Why are sewer hatches round. Why is the manhole cover round? Causes and Effects

Round? And what else can they be? In theory, the hatch can be square or rectangular. But such a construction is rather an exception to the rule. The hatch is not a simple access door, it must be securely closed. It should be easy to maintain and safe to use.

If convenience is not for everybody, then the round design of the lid can provide reliability at the level of standard loads. The configuration of the base depends on its shape, which, in fact, is a sewer hatch.

Waste system

Sewerage networks are a complex of structures intended for collection and disposal from users to treatment facilities. The easiest way to do this is to dig a trench, pipes are laid into it, through which drains will be discharged.

To be able to service the system at a certain distance, observation shafts are required. In the conditions of urban infrastructure with dense development, it is possible to install sewerage networks only along the roads or directly under them. In this case, the hatches should be securely closed during heavy traffic. But why are the sewers round? They must be strong enough to withstand the maximum possible traffic loads.

In a big city, the number of inspection hatches and all kinds of mines can be in the hundreds of thousands. After all, this is not only a sewerage system, it is also a communications network: water supply, heating networks, electricity, gas, telephony, and so on.

Inspection wells

For ease of access to communications, the well shaft is usually round. Sewer rings used for the construction of such structures are most often made of reinforced concrete.

The cylindrical shape of the well is most suitable for maintenance. It is more convenient to work in such mines. They are suitable for ventilation, as the air circulation in a cylindrical object is more intensive.

The cover size, base area and internal diameter are selected in accordance with the purpose of the inspection shaft. In this case, all elements of the system will correspond to each other as much as possible. The location, possible loads, traffic intensity are taken into account.

It depends on the shape of the cover. On the one hand, service personnel must have easy access to underground utilities... On the other hand, the well must be reliably closed in order to exclude the possibility of foreign objects getting inside, to ensure the safe movement of pedestrians and the passage of vehicles. A round lid is best suited for this, which means that the hatch itself must be of this shape.

Depending on the purpose, they are divided by the type of communications laid under them: engineering cable networks, water supply, gas mains, heating mains, storm and sewage sewerage. Manhole size in different countries different. In Russia, standard dimensions (645 and 800 mm) are most often used. Hatches that are not manufactured in accordance with GOST are designed and developed by manufacturers in accordance with the order and specific technical conditions.

This configuration has several advantages. Previously, hatches were made various shapes... They could be square, rectangular, oval or even triangular to indicate the direction of water flow. but round form the cover proved to be the most suitable.

She will never fall into the well, no matter how she is turned. A round lid is easier to open, so the point of application of force will be the same anywhere in the circle. It can be rolled by placing it on its edge. In manufacturing, such a design is more economical.

The round shape of the lid is less prone to sagging. It can withstand a lot of load at the same thickness, which means it can be made thinner without losing quality. During production, round castings give a lower percentage of rejects (shells, pores, cavities).

Material

The base and hatch covers for those in charge are most often made of cast iron. This material has strength, which makes it possible to withstand heavy loads, and corrosion resistance for a long time. The weight of the structures is sufficient so that passing vehicles cannot accidentally lift and move the cover. are made by remelting secondary raw materials, they are cheaper than steel counterparts.

In places where there is no heavy car traffic, it is impractical to install heavy and powerful structures. Recently, hatches made of plastic, polymers and composite material have appeared. They are lighter, cheaper, have a sufficient safety margin, and have a long service life.

In private houses, sewer rings made of reinforced concrete are used for arranging sewage systems, equipping inspection wells and septic tanks. In this case, it is quite justified to install the same base for the hatch on them from above. The cover is also made of concrete. It is made with a larger diameter, does not fit into the groove, but simply closes the hatch hole. The massive structure is quite heavy, it is impossible to accidentally move it. This provides the necessary operational safety.

Specification and marking

For increased loads on the roads, heavy hatches (class T) are used. They can weigh over 100 kg and be over 100 mm thick. Where car traffic is not foreseen, light hatches (class L) are used. Structures for gardens, lawns and other areas (class A) have a diameter of 540 mm and a thickness of 50 mm.

Why are sewer hatches round and marked? This is done for the convenience of recognizing their belonging to. Their covers have letters: ГС - gas network, MG - main gas pipeline, PG - fire hydrant, etc.

The text of the work is placed without images and formulas.
Full version work is available in the tab "Work files" in PDF format

1. Introduction

When our house was being built, they laid water and made a well, which was then covered with a special hatch cover. I noticed that in our city there are round-shaped covers everywhere: in our yard, on the roads, and near the school.

