142021.04
Different Types of Pressure Control Valves Part II

Pneumatic pressure control valves are used to regulate pneumatic pressure in a system. When system is below a set value pressure, pressure control valves allows air inlet, and vice versa.

There are different types of pneumatic pressure control valve, such as
1.  Relief valve
2.  Sequencing valve
3.  Counterbalance valve
4.  Safety valve
5.  Unloading valve

Most valves are normally closed status, except pressure reducing valve. All of the above pressure regulating valves require a restriction to reach the set pressure value. An exception is the air pilot pressure control valve, which relies on an external pressure source which actuates a diaphragm and produces a desired flow rate or pressure. The external pressure source can come from an electronic pressure regulator or a manual pressure regulator. In certain medical device, flow rate must be kept constant without large fluctuation, therefore a stable and repeatable pressure control valves are critical in some applications.

Here we will be introducing you different types of pneumatic pressure control valves:
Pressure Relief Valves
It is important to restrain the pneumatic pressure in a system , otherwise the system may get damaged by high air pressure and it may cause hazardous event. A pressure relief valve avoid this hazardous event by setting a maximum limit of pressure in a system by relieving the extra air pressure when system pressure gets above this limit. Cracking pressure is a term that defines this pressure limit. Pressure differential or the pressure override means that difference between cracking pressure and the full pressure in the system. KaoLu provides different types of proportional pressure relief valves and please refer to our website for further infomration.

Sequencing Valves
Sequencing valves are normally closed two-way valves, and they regulate the sequence in a circuit. Similar to a direct-acting relief, its spring chambers are drained externally. A sequencing valve allows pressurized gas and fluid to flow to a second function only after a priority function has been completed. When closed, a sequence valve allows gas to flow freely to the primary circuit. The sequencing can be achieved by using different sizes of cylinders according to the load they must displace. Sequence valves permit reverse flow from the secondary to the primary circuit. However, sequencing action is provided only when the flow is from the primary to the secondary circuit.

Pressure-Reducing Valves
Pressure-reducing valves are used to reduce the inlet primary pressure to the desired lower secondary pressure. It is usually a 2/2 way valve. There are 2 working principles of pressure reducing valves: pilot operated and direct acting. Direct acting valves limit the maximum pressure in the downstream pressure, regardless of fluctuations in the primary pressure. The difference between pressure reducing valve and the relief valve is that it is normally closed and that the valve can sense the outlet pressure and when the outlet pressure reaches the desired value it will close and the extra gas bleeds through side. With the pilot operated reducing valve, the internal spool is positioned at which the flow through the main valves equals the required amount. The valve will closes when there is no flow required. This type of valve has a wide range of adjustment of spring than direct-acting valve and has a higher repeatability. Here KaoLu provides proportional pressure control valve (also known as air pressure control valve)  from 29 psig up to 1015 psig with resolution fo 0.25% F.S of accuracy. Pleae also visit our youtube channel for further demonstration.

Counterbalance Valves
Counterbalance valves are used to counterbalance a weight in a circuit. As the name suggests, it is used to counterbalance a force or counteract a weight, applications such as keeping the press from free falling. One end of the cylinder is connected to the primary port, whilst a direction valve is connected to the other port of the valve. Pressure is set to a value higher than the pressure required to keep the press (load) from falling. As the load is raised, the integral check opens to allow the cylinder to retract. If necessary to release back pressure, the counter-balance valve can be operated from distant. When the cylinder extends, the valve open and its secondary port is connected to reservoir. When the cylinder retracts, it doesn’t matter that load pressure is felt in the drain passage because the check valve bypasses the valve’s spool.