Valve common faults and treatment

Writer： admin Time：2024-06-26 14:47:58 Browse：5℃

Valve common failures and processing:

　　First, the valve body leakage:

　　Causes:

　　1. The valve body has sand holes or cracks

　　2. Valve body patch welding cracks

　　Treatment:

　　1. on the suspected crack grinding, with 4% nitric acid solution etching, such as cracks can be displayed

　　2. Gouge the cracks at the patch processing.

　　Second, the valve stem and its with the silk nut thread damage or broken stem head, stem bending.

　　Causes:

　　1. Improper operation, excessive switching force, limit device failure, over-torque protection is not acted upon.

　　2. Thread fit is too loose or too tight

　　3. Too many operations, too long service life

　　Handling:

　　1. Improve the operation, not too much force; check the limit device, check the over-torque protection device

　　2. Choose the right material, assembly tolerance meets the requirements

　　3. Replacement of spare parts

　　Third, the valve cover combined surface leakage:

　　Causes:

　　1. Bolt tightness is not enough or tightening bias

　　2. Gasket does not meet the requirements or gasket damage

　　3. Combined surface defects

　　Treatment:

　　1. Retighten the bolts or make the door cover flange clearance consistent

　　2. Replace the gasket

　　3. disassembled to repair the sealing surface of the door cover

　　Fourth, the valve leakage:

　　Causes:

　　1. Closing is not tight

　　2. Combined surface damage

　　3. Valve spool and stem clearance is too large, resulting in valve spool sagging or bad contact

　　4. Poor sealing material or spool jamming.

　　Handling:

　　1. Improve the operation, re-open or close

　　2. Valve disassembly, spool, seat sealing surface regrinding

　　3. Adjust the valve spool and stem clearance or replace the valve flap

　　4. Valve disassembly, to eliminate jamming

　　5. Replacement or surfacing welding sealing ring

　　Five, the valve spool and stem detachment, resulting in switch failure.

　　Causes:

　　1. Improper repair

　　2. Valve spool and valve stem combination is corroded

　　3. Switching force is too large, resulting in the spool and stem combination is damaged

　　4. Spool check gasket loosening, wear and tear of the connection part.

　　Handling:

　　1. Pay attention to the inspection when overhauling

　　2. Replace the stem with corrosion-resistant material.

　　3. Operation is not strong switch, or not fully open after continuing to open the valve inlet pumps

　　4. Check and replace the damaged spare parts

　　Sixth, the valve spool, valve seat cracks:

　　Causes:

　　1. Poor quality of bonding surface surfacing

　　2. Large temperature difference between the two sides of the valve

　　Treatment:

　　Cracks in the patch welding, according to the provisions of the heat treatment, turning, and grinding.

　　Seven, the valve stem lift does not work or switch does not move.

　　Causes:

　　1. Cold closed too tightly after heat expansion or fully open too tightly

　　2. The packing is too tight

　　3. Valve stem clearance is too small and swelling

　　4. Valve stem and silk mother with too tight, or with the silk buckle damage

　　5. Packing pressure cover pressure bias

　　6. Door stem bending

　　7. Medium temperature is too high, poor lubrication, serious corrosion of the valve stem

　　Handling:

　　1. Try to open the valve slowly after heating the valve body with force or close the valve when it is opened sufficiently and tightly.

　　2. Slightly loosen the packing gland and then try to open.

　　3. Appropriately increase the valve stem clearance

　　4. Replace the valve stem and silk mother

　　5. Re-adjust the packing gland bolts.

　　6. Straighten the stem or replace it.

　　7. Use pure graphite powder as lubricant for the valve stem.

　　Packing leakage.

　　Reason:

　　1. Packing material is not right

　　2. Packing gland is not pressed or pressed bias

　　3. Incorrect packing method

　　4. Valve stem surface damage

　　Handling:

　　1. Correct selection of packing

　　2. Check and adjust the packing gland to prevent pressure bias.

　　3. Add packing according to the correct method

　　4. Repair or replace the valve stem