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What’s Diaphragm Valve?

Views: 92     Author: Site Editor     Publish Time: 2020-02-11      Origin: Site

What’s Diaphragm Valve?

Diaphragm valve is a stop valve which uses diaphragm as the opening and closing parts to close the flow passage, cut off the fluid, and separate the inner cavity of the valve body and the inner cavity of the valve cover. Diaphragm is usually made of rubber, plastic and other elastic, corrosion-resistant and non-permeable materials, while valve body is made of plastic, fiberglass, ceramic or metal rubber lining materials. It has the advantages of simple structure, good sealing and anti-corrosion performance, small fluid resistance. It is commonly used in medium with low pressure, low temperature, strong corrosiveness and suspended substance.

1. Introduction

Diaphragm valve is a new type of valve and a special type of block valve. Its opening and closing part is a diaphragm made of soft material, which separates the inner cavity of the valve body from the inner cavity of the valve cover and driving parts. Now it is widely used in various fields. 

Diaphragm valve is a kind of compression device with a flexible diaphragm or combined diaphragm installed in the valve body and bonnet. Its closing part is connected with the diaphragm. The valve seat can be weir shaped or the pipe wall through the flow channel. The advantage of diaphragm valve is that its operating mechanism is separated from the medium path, which not only ensures the purity of the working medium, but also prevents the possibility of medium in the pipeline impacting the operating parts of the operating mechanism. In addition, there is no usage of any form of separate seal at the stem, unless it is used as a safety facility in the control of harmful media. 

pneumatic TC Diaphragm Valve

In the diaphragm valve, because the working medium only contacts the diaphragm and the valve body, both of them can use a variety of different materials. Therefore, the valve can ideally control a variety of working medium, especially suitable for the medium with chemical corrosion or suspended particles. The operating temperature of diaphragm valve is usually limited by the materials used for diaphragm and valve body lining. Its operating temperature range is about - 50 ~ 175 ℃. The diaphragm valve is simple in structure and only consists of three main parts, valve body, diaphragm and valve head assembly. The valve is easy to disassemble and repair quickly. The replacement of diaphragm can be completed on site and in a short time. 

2. Working Principle and Composition

The valve body with corrosion-resistant lining and the corrosion-resistant diaphragm are used instead of the valve core components of the diaphragm valve, and the movement of the diaphragm is used for regulating. The valve body of diaphragm valve is made of cast iron, cast steel or cast stainless steel. It is lined with various corrosion-resistant or wear-resistant materials, diaphragm material rubber and polytetrafluoroethylene. The lining diaphragm has strong corrosion resistance, which is suitable for the adjustment of strong corrosive medium such as strong acid and strong alkali. 

The diaphragm valve has the advantages of simple structure, small fluid resistance, larger flow capacity than other valves of the same specification. It has no leakage, and can be used for the regulation of high viscosity and suspended particle medium. The diaphragm isolates the medium from the upper chamber of the valve stem, so it will not leak out without packing medium. However, due to the limitation of diaphragm and lining materials, the pressure resistance and temperature resistance are poor, which are generally only applicable to 1.6Mpa nominal pressure and below 150 ℃. 

The flow characteristic of the diaphragm valve is close to the quick opening characteristic, which is nearly linear before 60% stroke and little change after 60%. Pneumatic diaphragm valve can also be equipped with feedback signal, limiter, positioner and other devices to meet the needs of automatic control, program control or flow regulation. The feedback signal of pneumatic diaphragm valve adopts contactless sensing technology. The product adopts membrane type propulsion cylinder instead of piston cylinder. It eliminates the defect that the piston ring is easy to be damaged and causes leakage, which leads to the failure of valve opening and closing. When the air source fails, the hand wheel can be operated to open and close the valve.

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