With the question of why the sewer manholes round form many have encountered. Most have heard it during job interviews. In this way, “cunning” HR managers test the general erudition and ability for creative thinking of potential employees.
This question is also often used in various competitions and quizzes. If you study the design of sewer hatches, the answer to the question will become obvious and quite understandable. This is what we'll do.
Sewer hatch installation
A sewer well usually consists of a shaft and a working room, and the hatch serves as a cover. Workroom are arranged and located depending on the type of communications being 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 it can be more or less. The main criterion for its determination is the depth of communications. The length of the shaft directly depends on the depth of the room. Typically the shaft is round in shape and has a diameter of 0.7 meters. The shaft must have a ladder so that the worker can go down into the room. The material used for shaft construction is usually brick or concrete.
- A cover on the sewer hatch is necessary to prevent foreign objects and people from entering the mine. The round shape prevents the lid from falling into the shaft if someone steps on it, which means it protects against accidents. This is the most main reason, according to which the shape of sewer manholes is made round.
- Also, the lids have quite a large mass, and sometimes this also raises questions. This fact can also be easily explained. Very often, sewer manholes are located on the roadway and when driving, the car wheels hit the cover. If the lid were light, it would easily flip over, opening the shaft and creating the possibility of accidents. To avoid this, the lids are cast from cast iron, which is considered one of the heaviest metals.
- The surface of the lid usually has raised stripes, letters, or other designs or images. This was also not done by chance. The ribbed surface prevents slipping and increases the adhesion strength of car tires and pedestrian soles to the surface of the hatch. There are flat lids, and sometimes they are curved in the middle, but you will never see concave ones anywhere.
Cable duct wells usually have two covers at once - a protective cover and a shut-off cover.
The protective one is on top. There is an additional lock on the locking cover, which prevents unauthorized persons from entering the shaft to steal the cable. These lids are lighter than regular ones because they are made of steel.
Also, sewer manholes can be installed in gas, heat, water and other wells utility networks, and storm drains.
Each of them is designed to ensure that no unauthorized person or animal accidentally or deliberately enters sewer well, mine and did not receive unhindered access to underground communications.
Types 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 covers. Sewage hatches can be closed drainage systems, cable (electrical or telephone), storm drainage systems.
Depending on the material used in manufacturing, we can distinguish cast iron, plastic, composite, concrete, reinforced concrete and rubber hatches, as well as hatches made of a polymer-sand mixture.
Helpful information ! Each material has its own pros and cons, taking into account which you can choose best option for a certain situation. But anyway traditional option is a sewer manhole made of gray or high-strength cast iron. This material has high strength, is resistant to mechanical stress of various types, regardless of weather conditions, and its service life exceeds the shelf life of all other materials.
Safety of sewer manholes
The main purpose of making a sewer manhole round is to ensure the safety of the public. Unfortunately, cases of an adult or child falling into an open sewer shaft are not that rare. If the mine is shallow, then this can result in one or more fractures, but greater depth can even lead to death.
Common reasons Such falls include theft of a manhole cover.
Nowadays, many people, walking down the street, are distracted by talking on a mobile phone or writing SMS messages, sometimes so carried away that they forget to look at their feet. This kind of absent-mindedness leads to accidents.
Also, a car can get into the open hatch, which best case scenario will result in minor damage to the vehicle, and in the worst case, injury to passengers. Those who like to ride other types of transport - scooters, motorcycles, mopeds, bicycles, rollerblades or skateboards - are also at risk. Falling into a hatch at high speed can result in serious injury.
Fun facts about sewer manholes
If the manhole was installed long ago, opening it can be a serious problem. In this case, specialists weld a metal handle to the hatch on top, open the hatch, and necessary operations, closed, and then the handle is cut off.
Also, hatches with existing holes into which you can insert a hook and thus pull out the cover have long been put into production.
But such hatches cannot be used when closing electrical, telephone and cable networks. This is because water can get into the holes due to rain or melting snow, which can damage the network and negatively affect the operation of the entire system.
