fire hazard of liquefied petroleum gas

liquefied petroleum gas is a light organic compound obtained from oil and gas fields and petroleum refining, mainly a mixture of saturated and unsaturated hydrocarbons. Its components are low-carbon hydrocarbons such as propane (C3H8), propylene (C3H6), butane (C4H11), butene (C4H8), and a small amount of pentane (C5H12) and sulfide. Liquefied petroleum gas (LPG) is usually stored in liquid state at room temperature and pressure, and has the properties of gas and liquid phases. The fire hazard is mainly manifested in the following aspects:

(1) The burning speed is fast. Liquefied petroleum gas (LPG) combustion belongs to the mixed combustion of gas and liquefied gas, with fast combustion speed, fierce fire and rapid spread.

(2) The flame temperature is high and the radiant heat is high. The combustion heat value of liquefied petroleum gas is as high as 115111 kJ/m3, and the flame temperature is as high as 2111 degrees Celsius.

(3) The explosion speed is fast, and the shock wave is powerful and destructive. The explosion speed of liquefied petroleum gas is fast, reaching 2111-3111 meters per second.

(4) volatile. At room temperature, liquefied petroleum gas is volatile, and once exposed to air, it can quickly expand to more than 251 times.

(5) It is heavier than air, with low lower explosion limit and small minimum ignition energy. Liquefied petroleum gas is 1.5 to 2.5 times heavier than air, and it is easy to < P > flow to low-lying places and gather in the air. Liquefied petroleum gas has a low lower explosion limit, a large explosion range of 1.5%-9.5%, and a low minimum ignition energy of only 3×11-4 Joules.

(6) The risk of re-ignition and re-explosion is high. It is estimated that a bottle of 14.5 kg liquefied gas, once exploded, can produce the power equivalent to 72.5-145 kg TNT explosive. When liquefied petroleum gas leaks, it will form an explosive air mixture when mixed with air in a short time. Because the lower explosion limit is very low, it will explode chemically and burn violently when it meets an open flame. Under the action of external high temperature, the pressure of liquefied petroleum gas in the tank will rise rapidly. When it exceeds the design pressure of the tank wall, it will explode physically, resulting in multiple leaks, and the fire will be more violent, so there will be the resurgence and re-explosion of physical and chemical explosions, which will be extremely harmful.

liquefied gas safety accident case

Accident time: 2114

Location: a residential building in a city

Losses caused: 1 people were killed and some windows were damaged

Accident course: The angle valve of the steel cylinder used by the household was aging, resulting in a large amount of liquefied gas leakage. Because the household stored liquefied gas in a relatively sealed cupboard, a large amount of leaked liquefied gas was accumulated in the cupboard. When using liquefied gas, it detonated the leaked liquefied gas and caused a fire.

Cause analysis:

(1) The residents' lack of safety awareness is one of the reasons for the accident.

(2) The aging of the angle valve is one of the causes of the accident.

(3), in the case of liquefied gas leakage, the direct cause of the accident is still using liquefied gas

In summary, the reasons mainly come from two aspects:

(1), liquefied gas operators operate illegally and security inspection is not in place.

(2), the client's customers violate the rules and have a weak sense of safety.

therefore, to strengthen liquefied gas safety and reduce liquefied gas accidents, it is necessary for liquefied gas production enterprises and liquefied gas users to work together to put an end to illegal operations and create a good safety atmosphere. The following will take Taineng Liquefied Gas Company as an example to elaborate on two aspects: the company-side safety inspection and the common sense of safe gas use at the client side.

Company-side security measures

Liquefied Gas Company attaches great importance to the security of clients, and implements multi-angle and all-round security inspection activities in all aspects of cylinder circulation.

security check of filling process

The starting point of the company's liquefied gas cylinder circulation comes from the filling plant. Empty cylinders of liquefied gas from customers are transported to the filling plant in a unified way. The receiving and dispatching personnel of the filling plant first inspect the appearance of the cylinders, clean the cylinders that meet the filling requirements, and then use the manual filling scale to fill them.

