Questions regarding pipeline pressure regulation

This post was last edited by Qingcheng Jun on 2018-7-16 08:53 to correct the incorrect statements from a few days ago. I didn’t pay close enough attention to see that the pressure monitoring point is in front of the control valve; regulation is therefore based on the pressure before the valve. If the pressure before the valve is high, the valve is opened to release air downstream; if the downstream system cannot handle that amount of flow, the pressure there will rise, and the safety valve may then activate. This regulation is a bit strange – it uses a valve at the back to adjust the pressure upstream, and if the upstream flow rate cannot be controlled, then this regulation becomes very difficult. It provides some level of protection here, but the most effective way to achieve balance is by regulating the flow rates upstream and downstream

This post was last edited by ylb913 on 2018-7-14 08:18. This control valve is used to maintain the pressure before the valve; the pressure after the valve should decrease under normal conditions. However, this control valve cannot regulate the pressure after the valve. If no flow is required downstream, it may be difficult to keep the pressure there stable due to potential leaks from the control valve, and it is therefore the safety valve that ensures the pressure does not rise too high downstream. The stability of subsequent pressure depends on the basic balance between exhaust gas at the back and supply gas at the front. Otherwise, if too much air is supplied at the front, overpressure will inevitably occur at the back ； If the air supply to the front is reduced, the pressure at the back usually also decreases, but it depends on whether there are mechanisms in place to maintain pressure at the back.

Once the pipeline network is stabilized at 1.8 Mpa, the safety valve no longer activates

1. It is very important to select the right control valve; at least two process parameters need to be considered. 2. The pressure difference before and after the valve should not be too large, as fluctuations may occur. 3. Regularly adjust the safety valve!

1. This control valve is a back pressure valve; it merely regulates the pressure in front of the valve. 2. The system can operate stably provided that the pressure at the back, at 1.8 MPa, allows for stable control of the system downstream. 3. If the pressure in the upstream system rises suddenly and rapidly, it may result in delayed pressure relief, causing the safety valve to activate

This requirement makes the control valve serve a dual purpose; within certain pressure ranges in front of the valve, if things go well, the pressure behind the valve – that is, the pressure drop across the control valve – will meet the pressure drop requirements of the subsequent piping.

The control valve on the pipeline – as its opening changes, the resistance changes – can only alter the pressure downstream, not the pressure upstream.

As long as the control valve CV is set correctly, there will be no problem

It becomes simple to understand: a regulating valve is placed after the control valve and before the safety valve, with another regulating valve for pressure regulation in the reverse direction added as well.