How to inspect and repair a gate valve?

Gate valve is one kind of valve whose opening and closing part(valve disc) moves along the the vertical direction of the channel axis. It is widely used in the pipe line network to cut off the mediums flow in water treatment and supply industry, petrochemical industry, pharmacy industry, food industry, fire protection systems,etc, which is to achieve full open and close. Generally, the gate valve consists of valve body, valve seat, valve stem, valve disc, bonnet, sealing ring,etc.

But once our gate valve stop working, should we replace it or repair it? Here is going to offer you some idea about how to inspect and repair your gate valve.

Remove the fixing bolts of the upper frame of the bonnet, lift the four bolts on the bonnet to unscrew the nuts,turn the stem nut anticlockwise to make the frame separate from the valve body, then using a lifting tool to hoist the frame down and place it to a suitable position. The stem nut part is disassembled for inspection.
Take out the retaining ring at the sealing ring of the valve body, using a special tool to press down the bonnet to create a gap between the bonnet and the ring. Then take out the ring in sections. Finally, lift the bonnet together with the valve stem and valve disc out of the valve body with a lifting tool.
Clean the inside of the valve body, check the connect surface of the valve seat, and determine the maintenance method. Cover the disassembled valve parts with a special plate or other suitable cover.
Loosening the hinge bolts of the packing box on the bonnet, loosen the packing gland, and unscrew the valve stem.
Disassemble the upper and lower splints of the disc frame, take out the left and right discs, and then keep their internal parts and gaskets.