Introduction of manhole cover of fuel tanker (Part 2)

(continued from the preceding part)

Introduction of manhole cover of fuel tanker (Part 2)

- Technical requirements, test methods and inspection rules

1. Technical requirements

1.1.1 The manhole cover should meet the requirements of QC/T1065-2017 standard.

1.1.2 The raw materials, purchased parts, outsourced parts and other parts used for manhole cover should meet the requirements of relevant product standards with the product certificates of the manufacturer.

1.2. Structural and functional requirements

1.2.1. Manhole cover shall be equipped with feed port and emergency pressure release device.

1.2.2. The feed port should be fully openable and equipped with a secondary opening safety device

1.2.3. The manhole cover should be equipped with a spare interface for installing an oil and gas recovery valve, an anti overflow sensor, a breathing valve and other valves.

1.2.4 The emergency pressure release device should be designed to prevent icing caused by liquid accumulation.

1.2.5. When the emergency pressure release device is closed, keep the manhole cover in sealed state to prevent liquid or gas from flowing out of the tank.

1.2.6 When the pressure in the tank is lower than the release pressure, the emergency pressure release device should return to the closed state.

1.3 Materials

1.3.1. The material selection of manhole cover must fully consider the compatibility with the medium it contacts.

1.3.2. The manhole cover should be made of aluminum alloy, stainless steel or carbon steel, it should not be made of non-metallic materials.

1.4. Sizes and specifications

1.4.1 The nominal diameter shall not be less than 500mm.

1.4.2 The diameter of emergency pressure release device shall not be less than 250mm.

1.4.3. The vertical distance from the vertex of any part installed on the manhole cover to the installation sealing surface of the manhole cover shall not exceed 150mm.

1.5 Design temperature range

1.5.1 The design temperature of manhole cover is generally - 20 ℃ ~ 50 ℃. When there are special environmental requirements, the design temperature should be - 40 ℃ ~ 70 ℃

1.6 Pressure setting

1.6.1 The nominal pressure level of manhole cover shall not be less than 65 kPa.

1.6.2 The emergency release pressure of manhole cover shall be 21 kPa ~ 35 kPa.

1.7 Sealability of manhole cover and seat ring

1.7.1. When the manhole cover is under 1.5 times the nominal pressure, the leakage rate shall meet the requirements of Grade A in Table 1 below.

1.8 Emergency relief sealability

1.8.1 When the pressure higher than or equal to 21kPa, the leakage rate of manhole cover shall meet the requirements of grade B in Table 1 below

1.8.2. Under the pressure of 16.8 kPa, the leakage rate of manhole cover shall meet the requirements of Grade A in Table 1 below

1.9 Falling sealability

1.9.1 The leakage rate of manhole cover shall meet the requirements of grade F in Table 1 below within 1 min after falling

1.9.3 After the falling test, the manhole cover including the accessories installed on it shall not have visible leakage

Table 1. Maximum allowable leakage of each level of leakage rate(Unit: mm³ / s)

Test medium	Grade A	Grade B	Grade C	Grade D	Grade E	Grade F	Grade G
Liquid	No visible leakage during the test duration	0.01xDN	0.03xDN	0.1xDN	0.3xDN	1.0xDN	2.0xDN
Gas		0.3xDN	3.0xDN	30xDN	300xDN	3000xDN	6000xDN

Note: 

1. The leakage rate is only applicable to room temperature.

2. "No visible leakage" means that there is no visible water drop or continuous water drop or bubble and the leakage is less than level B.

1.10 Strength

When the manhole cover is under the pressure of 200 kPa or 3 times of the nominal pressure, there shall be no obvious deformation or damage.

1.11. Electrostatic resistance

Any conductive component on the manhole cover that may contact with the medium, the resistance with manhole cover shall not be greater than 10⁶Ω

1.12 Operability

The secondary opening device of manhole cover shall be able to open and close flexibly without jamming

2. Test method

2.1. Test quantity

The number of samples for product type test is 2 pieces.

2.2 Sealing test of manhole cover and seat ring

2.2.1 The test medium shall be air, nitrogen or one of other inert gases. The temperature of test medium shall be 5 ℃ ~ 40 ℃.

2.2.2 The duration of maintaining the test pressure shall not be less than 60 s.

2.2.3 The test process shall be carried out in the following sequence:

a) Install the manhole cover on the test device so that the installation state of the manhole cover is consistent with its normal working state;

b) Slowly increase the test pressure to the specified test pressure and maintain the pressure for the specified time;

c) Check the leakage of the sealing surface between the manhole cover and the seat ring.