And then I wondered why the manhole covers are round. Arose before me problem: there are many geometric shapes, and for some reason sewer manholes are made round, and perhaps there is another figure suitable for manholes.

TARGET: determination of the properties of the circle, which are used in manhole covers.

TASKS:

1. To get acquainted with the properties of the circle that are new to me and, with the help of experiments, establish the simplest connections and draw conclusions.

2. Look for material about other geometric shapes that could be used by humans in the manufacture of manhole covers.

3. Show the possibility of using circles (and if there is a figure similar in properties) in life.

Hypothesis:besides the circle, there are figures that can be used to make sewer covers.

Research methods

1. Conducting a survey "Why are sewer manhole covers round?"

2. Search for materials on the Internet.

3. Observations.

4. Conducting experiments.

2.MAIN PART

I asked my question to my parents, classmates and acquaintances and received different answers. Most people think that it is so convenient - it is easier to get into a round hole, several answers were - beautiful, and some answered that they did not know. Then I started looking for information on the Internet.

Experience 1. Round objects are easier to move - they can simply be rolled. While objects of rectangular and triangular shapes interfere with angles. And the covers of the sewer manhole are made even heavy - they are made of cast iron. Then we can conclude that the round heavy cover can be moved by one person. And a hatch of a different shape will have to be carried in several hands.

Experience 2. The round-shaped manhole cover will never fall into the well, which means it is best suited for performing a protective function. All this is because the diameter of the cover is always greater than the diameter of the well itself. And other shapes can fall through (for example, at an angle).

Test 3... Let's draw two parallel tangent lines and fix the distance between them. Let's start rotating the circle. He constantly touches these lines and one can say that a closed curve (a circle that describes a circle) has a constant width. This is also a property of the circle. And it is taken into account in the manufacture of manhole covers - there is less chance of making mistakes during production.

Experience 4. In the manufacture of round caps, less material and their cost is reduced.

Here are the reasons why manhole covers are round. But I am interested in one more question: is there a shape similar in properties to a circle. And here I was helped by the program that I watch - "Galileo". From it I learned that there is a shape similar in properties to a circle. This is the Reuleaux triangle. It was studied by the German scientist Franz Röhlau in the 19th century. Let's check it out.

Experience 5. The Reuleaux triangle is a shape with constant width. We draw two tangent straight lines, fix their width and begin to rotate the Reuleaux triangle. And always one point located in one of the "corners" of the Reuleaux triangle, and the other on the opposite arc of the circle, will touch the lines. Experience 6. An object made in the shape of a Reuleaux triangle can be rolled. Install a plank on 2 cylinders in the form of these triangles and see that it rolls over.

Experience 7. The Reuleaux triangle, if installed on the hatch, will not fail either. I have made such a layout and I suggest you make sure of this.

3. CONCLUSION

After carrying out the work, I was able to conclude that the hypothesis put forward by me - in addition to the circle, there are figures that can be used to make sewer manhole covers, was confirmed. But it is easier to make round lids - there is less chance of making a mistake and, therefore, they are made. And now I can answer a question that is often asked when applying for a job at Microsoft. These are the answers: safety, ease of movement, lower cost, fewer mistakes in their manufacture.

And I also learned very much interesting Facts.

1. When race cars are held on city streets, the covers are welded to the hatches. During the movement of racing cars, due to their aerodynamic characteristics, the air pressure between the road and the bottom of the car is so low that it is enough to lift the manhole cover.

2. In the early 2000s, Moscow hosted a large art project "Sewerage of all countries, unite!" - where were presented photos of sewer manholes from around the world.

4. LIST OF REFERENCES AND RESOURCES

1.http: //www.etudes.ru/ru/etudes/mazda

2.http: //otvetprost.com/387-pochemu-lyuki-kruglye.html

3.http: //expirience.ru/pochemu-lyuki-kruglye/

4. Recording of the program "Galileo" from May 2012.

Many people have come across the question of why the sewer manholes have a round shape. Most have heard it in job interviews. In this way, "insidious" HR managers check the general erudition and ability to creative thinking in potential employees.

Also, this question is often used in all kinds of contests and quizzes. If you study the device of sewer manholes, then the answer to the question will become obvious and quite understandable. This is what we will do.

Sewer hatch device

A sewer well usually consists of a shaft and a work area, and a hatch serves as a cover. The working room is equipped and located depending on the type of services served and the requirements for their operation. The depth of the shaft and the size of the room also depend on this.

