b'MULTI-WAY BALL VALVES - BV509/509A, BV2057, BVL50~L54, SL8142-FZ SERIESBall valves can trap pressurised fluid in ball cavity when in the closed position. Prior to maintenance, relieve the line pressure and put ball in the open position.A good program of inspection and maintenance cannot be overstressed. It is recommended that the valve be periodically and at least partially stroked/function tested to ensure the valve functions and prevent seizure/sticking of any mating surfaces. Duration depends on service, criticality etc. However it also must be factored in that if there are impurities or particulates in the line each operation could reduce seat life proportionately. Periodic inspection of critical leak-path areas such as body/bonnet joint, end connections, seating surfaces, and around the stem packing should be a requirement.The most common area for leakage is around the stem packing, this is usually due to wear and can normally be stopped by adjusting the packing. This procedure is performed by turning gland bolts or nut in very small increments until leakage stops. If leakage cannot be halted by adjusting packing, repacking of the valve is indicated. With self-wiping ball/seats, APV valves have a long, trouble free life, and maintenance is seldom required. But, when necessary, valves may be refurbished, using a small number of components, none of which require machining.APV valves are designed for easy service and assembly in the field. The following checks will help to extend valve life, or reduce plant problems.APV Ball Valves utilise live-loaded stem seals featuring Belleville washer (disc springs) that maintain constant pressure on the stem seal area even under a wide range of pressure and temperature fluctuations. However, regular stem packing tightening is required. Occasional replacement of packing may also be required dependant on service conditions.4.1 GLAND PACKINGIn case of slight leakage from the gland, nut can be lightly tightened up without effecting torque. For torques, see Appendix A. Do not over tighten as it will increase torque of the valve and could result in damage. If there is leakage, open and close the valve 30 to 60, if there is still leakage, replace packing as per 4.1.1.Do not attempt to repack or replace stem while the valve is in service! Only graphite packing and gaskets are to be used for oil & gas service, PTFE is not firesafe. 12 Flowturn - Installation, Operation and Maintenance Manual'