2.3. Emergency release sealing test

2.3.1. The test medium shall be one of water, air, nitrogen or other inert gases. The temperature of test medium shall be 5 ℃ ~ 40 ℃.

2.3.2. The duration of maintaining the test pressure shall not be less than 60 s

2.3.3. The test process shall be carried out in the following sequence:

a) Install the manhole cover equipped with the emergency release device on the test device, so that the installation state of the manhole cover is consistent with its normal working state;

b) Slowly increase the test pressure to be greater than or equal to 21 kPa and maintain the pressure for a specified time;

c) Check the leakage of emergency release device of manhole cover;

d) Reduce the test pressure to 16.8 kPa and maintain the pressure for the specified time;

e) Check the leakage of emergency release device of manhole cover

2.4. Release pressure test of emergency release device

2.4.1. The test medium shall be air, nitrogen or one of other inert gases. The temperature of test medium shall be 5 ℃ ~ 40 ℃.

2.4.2. The test process shall be carried out in the following sequence:

a) Install the manhole cover equipped with the emergency release device on the test bench so that the installation state of the manhole cover is consistent with its normal working state;

b) Slowly increase the test pressure to the emergency release pressure specified in 1.6.2

2.5. Drop test

2.5.1. Test equipment.

The main body of the drop test equipment is a container, and there is a flange for installing the test manhole cover on the side of the container. The experimental equipment shall meet the following requirements:

a) The dimension, tolerance and characteristic structure of the fall test equipment shall comply with the requirements in Appendix C;

b) The support foot shall be made of integral steel, and cannot be combined with other materials or adopt shock absorption design to absorb impact energy;

c) The impact zone (sandbox) at the foot of the support shall be as shown in Appendix C;

d) The lifting and release device shall be able to ensure that the impact test equipment can be lifted to the specified test height and fall freely from the height;

e) The lifting and guiding device shall not affect the free fall of the test equipment;

f) The design and operation of falling equipment shall meet the requirements of local safety regulations and have the function of preventing accidental falling;

g) The main body of the fall test equipment shall be capable of withstanding a pressure of more than 200 kPa.

2.5.2. Test method.

a) Install the manhole cover on the flange of the test container, and the central horizontal line of the manhole cover shall be aligned with the central horizontal line of the flange;

b) Inject water into the main container at 1300mm higher than the central horizontal line of the installation flange, and block the liquid level indicator hole;

c) Lift the test equipment to the release point to lift the equipment by 1200mm;

d) Stir the sand in the sandbox until it is soft and even, and then put a rubber pad on it;

e) Release the test equipment to make the equipment fall freely for 1200mm;

f) Within 1min after falling, wipe the manhole cover and installation flange to check the leakage of manhole cover.

2.6. Strength test

2.6.1. The test medium shall be water, kerosene or one of the non corrosive liquids with viscosity not higher than water. The temperature of test medium shall be 5 ℃ ~ 40 ℃.

2.6.2. The test pressure is 200kPa or 3 times the nominal pressure, whichever is greater.

2.6.3. The duration of maintaining the test pressure shall not be less than 10 min.

2.6.4. The test process shall be carried out in the following sequence:

a) Close the feed port and each standby port on the manhole cover;

b) Install the manhole cover on the test device;

c) Apply the test pressure to the lower part of the manhole cover, maintain the pressure for a specified time, and check the deformation and damage of the manhole cover

2.7. Electrostatic conduction test

The test shall be conducted in the following sequence:

a) The manhole cover and its parts shall be dried before the test;

b) Measure the resistance with a 500 V DC megger;

c) Measure the electrostatic resistance between any conductive part on the manhole cover assembly that may contact with the medium and the manhole cover body.

3. Inspection rules

3.1. Delivery inspection

Each manhole cover shall be subject to factory inspection according to the specified items, the products can be delivered after passing the inspection of the manufacturer with the product certificate.

3.1.1 Delivery inspection items:

a) Appearance;

b) Sealing test of emergency release device;

c) Electrostatic conduction test.

3.2. Type inspection

3.2.1 Type inspection should be carried out in any of the following situations:

a) When a new product is trial-formulated;

b) When the product is officially produced, it has been continuously produced for 3 years or the cumulative output is 10,000 units;

c) After the product is officially produced, there are major changes in structure, material, process, etc., which may affect the performance of the product;

d) When there is a huge difference between the delivery inspection and the type inspection of the product.

3.2.2 During the type inspection, in the case of two cases a) and b) in 2.2.1, the inspection shall be carried out according to the content of Chapter 1;

In the case of c) and d) in 3.2.1, only the affected items can be inspected.

By  WONDEE Autoparts

2022-9-5