How to Maintain Diaphragm Valve?

The diaphragm valve is a shut-off valve that uses a diaphragm as an opening and closing member to close the flow channel, cut off the fluid, and separate the inner cavity of the valve body from the inner cavity of the valve cover. The diaphragm is usually made of elastic, corrosion-resistant and non-permeable materials such as rubber and plastic. The valve body is mostly made of plastic, FRP, ceramic or metal rubber lining material. It has the advantages of simple structure, good sealing and anti-corrosion performance, and low fluid resistance. It is always used for low-pressure, low-temperature, highly corrosive and suspended substance-containing media. According to the structure, there are roof type, cut-off type and gate type. According to the driving mode, there are manual, pneumatic and electric type. 

The 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 material of the diaphragm valve is cast iron, cast steel, or cast stainless steel, and lined with various corrosion-resistant or wear-resistant materials. The lining diaphragm has strong corrosion resistance and is suitable for the adjustment of strong corrosive media such as strong acid and alkali.

1. Installation and Maintenance

1) Before installing the diaphragm valve, carefully check whether the operating conditions of the pipeline are consistent with the use scope specified by this valve, and clean the inner cavity to prevent dirt from blocking or damaging the sealing parts.

2) Do not paint grease or other similar things on the rubber lining and the surface of the rubber diaphragm to prevent the rubber from swelling and affecting the service life of the diaphragm valve. 

3) Hand-wheel or transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited. 

4) When manually operating the diaphragm valve, do not use the auxiliary lever to prevent excessive torque from damaging the driving parts or sealing parts.

5) Diaphragm valves should be stored in a dry and ventilated room. Stacking is strictly prohibited. Both ends of the inventory diaphragm valve must be sealed, and the opening and closing parts should be slightly opened.

2. Failures of the Diaphragm Valves

1) Hand-wheel operation is not flexible

Reasons:

① Stem is bent.

②The thread is damaged.

Elimination methods:

① Replace the valve stem.

② Trim the thread and add lubricant.

2) The pneumatic diaphragm valve cannot be opened and closed automatically

Reasons:

① The pressure of air supply is too low.

② The tightening force of spring is excessive.

③ The rubber diaphragm is damaged.

Elimination methods:

① Increase the pressure of air supply.

② Reduce the spring tightening force.

③ Replace the diaphragm.

3) Leakage at the connection between the valve body and the bonnet

Reasons:

① The connecting bolts are loose.

② The rubber layer in the valve body is broken.

Elimination methods:

① Tighten the connecting bolts

② Replace the valve body

3.The Selection of Main Parts

There are many parts for diaphragm valves, including ferrous metals and non-ferrous metals of different grades, alloys, and various non-metallic materials. The materials used to make diaphragm valve parts are selected based on the following factors:

1) Working conditions (pressure, temperature and characteristics of the working medium). 

2) The force of the part and its role in the diaphragm valve structure. 

3) It has good processability. 

4) In the case of meeting the above conditions, there must be a lower cost. 

Material of valve body, valve cover and valve plate (valve): The valve body, valve cover and valve plate are one of the main parts of the diaphragm valve, which directly bears the pressure of the medium. The materials used must meet the Regulations of ‘Pressure and Temperature Rating of Diaphragm Valve’.