GUIDELINES FOR HANDLING VALVES WITH CARE
1. Before mounting valves:
Before mounting valves, be sure that adequate valves have been prepared to exactly meet the service conditions including the maximum design pressures and temperatures. Foreign objects such as sands or scales may be left in the pipes, and care should be taken to remove all of them by filters or strainers to protect valves seat surfaces during subsequent valve commissioning.
2. Mounting valves:
On mounting valves, clean the inside of pipes again so that no welding spatters, chips, scales or sands are left. For installation of flanged end valves, flange bolts should be tightened alternately and diagonally. Where extraordinary external forces such as piping stress may be applied to the flanges of valves being mounted, provide valve supports or any other adequate protective measures.
3. Retightening valves glands:
When leakage is detected from the gland area while the valve is being in service, the gland should be immediately retightened. Tighten the gland slowly and gradually until the leakage stops, while rotating the valve hand wheel. In case the valve operating torque has been found considerably increased after these procedures, it is recommended to replace all packing rings at the time of valve maintenance.
4. Replacing packing rings:
It is recommended to replace packing rings during valve maintenance operation, but never while the valve is being pressurized in service, except the line pressure is reduced to the atmospheric level. If leakage from the gland area cannot be stopped by retightening the gland, operate the valve to its full open position and add a few packing rings or replace packing rings utilizing sealing function of these backseats. Sealing function of backseats is sometimes disturbed due to rust or other foreign objects trapped inside. It should be carefully checked before adding or replacing packing rings that backseats function properly. When the valve is highly pressurized, it sometimes causes danger to replace all of packing rings. In this case, adding a few new rings or replacing a few rings on top of the packing chamber is recommended as a first aid solution. For replacement of packing rings, first remove the gland bolts and then packing rings. Clean the packing chamber and the valve stem. After checking that all sliding parts are in good condition, securely install new packing rings. Press new packing rings lightly a few times with the gland and then evenly tighten the gland.