• Typically, the height of the room is 1.8 meters, but can be more or less. The main criterion for its determination is the depth of the communications. The length of the shaft directly depends on the depth of the room. The shaft is usually round and 0.7 meters in diameter. There must be a ladder in the shaft so that the worker can go down into the room. The material for the construction of a mine is usually brick or concrete.
• A cover on the manhole is necessary to prevent foreign objects and people from entering the mine. The round shape prevents the cover from falling into the shaft if someone steps on it, which means it protects against accidents. This is the main reason why manholes are made round.
• Also, the covers have a fairly large mass, and sometimes this also raises questions. This fact can also be easily explained. Very often, sewer hatches are located on the roadway and when the car's wheels move, they fall on the cover. If the cover were light, it would easily flip over, opening the shaft and creating the likelihood of accidents. To avoid this, the covers are cast from cast iron, which is considered one of the most heavy metals.
• The lid surface usually has raised stripes, letters, or other patterns and images. This is also not done by chance. The ribbed surface prevents slipping and increases the adhesion of car tires and pedestrian soles to the sunroof surface. There are flat lids, and there are also curved lids in the middle, but you will never find concave lids inward anywhere.

On the wells of the cable duct, two covers are usually located at once - protective and locking.

The protective one is on top. An additional lock is located on the closing cover, which prevents unauthorized persons from entering the shaft in order to steal the cable. These covers are lighter than conventional ones because they are made of steel.

Also, sewer hatches can be installed in gas wells, heat, water supply and other engineering networksas well as storm sewers.

Each one is designed so that none stranger or the animal accidentally or deliberately did not enter the sewer well, the mine and did not get unhindered access to underground utilities.

Varieties of sewer manholes

Sewer hatches can be divided into several types depending on the design, the material from which the hatch is made, and the type of communications that it closes. Sewer hatches can be closed drainage systems, cable (electrical or telephone), storm drain systems.

Depending on the material used in the manufacture, one can distinguish cast-iron, plastic, composite, concrete, reinforced concrete and rubber hatches, as well as hatches made of polymer-sand mixture.

Helpful information ! Each material has its own pros and cons, taking into account which you can choose the best option for a specific situation. But anyway traditional option is a gray or ductile iron manhole. This material has high strength, is resistant to mechanical influences of various nature, independent of weather conditions, and its service life exceeds the shelf life of all other materials.

Manhole Security

The main purpose of giving the sewer hatch a round shape is to ensure the safety of the population. Unfortunately, it is not uncommon for an adult or child to fall into an open sewer shaft. If the mine is shallow, then it can end with one or more fractures, but the great depth can even threaten death.

Theft of a manhole cover is a common cause of such falls.

Nowadays, many people, walking down the street, are distracted by talking on a cell phone or writing SMS messages, sometimes getting so carried away that they forget to look at their feet. This absent-mindedness leads to accidents.

Also, a car can get into the open hatch, which at best will lead to minor damage to the car, and at worst - to injuries to passengers. Those who like to ride other types of transport - scooters, motorcycles, mopeds, bicycles, roller skates or skateboards - are also in danger. Hitting a hatch at high speed will result in serious injury.

Fun facts about sewer manholes

If a sewer hatch was installed a long time ago, then opening it can be a serious problem. In this case, specialists weld a metal handle to the hatch from above, open the hatch, perform the necessary operations, close it, and then cut the handle off.

Also, hatches with already existing holes have been put into production for a long time, into which you can insert a hook and thus pull out the cover.

But such hatches cannot be used when closing electrical, telephone and cable networks. This is due to the fact that water can enter the holes due to rain or melting snow, which can damage the networks and negatively affect the operation of the entire system.

You should also explain the issue regarding the excessive mass of sewer hatches.

This weight is placed on the covers specifically to make it harder and sometimes to prevent theft. The fact is that free metal has always attracted fans to profit from the state. So, in the last decade of the twentieth century, several thousand covers from sewer manholes were stolen on the territory of the Soviet Union. Thieves handed them over for scrap, thereby earning substantial money.

Helpful information! To avoid theft, are currently used wooden boards, plastic hatches or concrete circles, which cover the main cover from above. Covers that are attached with metal hinges have also become widespread. They cannot be simply removed and carried away; you will have to use special equipment, which will complicate the theft process.

Also, the hatches are made so massive that teenagers do not play games in the sewers or use them for other, less decent things.

