Tanker Trailer Inspections:common defects, testing techniques and handling measures

Tanker trailers are a unique type of vehicle designed for transporting liquids or dry bulk materials.

The tests and inspections required for tanker trailers are: external visual inspection (V), internal visual inspection (I), lining test (L), pressure retest (P), leakage test (K), and thickness test (T).

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The wall thickness of the tank is not up to standard, the tank breakwater plate off, the beam connection weld cracking and other problems are the most common defects in the regular inspection of tankers.

Regular inspection of Tanker trailers in China, mainly using information review, visual inspection, wall thickness determination, weld surface nondestructive testing, safety accessories and pressure-bearing components, anti-static devices, painting, signs and markings to check, clear water static pressure test and gas tightness test and other methods. Due to the special nature of the tanker, the inspection process should focus on the following common defects.

1. thickness is not up to standard

Tank thickness is the basis of atmospheric tank strength, inspection of the tank is often found to have a tank wall thickness does not meet the standard problem. The reasons are as follows.

(1) some manufacturing plants to save costs, with substandard materials production.

(2) Some factories, the tank thickness is not manufactured according to the standard thickness of the material.

(3) the user's own modification or repair of the tank.

(4) tank thickness by corrosion thinning, etc.

Insufficient tank thickness, leaving a major accident hazard to the transport process of tankers. Therefore, the inspection should pay great attention to the detection of the tank wall thickness, the use of ultrasonic thickness gauge to measure the actual thickness of the tank, the first judgment whether to meet the minimum wall thickness of the tank requirements, followed by the corrosion rate of the tank materials to estimate the corrosion condition of the tank.

Wall thickness measurement of the site generally choose the liquid level often fluctuate parts, media stagnation of the bottom of the tank, processing and forming wall thickness thinning parts, easy to produce wear and tear deformation in the operation of the parts. For the inspection found in the tank mechanical damage, corrosion, should be polished to eliminate, can not meet the strength requirements, should be assessed as unqualified.

2. The wave guard inside the tank is damaged

During the operation of the tanker, the waveproof plate as a strengthening part directly bears the impact of liquid fluctuation. Due to the impact force of the liquid on the lateral waveguard inside the tank, the waveguard will appear wear, weld damage, deformation and distortion, cracking and other defects, and even the whole waveguard falls off. Due to the fall of the wave guard plate, in the tank with the liquid moving back and forth up and down, direct impact on the tank, resulting in tank wear thinning.

Therefore, the tanker inspection should strengthen the inspection of the anti-waves plate in the tank, to confirm its use of stable conditions, focusing on the anti-waves plate and the tank connection parts of the solid situation, you can use surface nondestructive testing, anti-waves plate thickness thinning, surface cracks, distortion, bolt loosening and other defects, should be promptly repaired.

3. Tanker trailer beam weld cracking

The tank body and frame beam connection weld is the main part of the vehicle running under stress load, where the weld is prone to penetrating cracking, mainly due to the following reasons.

(1) welding technology is poor. Tank and chassis welding, there is not welded through, not fused, slag, biting edge and other defects, these defects in the vehicle operation under the action of complex stress, stress concentration, become a cracking source of weld cracking.

(2) trailer overload problem. Vehicle overload so that the tanker in the turn, up and down the slope when the centrifugal force increases, acceleration and deceleration inertia increases, coupled with the main beam, sub beam and tank welding fillet weld itself there is stress concentration, it is easy to crack the weld.

Inspection should focus on checking the tank and chassis connection welds, using the tank dimensions, the volume of the tank is estimated, combined with the actual density of the medium, check the actual approved quality of the tanker, to stop the tanker overload operation.

4. The breathing valve of the tank is not qualified

Breathing valve is an important safety accessory of Tanker trailer, generally installed at the top of the tank, in the tanker operation under complex conditions (such as liquid shaking, temperature changes, violent vibration of the vehicle, etc.) to adjust the pressure difference between inside and outside the tank, to maintain the balance of air pressure in the tank, reduce media volatilization, the safe operation of the tanker plays an important role in the protection.

There are four common forms of breathing valve failure: air leakage, bonding, blockage, loss of breathing valve spool. For the inspection found that the breathing valve problems, must be repaired and processed, otherwise the tanker can not run.

5. Emergency shut-off valve failed

Emergency shut-off valve (also known as bottom valve), generally installed at the bottom of the tank, in the process of transport in the closed state, in the course of work, when the ambient temperature rises due to fire and other reasons automatically closed to prevent a large number of leaks in the loading and unloading system of atmospheric pressure tanks.

As an important valve of the pipeline at the bottom of the tank, when the impact force on the pipeline reaches a certain value, the body of the emergency shut-off valve will be disconnected to avoid damage to the tank from being hit, to protect the safe operation of the tanker.

In actual use, the emergency shut-off valve often fails. Tanker inspection should focus on checking whether the emergency shut-off valve is in a closed state; the appearance of corrosion, rust, cracks and other defects, the valve body has no loosening, leakage, deformation and other problems. Emergency shut-off valve exists to affect the normal use of the problem, must be repaired to eliminate the potential for accidents.

6. The quality of the conductive device is not qualified

Conductive device, also known as the elimination of static devices, used to eliminate the tanker in the loading and unloading, transportation process, the liquid in the container and the tank wall due to friction generated by static electricity. In the use of atmospheric tanks, in the process of road bumps, turning and shifting, as well as loading and unloading operations, the transport of liquid and tank wall friction generated static electricity, these static electricity if you need to export in time, otherwise it may generate static sparks, resulting in fire accidents.

Tanker trailer conductive device is generally installed in the vehicle beam on the conductive belt, need frequent inspection, maintenance and replacement. Tank, pipeline, valve and vehicle chassis between the conductive wire connection should be solid and reliable, the tank pipeline valve and conductive belt grounding resistance should not exceed 5 Ω; grounding wire cross-sectional area should be not less than 5.5 square millimeters; conductive belt must be grounded and reliable, the use of chains instead is strictly prohibited.

7. Conclusion

To ensure the safe operation of the Tanker trailer, in addition to focusing on common defects, it should also check the pipeline, loading and unloading valves, quick-fit joints, loading and unloading hoses and other components for leaks and problems affecting loading and unloading and transport safety. Tankers such as equipped with safety valves, pressure gauges, thermometers, should check whether its appearance is intact and within the validity period, rupture discs, vacuum valves, liquid level gauges, etc. are intact and effective; the type of fire extinguishers on board and the type of media shipped is appropriate, whether the pressure is normal, there is no expiration date, the number, placement is in line with requirements, etc. Only after all these facilities are checked and qualified tankers can safely run on the road.