A manhole (also known as a utility hole, maintenance hole, or sewage hole) is an entry into a restricted place such as a shaft, utility vault, or big vessel. Manholes are frequently used as underground public utility access points, allowing inspection, maintenance, and system improvements. The bulk of subsurface utilities, including water, sewerage, telephone, electricity, storm drains, district heating, and gas, have manholes.
Manholes are commonly seen in cities, on streets, and occasionally beneath sidewalks. Services such as telephones and electricity are typically carried on utility poles or pylons rather than underground in rural and underdeveloped regions.
What is the purpose of a manhole?
A grating or manhole cover, a flat stopper meant to prevent accidental or illegal entrance to the manhole, protects manhole closings. Traditionally, these coverings are made of metal, but they can also be built of precast concrete, glass reinforced plastic, or other composite materials (especially where cover theft is of concern). As a result of regulations limiting allowable manual handling weights, Europe has witnessed a shift toward lighter-weight composite manhole cover materials, which also offer improved slip resistance and electrical insulating qualities.
To facilitate straightforward descent into the utility space, manholes are typically supplied with metal, polypropylene, or fiberglass stairs on the wall’s inner side.
How to Choose the Right Manway Cover for Storage Tanks
When designing your storage tank system, it’s critical to consider the tank itself, fittings, and accessories. Your manway cover is a crucial component of your tank. Failure to comprehend the purpose and operation of the manway might endanger your employees’ safety and lead to leaks, tank damage, and environmental dangers.
Let’s look at three factors to consider while selecting a pressure manhole. We’ll also go through the best alternatives for each element.
1-The Chemical That Is Being Stored
The sort of chemical you’re storing is a crucial consideration when choosing the correct manway cover for your storage tank. We begin here since some substances necessitate their own carefully built systems. Water storage, for example, necessitates a different safety element than a caustic or dangerous substance, such as hydrochloric acid (HCl). Because HCl is very corrosive and produces poisonous fumes, a corrosion-resistant tank with an Integrally Molded Flanged Outlet® (IMFO®) System and a scrubber are required to prevent fumes from leaking into the environment. To allow the scrubber to work correctly, HCl tanks must have a fume-tight manway cover.
Hydrogen peroxide, on the other hand, decomposes quickly. Tanks frequently feature a hinged-weighted manway cap to reduce pressure buildup caused by decomposition.
2- How the tank is filled
Depending on how the tank is filled, some chemicals necessitate the use of a manway cover. Filling chemical storage tanks can be accomplished in three ways:
- Mechanical pump
- Gravity
- Pneumatic fill
Because the chemical is blasted into the tank, pneumatically filled storage tanks are subjected to extreme pressure. Tank systems should be outfitted with Poly Processing’s SAFE-Surge® manway cover or FS 2650 cover in such instances. The SAFE-Surge cover was first intended to provide emergency pressure relief. The lid burps at around 0.8 PSI when the pressure is released and then shuts. SAFE-Surge is not designed for use with vapor-emitting substances.
The FS 2650 is a mushroom-shaped cover that continually vents. Holes are drilled under the head to allow for venting, while the top of the head keeps rains and debris out of the tank. It can relieve a volume flow rate of up to 2650 ACFM. Only non-fuming chemicals should be used with the FS 2650. Tanks not pneumatically filled, such as sulfuric acid, require a fastened manway top to prevent exposure.
3- Required Access Type
How are you going to get to the chemical storage tank? The sort of manway cover you should employ is determined by the type of access you require. A fume-tight manway cover is necessary to protect people and equipment from vapors caused by hydrochloric acid. Entering the tank is not an option due to its corrosive nature, and your manway should reflect this. Scrubbers and a fume-tight manway should be installed for HCl. A threaded manway is appropriate for water tanks since water is not dangerous, and the tank will need to be drained and physically cleaned regularly.
Tanks that are not pneumatically filled, such as sulfuric acid, require a fastened manway top to prevent exposure.
The Appropriate Manway Cover for Your System
Choosing the correct manway cover for a safe, functional tank system is no easy task. The improper form of insurance may damage your employees, equipment, and the environment.
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