Why is the sewer hatch round. Why are sewer hatches round. Nowadays, many people, walking down the street, are distracted by talking on a mobile phone or writing SMS messages, sometimes getting so carried away that they forget to look at their feet. Such absent-mindedness and

A familiar familiar detail of the urban landscape is the cover of sewer manholes, almost everywhere, in all countries of the world, having a round shape.

Why exactly round - we will try to answer this question in detail.

Safety

The manhole cover of the sewer well is a massive cast iron product. It weighs more than 50 kilograms, and the weight of the hatches on the carriageway exceeds 78 kilograms.

This is not surprising, since the hatch cover on the sidewalk of the street must withstand a load of 12 tons, and the cover lying on the road - as much as 25 tons. This weight is due to the thickness of the cover, calculated taking into account the given load and the strength of the cast iron.

Now imagine the following situation: the hatch cover is open and lies next to the hatch, and people are working in the well below. If someone accidentally moves the round lid, in the worst case, it will simply close the hatch. In this case, a rectangular or square lid can fall into the hole right on the workers' heads, because the diagonal of a square or rectangle is always larger than either side of it. Therefore, the round shape of the lid is the safest in this case.

Strength

It has long been known to engineers that round objects are much more durable than square ones. The sewer hatch is not only round, but also slightly convex towards the middle: this shape provides the greatest resistance to mechanical stress from above.

Internal stresses in a hatch of this shape are evenly distributed over the metal, while in square, rectangular and any other covers under the action of load, the stresses are distributed unevenly, which leads to faster wear and, therefore, more frequent replacement of the covers.

In addition, one should not forget that cast iron is a rather fragile material, and if you drop a rectangular lid, a corner may well break off from it. It takes a lot more effort to crack the round manhole cover.


Judging by the fact that almost all lids are safe and sound for decades (and some for more than a hundred years), it is almost impossible to damage the round lid under normal conditions.

Saving metal

Why is the round shape of the hatches more optimal from the point of view of metal saving? With the same length of the perimeter of the round and rectangular hatches, the area of ​​the circle is always larger than the area of ​​the rectangle or any other geometric figure.

If we translate this into economic indicators, it turns out that the circle is the most advantageous shape of the hatch, since it requires much less cast iron on the cover (saving up to forty percent) than on a rectangular cover.

The optimal ratio of the length of the perimeter to the area makes it necessary to make round hatches not only for sewer wells, but also in much more serious structures - for example, between the compartments of submarines or spaceships. Round hatches are more economical and can handle heavy loads than any other shape.

Convenience of work

The round manhole cover is much more convenient when carrying out repair or maintenance work. If the rectangular lid needs to be lifted in order to move it a certain distance, which will require at least two adult men, then the round lid can be safely rolled over, placing it on its edge, and this task can be done alone.

And in order to fit the heavy cover in place, you do not need to rotate it, adjusting it to the hole configuration. The round lid will snap into place anyway, whichever side you install it.


So, there are more than enough reasons why you need to make the manhole cover round.

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 it is the round design of the lid that can provide reliability at the level of standard loads. The configuration of the base depends on its shape, which, in fact, is the sewer hatch.

Waste system

Sewer networks are a complex of structures designed 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 buildings, it is possible to lay sewer networks only along the roads or directly under them. In this case, during heavy traffic, the hatches must be securely closed. But why are the manholes 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 number in the hundreds of thousands. After all, this is not only a sewerage system, it is also a communications network: water supply, heating systems, 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 carry out work in such mines. They are suitable for ventilation, as the air circulation in a cylindrical object is more intensive.

The size of the cover, the area of ​​the base and the inner 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 convenient 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 their purpose, they are divided according to the type of communications laid under them: engineering cable networks, water supply, gas mains, heating mains, storm and waste sewerage. The size of the manhole varies from country to country. 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 in various shapes. They could be square, rectangular, oval, or even triangular to indicate the direction of water flow. However, the round shape of the lid was found to be the most suitable.

She will never fall into the well, no matter how she is turned. The round lid is easier to open, so the point of application of the 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 cost-effective.

The round shape of the lid is less prone to sagging. It can withstand a lot of stress 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 long-term 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 margin of safety, and 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 be over 100 kg in weight and over 100 mm in thickness. 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.
The full version of the work is available in the "Work files" tab 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 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 some other figure suitable for manholes.

PURPOSE: 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: in addition to 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 crawl 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 the objects of rectangular and triangular shapes interfere with the corners. 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 spinning 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 in production.

Experience 4. In the manufacture of round caps, less material is used 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 be convinced of this.

3. CONCLUSION

After doing 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 exactly. 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 underside 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 photos of sewer manholes from all over the world were presented.

