In fact, at first they were different: in many countries other forms were used, but the round ones were still the "winner". They are used all over the world to this day.
What is the difference between manhole covers? Everything except the form. On top of them at the dawn of their mass use, images of various coats of arms, motives of events, memorable dates could flaunt. Today everything is much simpler: an uncomplicated pattern and information about the manufacturer of the caps and the customer of their manufacture. "Decorative" are sometimes set up near their offices by large companies.
So why are the hatches round?
- Because the tunnels of the wells and the cross-section sewer pipes also round. Therefore, there is simply no point in using a different shape, round is the most convenient.
- Because the round manhole covers never fall into the well. But square ones, for example, can be without problems.
- Because it's cheaper that way. To cover a round “hole” with a diameter of 60 centimeters with a square lid, the area of such a lid should be 0.36 square meters. At the same time, this task can be performed using a round hatch with an area of 0.28 square meters. A noticeable difference?
Because it's more convenient to carry them this way. Or roll, because the weight is not small - from 50 to 110 kg: one person may not be able to cope. And if they were still square?
Because round hatches are more convenient for assembly and disassembly. They have load concentration points along the entire perimeter, and in square ones - only at the corners.
However…
“Who cares why sewer hatches round, ”you ask? I would like to answer that no one is interested in this, but there are precedents. And they happened at very serious events, in the offices of reputable companies. The fact is that sometimes HR managers like to ask unexpected questions during interviews to see how a person behaves in force majeure situations. So ask someone unexpectedly, why are the hatches round? Do you think you will immediately hear a clear answer? No! So they torture applicants for high positions in the private sector with insidious and at the same time stupid questions.
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 the course of your thoughts and the ways of solving the problem. It may well be that the task does not correct decision or a definite 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 by 8 equal parts 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 in one cut.
Dead man and match
Question: A dead man was found among 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 much tennis balls fit on the bus?
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.
Pills
Question: The doctor gave the patient 4 tablets of two types - 2 tablets each, which cannot be distinguished by 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, 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, creative and logical approach. 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 a desire to come to an answer will show you your best side and increase your chances of getting a job.
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 sewer 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 be in the hundreds of thousands. After all, this is not only a sewage 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, since the air circulation in the object cylindrical occurs more intensely.
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 lid. 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 the 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. Manhole size in different countries different. In Russia, standard dimensions (645 and 800 mm) are most often used. Manholes 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 of 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. 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. V recent times hatches made of plastic, polymers and composite material... They are lighter, cheaper, have a sufficient margin of safety, and have a long service life.
In private houses for the arrangement of sewage systems, equipment inspection wells and septic tanks use reinforced concrete sewer rings. 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.
And I involuntarily wondered - why is it round? And often hatches are never made square. What is this standard? Or a conspiracy of plumbers and electricians? With this question, I turned to professional master, it turns out this question is almost the very first for beginners in this area. It turns out everything is quite prosaic ...
To begin with, the guys propose to put everything on the shelves, and tell what these covers are, which, in fact, are closed by various wells. Do not worry, the answer will be below, it will definitely be - we read to the end.
Types of hatches
It is a mistake to think that the hatches that close the wells embedded in the ground are of the same type. A fairly large infrastructure is laid out underground, therefore, various types are distinguished:
- Gutter hatches
- For storm systems
- For electrical networks
- For communication
Initially, hatches were made of very strong materials, usually steel or black cast iron. Thus, it was very difficult to remove and carry him away, and the cars that ran into him could not turn him over. However, with the era of "perestroika", the metal variants began to be stolen anyway and handed over to the metal (and they were simply smashed),
therefore, it was not uncommon for the wells to be open (oh, it was terrible time), therefore, in those days, they began to close the wells with round concrete (as I call them) "undershoots". It was even more difficult to carry them away, and there was no need, because you can't hand over concrete!
Now, of course, new polymer or sand-polymer options are appearing, they are also durable - they can withstand a load of up to 3 tons, are also resistant to high and low temperatures, do not rot - they do not rust, and they practically do not steal them, because, again, you will not give up!
However, all of these types make it invariably round! But why - everything is banal and simple.
Causes and Effects
Any mine consists of several parts:
- This is the upper part of the lid itself (the main purpose is to protect the internal components from dirt, sediment and other debris).
- Medium shaft - usually made of a round size with a diameter of 70 cm, deepening up to 3 meters.
- The latter is the lower part, here they can be of various sizes and shapes, for example, in some communication wells they have a square shape.
But the main question is - why is the lid round? Guys, this is a safety requirement.
The fact is that the round hatch cannot fall into the well shaft, no matter how cool it is. Try it at your leisure, whatever one may say - but there is a circle everywhere. But if the covers were square, or triangular, etc., then at a certain angle they could fall down, and if this is a sewer well, how to get it back? Hard!
Yes, both children and large equipment will not be able to somehow overturn or push such a hatch down, everything is done wisely. It is worth noting that the weight of the metal versions is 50 kg, so that no traffic flow will be able to overturn it. Here is the answer.
It is worth noting also the lateral "ears" are special branches from the circle, they are made so that the lid "does not go", but sits tightly in place.
Interesting facts about "well covers"
It should be noted that they were not always made round - there were also square versions and triangular and polygonal.
But they were all dangerous and often simply failed, leaving an open mine.
However, triangular covers were appreciated to the last, all because the corners of the structure showed the direction of pipes or communications. Therefore, when the repairmen descended, they were already informed.
Also, hinged hatches and a kind of "down" door were not uncommon before. The hinges also provided some protection against theft. However, with high traffic flows, they were often broken and the covers fell through, so over time they were also replaced with round ones.
Here is such an article turned out, now watch a cool video.
I will end on this, read our construction site, there will be a lot of interesting things.