Solutions regarding steam discharge
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I’m seeking help from experts regarding the following issue encountered in our unit: There is a steam pipeline that needs to be heated by water. In front of the water tank, there is a solenoid valve, and the opening and closing of this valve are controlled by the water temperature. When the water temperature drops below a certain level, the solenoid valve opens, allowing steam to heat the water； When the water temperature reaches a certain level, the solenoid valve closes and steam heating stops ； I’m facing this problem now: since steam is constantly flowing in the pipes, and the opening and closing of the solenoid valve are controlled by the water temperature, the valve doesn’t open frequently. As a result, a large amount of steam accumulates in the pipes, which causes the safety valve located before the solenoid valve to activate and release large quantities of steam. I would appreciate it if experts could suggest solutions. Thank you.
Adding a reliable pressure relief valve at the front will solve the problem. The pressure relief valve has sufficient shut-off capability, so no overpressure occurs even when the downstream load is zero (when the solenoid valve is closed).
Where the pipe connects to the main steam line, there should be valves installed; a regular globe valve can also serve as a pressure reducing valve, but it’s best to use a dedicated pressure reducing valve. If that’s not the case, it’s possible that the setting for the safety valve’s operating pressure is too low – the valve won’t activate when it’s in the open position, but it will activate when it’s closed.
Please describe the operating conditions on site. If the pressure is not high, you can remove both the solenoid valve and the safety valve, and replace them with a self-acting temperature control valve
I would like to ask: if a pressure relief valve is added, will the steam behind it not build up pressure over time? Our current situation is as follows: everything is normal at the start of ventilation, but after a few hours of ventilation, the pressure builds up because the solenoid valve remains closed for an extended period of time, which causes the safety valve to activate.
The steam pipeline system is supplied with steam at a pressure of 0.3 MPa, while the setting pressure of the safety valve is 0.5 MPa. Since the solenoid valves downstream are not kept open for long periods, steam accumulates, resulting in a steam pressure in the pipes that exceeds the setting pressure of the safety valve.
Where is the pressure relief valve installed? Is it at the outlet of the main pipeline, in front of the safety valve?
Near where you use steam equipment, that is in front of the solenoid valve and in front of the safety valve. Also, the setting for the pressure at which your safety valve activates has been set a bit higher. Moreover, using solenoid valves is troublesome; it offers on-off control and the load changes too rapidly, so it’s better to switch to regulated control
This post was last edited by I love engineering on 2011-11-18 at 20:16. I think installing pressure regulators won’t yield very good results. What the original poster is saying is that once the valve is closed, the safety valve will open. After the solenoid valve is closed, the pressure in the pipeline ahead of the solenoid valve should be the same as the pressure at the steam main (the pressure at the point where the main pipe meets the branch pipes) ； If the steam flow in other branches of the main steam pipe decreases, it will cause the pressure in the main pipe to rise, which in turn increases the pressure in that particular steam branch as well. So I think it’s probably because the relief valve’s set pressure is too low.
A small solenoid valve can be installed by making a hole at the bottom of the pipe ahead of the solenoid valve; its diameter should be small, ideally with effects similar to those of a needle valve. The outlet leads to a water tank, where the heating solenoid valve controls its operation – it opens when the heating solenoid valve is closed, and it closes when the heating solenoid valve is open. This valve is used to remove condensate from the pipes and to relieve pressure. (The steam pipeline is supplied with steam at a pressure of 0.3 MPa, while the set pressure of the safety valve is 0.5 MPa. Since the solenoid valve downstream is not kept open for long periods, steam accumulates, resulting in a steam pressure in the pipes that exceeds the set pressure of the safety valve.) ) According to you, the setting pressure of the safety valve is 2 KG higher than the pressure in the pipeline network; the likely cause of its activation is excessive local pressure
"A large amount of steam accumulates inside the pipes”? The heated steam pipeline is connected to the main steam pipe, and its pressure should be roughly the same as that of the main steam pipe; I don’t understand why accumulation occurs.