Filling personnel fill in strict accordance with the filling standards stipulated by the state. After filling, they come to the important link-cylinder leak detection. The leak detection of steel cylinders is divided into two steps: dynamic leak detection and static leak detection.

dynamic leak detection, that is, simulating the situation of steel cylinders in use, and detecting whether there is a leak point during use. Specific inspection method: screw the leak test valve to the air outlet of the angle valve, open the angle valve, and use the instrument to detect the leak, or smear the valve root and screw rod of the angle valve with soap solution to see if there are bubbles. If bubbles are generated, it indicates that there is dynamic air leakage in this cylinder, and it needs to be removed, depressurized and repaired separately.

static leak detection, that is, simulating whether there is a leak point when the cylinder is not in use and the angle valve is closed. Specific inspection method: close the angle valve of the steel cylinder, and apply soap solution to the outlet and root of the angle valve to see if there are bubbles. If there are bubbles, it means that there is static air leakage in the steel cylinder, so it is necessary to pour the residual, relieve the pressure and repair it separately.

after checking the static and dynamic leak detection, it is confirmed that the cylinder is airtight and conforms to the factory regulations, and the staff hangs the filling label and seals the cylinder, waiting for the factory.

"four re-inspections" before the transfer station leaves the warehouse

The filled steel cylinders are transported to the transfer stations in the city in a unified way by the rail car to be sent to customers' homes. When receiving the delivery task, the company's distribution personnel first conduct a "four-time re-inspection" on each cylinder. The "four-time re-inspection" work is an important link in the company's cylinder management, and it is a re-inspection of the security inspection in the previous filling process, which is related to the safety of the outgoing cylinders and has great significance.

1 Check whether the seal is complete:

Check whether the seal of the bottle body is damaged, falls off or the seal is not in place (the angle valve is not completely wrapped).

2 Check whether the fittings of the bottle body are complete:

Check whether the shield and base of the bottle body are welded, whether there is air leakage at the middle weld of the bottle body, whether the ceramic bar code at the position of the shield is lost, and whether the filling label of the cylinder is lost or defiled.

3 Check whether the weight of the steel cylinder meets the requirements

Check that the actual weight of the steel cylinder is greater than 31.5Kg before leaving the warehouse. The empty bottle is 16.5Kg and the filling weight is 14.5+1.5Kg.

4 check whether the appearance of the cylinder is clean

check whether the cylinder is clean, wipe off the floating ash on the surface of the cylinder with a dry cloth again, and check whether the bottle sleeve is not covered and stained.

5 after the inspection is completed according to the contents of "Four Re-inspection", the relevant personnel shall truthfully fill in the bottle number, weight and four re-inspection places on the Registration Form for Incoming and Receiving, and sign it, indicating that the "Four Re-inspection" has been carried out.

requirements for security inspection at home

1 Before coming to the customer's home, the company requires the delivery personnel to wear company work clothes, work permits, shoe covers and emergency tools before delivering for the customer.

2 When delivering air to the door, the delivery personnel must knock on the door politely, take the initiative to show signs, use polite expressions, and wear shoe covers after obtaining the user's consent before entering the user's home;

3 come to the customer's home, replace the liquefied gas cylinder for the customer, put the cylinder in place according to the customer's requirements, and install and inspect it according to the following standards:

① Check whether the sealing rubber pad of the pressure reducing valve is intact in sequence, and then connect the pressure reducing valve, whether the pressure reducing valve, hose and connecting parts meet the safety specifications, whether the pressure reducing valve is aging and whether the vent hole works normally;

② The hose connecting the liquefied petroleum gas cylinder and the gas appliance should be a special gas pipe, and the length of the hose should not exceed 2m or be shorter than 1.5m, and it is recommended to replace it once every 18 months; Both ends of the hose must be fastened with clamps; If the hose is found to be aging (yellow and hard), damaged or cracked, it should be replaced in time; You can't use hoses through doors and walls. It is forbidden to connect the hose to the "three links";

