I. Basic knowledge of liquefied petroleum gas (LPG), source and composition of LPG.

Liquefied petroleum gas (LPG) refers to oil and gas fields and the tail gas in the process of petroleum distillation and the by-products of chemical production. It is composed of a variety of hydrocarbons, mainly by propane, butane, propylene, butene and other low molecular hydrocarbon mixture, also contains a small amount of impurities, commonly known as carbon three carbon four.LPG, abbreviated as LPG or LPG for short, is a liquid mixture of propane (C3H8) and butane (C4H10), which is mainly composed of propane (C3H8) and butane (C4H10), and usually stored under pressure or low temperature. It is usually accompanied by a small amount of propylene (C3H6) and butene (C4H8), as well as a small amount of alkane (C5H12) and pentene (C5H) 10) and other components, is a clean gas energy, mainly used for catering, civil and industrial and commercial combustion needs and such as gasoline additives, synthetic plastics, rubber, fiber and production of medicine, explosives and other chemical deep processing needs.

LPG tank trailer structure

II. Classification of LPG liquefied gas tank trailer.

1. LPG liquefied gas transport tank semi-trailer

LPG Semi Truck Configuration

Standard: single liquid, double side loading and unloading, double valve box, safety valve, liquid level gauge, thermometer, pressure gauge, emergency cut-off valve, 12TBPW shaft disc type, aluminum alloy steel ring, 12.00 double money vacuum tire, one spare tire, Jost leg, Jost traction pin, fire extinguishing bottle, anti-static grounding tape, iron fender, ABS.

Optional: double independent liquid adding, hose box to water tank, Fuwa bridge double axle. Float level gauge. Aluminum panel sunshade (export).

Can be divided into single liquid and double liquid.

2. LPG liquefied gas carrier (bicycle)

37.2 cubic HOWO front four and back eight liquefied gas truck,

vehicle size :11220×2500×3800mm,

dead weight: 15.6 tons,

load capacity: 16.2 tons, high top two recuperator cab, FAW Dazhai 320 horsepower engine, FAW nine speed transmission,

wheelbase :1950+4550+1350mm, air conditioning, electric glass, Central control lock, remote control key, power steering, airbag seat, front exhaust pipe, front disc and rear drum brake, air brake, rear axle air suspension system, with ABS, 12R22.5 vacuum tire, aluminum alloy wheels.

Tank size: 8.18m x 2.49m, Q370R steel plate, 12mm thick cylinder wall, 10mm thick round head, valve box, safety valve, thermometer, pressure gauge, emergency cut-off valve, anti-static grounding tape.

3. LPG liquefied gas refueling truck (export)

The tank of LPG refueling truck is made of Q345R with elliptical head structure design. The cylinder diameter is 2050mm, the cylinder thickness is 10mm, and the head is 12mm. With JAC210hp chassis, LPG flow meter, LPG safety return valve, LPG coil and air gun are installed at the tail, which can realize the direct filling operation of small cylinders. The customer ordered one in our company before, and felt the quality was good, so he added two orders with the same configuration.

The LPG storage tank, LPG buried tank and other pressure vessel products produced by SUNSKY are sold overseas every year with convenient use and guaranteed quality, which are deeply loved by overseas customers. It is one of the best liquefied gas tank manufacturers in China.

III. The basic countermeasure of accident disposal of LPG tank trailer truck

LNG, CNG and LPG are three common hydrocarbon fuel transport vehicles. The structure, storage medium and storage mode of the three tank trailers are different, so the accident disposal methods of the three vehicles are also different. We should first have a preliminary understanding of each tank trailer and apply relative disposal techniques and tactics for different vehicles.

1. LPG tank trailer truck structure

The structure of liquefied petroleum gas tank trailer is relatively simple, the main components are: car body, tank body, loading and unloading device, safety device, the following brief introduction of several important parts of the tank trailer.

The semi-trailer has two handling boxes and the mobile has only one, both located in the middle of the tank.

(1) Emergency cut off device

The emergency cut-off device is a valve connecting the tank and the pipeline, which is equivalent to the root valve of the petrochemical storage tank. It is a device for emergency cut-off in case of pipeline leakage. Generally, it is closed in the process of transportation and opened during loading and unloading. Common emergency cutting device has mechanical pull type and hydraulic type two kinds, hydraulic pressure is open when the pressure is closed valve state, pull type to pull out is open state, push in is closed state.

(2) loading and unloading pipeline

The loading and unloading pipeline is divided into gas phase pipeline and liquid phase pipeline. The liquid phase pipeline is larger than the gas phase pipeline.

(3) Liquid level gauge

Liquid level gauge is used to observe and control the tank trailer filled with liquid amount (volume or weight) device, generally located in the rear of the tank trailer, commonly used with spiral, buoy, slide tube. When the tilting Angle of the tank trailer is greater than 30 degrees, the liquid level gauge will fail, that is, it cannot judge the liquid level according to it.

(4) Safety release device

Mainly refers to the safety relief valve and bursting disc combination of safety relief device. The safety valve of the device is combined in series with the bursting disc and communicated with the gas of the tank body, and is arranged above the tank body.

When the tank trailer rolled over 30°, when the tank overpressure, the safety valve will leak the liquid medium, remember not to water the safety valve when cooling, otherwise it will freeze the safety valve, so that the tank trailer loses the essential safety.

2. Common accidents of liquefied petroleum gas tank truck and countermeasures

The bottom line of LPG tank truck accident prevention and control is the tank disintegration and explosion. We should always pay attention to the pressure and temperature of the tank. According to the pressure and temperature of the tank, we should judge and select targeted measures such as decompression release, emergency cut-off, inverted tank transfer, drainage and burning control.