The issue regarding the excessive mass of sewer manholes should also be explained.
This weight is given to the lids specifically in order to make it difficult and sometimes even prevent their theft. The fact is that free metal has always attracted those who like to make money at the expense of the state. Thus, in the last decade of the twentieth century in the territory Soviet Union Several thousand manhole covers were stolen. Thieves sold them for scrap metal, thereby earning significant money.
Helpful information! To avoid theft, they are currently used wooden boards, plastic hatches or concrete circles that cover the main cover on top. Covers that are secured using metal hinges. They cannot simply be removed and carried away; special equipment will have to be used, which will complicate the theft process.
Also, the hatches are made so massive that teenagers do not play in the sewers or use them for other, less decent things.
There are several other explanations for why sewer manholes are round.
- Firstly, this shape makes it easier to transport. The hatches are quite heavy and to move a lid, for example, a square one, you need to use the strength of one or even two adult men. The round lid can easily be rolled along the ground by any teenager and over any distance.
- Secondly, there are no problems when installing the cover. It is unlikely that anyone will have questions about its location in the well hatch. The only mistake here could be installing it the wrong way up, but this is not very critical for operation.
- Well, and thirdly, less material is used for the production of round products.
Modern public utilities emerged in the world in the 1930s. Despite the variety of shapes, greater preference was given to round lids. Currently, manufacturers of manholes for sewer systems produce exclusively round shapes.
Covers for manholes: weight and maximum load
Although sewer systems modern type V various countries appeared at different time periods, the only similarity was the need to install sewer hatches. The urgent need for cast iron hatches arose primarily in large cities with asphalt roads for safety reasons. Still, moving a lid weighing from 45 to 160 kg is many times harder wooden flooring and barriers that were previously used.
Note! Last years Along with cast iron lids, cheaper analogues from polymer materials, the minimum weight of which is considered to be 15 kg, the maximum – 48 kg.
Sewer cover shape
The main reason why the manhole cover is round comes from the following considerations.
- The triangular shape is not suitable based on the structural features of the human body. Otherwise, the size of the hatches would be much larger than modern round ones. And this entails extra hassle in the form of an increase in the necessary raw materials for the production of the lid, therefore, its cost increases.
- A square-shaped hatch may eventually fall into a well. Moreover, the shape of the well is round. Engage in changing the transitions of the sewer manhole shaft to the surface from round to square shape- not an easy task, it requires increased financial costs for production and replacement.
The round shape of the lid has a more than one-sided nuance: such a lid is convenient to carry – i.e. roll, as opposed to square or triangular. But with the increase in the number of thefts in and nearby CIS countries for the sake of profit, the authorities began to look for a way out of the current situation by producing from other materials.
In the United States, lids with grooves or latches are made as “anti-theft” measures. European countries They use a combined material to make the lid - they combine concrete with cast iron. This helps prevent theft because scrap metal collection centers do not accept hybrid material.
Interesting fact! Enthusiasts do not lose heart and on the Internet users are organizing exhibitions of discovered samples with unusual design with the addition of the city. The art of cast lids dates back about 150 years; every day the global public gallery is replenished with new unusual examples of modern and ancient products.
Modern and ancient manhole covers differ in appearance. If on the old ones you can find engraved coats of arms, various inscriptions and drawings, then modern analogues are designed in a serious style: production number, name of the manufacturing company, date of manufacture. Some organizations request “unique” copies on order, which contain detailed information: the company logo, a short list of services provided, and more.
The main reasons why the manhole cover is round
- In Russia and neighboring countries, wells and sewer pipes have round section. This is the main factor influencing the shape of the lid. In some European and Asian countries there are square options. However, these are exceptions to the rule rather than the norm, because in the same Czech Republic or China, where people discovered covers in the shape of a square, sections of pipes and wells sewer system also have a round shape.
- Cost reduction. Unlike a round one, the manufacture of a square manhole cover will require 30% more raw materials.
