What are the reasons why the outlet pressure of a self-acting pressure regulating valve with post-valve control does not reach the desired level?
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I am replacing a control valve in the main steam pipeline of my workshop; the parameters I provided to the manufacturer are an inlet pressure of 1.5 MPa and a control range of 480–620 KPa. Currently, the inlet pressure is only 1.1 MPa, while the outlet pressure is only 0.2 MPa. The adjustment spring cannot be used to increase these pressures either; I would appreciate some advice. Thank you so much.
I called the manufacturer, who said that the inlet pressure is not high enough, which is why the outlet pressure cannot be high enough as well. I don’t think that’s the case.
Outside the adjustment range, internal debris, insufficient inlet pressure, valve damage – a probability of around 1.4 is high
Such pressure regulating valves all have a regulation range and inlet pressure requirements
Are you saying that the intake pressure must reach 1.5 MPa?
Release all the springs, without pre-tensioning, and see how high the output can reach If the change is not noticeable, the likelihood of the valve being blocked is relatively high. Otherwise, it is P1, that is, the effect of inlet pressure. For this type of pressure control valve, ask the manufacturer for the curve; it can be checked.
Let’s start by discussing the structure of valves: Self-acting pressure control valves come in balanced and unbalanced types. In the case of balanced self-acting pressure control valves, the set pressure downstream of the valve is hardly affected by changes in the pressure upstream of it. However, many manufacturers use unbalanced types in order to save costs. With unbalanced self-acting pressure control valves, the set pressure downstream is affected by changes in the upstream pressure, and the extent of this influence increases as the range of pressure changes and the valve diameter increase. The larger the diameter, and the greater the pressure changes, the more significant the variation in the set pressure downstream. Solution: 1. If the valve diameter is large, above DN100, ask the manufacturer to recalculate it; it may be necessary to replace the actuator. 2. As mentioned on the 7th floor ； Excessive steam consumption downstream of the valve results in a flow rate that cannot keep up, preventing the pressure from rising. It can be tested on-site by trying to compress the spring as much as possible using the adjustment knob; at this point the valve core should be fully open. If the pressure still doesn’t increase even when the valve core is fully open, it means the flow rate is insufficient. Consult the manufacturer to find out whether the valve core has a reduced diameter. 3. Other mechanical failures, such as a stuck valve core, can prevent the valve from opening.
Start by investigating the process: gradually increase the flow through the bypass and check whether the outlet pressure rises. If it does, remove the control valve to examine for any blockages or sticking issues, as well as to verify that the valve stem and valve core are in good condition. If the problem remains unresolved, then turn to the design aspects for further investigation； It can also be operated temporarily using manual control via a bypass.