lR+ lV+ lh,
Where lb=(1,5…2)∙ t- the length of the drum required for spare turns ,
lb=(1,5…2)∙9,81=13,65…18,2 mm ,
accept lb=18 mm
lh – the length of the drum required to secure the rope
Calculation of steel ropes
When performing rigging work related to the installation of various technological equipment and structures, steel ropes are used. They are used for the manufacture of slings and cargo suspensions, as braces, braces and rods, as well as for equipping chain hoists, winches and cranes.
Regardless of the purpose in rigging, it is necessary to use steel ropes that meet the following general requirements:
by design - double lay;
by the type of strands - with a linear touch of the wires between the layers (LC) and as a replacement - with a point-linear touch (TLK);
according to the core material - with an organic core (OC) and as a replacement - with a metal core (MC) from a rope wire;
according to the laying method - non-untwisting (N);
in the direction of the lay - cross lay;
according to the mechanical properties of the wire - grade I ropes and as a replacement - grade II ropes;
according to the marking group - with a tensile strength of 1764 MPa and more; as an exception, it is allowed to use ropes with a strength of at least 1372 MPa;
by the presence of coating - for work in chemically active environments and water - ropes with galvanized wire;
by appointment - cargo (D).
Depending on the purpose, the following types of ropes are used:
for slings, cargo suspensions and equipment of chain hoists, winches, cranes - more flexible ropes of the LK-RO type of design 6x36 (1 + 7 + 7/7 + 14) + 1 o. With. (GOST 7668-80); as a replacement, ropes of the TLK-0 type of design 6x37 (1 + 6 + 15 + 15) + 1 o can be used. With. (GOST 3079-80);
for braces, braces and rods - more rigid ropes of the LK-R type of design 6 x 19 (1 + 6 + 6/6) + 1 o. With. (GOST 2688-80); as a replacement, it is allowed to use ropes of the LK-0 type of construction 6x19 (1 + 9 + 9) + 1 o. With. (GOST 3077-80). Technical data of recommended rope types are given in app. 1.
Steel ropes are calculated for strength by determining the maximum design forces in the branches, multiplying them by the safety factor and comparing the obtained values with the breaking force of the rope as a whole. At the same time, the design forces acting on the rope include the standard loads without taking into account the overload coefficients and dynamism from the mass of the lifted loads, together with mounting devices and the efforts in guy wires, rods.
The calculation of the steel rope is performed in the following order:
1. Determine the breaking force of the rope (kN):
where S is the maximum design force in the rope, kN; Kz-factor of safety factor. (app. 2)
2. Depending on the purpose, a more flexible (6x36) or more rigid (6x19) rope is selected and, according to the GOST table (Appendix I), its characteristics are set: type, design, tensile strength, breaking force (not less than the calculated one) diameter and weight .
Solution 1 . We calculate the breaking force in the rope, having determined by app. 2 safety factor k z \u003d 5 for a cargo rope with light duty:
R k \u003d Sk z \u003d 100 * 5 \u003d 500 kN.
2. We choose for the winch a flexible rope of the LK-RO type of design 6x36 (1 + 7 + 7/7 +14) + 1 o. With. (GOST 7668-80) and according to the GOST table (Appendix I) we determine its characteristics:
tensile strength, MPa………………………1764
breaking force, kN………………………………………….…517
rope diameter, mm…………………………………………….……31
weight of 1000 m rope, kg…………………………………………..3655
Task options for the selection of a steel rope for an electric winch with traction, see Appendix 11.
Calculation of welded and plate chains
chains in installation work are of limited use. Welded non-calibrated chains are usually used as slings, welded calibrated and plate chains - in lifting mechanisms.
For welded and plate chains, the permissible force on a branch in the chain (kN) is determined by the formula:
where R is the breaking load, kN (selected according to the GOST tables: for welded chains - Table 1, for lamellar chains - Table 2); kz - safety factor for chains (selected depending on their purpose according to Table 3).