- Convenience. To install a hatch cover of any other shape will require more costs: incl. human effort and time to install it: the lid will not have to be moved (taking into account the minimum weight of a cast-iron specimen of 65 kg, a square one, based on the increase in raw material costs, will be approximately 30% heavier - i.e. about 85 kg).
- A round-shaped sewer manhole will not fall into the well due to its increased diameter compared to the cross-section of the well.
- Installation and dismantling of round covers is faster and there are a number of reasons for this:
no need for more installers for moving the hatch;
the time spent on moving it is reduced - it is easier to roll a round hatch; this method will not work with a square or triangular cover. - Load concentration distribution. For a round lid, distribution is carried out over the entire area. Angular lids cannot boast of this - it is the corners that will act as the main load points.
- It is more difficult to damage the edges of a round hatch than an angular one. During transportation, it can be chipped. Considering that it is the corners that act as the main reference point for distributing the load, a broken piece, regardless of its size, breaks the system and the load is distributed to the remaining corners.
- Wear resistance. The service life directly depends on the integrity of the manhole cover. If a part breaks off on angular lids, the load is distributed unevenly. Over time, this will cause damage to other supporting corners.
The question of why sewer manholes are made round has already become a household word. It is asked in many academic 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 design of hatches and the facts associated with them. So, first things first.
Sewer hatch installation
A sewer inspection well usually consists of a shaft, a working room and a cover. The type of workspace arrangement, as a rule, depends on the type of underground communications. The dimensions of the room are selected based on the requirements for servicing specific communications.
The depth of the room is selected based on the depth of their location. 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 0.7 m. Shafts are most often assembled from brick or cast from concrete. Equipped with a ladder for worker descent.
The sewer hatch is covered with a lid to prevent foreign objects from entering the system and to prevent accidents. In most cases, the lid has a round shape, which is caused by the following: in any position, the lid cannot fall into the hatch.
This is the first answer to the question “why are sewer manholes round?”
To prevent accidental opening during heavy vehicle traffic, hatch covers are made of cast iron, making them very heavy.
The surface of the cover is ribbed to increase the strength properties of the hatch, as well as the traction of the soles of pedestrians and car tires with its surface. There are lids either convex in the middle or flat - there are no concave ones.
Cable duct wells are usually equipped with two covers at the same time.
Namely:
- protective;
- constipated
Locking covers are made of steel, they are much lighter than usual and are equipped with a lock to prevent unauthorized persons from entering and stealing the cable. The locking cover is located under the protective cover.
Installation of sewer hatches is also carried out in wells engineering communications located underground: cable, gas, heating networks, sewerage and water supply.
Sewer hatches are designed to protect wells from damage, to prevent foreign objects or persons from entering the mines, to ensure unhindered movement of vehicles and pedestrians, and to provide access to communications located underground.
Types of sewer manholes
Sewage hatches are classified as follows:
- depending on the design of the product;
- by the type of communication networks passing under them;
- according to the material of manufacture.
In addition to the question of why sewer manhole covers are round, we will answer the question of what communication networks are covered with the help of such manholes.
This:
- drainage systems;
- cable - telephone and electrical networks.
The main materials for the manufacture of sewer manholes are the following:
- high-strength and gray cast iron;
- plastic;
- polymer-sand mixture;
- composite mixture;
- reinforced concrete or concrete mixture;
- rubber.
Advice! Each type of hatches has its own disadvantages and advantages, but still cast iron is considered the traditional material for making hatches. Hatches made of cast iron are reliable, durable, resistant to aggressive environments and durable.
Safety of sewer manholes
Why are sewer manholes made round? To protect the population from falling in them - this is one of those disasters that people begin to be warned about from childhood.
However, despite such warnings, such cases occur quite often. Previously, this was caused by absent-mindedness, but now it has been added to by distraction by talking on mobile phone or writing text messages.
The large number of thefts of manhole covers only aggravates the current situation. Falling into a hatch can not only result in broken legs, but can also lead to death if the depth of the hatch is sufficiently deep.