(1) The accident form:

① No leakage accident

LPG tank trailer rear-end, overturned, collision, the tank is not damaged, there is no leakage, but at this time, the pressure resistance of the tank may be affected, as time goes on, the temperature rises, saturated steam pressure increases, vehicle tank may occur instantaneous pressure relief fire accident.

② Leakage accident

After the traffic accident of the LPG tank truck, the liquid phase or gas phase leakage occurred.

③ Leakage, combustion and explosion accident

The gas phase or liquid phase leaked after the traffic accident of the tank trailer, and the explosion and combustion accident occurred, or the downhill braking system of the tank trailer overheated, and the combustion of tires and other parts occurred.

(2) The disposal way:

① Cooling

LPG tank trailer is a high pressure normal temperature tank, in the vehicle accident should be the first time to use fog water uniform cooling, reduce the saturated steam pressure in the tank to prevent the overpressure explosion of the tank. But it must be noted that water must not be sprayed to the position of the safety valve, the type of tank car should be identified, and water cooling should not be injected to the LNG tank trailer. (The first step to get out of the water when this kind of trailer has an accident)

② Dilution inhibition

When the tank leakage should be timely water use spray water or water curtain belt to dilute the gas at the leak site, to prevent the gas from reaching the explosion concentration and fire explosion. Note that direct water can not be used, direct water impact objects easy to produce static electricity. At the same time, the safety valve should be avoided in the dilution process. When the tank trailer leaks, the high-speed injection of gas is also easy to cause static electricity. Therefore, the conductive device at the tail of the tank trailer should be inserted into the earth in the disposal process.

③ Empty risk exclusion

When the tank truck accident does not have the measures to pour the tank, can carry out natural empty-out disposal, but the use of this way of risk removal should pay attention to the following points: 1, no residential areas around; 2. The leaked gas will not affect the surrounding tunnels, highways, railways, etc. When the regional conditions are limited, the water belt can be used to guide the flow to the safe area to vent.

④ Close the valve and break the material

The emergency shutoff valve can be closed at the rear of the tank trailer in the event of a leak in the pipeline or equipment in the operating tank.

LPG storage tank

⑤ Plugging

When the pipeline of the tank trailer leakage or tank leakage can be used in various ways to plug the leak, in the process of plugging the leak must be put an end to fire, the use of sparkless tools to operate, to the tank plugging should pay attention to the occurrence of cold and brittle, plugging can not use brute force hitting the tank or with iron hitting the tank.

⑥ Pour a can and turn it into a bowl

This is the operation of using the differential pressure of the tank or the transfer equipment to transfer the liquefied petroleum gas from the accident tank to the safety tank to eliminate the dangerous source. Pour can transfer need a security expert, under the professional operation, attention should be paid to control the content of oxygen when tank, because the liquefied petroleum gas (LPG) contains butadiene, this kind of substance autocatalytic oxygen can occur, since decomposition reaction, there is the risk of explosion, so be on the safe cans and lose nitrogen injection loafing in line, in the pot to downwind direction setting spray on hand, Dilute the leakage gas (this is a good risk prevention method).

LPG tank trailer truck

⑦ Drainage control fever

Due to the regional limitations of the tank can not be vented naturally, the way of drainage and controlled burning can be carried out. The gas in the tank can be guided to the downwind safe area for burning by conduit. This way takes a long time to dispose of, and liquid drainage can also be used.

⑧ Hoisting transport

The use of lifting transport way to bind the wire rope with butter soaked to prevent sparks, lifting wire rope bundling method should have a self-tightening function, before lifting to the tank pressure relief, avoid high pressure lifting, in the lifting process can not play water cooling, to prevent the safety valve accident.

⑨ Safety monitoring

When the tanker is transferred, there is still liquefied petroleum gas in the tank, or the method of temporary plugging is adopted, etc. In the process of transport, the vehicle needs to be monitored during the transport process.

IV. Why does a liquefied petroleum gas (LPG) tank trailer truck explode and cause so much damage?

Liquefied petroleum gas (LPG) is a gaseous by-product of petroleum catalytic cracking, liquefied after pressure and cooling, and stored in cans in the form of colorless volatile liquid. They are mainly propane and butane, which generally contain more than 60%. Once the tanks, valves and pipeline rupture, liquefied petroleum gas, meets the air will get back in the gas phase, in general, propane and butane "flash point" and "spontaneous combustion point" are very low, flash point is 104 ℃ - propane, butane flash point is - 60 ℃, volatile in the air after reaching a certain concentration range, electrostatic or fire explosion would happen the first time.

The ignition temperature of LPG is lower than that of other fuels, generally between 430℃ and 460℃. The explosion limit is narrow, 1.5%-9.5%, and the lower limit of explosion is lower than other gas, so the risk is relatively large, sporadic electric spark can cause combustion and explosion. Therefore, in the storage and transportation of such dangerous chemicals as liquefied petroleum gas (LPG), the high pressure resistant storage vessels used, the safety awareness of transportation and storage personnel, and the safety accessories of tank trucks (including safety valves, valve sealing gaskets, weld quality, compressive strength, etc.) are all required. However, the reality is that due to the high maintenance and management costs in the later stage, production enterprises often do not pay much attention to end-product management based on cost and other factors. Therefore, transportation enterprises need to constantly strengthen management, strictly in accordance with the normative operation, and strengthen the safety education and emergency drills of management and transportation personnel.