The diameters of the drums and sprockets wrapped around by the welded chain must be at least: for a manual drive - 20 link diameters, for a machine drive - 30 link diameters. The number of teeth of sprockets for leaf chains must be at least six.
Example 2 Determine the allowable force in a welded load chain with a chain steel diameter of d = 8 mm for a manual hoist.
Solution. 1. We find the value of the breaking load for a given chain according to
tab. 1: R = 66 kN.
Table 1. Round link and traction chains.
(GOST 2319-81, ST SEV 2639-80)
| Chain steel diameter, mm | Chain pitch, mm | Weight of 1 m chain, kg | Chain steel diameter, mm | Chain pitch, mm | Weight of 1 m chain, kg | ||
| 0,75 | 2,25 | ||||||
| 1,00 | 2,70 | ||||||
| 1,35 | 3,80 | ||||||
| 1,80 | 5,80 |
Table 2. Lamellar cargo chains.
(GOST 191-82, ST SEV 2642-80)
| Chain type | Pitch t, mm | Distance between inner plates, l in, mm | Plate dimensions, mm | Roll dimensions, mm | Weight l m chain, kg | ||||||
| Thickness δ | Length L | Width B | Length l, mm | Diameter of the middle part d s, mm | Neck diameter for plates d w, mm | Number of plates in one link | |||||
| I | 2.5 | 1,4 | |||||||||
| 2.5 | 2,7 | ||||||||||
| 3.0 | 3,4 | ||||||||||
| II | 3.0 | 7,0 | |||||||||
| 4.0 | 10,5 | ||||||||||
| 5.0 | 17,0 | ||||||||||
| 5.0 | 23,0 | ||||||||||
| III | 8.0 | 53,0 | |||||||||
| 8.0 | 89,0 | ||||||||||
| IV | 8.0 | 150,0 | |||||||||
| 10.0 | 210,0 | ||||||||||
| 10.0 | 305,0 |
Note. Load leaf chains are manufactured in four types
I- with riveting without washers; III - with riveting on washers;
II - on cotter pins; IV - with smooth rollers.
Table 3. Safety factor
2. We determine the allowable force in the chain at k s \u003d 3:
S \u003d R / k s \u003d 66/3 \u003d 22 kN.
Example 3. To select a leaf chain for a machine-driven hoist with a maximum load on the chain branch S= 35 kN.
Solution . 1. Find the breaking load in the chain branch:
R \u003d Sk z= 35*5 = 175 kN.
2. Using the table. 2, we select a leaf chain with the following characteristics:
Chain type ………………………………………………….….11
Chain pitch t, mm…………………………………………….…60
Plate width B, mm…………………………………....38
Diameter of the middle part of the roller d, mm………………….…...26
Roller length l, mm……………………………………….….97
Number of plates in one link……………………..…...4
Options for tasks for the selection of a plate chain, see. Annex 12.
Calculation of rope slings
Slings made of steel ropes are used to connect mounting chain hoists with hoisting and transport vehicles (masts, portals, chevres, booms, mounting beams), anchors and building structures, as well as for slinging lifted or moved equipment and structures with hoisting and transport mechanisms.
In the practice of installation, the following types of rope slings are used: conventional, which include universal and one-, two-, three- and four-legged ones, fixed on the lifted equipment with strapping or inventory grips, as well as twisted and towel ones.
For slinging heavy equipment, inventory twisted slings are mainly used, which are made in the form of a closed loop by successively parallel dense laying of interlaced coils of rope around the initial central coil. These slings have a number of advantages: uniform distribution of the load on all turns, reduction of rope consumption, lower labor intensity of slinging.
Towel slings are also made in the form of a closed loop of tightly packed turns of the rope, placing them in a single layer on the gripping device and the element of the lifted equipment (mounting fitting, pin, shaft). This ensures uniform tension on the individual branches of the sling. The ends of the rope are fixed in a loop with clamps.
Methods for the manufacture and use of twisted and towel slings are described in the industry standard OST 36-73-82.
A twisted sling approved for use is supplied with a metal tag indicating the main technical data.
Rope slings are calculated in the following order (Fig. 1, A).
