Pressure control valves, also called pressure valves in short, can control the pressure to meet the force and torque of actuators. There are several types of pressure control valves, like safe relief valve, pressure reducing valve, sequence valve, safety valve and etc. In this article, we will have a brief introduction of different pressure control valves. 1. Relief Valve The main function of relief valve is to keep hydraulic system stable and safe, preventing the overloading of system. 2. Sequence Valve Sequence valve can control the sequence of actuator by changing the pressure in hydraulic system. It has almost the same structure and working principle as the relief valve. The main difference lies in that the outlet of sequence valve is not connected to tanks. In this way, the internal leaking oil cannot channel directly to the oil chamber with pipeline, but by using a special pipeline instead. 3. Pressure Reducing Valve The pressure reducing valve consists of two parts: pilot valve and main valves. Its major function is to adjust oil pressure. The high-pressure oil enters into oil mouth, goes through the path of spool and orifices, then comes out from outlet of pressure reducing valve in a lower pressure state. In a short conclusion, although there are many varieties of pressure control valves, their fundamental purpose is the control of oil pressure.

Butterfly valve owns simple and compact structure with light weight. It can be easily and quickly operated by a 90° rotation. In addition, it has good performance on fluid control. The thickness of disc is the only resistance when the valve is in fully open condition, thus the flow resistance of butterfly valve is very small and can cause a minimum pressure loss to application. Due to its characteristic structure, butterfly valves are more suitable for large diameter valves. They are widely used in oil & gas, water treatment, petrochemical, as wells as thermal power station’s cooling water system. There are metal to metal sealing and soft sealing for butterfly valves. Although it does not has sealing performance as good as soft seal, metal to metal sealing butterfly valve can work in wider temperature range and application with particulates. Also, in terms of connection type, butterfly valves can be divided into wafer type butterfly valve and flanged butterfly valve. In conclusion, butterfly valves have advantages of good sealing performance, light weight, convenient operation, wide and flexible applicability, relatively lower cost and so on.

Features of underground fully welded ball valve 1. Due to its structure with minimum bolt connection, the valve often has light weight. 2. The valve stem is made of stainless steel with two anti-blowout o rings to ensure the operation. Its upper container can be replaced. Thus, buried fully welded ball valves can have long service life. 3. There are two mainly connection type, welded and flange connection. Strengths of underground fully welded ball valve 1. Emergency grease sealing system In case of leaking caused by application objects or fire accident, the emergency grease sealing system can ensure a temporary sealing by injecting grease into seat through grease gun. 2. Reliable stem sealing: Besides standard sealing ring, there is an additional O-ring in the packing gland to double secure the reliability. 3. Full bore and reduced diameter Full bore or reduced bore are available for users. 4. Extended stem option The valve stem can be extended according to customer’s actual needs, which is especially suitable for underground application. 5. Easy operation With superior self-lubricating property and small friction, the valve torque can be very small for easy operation.

The main differences between electric butterfly valve and electric gate valve lie in structure, operation time, size, price, sealing performance and so on. In this article, we will discuss these differences in detail. 1. Compared to gate valve, electric butterfly valve owns simpler structure, smaller volume, lighter weight, so smaller installation space. 2. Butterfly valve’s operation time is shorter and its flow resistance coefficient smaller. 3. Electric gate valves can handle higher pressure and create a better sealing performance than electric butterfly valves. 4. Electric gate valves are only suitable to cut off the flow, but electric butterfly valves can adjust the flow and cut off flow at the same time. 5. Unlike electric butterfly valves, electric gate valves can work in higher temperature and pressure conditions because of its wear ability. 6. Overall, electric gate valves are more expensive than butterfly valve. 

The pneumatic cut-off ball valve is equipped with a stroke limit switch, a solenoid valve, a pressure reducing valve and a 0.4-0.7 Mpa air source, which can realize the switching operation and send out two passive contact signals indicating the valve switch. Actuators can be divided into two types: single-acting actuators and double-acting actuators. The unique advantage of single-acting actuators is that in the event of a power failure, the pneumatic shut-off ball valve will automatically open or close according to system requirements. Pneumatic cut-off valve is widely used in chemical, petroleum, textile, electric power, food and pharmaceutical, refrigeration, aviation, aerospace, papermaking and other industries. It can not only control gas, liquid and vapor media, but also can be applied to sewage control. Characteristics of pneumatic cut-off ball valve 1. The fluid resistance is small, the ball valve is one of the valves with the smallest fluid resistance. Even if the ball valve is reduced, its fluid resistance is very small. 2. Thrust bearing can reduce the friction torque of the valve stem and make the valve stem smooth and flexible. 3. Good valve seat sealing performance. Sealing rings are made of Teflon and other elastic materials for excellent sealing work. In addition, with continued high and medium pressure, the sealing capacity of the ball valve will increase. 4. Reliable valve stem sealing performance. Because the valve stem itself can only perform rotary motion instead of lifting movement, the packing seal of the valve stem is not easy to be damaged, and its sealing performance will be better as the medium pressure increases. 5. Due to the good self-lubricating performance and small friction loss of Teflon and other materials, the pneumatic cut-off ball valve can have a longer service life.

Generally speaking, we have five main principles for valve electric actuator selection.   1. Operation torque is one of the most critical parameters in selecting actuator. We should bear in mind that the electric actuator’s output torque should be 1.2~1.5 times larger than the maximum valve operation torque.   2. We should control the opening and closing speed of valve by regulating the output speed of actuator in a proper range, otherwise it will appear water hammer easily.   3. There are two kinds of master structures to operate the trust of electric actuator: one is not configured with trust plate but outputting the torque directly, while the other one is outputting the switched torque by stem nut.   4. The rotation numbers of output shaft is related to nominal diameter, stem pitch and number of starts. And the formula is M=H/ZS. (M is the total number of rotation number, H is the operation height of the valve, S is the stem pitch and Z is the number of starts)   5. Valve electric actuator has its own special requirements and it must be able to limit the torque and axial force. Normally, electric actuator is equipped with coupling to limit the torque. After the standard of an electric actuator is determined, the torque is also determined.