What is the principle of a self-acting control valve? Is there a difference between pressure-relieving and pressure-discharging types?
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1. What is the principle of a self-acting control valve? 2. What are the situations in which pressure measurement before the valve and pressure measurement after the valve are used respectively? 3. Why is there a difference between pressure-reducing and pressure-relieving types? Everyone, please participate more; I will give scores.
A self-acting control valve is called \"self-acting\" not because it generates its own energy; since no perpetual motion machine has yet been invented, this type of control valve requires external energy supply. This energy is obtained from the pressure of the medium being controlled – specifically, a pressure balance is achieved through the pressure of the medium itself and the elastic force of the compression spring preset in the control valve, which in turn causes the valve stem to move up and down. Since no additional external supply is needed for this energy, it is referred to as a self-acting valve. Taking pressure readings in front of the control valve involves comparing the pressure there with that of the valve’s spring, thereby maintaining stability in the pressure ahead of the valve. Similarly, taking pressure readings behind the valve serves to keep the pressure there stable as well. If pressure is measured in front of the valve, then it functions as a pressure relief valve: when the pressure exceeds the level set by the compression spring, the control valve opens to release pressure. If pressure is taken after the valve, it is a pressure stabilizing valve; it will open to supply additional pressure when the pressure drops below the set value of the control valve.
Taking pressure readings before the valve is done to maintain a constant pressure there, while taking pressure readings after the valve is done to maintain a constant pressure there as well? What does pressure relief mean?
In my understanding, the term \"pressure relief\" or \"pressure stabilization\" does not refer to self-acting control valves; rather, it relates to the operational requirements dictated by the process. The purpose of installing a self-acting control valve is to maintain stable pressure levels of the medium used in subsequent equipment, or to ensure the safety of the pressure of the medium in the pipelines ahead of the control valve. When the pressure exceeds the specified limits, the control valve opens to release pressure, thereby achieving pressure relief.