What is PVC plastic diaphragm valve

Update:14 Aug 2020

1. Working principle of PVC plastic diaphragm valve:

The plastic diaphragm valve uses a corrosion-resistant lining valve body and a corrosion-resistant diaphragm instead of the valve core assembly, and the movement of the diaphragm is used for adjustment. The valve body of the diaphragm valve is made of cast iron, cast steel, or cast stainless steel, and lined with various corrosion-resistant or wear-resistant materials, UPVC diaphragm material rubber and polytetrafluoroethylene. The lined PVC diaphragm has strong corrosion resistance and is suitable for the adjustment of strong corrosive media such as strong acid and strong alkali.

The structure of the plastic diaphragm valve is simple, the fluid resistance is small, and the flow capacity is larger than other types of valves of the same specification; it has no leakage and can be used for the adjustment of high viscosity and suspended particles. The diaphragm isolates the medium from the upper cavity of the valve stem, so there is no packing medium and no leakage. However, due to the limitation of diaphragm and lining material, the pressure resistance and temperature resistance are poor, and it is generally only suitable for 1.0MPa nominal pressure and below 100°C.

The flow characteristic of Huanqi PVC diaphragm valve is close to the quick-opening characteristic. It is approximately linear before 60% of the stroke, and the flow rate after 60% does not change much. Pneumatic diaphragm valves can also be equipped with feedback signals, stoppers and positioners to meet the needs of automatic control, program control or flow adjustment. The feedback signal of the pneumatic diaphragm valve adopts non-contact sensing technology. This product uses a membrane type propulsion cylinder instead of a piston cylinder, eliminating the disadvantage of easy damage to the piston ring, causing leakage and unable to push the valve to open and close. When the air source fails, the handwheel can still be operated to open and close the valve.


2. Overview of PVC plastic diaphragm valve:

The structure of the PVC diaphragm valve is very different from the general valve. It is a new type of valve and a special form of cut-off valve. Its opening and closing part is a diaphragm made of soft material, which connects the inner cavity of the valve with The inner cavity of the valve cover and the driving parts are separated and are now widely used in various fields. Commonly used diaphragm valves include rubber-lined diaphragm valves, fluorine-lined diaphragm valves, unlined diaphragm valves, and plastic diaphragm valves.

The plastic diaphragm valve is equipped with a flexible diaphragm or combined diaphragm in the valve body and the valve cover, and the closing part is a compression device connected with the diaphragm. The valve seat can be a weir shape or a pipe wall that directly leads to the flow channel. The advantage of Huanqi's plastic diaphragm valve is that its operating mechanism is separated from the medium passage, which not only ensures the purity of the working medium, but also prevents the possibility of the medium in the pipeline from impacting the working parts of the operating mechanism. In addition, there is no need to use any form of separate seal at the valve stem, unless it is used as a safety facility in the control of hazardous media. In the diaphragm valve, since the working medium is only in contact with the diaphragm and the valve body, both of which can use a variety of different materials, the valve can ideally control a variety of working media, especially suitable for chemically corrosive or suspended particles medium. The working temperature of Huanqi diaphragm valve is usually limited by the materials used in the diaphragm and valve body lining. Its working temperature range is about -50~175℃. The diaphragm valve has a simple structure, consisting of only three main parts: the valve body, the diaphragm and the valve head assembly. The valve is easy to quickly disassemble and repair, and the replacement of the diaphragm can be completed on site and in a short time.

3.PVC plastic diaphragm valve structure classification:

According to the structure of the plastic diaphragm valve, it can be divided into six types: house type, direct current type, cut-off type, straight type, gate type and right angle type; the connection form is usually flange connection; according to the driving mode, it can be divided into three types: manual, electric and pneumatic. Among them, pneumatic drives are divided into three types: normally open, normally closed and reciprocating.