What are the materials of the diaphragm valve? How to maintain the diaphragm valve? How to solve common faults of diaphragm valves?

The structure of the diaphragm valve is very different from that of ordinary valves. It is a new type of valve and a special form of shut-off valve. Its opening and closing part is a diaphragm made of soft The inner cavity of the cover and the driving part 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.

Diaphragm valve is equipped with a flexible diaphragm or combined diaphragm in the valve body and valve cover, and its closing part is a compression device connected with the diaphragm. The valve seat can be weir type or straight-through type.

The advantage of the 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 impacting the working parts of the operating mechanism. Additionally, no separate seal of any kind is required at the stem, except as a safety feature 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, so the valve can ideally control a variety of working media, especially suitable for chemical corrosive or suspended particles. medium.

The operating temperature of the diaphragm valve is usually limited by the materials used for the diaphragm and valve body lining, and its operating temperature range is about -50 to 175 °C. The diaphragm valve has a simple structure and is only composed of three main parts: the valve body, the diaphragm and the valve cover assembly. The valve is easy to disassemble and repair quickly, and the replacement of the diaphragm can be done on site and in a short time.

Diaphragm valve material:

Lining material (code), operating temperature (℃), suitable medium

Hard rubber (NR) -10~85℃ Hydrochloric acid, 30% sulfuric acid, 50% hydrofluoric acid, 80% phosphoric acid, alkali, salts, metal plating solution, sodium hydroxide, potassium hydroxide, neutral saline solution, 10% Sodium hypochlorite, warm chlorine, ammonia, most alcohols, organic acids and aldehydes, etc.

Soft Rubber (BR) -10~85℃ Cement, clay, cinder ash, granular fertilizer, solid fluid with strong abrasiveness, various concentrations of thick mucus, etc.

Fluorine rubber (CR) -10~85℃ Animal and vegetable oils, lubricants and corrosive mud with a wide range of pH values.

Butyl rubber (HR) -10~120℃ Organic acids, alkalis and hydroxide compounds, inorganic salts and inorganic acids, elemental gas alcohols, aldehydes, ethers, ketones, etc.

Polyvinylidene fluoride propylene plastic (FEP) ≤150℃ Hydrochloric acid, sulfuric acid, aqua regia, organic acid, strong oxidant, alternating concentrated acid, alternating acid and alkali and various organic acids except molten alkali metals, elemental fluorine and aromatic hydrocarbons solvent, etc.

Polyvinylidene fluoride plastic (PVDF) ≤100℃

Polytetrafluoroethylene and ethylene copolymer (ETFE) ≤120℃

Meltable polytetrafluoroethylene plastic (PFA) ≤180℃

Polychlorotrifluoroethylene plastic (PCTFE) ≤120℃

Enamel ≤100℃ Avoid sudden temperature change except hydrofluoric acid, concentrated phosphoric acid and strong alkali.

Cast iron without lining Use temperature according to diaphragm valve material Non-corrosive medium.

Stainless steel unlined General corrosive media.

Maintaining Diaphragm Valves

1. Before installing the diaphragm valve, carefully check whether the operating conditions of the pipeline are in line with the specified range of use of the valve, and the inner cavity should be cleaned to prevent dirt from getting stuck or damaging the sealing parts.

2. Do not paint the surface of the rubber lining layer and rubber diaphragm with grease to prevent the rubber from swelling and affecting the service life of the diaphragm valve.

3. The handwheel or transmission mechanism is not allowed to be used for lifting, and collision is strictly prohibited.

4. When operating the diaphragm valve manually, the auxiliary lever should not be used to prevent damage to the driving parts or sealing parts due to excessive torque.

5. Diaphragm valves should be stored in a dry and ventilated room, and stacking is strictly prohibited. Both ends of the stock diaphragm valve must be sealed, and the opening and closing parts should be in a slightly open state.

Solve common faults of diaphragm valves

1. The operation of the handwheel is not flexible: ①The valve stem is bent ②The thread is damaged ①Replace the valve stem ②Treat the thread and add lubricant

2. The pneumatic diaphragm valve cannot open and close automatically: ①The air pressure is too low ②The spring force is too large ③The rubber diaphragm is damaged ①Increase the air supply pressure ②Reduce the spring force ③Replace the diaphragm

3. Leakage at the connection between the valve body and the bonnet: ①The connecting bolt is loose ②The rubber layer in the valve body is broken ①Tighten the connecting bolt ②Replace the valve body

Post time: Aug-19-2022