(3), check the connection parts of the pipeline with a leak detector, and switch the angle valve of the steel cylinder for leak test;

(4), cylinders must be placed upright, and inflammable and explosive articles shall not be piled up near cylinders or gas stoves;

⑤. Ignition shall be carried out in sequence during the fire test: the ignition sequence is to open the angle valve on the steel cylinder with one hand (rotate counterclockwise, at this time, you can't leave the handwheel of the angle valve until the fire is successfully adjusted; In case of emergency, immediately close the angle valve clockwise), and open the valve of the gas cooker with the other hand. If there is no automatic ignition device, you should first strike a match and get close to the fire hole, and then turn on the switch of the gas cooker.

⑥. When the gas test is finished, the angle valve on the steel cylinder should be closed first, and then the gas appliance valve should be closed. It is strictly forbidden to close only the valves of gas appliances. ?

⑦. Inform users to check the closing of angle valves and gas appliances of liquefied petroleum gas cylinders after each gas use to prevent gas leakage.

⑧. Publicize the safe use of liquefied gas to customers, and explain the emergency response measures after gas leakage and the company's emergency call.

4. Record the security information truthfully on the delivery list, and the user will sign it for confirmation; If there are hidden dangers, issue a Notice of Hidden Danger Rectification to the customer, notify the customer in writing to rectify the hidden dangers, and the customer will sign for it.

Common sense of safe gas use at client

We have summarized many liquefied gas accidents, many of which were caused by customers' poor safety awareness, the use of non-compliant gas appliance and illegal operation. In fact, many accidents can be avoided if we master the following common sense of safe gas use.

1 The hose connecting the liquefied petroleum gas cylinder and the gas appliance should be a special gas pipe, and the length of the hose should not exceed 2 meters or be shorter than 1.5 meters, and it is recommended to replace it once every 18 months; Both ends of the hose must be fastened with clamps; If the hose is found to be aging (yellow and hard), damaged or cracked, it should be replaced in time; You can't use hoses through doors and walls. It is forbidden to connect the hose to the "three links";

2 the regulator must use a special liquefied gas regulator, and the service life of the regulator shall not exceed 5 years.

3 The service life of the gas cooker shall not exceed 8 years, and there is no tempering phenomenon during combustion; Must be equipped with flameout protection device, and the device is effective;

4 The service life of the gas water heater shall not exceed 6 years, and it must be a forced exhaust water heater, and the flue shall conform to the gas usage specification and be communicated to households;

5 if you suddenly smell a "bad smell" indoors, it means that liquefied gas is leaking. Soap water can be used to spray all the joints, and do not use open flame to check for leaks.

6 in case of air leakage (strong irritating smell), immediately close the cylinder angle valve, quickly open the doors and windows, strengthen ventilation, and prohibit all kindling from entering the room. Electric equipment such as electric lights and ventilator shall not be switched on or off at the site, and telephones, mobile phones, lighters and doorbells shall not be used to prevent explosion and fire accidents.

7 when the rubber hose falls off or cracks due to aging, which causes combustion, you should immediately turn off the valve and cut off the gas source, and the fire will be extinguished.

8 once the valve leaks and catches fire, it can be sprayed at the root of the fire with a dry powder fire extinguisher or covered with a soaked quilt, blanket, towel, etc. Close the valve with a wet towel immediately after the fire goes out.

9 if the cylinder leaks continuously, the cylinder should be moved to an outdoor open place quickly after closing the angle valve, and the emergency rescue team of the company should be informed in time, or call 119 immediately; When conditions permit, the vat can be filled with water, and the leaking point of the bottle body can be immersed in water, which can prevent the gas from diffusing into the air and causing deflagration and fire.

11. For liquefied gas cylinders, it is forbidden to use boiling water for heating, roasting and sun exposure. Don't put it horizontally, pour residual liquid and shake it violently.

