Liquid ammonia, as a hazardous chemical, is prone to leakage accidents during production, transportation, and storage due to human error, such as overpressure, overtemperature, equipment malfunction, or corrosion. These accidents pose a serious threat to human life and may even lead to death. To effectively prevent major accidents, the following details the key inspection points, precautions, and unloading procedures before transporting liquid ammonia.
I. Inspections and Precautions Before Transporting Liquid Ammonia
Inspect the Metal Mesh:Carefully inspect the metal mesh for integrity, breaks, or severe corrosion, ensuring its structural stability.
Inspect the Hoses:Check the hoses for damage, cracks, or other defects, ensuring their integrity and safety.
Inspect the Metal Hoses and Tank Truck Connection:Confirm that the fit between the metal hose and the tank truck connection is secure and reliable, checking for leaks at the sealing surfaces to ensure a tight connection.
Check the Metal Hoses Certificate and Expiry Date:Verify the validity of the metal hose certificate and check its expiry date to ensure the hose is within its safe operating period.
Inspect Joints:Check joints for integrity, corrosion, deformation, or cracks to ensure their completeness and reliability.
Inspect Gaskets and Quick-Connect Fasteners:Ensure gaskets are intact and quick-connect fasteners are secure and reliable to prevent leaks due to fastener issues.
Inspect Transport Equipment Casing:Transport equipment should have a robust casing with strong shock absorption to cushion movement and facilitate rapid heat dissipation.
Select Suitable Internal Container Materials:Internal container materials should possess sufficient heat resistance and corrosion resistance to accommodate the unique properties of liquid ammonia and ensure safe transport.
Monitor Weather Conditions:Check weather forecasts in advance and protect liquid ammonia transport equipment accordingly. In summer, cover the equipment with sun-protective materials; in rainy weather, use waterproof materials to prevent water damage and surface corrosion; in winter, choose materials with good antifreeze properties to ensure equipment safety in low-temperature environments.
Select a Suitable Transport Route:Transport routes should avoid densely populated areas to minimize the risk of harm from liquid ammonia leaks.
Choose a Suitable Transport Route:Transport routes should avoid densely populated areas as much as possible to reduce the risk of injury from liquid ammonia leaks.
II. Preparations Before Unloading Liquid Ammonia
1. Check the Liquid Ammonia Tank Level:Before unloading, carefully check the liquid ammonia tank level and record it in detail to understand the tank's capacity.
2. Verify the Qualifications of Transport Personnel:Check whether the liquid ammonia transport personnel hold valid dangerous goods transport permits, dangerous goods escort permits, dangerous goods driver's licenses, and dangerous goods transport permits issued by the company's fire department, ensuring all permits are valid.
3. Check the Tank Truck and Protective Equipment:Check whether the liquid ammonia tank truck has obtained the necessary permits to enter the production area. Confirm that the tank truck is equipped with qualified flame arresters, fire extinguishers, grounding wires, and other protective equipment, and proceed to the loading site according to the designated route. After the tank truck is in position, stop the engine, remove the ignition key, and the driver must leave the cab. Wheel alignment is required, and the rear grounding wire must be in contact with the ground. The driver and escort personnel must wear safety helmets and work clothes and proceed to the unloading waiting area.
4.Check Unloading Procedure and Valve Status:Check the unloading procedure and valve status of all valves on the tank truck, especially ensuring the safety valves are open to guarantee a smooth unloading process.
Check Metal Hoses and Connections:Unloading personnel should first check and confirm the metal hoses and connections are intact before connecting the tank truck to the metal hoses, ensuring the interface clamps are secure and will not come loose.
Connect Static Grounding Wire:Connect the fixed static grounding wire to the tank truck, ensuring good grounding, and simultaneously secure the wheels to prevent vehicle slippage.
Check Firefighting Facilities:Check and confirm that nearby fire monitors and other firefighting facilities are in good working order to ensure timely rescue in case of an emergency.
Maintain Communication with Control Room:Unloading personnel must maintain constant communication with the control room using walkie-talkies (explosion-proof type) for timely information exchange.
Comply with Summer Unloading Regulations:If the temperature exceeds 35℃, strictly follow the relevant summer unloading regulations and take appropriate cooling measures.
Inspect and Record Metal Hoses:Carefully inspect and record the metal hoses before unloading. If any problems or defects are found in the metal hose, unloading should be stopped immediately, and the equipment should be reported for repair or replacement.
III. Key Points for Unloading Liquid Ammonia
Obey Command and Division of Responsibilities:After the tanker trucks transporting liquid ammonia arrive at the site, they must obey the instructions of the unloading personnel at the platform. The truck escort is only responsible for connecting the hoses on the truck and must not operate the equipment, valves, or other components at the unloading platform. The unloading personnel are responsible for connecting the pipelines and operating the valves.
Checking for Leaks by Opening Valves:Slowly open the gas phase inlet valve and the ammonia unloading pump inlet valve, carefully checking the system for leaks. After confirming there are no leaks, fully open the pump inlet and outlet valves and the gas phase inlet valve. After confirming that the pressure of the tanker truck and the ammonia pump system is balanced, close the ammonia pump outlet valve and start the ammonia unloading pump.
Controlling Residual Pressure in the Tank:During unloading, a residual pressure of at least 0.05 MPa should be maintained in the tank, but it must not exceed the saturation pressure of the medium at the ambient temperature. For pressure vessels being filled for the first time, the vacuum level must not be lower than 650 mmHg, or the oxygen content of the gas in the tank must not exceed 3%. Flow Rate Adjustment and Liquid Level Observation: Slowly open the pump outlet valve to adjust the flow rate, while closely observing the rise in the ammonia tank level to ensure a smooth unloading process.
On-site Monitoring and Operation:During liquid ammonia unloading, unloading personnel must remain on-site and closely observe the pressure and liquid level changes in the liquid ammonia tank and the tanker truck. After unloading is complete, stop the ammonia unloading pump and close all relevant valves.
Ventilation and Equipment Disconnection:Vent and depressurize the tanker truck. After depressurization, disconnect the feed liquid phase pipe and gas phase balance pipe from the tanker truck, and simultaneously remove the tanker truck's grounding wire to complete the unloading operation.
The above content re-describes the key points and precautions for pre-transport inspection and unloading operations of liquid ammonia. The aim is to emphasize the safety importance during liquid ammonia transportation and unloading, ensuring that operators strictly adhere to regulations and effectively prevent accidents.