There are several other explanations for why manholes have a round shape.

• Firstly, this shape facilitates transportation. The hatches are heavy enough and to move a cover, for example, a square one, you need to use the power of one or even two adult men. The round lid can be easily rolled on the ground by any teenager and at any distance.
• Secondly, there are no problems when installing the cover. It is unlikely that anyone will have any questions about its location in the well hatch. The only mistake here may be installing it with the wrong side up, but this is not very critical for operation.
• Well, and thirdly, less material is used for the production of round products.

The eternal question: "Why is the hatch round?"

Almost all hatches in the city are covered with special round-shaped covers. If you carefully examine such items, it turns out that they are the same all over the world. This involuntarily prompts the question: “Why are the covers on the sewer manholes round? Why do technical objects themselves have exactly this shape, and, for example, not square? " It turns out that the answers are on the surface.

Some details about sewer manholes

The described items are made of cast iron or concrete. They are specially made heavy and unbearable, so that no one has a desire to take with them a "useful" thing. It is not so easy to open a technical opening on your own, and this is specially provided for in the design for the safety of passers-by.

Sewer hatches have a conditional classification. They are divided by the material of manufacture and by the type of communications passing under the release shafts. Therefore, experts distinguish:

1. Drainage systems.
2. Storm sewers.
3. Electrical networks.

Hatches are made of high-strength cast iron and plastic, special polymer-sand mixture, composite materials and reinforced concrete. But their shape is invariably round. Why, let's figure it out.

Logical explanation

So why is the manhole round? The described technical object consists of several parts - a round shaft, an observation room and a cover.

The observation room may have different shape... It all depends on what kind of communications are laid in the well. The dimensions are chosen taking into account the convenience of their maintenance. But the mines are invariably made round. The diameter of the oval is 0.7 meters. They are assembled from bricks and additionally equipped with a ladder that helps the attendant to descend without hindrance.

From above, such a hatch must be closed with a lid. It prevents various kinds of third-party objects from entering the sewer system that can provoke accidents. Almost everywhere the lid is round. Why not square? Because in any position, such a lid will never fall inside and will not hit the person who is there.

Under the influence of vehicles, the square cover can easily fall inward, slipping through it with a corner. After all, the diagonal of a square is always greater than any of its sides. The circle has the same radius, whatever one may say.

Typically, manufacturers make caps weighing more than 50 kg. This is done so that no heavy traffic of cars could move them.

Other explanations for the shape of the hatches

It is very rare to find such a form.

There are several other explanations to help you understand why manhole covers are round:

• First, the ratio of the cross-sectional area to the circumference of a circle has a higher ratio than a square or rectangle. This allows you to reduce material costs and save on production during the production of caps.
• Secondly, the circular shape reduces the internal forces that invariably arise when fitting any cover onto an object. And this also provides savings in the production of the product, since in this case it is possible to produce lids with a smaller thickness.
• Thirdly, the round shape helps to reduce the production of defective products. With a decrease in the number of reference lengths, the likelihood of errors, leading to the appearance of uneven protrusions and other characteristic defects, decreases.

And further. The round lid is much easier to transport by one person. He can just roll her to the spot. And a square or rectangular one will have to be carried in several hands.

The above arguments show that the choice of form is explained by elementary practicality.

Interesting facts

In the world, there are cases of using caps of other shapes. For example, in the American city of Nashua, you can still see sewer wells covered with triangular covers. Their sharp corners indicate the direction of flow wastewater, and until recently, this helped repair crews to orientate themselves well. But today their use is recognized as unsafe, so the prefecture dismantles them and replaces the triangles with circles.

There are also other forms

Now you know why sewer manholes are made round. But why they are performed so massive and heavy is also an interesting question. Although the explanation lies on the surface. Weight provides relative safety against theft and delivery of the described products to metal collection points. About 10 years ago, a wave of typical crimes swept across the country. The covers began to disappear en masse, then the designers came up with an interesting solution.

Most modern sewer wells not just cover with a massive object on top, which one person is not able to carry. The covers were put on strong hinges, and they turned into real doors, which are additionally locked with a lock.

It is impossible to leave the wells open in any way, especially those in which storm sewer and plumbing. Their depth sometimes reaches 6 meters, and there are many protruding pipes and pieces of reinforcement at the bottom of the technical room. If a person falls there in the dark, the case will end in death. Therefore, those who are responsible for the sewer hatches - and this is the district administration - has a great responsibility for the safe use of this technical structure.

