Problem of pressure fluctuations in the output stream after steam depressurization
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Dear colleagues, the pressure in our unit’s main steam pipeline is 0.9 MPa; it is reduced to 0.3 MPa using a control valve for use in Plant 1’s production processes. However, during operation, the pressure after reduction remains unstable, fluctuating by 0.25–0.35 MPa, and the steam flow also varies significantly, ranging from 2.5 to 5 tons per hour. When Unit 2 is in operation simultaneously (using a branch from the same steam main), the pressure remains stable after depressurization; however, once Unit 2 stops operating, the pressure of steam in Unit 1 fluctuates again. After checking the control valves and pipelines, no issues were found. It is now suspected that there is a problem with the quality of the steam – either it is not properly superheated or it contains condensate. I wonder if other sailors have encountered similar problems – what are the causes, and how can they be resolved?
It’s likely that the pressure relief control valve has poor regulating performance at low flow rates.
It’s a problem with the control valve; if it’s the piston, then it’s indeed a problem with the control valve. Doesn’t the pipeline vibrate? The pipes were vibrating at that time
Adjusting the PID parameters of the pressure relief valve should do the trick.
The steam consumption decreases under dual-load and single-load conditions, and the control curve of the control valve is not linearly proportional. Under single-load conditions, the range of adjustment falls within the region where flow changes are sensitive; it is recommended to replace it with a linearly proportional control valve.
It should be a pressure-reducing valve regulated by a piston; when the flow rate is high, the air supply remains stable, while at lower flow rates, there are fluctuations. The main issue is that the piston does not move smoothly. It is recommended to increase the frequency of disassembly and inspection, or replace it with a high-quality steam pressure relief valve. It could also be due to poor quality of the steam; if water hammer occurs, more steam traps should be installed in the pipeline ahead of the valve ； It could also be steam corrosion, with rust residues inside the pipes, which requires increasing the mesh size of the filter before the steam pressure regulator.
The valve’s sensitivity is insufficient, resulting in a large pressure drop per reduction; could trying a two-stage pressure reduction be an option?
The preliminary judgment is that it’s a steam issue; oversaturation is suspected. Will adding a buffer hydroscopic tank solve the problem?