Introduction of manhole cover of fuel tanker (Part 1)

Introduction of manhole cover of fuel tanker (Part 1)

- composition, quality standard, definition, installation, operation and maintenance

1. Product introduction

The manhole cover is installed on the top of the tank of the fuel tanker with the functions of internal breathing and emergency exhaust. The internal breathing valve keeps the internal pressure and the external pressure of the tank in balance during the oil transportation. When the pressure inside the tank rises sharply, the emergency exhaust device will automatically start to release the internal pressure. Even in the event of an accident of the fuel tanker, the anti overflow device of the internal breathing valve remains sealed, and the medium in the tank will not be leaked to prevent major accidents. The manhole cover can be installed with oil and gas recovery valve, oil measuring hole, anti overflow probe rod, etc. As shown in Figure 1 below.

(Figure 1. Manhole cover)

2. Structure & composition

Manhole cover assembly is mainly composed of a manhole cover plate, feed port cover plate (including 2 breather valves, an upper pressure plate, a lower pressure plate and 4 emergency ventilation pressure springs), 2 reserved port cover plates and seals, as shown in Figure 2 below.

(Figure 2. Structure of manhole cover)

3. Quality standard

Manhole cover shall comply with QC/T1065-2017(Road Tanker for Flammable Liquid Goods Transportation-Manhole Cover) automotive industry standard.

4. Common terms and definitions

(1) (manhole)

An opening in the tank body that allows personnel to enter and exit.

(2) (manhole cover)

The cover plate that closes the manhole, after opening, personnel can enter and exit the tank.

(3) (manhole cover neck-ring seat)

Structural parts on the tank body for fitting manhole covers.

(4) (manhole cover gasket)

Sealing element between manhole cover and manhole seat.

(5) (emergency pressure release device)

A device for quickly releasing the pressure in the tank when the pressure in the tank is abnormal.

(6) (emergency release pressure)

The release pressure set by the emergency release device.

(7)  (feed port)

An opening in the manhole cover for medium loading.

(8)  (secondary opening safety device)

A device for releasing the gas pressure in the tank in advance before the feed port is fully opened.

5. Installation of manhole cover

When installing the manhole cover, The rotating hinge shaft shall be perpendicular to the length direction of the vehicle’s beam. The user can also change the installation direction according to the actual needs. In the process of installation and handling, pay attention not to damage the installation joint surface of manhole cover to avoid affecting the sealing performance. Special attention shall be paid to the sealing washer of manhole cover and tank vehicle to avoid scratch damage during installation, which will affect the sealing effect.

Emergency exhaust device: this device can automatically exhaust air in case of an accident of the fuel tanker or when the tank is in a fire and the pressure in the tank needs to be released under high temperature to prevent explosion. When the pressure in the tank reaches 21-35kpa, the emergency exhaust device will start working, and the maximum exhaust volume is 7000m³/h or more. It can effectively prevent explosion accidents of tankers.

6. Use, operation and maintenance

Use: the manhole cover has been tested before delivery and can be used after installation. During the use, it is not allowed to adjust the breathing valve and emergency ventilation valve device (such as spring).

Operation:

(1) The opening sequence is as follows:

a. Insert the key into the key hole of the manhole cover;

b. Turn the key counterclockwise by 30 °;

c. Pull the upper pressing plate upward;

d. Push open the locking hook in the square hole of the lower pressing plate

and lift up another end of the lower pressing plate to open the manhole cover.

(2) Close the manhole cover

a. Pull another end of the lower pressing plate to rotate around the fixed shaft to close the manhole cover;

b. Pull another end of the upper pressing plate to rotate around the fixed shaft to lock it.

By  WONDEE Autoparts

2022-8-18