Who else can be responsible for the hatches?

But the Russian people are still used to seeing such a hatch

There are wells that are not municipal property, but belong to property apartment building or to the property of a specific legal entity.

All abandoned objects are first registered by the body that registers the right to property. This happens at the request of the local government. Then, through the court, everyone can challenge their own right. If those who wish are not present for a year, all abandoned objects are transferred to the departments of specialized companies.

Generalization on the topic

The round shape of the manholes is more practical than all other varieties. The long-term service life of sewer structures has proven that round holes are more technological and have a longer service life. And all because such a hatch is more resistant to temperature extremes.

Hello always, dear friend!

There is a type of question that is generally considered to be a smart question. Sometimes this is true. But more often such questions are asked at once with several purposes.Why hatches round is a question in this series. Although it is found less and less, for it has already lost its former originality and the effect of surprise.

Let's remember that at the interview they want to evaluate not so much “Who are you?” As “What are you?”.

1. How do you respond to this question? - the first goal of your interlocutor.

He wants to understand the degree of your emotional maturity.

2. Will you be looking for an answer to this question? - the second goal.

Let's remember that the employer is interested in several, which he never asks directly. One of them: will you solve the problems that will inevitably arise in the course of your work.

Either you will look for reasons why the problem cannot be solved, or you will pass problems onto other people, including the leader.

3. The very content of the answer - the third goal.

Will you be able to solve problems that require ingenuity and analytical thinking, logic?

If instead of answering you say “I don’t know” or “I’m at a loss to answer,” it means that when faced with a difficult task, you will most likely fold.

How to react?

Let's agree right away that we define this question “why are the hatches round” as, and not manipulative and not. Therefore, we answer constructively.

The worst thing you can do is puff out your cheeks and freeze something like this:

"Listen, what does this have to do with the subject of our meeting?"

After that, consider that you have not passed the test, although in fact you are right. The reason is that you did not accept the rules of the game that are offered to you. I repeat, this question is constructive and is not an attack on your personality. Therefore, it should be answered constructively.

Let's recall the principles of answering constructive questions in an interview:

1. If you get asked questions, that's fine. If you are not asked about anything, how will they know that you are the best candidate?
2. As a consequence of point # 1: Just give the interlocutor the right to ask any questions. Any question is your opportunity to be better than other candidates.You will answer confidently and calmly, and there is no reason to be afraid and nervous.
3. Most are asked in order to get to know you better, and not then to hear the correct answer. That's why you came so that they would know what a wonderful candidate you are.

How to answer?

1. Listen to the end.
2. Verbal reaction - and with the tips of the lips (teeth closed!), A slight nod.
3. A short pause.
4. Answer.

The simplest and most logical answer to this question:

Round hatch, - cannot fall into a well. No matter how hard you try and twist it. The square has a diagonal longer than its sides, and when lifted it can slide down into the well. Drown or even injure someone. Besides - the diameter of the top of a round hatch is usually larger than that of the bottom, and under no circumstances can it slide inward.

In addition, round hatches are easier to move - they can be rolled.

A couple more questions from the same series

About cake

Myself Question: How to divide the cake into eight identical pieces using 3 cuts?

Answer: First, you should make a cross-to-cross cut, thereby dividing the cake into 4 equal parts. Next, make one cut horizontally in half along the entire diameter. The pieces are lower, but the problem is solved - you have 8 equal pieces.

Second option: after your two cuts, we have 4 pieces. We can put them on top of each other. Then split in half all four pieces with one cut.

About light bulbs

There are three bulbs in the room. There are three switches in the hallway leading to the room.

Question: How many times do you need to open the door to determine which light bulb corresponds to which switch?

Answer: It is enough to open the door once. We turn on 2 switches at the same time, then turn off one. We enter the room: we see that one lamp is on. She is from the first switch. We place our palm on each of the remaining two bulbs. Which is warm from the second switch, respectively cold from the third.

In the event that, if any intelligible answer does not come to mind, start thinking out loud. Trying to find a suitable one is much better than a nervous reaction or a “hard to answer” answer. Keep in mind that some of these questions don't have a clear answer at all.

Your attempts to find the answer, your train of thought, your options are often more important than the answer itself.

Thank you for your interest in this article. I would be grateful for your comment (at the bottom of the page).

Subscribe to blog updates (form under the social media buttons) and receive articles on your chosen topics to your mail.

Have a good day and good mood!