1. Determine the tension (kN) in one branch of the sling:
S \u003d P / (mcos α),
where P is the design force applied to the sling, without taking into account the overload and dynamic factors, kN; m - the total number of branches of the sling; α is the angle between the direction of the calculated force and the branch of the sling, which is set based on the transverse dimensions of the equipment being lifted and the method of slinging (this angle is recommended to be set no more than 45 °, bearing in mind that with its increase, the force in the branch of the sling increases significantly).
2. Find the breaking force in the branch of the sling (kN):
where kz is the safety factor for the sling (determined according to Appendix 2, depending on the type of sling).
| 2α |
| α |
Fig.1. Calculation schemes of slings a- rope sling; b- twisted sling
3. According to the calculated breaking force, using the GOST table (Appendix I), the most flexible steel rope is selected and its technical data, type and design, tensile strength, breaking force to diameter are determined.
Solution: 1. Determine the tension in one branch of the sling, given the total number of branches m = 4 and their angle of inclination α = 45 o to the direction of the calculated force P:
S = P/ (m cosα) = 10 G o /(m cosα)=
10×15/(4×0.707)=53 kN.
2. We find the breaking force in the branch of the sling:
R n \u003d Sk z \u003d 53 * 6 \u003d 318 kN.
3. According to the breaking force found, using app. 1, we select a rope of the LK-RO type of construction 6 × 36 (1 + 7 + 7 / 7 + 14) + 1o.s. (GOST 7668-80) with characteristics:
Tensile strength, MPa…………….…………1960
Breaking force, kN…………………………………..….………338
Rope diameter, mm………………………………….…….………23.5
Weight of 1000 m rope, kg…………………………………………..2130
Task options for calculating a steel rope for a sling, see Appendix 13.
4. Calculation of a twisted sling (Fig. 1, b)
1. Determine the tension (kN) in one rope turn of the sling:
S = P/(mncos α),
where P is the force applied to the sling, kN; m - the number of branches of the sling (for a twisted sling m=2); n is the number of rope turns in the cross section of one branch of the sling (usually n = 7.19 or 37 turns); α- angle between the branch of the sling and the direction of the force P (recommended a≤30 o).
2. Find the breaking force (kN) in one rope turn of the sling:
where kz is the safety factor (Appendix 2).
3. According to the calculated breaking force, using the GOST table (Appendix 1), select a steel rope for a twisted sling and determine its technical data.
4. Find the calculated diameter d from the cross section of the branch of the sling (mm) depending on the number of turns in the cross section of one branch:
7 turns…………………………d c = 3d
19 turns……………………..…d c = 5d
37 turns……………………..…d c = 7d
where d is the diameter of the rope for the turns of the sling.
5. Find the minimum diameter of the gripper:
D a \u003d k c d c,
Where to s - the ratio of the diameters of the gripping device and the cross section of the branch of the sling; its minimum value is:
for double curvature gripper (bucket type)….. k s ≥ 2
for a cylindrical gripper ……………. k s ≥ 2
6. Calculate the length of the rope (m) for the manufacture of a twisted sling
L k \u003d 2.2nl + 2t,
where l is the required length of the sling along the central coil, m; t- sling pitch equal to 30 d, m.
Solution. 1. We determine the tension in one rope turn of the sling, setting the angle α - 20°, the number of rope turns in one branch of the sling n = 19 pcs. and bearing in mind that P = 10G o:
S = P/(mncosα) = 10×300/(2×19×0.94) = 84 kN.
2. We find the breaking force in one rope coil:
R to \u003d Sk z \u003d 84 * 5 = 420 kN.
3.According to app. I select a steel rope type JIK-PO construction 6×36 (1+7+7/7+14)+1o.s. (GOST 7668-80) with characteristics:
Tensile strength, MPa………………………1960
Breaking force, kN……………………………………………430.5
Rope diameter, mm…………………………………………….……27
Weight of 1000 m rope, kg…………………………………………..2800
4. Find the calculated cross-sectional diameter of the sling branch
d c \u003d 5d \u003d 5 * 27 \u003d 135 mm.