4.11. When liquefied gas and gas burning appliances are arranged in the same room, the total weight of stored bottles shall not exceed 111 kg (equivalent to 2 bottles of 51 kg or more than 7 bottles of 15 kg). It is forbidden to use bottled liquefied petroleum gas in underground and semi-basement.

12, it is forbidden to live in the kitchen, don't work or sleep in the gas cylinder room, and it is forbidden to have other open fire sources in the place where liquefied gas is used.

once the liquefied petroleum gas leaks, 1L liquefied petroleum gas can quickly volatilize into gaseous petroleum gas of more than 251L, which is not easy to spread in the air and accumulate on the ground, and can form explosive gas in a large range, with minimal explosion energy and extremely destructive combustion explosion. The "11 23" explosion in Shouyang Hotpot Restaurant in Shanxi Province is a typical case of explosion and combustion caused by the leakage of liquefied gas cylinders, resulting in 14 deaths and 47 injuries. This paper analyzes and compares the accident scene caused by liquefied gas explosion in Nanjing "August 18" box lunch production site to determine the specific leakage quantity and time, and puts forward some guiding suggestions for the safety countermeasures to be taken after the leakage.

Overview of the accident site

At 7:26 am on August 8th, the facade of No.5 Building of Xinhe No.1 Village was the box lunch production point of China Construction Bank Gulou Sub-branch (hereinafter referred to as the box lunch point). The explosion caused by the leakage of liquefied gas cylinders caused five pedestrians to be injured, of which 1 were seriously injured and 4 were slightly injured. The explosion produced a powerful shock wave and strong vibration of the building, which caused the facade and adjacent buildings to be damaged to varying degrees, as shown in Figure 1. Damage to the building:

(1) The glass windows of the facade room of the fast food restaurant near the road were all shattered, and the window frames were severely distorted, and the door near the road flew 35m. The door head directly above the window outside the store was knocked down by the shock wave, the aluminum alloy frame was severely distorted, and the debris outside the house was a mess. A wall and a door adjacent to the pickled fish restaurant were knocked down, and debris was scattered all over the floor.

(2) There are two large cracks and several small cracks in the wall adjacent to the fast food restaurant, which have been displaced, so it is very dangerous to break the wall. The roof and ceiling collapsed and hit the lobby on the first floor.

(3) There are obvious signs of burning in the upper part of the indoor air conditioner. Observing the space and the top of the store, the burning phenomenon is not obvious after the explosion; There is no trace of explosion in the gas cylinder storage room, and the gas hose above the ceiling of the fast food restaurant is still intact; The oil spots on the nozzle of the stove head are still clearly visible and have not been baked by the flame.

general situation of leakage at the site

through on-the-spot investigation of the accident site, it is known that four facade houses at No.5 Xinhe No.1 Village, Gulou District, Nanjing are located on the east side of Zhenghe South Road, and the site plan is shown in Figure 2. On the right, there is a fish house with pickled vegetables, and on the left, there is a pedicure house, which is located in the downtown area. There are many residents nearby, and the situation is complicated. At the time of the incident, it was at the peak of work, and people were highly mobile. There were many liquefied gas cylinders stored on site.

this fast food restaurant has three 49kg liquefied gas cylinders, three of which are stored in a small storage room alone, two of which are connected to the bus, and the liquefied gas is distributed to four stoves for use through gas hose, and the other cylinder is reserved. After the accident, during the emergency treatment of the accident by firefighters, it was found at the investigation site that the valves of two liquefied gas cylinders connected with the gas hose were not closed. According to the field situation, it is preliminarily analyzed that liquefied gas leaks in fast food restaurants due to gas pipeline leakage. After further tests, it is determined that the leakage port is located at the joint of the stove, and there is a crack at the joint between the connecting hose and the stove. After confirmation, no other leakage port is found in the whole pipeline. It is confirmed that only this crack leads to liquefied gas leakage.