A very simple but difficult question to answer——regarding the issue of high pressure leaking into low pressure
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As we all know, in petrochemical plants, equipment of various pressure levels is connected together. The design pressure of high-pressure equipment must be much higher, but when it is connected to low-pressure equipment, especially in the gas phase, it is necessary to prevent high pressure from leaking into the low-pressure area – this is for the sake of equipment safety. But in some cases, such as in the return lines of compressors, isn’t there also a situation where high pressure from the gas phase leaks into the low-pressure area? Isn’t that a risk? Please explain this question?
This backflow should have been depressurized, and its volume is relatively small; it poses no hazard.
In fact, when high-pressure fluid flows into low-pressure areas, it is usually depressurized through valves, and the pipe diameters are also different
It is dangerous to connect high-pressure gas phases to low-pressure ones; buffer equipment or pressure relief valves should be used； The return line of a compressor is generally much thinner than the main pipeline, and there is definitely a check valve in front of it, so there is no hazard.
Due to the small volume of gas, the high-pressure gas has already been depressurized as it flows through the compressor’s return line; therefore, such a problem does not exist in the compressor circuit. It has already been taken into account in the design.
It has already been depressurized through a pressure relief valve.
When the high pressure from the compressor is connected to the low pressure side (that is, the return gas), first, the volume of gas is small, so it has no significant impact on the low pressure side during normal operation. Second, safety valves are installed on the low pressure side, which will release gas automatically in case of overpressure; therefore, there is no danger. According to relevant regulations, in a high-voltage series low-voltage system, a safety valve must be installed on the low-voltage side! ! !
Whether it’s high pressure or low pressure, it enters after being depressurized; there’s nothing special about that.
Sometimes the pressure relief valve may fail, so a safety valve must be present on the low-pressure side.
The return line of the compressor is specifically designed for starting up the compressor and regulating flow; it returns from the compressor outlet to the inlet, rather than directly from the high-pressure system behind the compressor. This approach helps to prevent an excessive increase in pressure on the low-pressure side due to high pressure flowing into it. Of course, if there are issues with the system that allow high-pressure fluid to flow directly into the compressor inlet, this could also lead to dangerous situations
I haven’t dealt with this area before, but could it be controlled using a one-way valve? :lol
For example, in the return line of a compressor, isn’t it also high-pressure gas flowing into low pressure? Is there no risk in that? The return line at the compressor outlet should be equipped with a pressure control valve at the outlet; when the outlet pressure is high, the control valve opens, allowing the fluid to flow back to the compressor inlet after being depressurized (the diameter of the pipe downstream of the valve increases to match that of the inlet pipe). There is no harm; it is normal control.
In designs, there are usually buffer devices for handling the transition from high pressure to low pressure, as well as anti-riot systems, so there’s no need to worry!
There should be pressure regulation devices such as pressure relief valves, buffer tanks, and reducers, as well as safety devices like safety valves and explosion-proof membranes. :lol
The hazard of high-pressure gas entering a low-pressure system lies in the fact that this can cause the pressure in the low-pressure system to reach the limit tolerable by the equipment in a very short time, or it can disrupt the normal operation of the low-pressure system. And the series pressure from the outlet to the inlet of the press will not exhibit the aforementioned situation, provided that the press is operating properly. As long as the press is operating properly, there will be no overpressure at the inlet, and thus no danger will arise! Sometimes, the return inlet at the compressor outlet remains the main means of maintaining normal compressor operation, such as adjusting the outlet temperature and preventing compressor surging.
The return valve of a compressor can be regarded as a throttle valve; the diameter of the pipeline downstream of the valve is large, allowing for safe pressure reduction. Generally, when the compressor is started, the pressure in the circuit is reduced step by step, so no problems occur. However, in emergency situations, such as when there is a large pressure difference between the high-pressure side and the low-pressure side, care must be taken regarding the opening degree of the valves when opening the circuit. Many manufacturers have experienced accidents involving shutdown for pressure relief or explosions on the low-pressure side due to oil or water discharge.
In a high-pressure series low-pressure system, a safety valve should be installed on the low-pressure side. The pressure in the compressor’s return line is not determined by the compressor’s outlet pressure, but rather by the pressure drop in the return line and the pressure in the inlet line! A safety valve should also be installed on the return line to prevent overpressure in that line or in the inlet line in case the valve there is accidentally closed. Last edited by lss_bms on 2009-4-20 09:47
Comparing high voltage with low voltage is dangerous; in fact, such devices are equipped with regulating valves at their high-voltage outlets. Under normal circumstances, these regulating valves are not fully open, and they also have the function of throttling and reducing voltage
It is inevitable for the process pipelines to be connected from high pressure to low pressure; pressure must be released from high to low. However, depending on the diameter of the pipes and the level of resistance, it is necessary to control the flow rate and volume of the fluid, otherwise accidents may occur in the pipes and equipment due to excessive pressure buildup. This is what is referred to as high pressure leaking into low pressure systems.
Current popular analysis methods such as HAZOP can be used to analyze and solve it! When dealing with high pressures and low pressures, it’s not just about reducing pressure; backflow prevention and safety valves also need to be taken into consideration sometimes. There is another situation that is often overlooked in the design process, leading to serious mistakes. For example, in the case of two booster pumps, one of them needs to be repaired; the outlet check valve shows signs of leakage, but the amount of leakage is very small. Can the pump still be repaired under these conditions? ! It depends on the design pressures before and after the pump; if the pressure levels are different, the pump inlet valve cannot be closed, which means the pump cannot be isolated for maintenance. Something happened at a company’s power plant before; it’s a lesson! Therefore, hazard identification is very important, and the people involved in the identification are even more crucial!
Generally, on the low-pressure side, there are buffering and safety devices such as check valves and safety valves