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.

Job candidates are asked logic puzzles to assess their analytical skills. Anyone can face similar questions. But even if this does not happen to you, it will be just interesting to study them for preparation.

Jobseekers who are faced with puzzles during the interview process should not panic and get lost. As a rule, in most cases it is enough to show your train of thought and ways of solving the problem. It may well be that the problem does not have a correct solution or an unambiguous answer. In no case should you say “I don’t know” or “I’m at a loss to answer,” just think aloud.

So that you know what to be ready for and not get confused, we have collected the most popular puzzle questions and prepared answers and recommendations for them. Who knows, you may come across these tasks.

Sewer hatches

This is perhaps the most common question among all the puzzles.

Question: Why are the sewer manholes round?

Answer: There are several options. Since the diameter of the circle is the same, no matter how you twist it, the round hatch cannot fall into the well. A square, for example, has a larger diagonal than its sides, so the lid could fall off. You can also answer that round hatches are easier to transport and move.

Light bulbs

Question: There are 3 light bulbs in a closed room, and 3 switches in the corridor. For what is the minimum door opening, you can determine which switch belongs to which lamp?

Answer: For one discovery. We turn on 2 switches at the same time, after a while we turn off the second one. We go into the room: one of the bulbs remained on - this is the first switch, then we probe the remaining bulbs - warm and will be the second switch, and cold, respectively, the third.

Cake

Question: How to divide a cake into 8 equal parts with three cuts?

Answer: First you need to make 2 cross-to-cross cuts, dividing the cake into 4 equal parts. And then cut the cake horizontally in half. So what if the pieces are not high, but you have 8 equal parts. After the first two cuts, you can also fold the pieces on top of each other and halve them with one cut.

Dead man and match

Question: A dead man was found in the middle of the field with a match in his hands, there are no traces. What did he die of and under what circumstances?

Answer: A man died from a fall from an airplane, which began to lose altitude, and the accident was inevitable. One parachute was not enough for all passengers and they drew lots. He got a short match and was forced to jump without a parachute.

Bus and balls

Question: How many tennis balls can the bus fit?

Answer: The recruiter himself does not know the exact correct answer, since it is not specified what the balls and the bus are - their sizes are not known, and no one has thoroughly checked it. Therefore, the course of your thoughts is important here, you can only guess. What are the approximate length, width and height of the bus, the size of one ball. Calculate the volume of the bus and the ball - this is how you will find out how many balls can fit on an empty bus. Decrease approximately this value, taking into account the seats and other details of the bus, make an allowance for the fact that the balls are not square, and give an answer. In this case, the process of finding an answer is more important than the answer itself. Variants of the question may be different: balls - football, instead of a bus - a room, etc.

Tablets

Question: The doctor gave the patient 4 tablets of two types - 2 tablets each, which cannot be distinguished by their appearance. The tablets must be drunk in two doses: in the morning, one tablet of each type and in the evening. If the dosage is violated or the pills are not taken, the patient will die. It so happened that the tablets were mixed. How to get treatment and survive?

Answer: Of course, we can say that it is better to go to the doctor and ask for more, it’s still a matter of life and death. But these may be the only pills on Earth, the doctor may disappear under mysterious circumstances, etc. So you still have to answer. In addition, everything is quite simple: you need to divide each tablet into 2 parts and drink half of each tablet in the morning and in the evening.

Finally

Remember that, first of all, such tasks and puzzles are designed to test the candidate's behavior in non-standard situations, to assess the ability to think, be creative and logical. Alas, there are often cases when the interviewer cannot correctly interpret the results of such questions, or does not understand their purpose at all. But even in this situation, confident behavior and the desire to come to an answer will show you your best side and increase your chances of getting a job.

The question of why sewer manholes are made round has already become a household name. It is asked in many erudite quizzes and even when applying for jobs in relatively serious organizations. In search of an answer to this question, you should find out more about the structure of the hatches and the facts associated with them. So, first things first.

Sewer hatch device

An inspection well usually consists of a shaft, a work area and a cover. The type of device in the working room, as a rule, depends on the type of underground utilities. The dimensions of the premises are chosen based on the requirements for the maintenance of specific communications.

The depth of the location of the room is chosen based on the depth of their occurrence. The height of the room is about 1.8 meters. The shaft is usually round in shape, its length depends on the depth of the working room, and its diameter is 0.7m. Mines are most often assembled from bricks or cast from concrete. Equipped with a ladder for lowering the worker.

The sewer hatch is closed with a lid to prevent foreign objects from entering the system and to prevent accidents. In most cases, the cover has a round shape, which is caused by the following: in any position, the cover cannot fall into the hatch.

This is the first answer to the question "why are sewer manholes round?"

