Do pipelines for transporting liquid ammonia need to be equipped with safety valves?
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Question: Do pipelines for transporting liquid ammonia need to be equipped with safety valves? If necessary, what should be the setting for the opening pressure of the safety valve? Temperature range (–10～40)
According to the regulations, safety valves should be installed in the liquid ammonia delivery pipelines between the two isolation valves. The function of a safety valve is to prevent overpressure in the pipes caused by high temperatures during accidents. As for the starting pressure, it depends on the design pressure of the piping system.
Safety valves must be installed, but in engineering design, the outlet pipeline of the safety valve is generally not connected directly to the atmosphere to avoid pollution; if the enterprise has an ammonia recovery system, the outlet pipeline of the safety valve is usually connected to the inlet of the ammonia absorption tower or the inlet of the ammonia water tank. The setting pressure of the safety valve is determined in accordance with the relevant provisions of the \"Regulations on Safety Supervision of Pressure Vessels\", and it should be less than or equal to the design pressure.
Based on actual production operations, it is too troublesome to install safety valves on the liquid ammonia pipelines that feed into the system; this is mainly due to the complexity involved in installing the piping for venting. The best solution is to install them on the buffer tank, as this makes implementation easier.
It is best to install the safety valve on top of the liquid ammonia buffer tank, and then connect the safety valve to the atmospheric pressure tower.
A safety valve must be installed; the original ammonia pipeline design in our company did not include one. As a result, once the valves at both ends were closed, the pressure exceeded twice the design value and continued to rise. Fortunately, it was detected and addressed in time; otherwise, the consequences would have been severe. Safety valves are currently being purchased.
The installation of safety valves on liquid ammonia pipelines is primarily aimed at ensuring that, in the event that both end valves of the pipeline are closed during shutdown, there is a safety valve in place to prevent safety incidents caused by an increase in pressure within the pipeline due to rising temperatures If the valve on the pipeline leading liquid ammonia into the buffer tank is not closed when the tank is parked, it is acceptable not to install a safety valve, but a safety valve must be installed on the buffer tank itself.
If the saturated vapor pressure of ammonia at 40 degrees is around 17 kilograms, then the system design pressure is set at 17. Should the safety valve value be set at 17, or at 1.05 to 1.2 times that amount?
A painful lesson. In the 1980s, during a night shift at our factory, the valves in the production tank were shut off due to ammonia theft, which caused the ammonia release pressure to rise rapidly and far above 1.6 MPA. This caused an explosion of the valve for 25 kilograms of ammonia in the storage tank, resulting in a leak of 800 kilograms of liquid ammonia, with extremely severe consequences.
Liquid ammonia pipelines generally do not have safety valves; safety valves are installed on the containers connected to the pipelines. Regulations prohibit the storage of liquefied gases such as liquid ammonia in pipes with both ends sealed.
Safety valves are required to be installed on the storage tanks according to regulations – didn’t you install them? I want to know that if a safety valve is installed on the pipeline and its setting pressure is set at 16 kilograms, should it be set at 1.05 to 1.2 times that value?