The danger of open hatches is no less evident on highways. Colliding with a car on an open hatch can cause serious damage to the suspension and wheels, and also very dangerous accidents for cyclists and motorcyclists - even fatal.
Fun facts about sewer manholes
- If the installation of a sewer manhole was carried out many years ago, especially on the roadway, what to open such a manhole in the usual way(by prying) is often not possible.
Then a handle made of metal fittings is welded to the top of the hatch, 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 manhole covers modern production(in addition to communication lines) are equipped with a factory hole, through which the hatch can be opened using a hook.
In many CIS countries, manhole covers also often have two slots on the sides. However, due to the water that penetrates through the slots during precipitation, holes are made only in water supply, sewer, storm, and drainage hatches. It is prohibited to make slits in the hatches of electrical networks, cable and telephone communications.
- In addition to the dilemma of why are sewer manholes round, you should be interested in another question: why are manholes so massive?
And so that the most active part of society - teenagers - does not physically have the opportunity to make shelters and the like from sewers. However, the mass of hatches does not stop lovers of relatively easy money. From the 1990s to the 2000s, thousands of thefts of sewer manholes were committed in all countries of the former Soviet Union for the purpose of scrap metal.
In addition to standard cast iron manholes, steel manholes and storm grates were also stolen. For example, in the city of Kharkov in the Saltovsky district, in just one night, about 50 cast iron hatches were stolen by attackers using technology. And in 2009, more than 1,300 hatches were stolen in Kiev.
For this reason, in large cities, especially on their outskirts, sewer shafts are forced to be covered with concrete circles, wooden panels or plastic stationary hatches. Regarding the latter, their production is established in many regions.
- 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 the help of a cutter). Many hatches are also equipped with locks - this often applies to communication line hatches.
- The most dangerous from the point of view of injuries are stormwater wells, water supply and sewerage wells - their depth reaches 6 meters, and in addition, protruding fittings and pipes are usually located inside them.
A couple more explanations
Another reason why a manhole cover is round is because it is easy to transport.
For example, a square lid can only be transported by carrying it, which is often beyond the capabilities of one person. The round lid can be rolled, which an adult man can easily handle alone.
In addition, less material is required to make a round manhole cover. In addition, there is no need to rack your brains over how to install a round sewer hatch - just don’t install it upside down, otherwise there are no difficulties.
Round? What else could they be? Theoretically, the hatch can be square or rectangular shape. But this design is rather an exception to the rule. A hatch is not a simple hole; it must be securely closed. It must be easy to maintain and safe to use.
If convenience is not an acquired taste, then reliability at the level of standard loads can be ensured by round design covers. The configuration of the base, which, in fact, is the sewer hatch, depends on its shape.
Waste system
Sewer networks are a set of structures designed to collect and drain from users to treatment facilities. The easiest way to do this is by digging a trench and laying pipes in it through which the wastewater will be drained.
In order to be able to service the system over a certain distance, inspection shafts are required. In urban infrastructure with dense buildings, it is possible to install sewer networks only along roads or directly under them. In this case, during heavy traffic, the hatches must be securely closed. But why are sewer manholes round? They must have sufficient strength to withstand the maximum possible transport loads.
IN big city the number of inspection hatches and various shafts can amount to hundreds of thousands. After all, this is not only a sewer system, it is also a communications network: water supply, heating networks, electricity, gas, telephony, etc.
Manholes
For ease of access to communications, the well shaft is usually made in a round shape. The 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 air circulation in a cylindrical object occurs more intensively.
The size of the cover, 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, and traffic intensity are taken into account.
It depends on the shape of the lid. On the one hand, maintenance personnel must have convenient access to underground communications. On the other hand, the well must be securely closed to prevent foreign objects from getting inside, to ensure the safe movement of pedestrians and vehicles. A round lid is best suited for this, which means the hatch itself should 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 sewerage. Manhole size in different countries different. In Russia, standard dimensions are most often used (645 and 800 mm). Hatches manufactured not in accordance with GOST are designed and developed by manufacturers in accordance with the order and specific technical conditions.