5. We calculate the minimum diameter of the gripper
D s \u003d k with d c \u003d 4 * 135 \u003d 540 mm.
6. We determine the length of the rope for the manufacture of the sling, setting its length l \u003d 1.5 m:
L k \u003d 2.2nl + 2t \u003d 2.2 × 19 × 1.5 + 2 × 0.8 \u003d 64.3 m, where t \u003d 30d - 30 × 0.027 \u003d 0.8 m.
Task options for calculating a twisted sling, see Appendix 14.
Rice. 2. Calculation scheme of the mounting beam
2. The maximum bending moment is calculated by the formula
M max= 
,
Where l- span of the mounting beam.
3. Calculate the required moment of resistance, according to which a standard profile is selected
W tr = 
,
Where R- design resistance, MPa (Appendix 3); m- coefficient of working conditions (Appendix 4).
Example 6 Calculate the mounting beam with a span of l = 3 m for lifting an apparatus weighing 18 tons with one chain hoist fixed to the middle of the beam, if it is known that the mass of the chain hoist G p \u003d 1.2 t, the force in the running branch S p \u003d 35 kN. Beam material St.3.
1. We determine the force acting on the mounting beam at the suspension point of the chain hoist:
R= 10 G O TO P TO d +10 G P TO n+ S n \u003d 10 18 1.1 1.1 + 10 1.2 1.1 + 35 \u003d 266 kN.
2. The maximum bending moment in the mounting beam is calculated by the formula
M max= 
kN cm
3. We find the required moment of resistance of the cross section of the mounting beam
W tr = 
=
19950 / (0.85 0.1 210) \u003d 1117.6 cm 3 .
4. For a beam of solid section (Appendix 5), we accept an I-beam№ 45with W x = 1231cm 3 , which satisfies the condition W x >W tr.
Task options for calculating the mounting beam, see Appendix 15.
Calculation of traverses
Traverses are rigid lifting devices designed to lift large, long, and thin-walled equipment, such as shells.
One of the important purposes of the traverse when mounting thin-walled apparatus is to absorb the resulting compressive forces and bending moments in order to prevent deformation of the lifted apparatus.
Typically, the traverse is a beam made of single I-beams, channels or steel pipes. various sizes. Sometimes the traverse is made of paired I-beams or channels connected by steel plates, or steel pipes reinforced with fluid elements.
When lifting equipment with several cranes of different carrying capacity, balancing or balancing traverses with different shoulders are used.
The traverse works in bending and compression. The mass of the traverse is an insignificant fraction of the mass of the lifted load (as a rule, no more than
1%), therefore, in practical calculations, the bending moment in the traverse and the deflection from its own mass can be neglected.
Task options for calculating the cross section of a traverse beam, see Appendix 16.
