10 Feb Vertical step-ladders for manholes
It doesn’t matter how far the progress has stepped, the replacement for simple and reliable things that have served man for centuries, hasn’t been found. This also applies to ladders C1-01, better known to a layman as vertical ladders for manholes. Its peculiarities and types and will be discussed in this article.
- 1 The scope use of the sewer ladders
- 2 Design features and assembly of C1 wells
- 3 Specifics of the installation of stepladders
- 4 The nomenclature of the sewer ladders
- 5 Useful tips if you don’t want to miscalculate the price
- 6 How to ensure the durability of the ladders
- 7 Know-how in the ladders
The scope use of the sewer ladders
If you have looked in the sewer pit at least once in your life, you have probably a ladder there. This is C1, a ladder, providing specialist access to the well for maintaining the given communications or cleaning. Mostly these ladders are installed in drainage systems, but they can be found in the water supply, observation or inspection chambers and even thermal cameras.
Design features and assembly of C1 wells
Due to its construction, these ladders have a fairly simple technology of manufacturing according to the drawings submitted by regulatory document «ТПР 902-09-22.84-КЖИ». The 7th section “Sewer Manholes” of these standard design solutions regulates the following options:
|Length of a ladder||Width of a ladder||Step tread||Material of vertical stands||Material of steps|
|from 0.6 to 4.2 m||500 mm||250 – 440 mm||hot-rolled steel area with cross-section 50×50×5 mm||steel round rod Ø 18 mm|
The ladder assembly is made by means of electric welding.
The materials themselves and a method of manufacturing indicate the strength and durability of this design. Sometimes, there can be deviations in the use of the material in steps in order to provide an additional margin of safety during the assembly of the ladders. A steel rod is replaced by a valve of the class A3 Ø 22 mm, which can withstand more weight without a deformation and it provides extra grip with the shoes due to the embossed surface. Ladders of this configuration contribute to the prevention of accidents during work in wells.
The use of inexpensive metal makes these products very cost-effective in price and provides a relatively small weight. For example, the weight of the ladder “C1-01” for «ТПР 901-09-11.84» with a length of 0.9 m is only 9.7 kg.
Specifics of the installation of stepladders
According to the requirements of the applicable Sanitary Norms and Rules (SNiP 2.04.03-85) step ladders should be equipped with manholes that meet certain parameters. In particular, the diameter of the round tubes for the mounting of the ladders for “C1” should be between 150 to 1500 mm. The tubes of rectangular cross section demand the minimum diameter of 1000 mm. If the diameter of the pipe is more, then you should use ladders with additional safety features. This rule applies to the depth of the wells: according to the technology, the maximum height of a stepladder C1 does not exceed 4.2 m (according to the official classification, theses are ladders “C1-12”).
The internal wall surface of the wells is used for the the installation of ladders. Drainage ladder is mounted on special brackets manufactured from hot-rolled steel with angle section of 50×50×5 mm. The distance from ladder to wall in this embodiment should not be less than 100 mm. Another important point is that the lower level of the ladder cannot fall lower than 300 mm from the bottom of the well. This is necessary for easier lowering and rising and also prevent corrosion of the bottom of the ladders.
The ladders may be executed in a removable version to provide additional protection from intrusion into the wells with important communications or high-risk level. The top of these ladders has a special adjustable metal hooks that hold it on the surface, and the lower is supplemented by the thrust.
The nomenclature of the sewer ladders
Today the market of building materials is full of manufacturers offering sewer stepladders on a variety of prices. When choosing such products, the buyer may face a situation when the same type of ladders represents different sizes and weight, respectively. So, you should have a clear idea about the marking and classification in order not to waste your money.
“C1” is used to denote all ladders for manholes. The remaining digits indicate the size of the ladders. For example, a combination of “C1-05” indicates that its height is 2.1 m. Occasionally, the price-list can have the name “ladder C2, C3, C4, etc.”, not like the usual designation.
This deviation from the officially accepted system of labeling is used by manufacturers and sellers to simplify titles and to clarify the characteristics of the structures. So, the designation “C3” means the model “C1-02”. The main difference between these 2 ladders is that they have different heights.
Let’s note that in accordance with “TПР 901-09-11.84” the height of the model “C1-02” is 1.2 m, while the “C3” is already 1.8 m. That’s why the price of the ladder “C2” or “C3” will be higher (about 1 500 -1 800 RUB.). Similarly the weight changes as well: ladders “C1-02” must have weight equal to 12.9 kg and “C3” should be harder according to length.
In order to avoid problems when choosing a ladder, you should know that the height of a step of the ladders marked “C2”, “C3”, “C5”, etc. is always equal to 300 mm.
If you want to choose the ladder “C1” according to “ТПР 901-09-11.84”, we propose to use the following table.
The main dimensions of stepladders for the descent in typical water wells of C1 type
|Type of ladder||Length, m||Weight, kg|
Useful tips if you don’t want to miscalculate the price
Given the fact that all manufacturers of classic models of the sewer ladders use the same material and technology, the prices of C1 ladders are almost not different on the market of building material. For example, the average price of a stepladder “C1-01” at the beginning of 2015 ranges from 720 to 830 rubles. The ladder “C1-04” with weight of 19.5 kg will cost approximately $40. You can easily navigate the price thanks to the various web-based resources. You can avoid extra costs buying the ladder directly from the manufacturer, the most popular of which are the companies «Grand- Build» or «Vik-М».
If you wish to easily save time and money by buying the necessary materials, you can make a stepladder “C1-04” by yourself.
How to ensure the durability of the ladders
Ladders are installed in the wells not for a year or two. They should serve reliably for decades, and that’s why you need to adhere to certain rules of operation.
Any sewer or manhole is already aggressive environment, where the main enemy of steel products is corrosion. That is why the manufacturers cover its products with several layers of oil paint or iron minimum “MA-15” according to the standards for corrosion protection. According to the standards of a ladder, this type can be painted either in black or in gray.
The layers of paint protect the ladders from the effects of external factors around a year even in temperate climates. Therefore, re-colouring is carried out annually to increase the lifetime of the product.
Know-how in the ladders
The progress is moving concerning even simple things. Today, some manufacturers modify the sewer stairs, applying advanced composite fiberglass materials for their manufacture. Compared to steel, they have a lot of advantages, the main of which are:
- increased resistance to corrosion and aggressive environments;
- high mechanical strength and reliability;
- light weight;
- minimum rates of water absorption;
- excellent dielectric properties.
The only disadvantage of the fiberglass profile is its higher price. The cost of ladders or fiberglass dielectric ladders will exceed the steel product in about 3 times.
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