This configuration has a number of advantages. Previously, hatches were made 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 turned out to be the most suitable.
It will never fall inside the well, no matter how much it is turned. A round lid is easier to open, since the point of application of force anywhere on the circle will be the same. It can be rolled by placing it on its edge. This design is more economical to manufacture.
The round shape of the lid is less susceptible to sagging. It can withstand greater loads with the same thickness, which means it can be made thinner without losing quality. During production, round castings produce a lower percentage of defects (shells, pores, cavities).
Material
The base and manhole 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 traffic cannot accidentally lift and move the cover. They are made by melting down recycled materials and are cheaper than their steel counterparts.
In places where there is no heavy traffic, it is not practical to install heavy and powerful structures. Recently, 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, sewer rings made of reinforced concrete are used to install sewage systems, equip inspection wells and septic tanks. In this case, it is quite justified to install the same base for the hatch on top of them. The lid is also made of concrete. It is made of a larger diameter, does not fit into the groove, but simply covers the hatch hole. The massive structure is quite heavy and cannot be accidentally moved. This provides the necessary safety during operation.
Specification and marking
For increased loads on roads, heavy hatches (class T) are used. They can have a weight of over 100 kg and a thickness of over 100 mm. Where vehicular traffic is not provided, lightweight 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 manholes round and marked? This was done for the convenience of recognizing their belonging to. On their covers there are letters: GS - gas network, MG - main gas pipeline, PG - fire hydrant, etc.
And I couldn’t help but wonder – why is it round? And often hatches are never made square. What is this standard? Or a conspiracy of plumbers and electricians? I turned to a professional master with this question; it turns out that this question is almost the very first one for beginners in this field. It turns out everything is quite prosaic...
To begin with, guys, I suggest you put everything on the shelves and tell us what these lids are, which actually close various wells. Don’t worry, the answer will be below, it will definitely be – read to the end.
Types of hatches
It is a mistake to think that the hatches that cover wells embedded in the ground are of the same type. There is quite a large infrastructure laid out underground, so different types are distinguished:
- Hatches for drainage systems
- For storm systems
- For electrical networks
- For contact
Initially, hatches were made of very durable materials, usually steel or black cast iron. Thus, it was very difficult to remove and carry it away, and the cars that ran over it could not turn it over. However, with the era of “perestroika”, metal versions still began to be stolen and sold for metal (and they were simply broken),
therefore, wells were often open (oh, it was a terrible time), so in those days they began to cover the wells with concrete round (as I call them) “short-holes.” 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 durable - they can withstand loads of up to 3 tons, they are also resistant to high and low temperatures, they don’t rot, they don’t rust, and they practically don’t steal them, because again, you can’t hand them over!
However, all these types are invariably round! But why - everything is banally 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).
- The middle shaft is usually made of a round size with a diameter of 70 cm, a recess of up to 3 meters.
- The last one is the lower part, there may be 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 a round hatch cannot fall into the well shaft, no matter how hard you twist it. 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 can you get it back? Difficult!
Yes, both children and large equipment will not be able to overturn or push such a hatch down in any way, everything is done wisely. It is worth noting the weight metal options, is 50 kg, so no traffic flow can tip it over. That's actually the answer.
It is also worth noting the side “ears” - special branches from the circle; they are made so that the lid “does not move”, 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, triangular and polygonal options.
But they were all dangerous and often simply fell through, leaving an open shaft.
However, triangular covers were valued to the last, all because the corners of the structure showed the direction of pipes or communications. Therefore, when the repairmen came down, they were already aware.
Also, hatches on hinges and some kind of “down” door were not uncommon in the past. The hinges also provided some protection against theft. However, during large traffic flows they were often broken and the lids fell through, so over time they were also replaced with round ones.
This is how the article turned out, now watch the cool video.
I’ll finish here, read our construction site, there will be a lot of interesting things.