Annex 3
Appendix 4
Appendix 5
Appendix 6
Channels (GOST 8240–72)
| Channel No. | Dimensions, mm | F cm 2 | Weight 1m, kg | Reference values for axes | |||||||
| h | b | s | x-x | y-y | |||||||
| I x, cm 4 | W x, cm 3 | rx, cm | I y, cm 4 | W y, cm 3 | r y, cm | ||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 4,4 | 6,16 | 4,84 | 22,8 | 9,10 | 1,92 | 5,61 | 2,75 | 0,95 | |||
| 6,5 | 4,4 | 7,51 | 5,90 | 48,6 | 15,0 | 2,54 | 8,70 | 3,68 | 1,08 | ||
| 4,5 | 8,98 | 7,05 | 89,4 | 22,4 | 3,16 | 12,80 | 4,75 | 1,19 |
Continuation of Appendix 6
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 4,5 | 10,90 | 8,59 | 174,0 | 34,8 | 3,99 | 20,40 | 6,46 | 1,37 | |||
| 4,8 | 13,30 | 10,40 | 304,0 | 50,6 | 4,78 | 31,20 | 8,52 | 1,53 | |||
| 4,9 | 15,60 | 12,30 | 491,0 | 70,2 | 5,60 | 45,40 | 11,00 | 1,70 | |||
| 14a | 4,9 | 17,00 | 13,30 | 545,0 | 77,8 | 5,66 | 57,50 | 13,30 | 1,84 | ||
| 5,0 | 18,10 | 14,20 | 747,0 | 93,4 | 6,42 | 63,30 | 13,80 | 1,87 | |||
| 16a | 5,0 | 19,50 | 15,30 | 823,0 | 103,0 | 6,49 | 78,80 | 16,40 | 2,01 | ||
| 5,1 | 20,70 | 16,30 | 1090,0 | 121,0 | 7,24 | 86,00 | 17,00 | 2,04 | |||
| 18a | 5,1 | 22,20 | 17,40 | 1190,0 | 132,0 | 7,32 | 105,0 | 20,00 | 2,18 | ||
| 5,2 | 23,40 | 18,40 | 1520,0 | 152,0 | 8,07 | 113,0 | 20,50 | 2,20 | |||
| 20a | 5,2 | 25,20 | 19,80 | 1670,0 | 167,0 | 8,15 | 139,0 | 24,20 | 2,35 | ||
| 5,4 | 26,70 | 21,00 | 2110,0 | 192,0 | 8,89 | 151,0 | 25,10 | 2,37 | |||
| 22a | 5,4 | 28,80 | 22,60 | 2330,0 | 212,0 | 8,99 | 187,0 | 30,00 | 2,55 | ||
| 5,6 | 30,60 | 24,00 | 2900,0 | 242,0 | 9,73 | 208,0 | 31,60 | 2,60 | |||
| 24a | 5,6 | 32,90 | 25,80 | 3180,0 | 265,0 | 9,84 | 254,0 | 37,20 | 2,78 | ||
| 6,0 | 35,20 | 27,70 | 4160,0 | 308,0 | 10,9 | 262,0 | 37,30 | 2,73 | |||
| 6,5 | 40,50 | 31,80 | 5810,0 | 387,0 | 12,0 | 237,0 | 43,60 | 2,84 | |||
| 7,0 | 46,50 | 36,50 | 7980,0 | 484,0 | 13,1 | 410,0 | 51,80 | 2,97 | |||
| 7,5 | 53,40 | 41,90 | 601,0 | 14,2 | 513,0 | 61,70 | 3,10 | ||||
| 8,0 | 61,50 | 48,30 | 761,0 | 15,7 | 642,0 | 73,40 | 3,23 |
Annex 7
Basic design data for steel seamless pipes (GOST 8732– 78)
| Diameter, mm | Wall thickness, mm | Cross-sectional area F, cm 2 | Moment of inertia I, cm 3 | Moment of resistance W, cm 3 | Radius of inertia r, cm | Weight l m, kg | |
| outer d n | interior d V | ||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 12,3 18,1 23,6 28,9 33,9 38,7 43,2 | 29,0 41,0 51,6 60,6 68,6 75,3 81,0 | 3,47 3,40 3,34 3,27 3,21 3,15 3,09 | 9,67 14,21 18,55 22,69 26,63 30,38 33,93 | ||||
| 13,1 19,2 25,1 30,8 36,2 41,3 46,2 | 32,8 46,5 58,4 69,1 78,3 86,5 93,4 | 3,68 3,62 3,55 3,48 3,42 3,36 3,30 | 10,26 15,09 19,73 24,17 28,41 32,45 36,30 | ||||
| Continuation of Appendix 7 | |||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 13,8 20,4 26,6 32,7 38,4 44,0 49,2 | 36,7 52,3 66,0 78,2 88,9 98,5 106,0 | 3,89 3,83 3,76 3,70 3,63 3,57 3,51 | 10,85 15,98 20,91 25,65 30,19 34,53 38,67 | ||||
