Manhole, normal pressure manhole, quick opening manhole, square manhole, venting manhole

Description :

Manhole is an opening device with a sealed cover plate for personnel to enter and exit sealed containers/pipelines/underground structures, which is different from a handhole that can only extend tools; The core purpose is internal installation, maintenance, cleaning, testing, and also serves as a ventilation/exhaust outlet; It is a legally necessary safety facility for pressure vessels, storage tanks, pipelines, and municipal shafts.

2、 Structural composition

Standard components: cylinder section (short pipe)+flange+cover plate (manhole cover)+sealing gasket (winding gasket/graphite gasket, etc.)+fasteners (bolts and nuts)+hinge/lifting ear/ladder; The commonly used materials are carbon steel and 304/316 stainless steel, and special alloys are used for high-pressure/corrosive conditions; Common circular DN600, elliptical 300 × 400mm and above.

 3、 Main categories

1.  According to the opening and closing methods: vertical hanging cover, horizontal hanging cover, rotating cover (HG/T 21514-21535 standard series);

2.  Pressure: atmospheric pressure manhole, pressure vessel manhole (with neck welding/flat welding flange), emergency pressure relief manhole (equipped with flame retardant breathing valve);

3.  By location/scene: tank top/wall manhole, boiler manhole, municipal underground pipeline manhole (inspection well);

4.  By shape: circular (optimal pressure bearing), elliptical (convenient for lateral entry and exit), rectangular.

4、 Common standards

-Chemical industry: HG/T 21514-21535; Pressure vessels: NB/T 47041, GB 150;     Boiler: NB/T 47040; Tank: SH 3046

5、 Typical application areas

1.  Petrochemical industry: vertical storage tanks, spherical tanks, reactors, and towers are often installed at the top/bottom;

2.  Energy and electricity: boiler drum, deaerator, condenser;

3.  Municipal engineering: sewage/rainwater pipelines, gas pipelines, communication wells;

4.  Ship: Cabin, oil tank, ballast tank manhole cover (watertight/oil tight).

6、 Selection and safety points

1.  The selection must be clear: design pressure, temperature, corrosiveness of the medium, installation position, flange standard, and sealing grade;

2.  Mandatory gas detection, ventilation and replacement, hanging and locking, and dual person supervision before homework. It is strictly prohibited to enter the manhole alone;

3.  The cover plate must have anti fall and anti-static measures, and it is strictly prohibited to use non-standard parts instead of seals/fasteners.

Contact phone number: 18303265299

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