To prevent arbitrary opening during heavy traffic, manhole covers are made of cast iron, making them very weighty.

The surface of the cover is ribbed to increase the strength properties of the hatch, as well as the adhesion of the soles of pedestrians and car tires to its surface. There are covers that are either convex in the middle, or flat - there are no concave ones.

Cable duct wells, as a rule, are equipped with two covers at the same time.

Namely:

• protective;
• shut-off.

Locking covers are made of steel, they are much lighter than conventional ones and are equipped with a lock to prevent unauthorized persons from entering the cable in order to steal the cable. The locking cover is located under the protective cover.

Installation of sewer hatches is also carried out in the wells of utilities located underground: cable, gas, heating networks, sewerage and water supply.

Sewer hatches are designed to protect wells and wells from damage, to prevent foreign objects or persons from entering the mines, to ensure the unimpeded movement of vehicles and pedestrians, to access communications underground.

Varieties of sewer manholes

Sewer hatches are classified as follows:

1. depending on the design of the product;
2. by the type of communication networks passing under them;
3. by material of manufacture.

In addition to the question of why the sewer hatch covers are round, we will answer the question of what communication networks are covered with such hatches.

This:

• drainage systems;
• cable - telephone and electrical networks.

The main materials for the manufacture of sewer hatches are as follows:

• ductile and gray cast iron;
• plastic;
• polymer-sand mixture;
• composite mixture;
• reinforced concrete or concrete mix;
• rubber.

Advice! Each type of hatches has its own disadvantages and advantages, but cast iron is still considered the traditional material for manufacturing hatches. Cast iron hatches are reliable, durable, resistant to aggressive environments and durable.

Manhole safety

Why are sewer manholes made round? To protect the population from falls in them - this is one of those troubles that people begin to warn about from childhood.

However, despite such warnings, such cases occur quite often. Previously, this was caused by distraction, but now it has been added to the distraction of talking on a cell phone or writing text messages.

The large number of thefts of hatch covers, closing, only exacerbate the current situation. Falls into the hatch are fraught with not only leg fractures, but also fatal if the hatch is deep enough.

The danger of open hatches is no less evident on highways. A car hitting an open hatch can cause serious damage to the suspension and wheels, and besides, very dangerous accidents for cyclists and motorcyclists - up to and including death.

Fun facts about sewer manholes

1. If the installation of a sewer hatch was carried out many years ago, especially on the roadway, it is often not possible to open such a hatch in the usual way (prying).

Then a handle made of metal reinforcement is welded to the hatch from above, which is cut off after opening, or a small hole is drilled in the hatches, a hook is inserted from below and opened in this way.

Most modern manhole covers (in addition to communication lines) are equipped with a factory opening through which the hatch can be opened with a hook.

In many CIS countries, hatch covers also often have two slots on the sides. However, because of the water that penetrates through the slots during precipitation, holes are made only in water supply, sewer, storm, drainage hatches. It is forbidden to make slots in the hatches of electrical networks, cable and telephone communications.

1. In addition to the dilemma of the type - why are the sewer hatches round, one should be interested in one more question: why are the hatches so massive?

And so that the most active part of society - adolescents, physically did not have the opportunity to make shelters out of sewers and the like. Nevertheless, the mass of hatches does not stop lovers of relatively easy money. From the 1990s to the 2000s, thousands of sewer manhole thefts were committed in all countries of the former Soviet Union for the purpose of scrapping.

In addition to the standard cast iron hatches, steel hatches and storm grates were also stolen. For example, in the city of Kharkiv in the Saltovsky district, in just one night, using technology, attackers stole about 50 cast iron hatches. And in 2009 more than 1,300 hatches were stolen in Kiev.

For this reason, in large cities, especially on their outskirts, sewer shafts have to be closed with concrete circles, wooden shields or plastic stationary hatches. Regarding the latter, their production has been established in many regions.

1. Now the installation of a modern sewer hatch is carried out taking into account this feature - the hatches are equipped with hinges and open like a door with the impossibility of theft (except with a cutter). Many hatches are also equipped with locks - this often concerns communication hatches.
2. The most dangerous from the point of view of injury are storm wells, water supply and sewerage wells - their depth reaches 6 meters, and in addition, there are usually protruding fittings and pipes inside them.

A couple more explanations

Another explanation for why the manhole cover is round is the ease of transportation.

For example, a square lid can only be transported by carrying, which is often not possible for one person. The round lid can be rolled, which an adult man can handle alone.

In addition, less material is spent on the manufacture of a round manhole cover. In addition, there is no need to puzzle over how to install a round-shaped sewer hatch - it just should not be put upside down, otherwise there are no difficulties.