| 14,7 21,7 28,4 34,9 41,1 47,1 52,8 58,3 | 41,6 59,4 75,3 89,5 102,0 113,0 123,0 132,0 | 4,14 4,07 4,00 3,94 3,88 3,81 3,76 3,70 | 11,54 17,02 22,29 27,37 32,26 36,94 41,43 45,72 | ||||
| 15,5 22,8 29,9 36,8 43,4 49,7 55,8 | 46,1 65,9 83,8 99,8 114,0 127,0 138,0 | 4,35 4,28 4,22 4,15 4,09 4,02 3,96 | 12,13 17,90 23,48 28,85 34,03 39,01 43,80 | ||||
| 16,2 23,9 31,4 38,6 45,6 52,3 58,8 | 50,8 72,7 94,3 111,0 127,0 141,0 154,0 | 4,57 4,49 4,43 4,36 4,30 4,24 4,18 | 12,73 18,79 24,66 30,33 35,81 41,09 46,17 | ||||
| 25,3 33,8 40,8 48,3 55,4 62,3 69,0 75,4 | 81,1 104,0 124,0 142,0 159,0 174,0 187,0 199,0 | 4,74 4,68 4,61 4,55 4,49 4,42 4,36 4,30 | 19,83 26,04 32,06 37,88 43,50 48,93 54,16 59,19 | ||||
| 26,4 34,7 42,7 50,5 58,0 | 88,8 114,0 136,0 157,0 175,0 | 4,95 4,89 4,82 4,76 4,70 | 20,72 27,23 33,54 39,66 45,57 |
Continuation of Appendix 7
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 65,3 72,4 79,2 | 192,0 207,0 221,0 | 4,64 4,57 4,51 | 51,30 56,98 62,15 | ||||
| 27,5 36,2 44,6 52,8 60,7 68,4 75,8 82,9 | 96,6 124,0 149,0 171,0 192,0 212,0 228,0 243,0 | 5,17 5,10 5,03 4,97 4,90 4,85 4,78 4,72 | 21,60 28,41 35,02 41,43 47,65 53,66 59,48 65,1 | ||||
| 28,8 37,9 46,8 55,4 63,8 71,9 79,7 | 5,41 5,35 5,28 5,21 5,15 5,09 5,03 | 22,64 29,79 36,75 43,50 50,06 56,43 62,59 | |||||
| 30,5 40,2 49,6 58,8 67,7 76,4 84,8 93,0 | 5,74 5,66 5,60 5,53 5,47 5,40 5,34 5,28 | 23,97 31,57 46,17 53,17 59,98 66,59 73,00 | |||||
| 35,4 46,7 57,8 68,6 79,2 | 6,65 6,59 6,51 6,46 6,38 | 27,82 36,70 45,38 53,86 62,15 |
Continuation of Appendix 7
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 89,5 99,5 109,0 | 6,32 6,26 6,20 | 70,24 78,13 85,28 | |||||
| 32,8 43,2 53,4 63,3 73,0 82,4 91,6 101,0 | 6,15 6,09 6,03 5,96 5,89 5,83 5,76 5,69 | 25,75 33,93 41,92 49,72 57,31 64,71 71,91 78,92, | |||||
| 35,4 46,7 57,8 68,6 79,2 89,5 99,5 109,0 | 6,65 6,59 6,51 6,46 6,38 6,32 6,26 6,20 | 27,82 36,70 45,38 53,86 62,15 70,24 78,13 85,28 | |||||
| 36,9 48,7 60,5 72,2 83,2 94,2 104,4 114,6 | 6,97 6,90 6,83 6,76 6,69 6,62 6,55 6,48 | 29,15 38,47 47,60 56,52 65,25 73,79 82,12 90,26 | |||||
| 40,1 53,0 65,6 78,0 90,2 | 7,53 7,47 7,40 7,33 7,27 | 31,52 41,63 51,54 61,26 70,78 | |||||
| 59,6 73,8 87,8 102,0 | 8,38 8,32 8,25 8,19 | 46,76 57,95 68,95 79,76 |
Continuation of Appendix 7
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 115,0 128,0 141,0 | 8,12 8,06 7,99 | 90,36 100,77 110,98 | |||||
| 66,6 82,6 98,4 114,0 129,0 144,0 159,0 | 9,37 9,31 9,23 9,18 9,12 9,04 8,97 | 52,28 64,86 77,24 89,42 101,41 113,20 124,79 |
Appendix 8
Effective length reduction factor μ for bars of constant cross section
Annex 9
Ultimate flexibility of compressed elements[λ]
Annex 10
Buckling coefficient φ of centrally compressed elements
For steel grade Ct.3.
| Flexibility λ | ||||||||||
| 1,00 0,99 0,97 0,95 0,92 0,89 0,86 0,81 0,75 0,69 0,60 0,52 0,45 0,40 0,36 0,32 0,29 0,26 0,23 0,21 | 0,999 0,998 0,968 0,947 0,917 0,887 0,855 0,804 0,774 0,681 0,592 0,513 0,445 0,396 0,356 0,317 0,287 0,257 0,228 0,208 | 0,998 0,986 0,966 0,944 0,914 0,884 0,850 0,798 0,738 0,672 0,584 0,506 0,440 0,392 0,352 0,314 0,284 0,254 0,226 0,206 | 0,997 0,984 0,964 0,941 0,911 0,811 0,845 0,792 0,732 0,663 0,576 0,499 0,435 0,388 0,348 0,311 0,281 0,251 0,224 0,204 | 0,996 0,982 0,962 0,938 0,908 0,878 0,840 0,786 0,726 0,654 0,568 0,492 0,430 0,384 0,344 0,308 0,278 0,248 0,222 0,202 | 0,995 0,980 0,960 0,935 0,905 0,875 0,835 0,780 0,720 0,645 0,560 0,485 0,425 0,380 0,340 0,305 0,275 0,245 0,220 0,200 | 0,994 0,978 0,958 0,932 0,902 0,872 0,830 0,774 0,714 0,636 0,552 0,478 0,420 0,376 0,336 0,302 0,272 0,242 0,218 0,198 | 0,993 0,976 0,956 0,929 0,899 0,869 0,825 0,768 0,708 0,627 0,544 0,471 0,415 0,372 0,332 0,299 0,269 0,239 0,216 0,196 | 0,992 0,974 0,954 0,926 0,896 0,866 0,820 0,762 0,702 0,618 0,536 0,464 0,410 0,368 0,328 0,296 0,266 0,236 0,214 0,194 | 0,991 0,972 0,952 0,923 0,890 0,863 0,815 0,756 0,696 0,609 0,528 0,457 0,405 0,364 0,324 0,293 0,262 0,233 0,213 0,192 |
Annex 11
Job options for the selection of a steel rope for an electric winch with the following traction forces :
| Option | ||||||||||||||||||
| kN |
| Option | ||||||||||||
| Go |
| Option | ||||
| Go |
Annex 15
Task options for calculating the mounting beam for lifting the apparatus with one chain hoist:
| Option | ||||||||||||||||||
| L,m | ||||||||||||||||||
| weight | ||||||||||||||||||
| Gp | 1,2 | 1,3 | 1,5 | 1,6 | 1,7 | 1,8 | 1,9 | 2,1 | 2,2 | 2,3 | 2,4 | 2,5 | 2,6 | 2,7 | 2,8 | 2,9 | ||
| S P | ||||||||||||||||||
| Beam material | ST3 | ST5 | Steel 45 | Steel 40X | ST3 | ST5 | Steel 45 | Steel40X | ST3 | ST5 | Steel 45 | ST3 | ST5 | Steel 45 | Steel40X | ST3 | ST5 | Steel 45 |
Appendix 15 continued
| Option | ||||||||||||
| L,m | ||||||||||||
| weight | ||||||||||||
| Gp | 1,1 | 1,2 | 1,3 | 1,4 | 1,5 | 1,6 | 1,7 | 1,8 | 1,9 | 2,1 | 2,2 | |
| S P | ||||||||||||
| Beam material | Steel 40X | ST3 | ST5 | Steel 45 | Steel40X | ST3 | ST5 | Steel 45 | Steel40X | ST3 | ST5 | Steel 45 |
Annex 16
Variants of tasks for calculating the cross section of a traverse beam.
| Option | ||||||||||||||||||
| Go, t. |
| Option | ||||||||||||
| Go, t. |
Kp and Kd take equal to 1.1
Annex 17
Task options for calculating a traverse working in compression for lifting a horizontal cylindrical drum:
| Option | ||||||||||||||||||
| Go, t. | ||||||||||||||||||
| L,m |
| Option | ||||||||||||
| Go, t. | ||||||||||||
| L,m |
Bibliography
Slings made of vegetable and synthetic fibers must be made with a safety factor of at least 8.
ATTENTION! Although the slings are designed with a safety factor, it is unacceptable to exceed the load capacity of the sling indicated on the tag.
What determines the tension of the branches of the sling? What angle between the branches are the slings designed for?
The tension S of the branch of a single-branch sling is equal to the mass of the load Q (Fig. 3.13). tension S in each branch of a multi-branch sling is calculated by the formula
S= Q/(n cos b),
Where P- number of branches of the sling; cos b- cosine of the angle of inclination of the sling branch to the vertical.
Of course, the slinger does not have to determine the loads in the branches of the sling, but he must understand that with an increase in the angle between the branches, the tension of the branches of the sling increases. On fig. 3.14 shows the dependence of the tension of the branches of a two-branch sling on the angle between them. Remember, when you carry buckets of water, the load increases when you spread your arms. The tensile force in each branch of a two-leg sling will exceed the mass of the load if the angle between the branches exceeds 120°.
Obviously, with an increase in the angle between the branches, not only the tension of the branches and the probability of their rupture increases, but also the compressive component of the tension 5 SG (see Fig. 3.13), which can lead to the destruction of the load.
ATTENTION! Branch rope and chain slings designed so that the angles between the branches do not exceed 90°. Estimated angle for textile slings 120°.
 |
What are traverses for? What designs of traverses are used for slinging loads?
Traverses are removable lifting devices designed for slinging long and bulky loads. They protect the load being lifted from the effects of compressive forces that occur when using slings.
By design, traverses are divided into planar and spatial.
planar traverses (Fig. 3.15, A) used for slinging long loads. The main part of the traverse is a beam 2, or a truss that takes bending loads. Rope or chain branches are suspended from the beam 1.
Traverses with the possibility of moving clips 4 along the beam called universal (Fig. 3.15, b). Equalization blocks 5 are installed in the clips, which ensure uniform distribution of loads between the branches of the traverse S 1 = S 2 . For this reason, such a traverse is called balancing. Leveling blocks can also be used in rope sling designs with more than three branches.
Spatial traverses (Fig. 3.15, V) used for slinging volumetric structures, machines, equipment.
I diversify the balancing traverse (Fig. 3.15, G) used to lift cargo with two cranes, it allows you to distribute the load between the cranes in proportion to their lifting capacities.
Traverse signs of rejection:
Ø no hallmark 3 or tag;
Ø cracks (usually occur in welds);
Ø deformation of beams, struts, frames with a deflection boom of more than 2 mm per 1 m of length;
Ø damage to fastening and connecting links.
What are the grips?
Clamps are the most advanced and safe lifting devices, the main advantage of which is the reduction manual labor. Clamps are used in cases where you have to move the same type of cargo. Due to the wide variety of goods to be transported, there are many different designs of grabs. Most of them can be attributed to one of the following types.
Tick-borne grips (Fig. 3.16, A) hold the load with levers 1 for its protruding parts.
Friction grippers hold the load due to friction forces. Lever friction grips (Fig. 3.16, 6) clamp the load with levers 1. Lever-rope friction grips (Fig. 3.16, V) have ropes 3 with blocks, they are used for slinging bales, bales.
IN eccentric captures (Fig. 3.16, G) the main part is the eccentric 4, which, when turned, securely clamps sheet materials.
There are also load-handling devices that provide automatic (without the participation of a slinger) unslinging of the load.
