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SERVICE AND MAINTENANCE TROUBLESHOOTING VALVE LEAKS Hansen steel butt welding shut-off valves require On the rare occasion when a small valve leak is practically no service or maintenance due to the discovered, the following procedures may help: combination of polished stainless steel stems and reliable Stem seal leaks - The possibility of this occurrence O-ring stem seals plus graphite composite packing.This is based on many factors, such as frequency of use, almost entirely eliminates stem leakage, the common exercising, debris or rust on stem, etc. First, simply ailment of shut-off valves. tighten the packing nut to see if this eliminates the leak. To help ensure safety,verify the tightness of the packing If not, back seat the valve or isolate it entirely from the nut whenever the position (open or closed) is changed refrigeration system. See Stem Packing section of this on isolation shut-off valves before opening the system. bulletin. Ensuring that the packing nut is tight helps reduce the Bonnet gasket leaks- If a gasket leak is discovered at possibility that any line or system vibration may cause the bonnet-to-body interface, first bring the pressure a slight unseating of a closed valve. in the valve to zero pressure and check the bonnet bolt STEM PACKING tightness. If the leak persists, isolate the valve from the refrigeration system and disassemble the valve. Check When verifying the tightness of the packing nut, use an the gasket sealing surfaces on the bonnet and valve adjustable wrench.Extrusion of some black graphite packing body for scratches or gouges. These scratches can material along the stem is normal.If the O-ring or the adjustable sometimes be polished smooth. Install a new gasket packing ever needs replacement as evidenced by refrigerant and reassemble the valve. Evenly tighten all bolts to or oil leakage at the stem, open the valve stem firmly to the properly seat the bonnet. Repeat the pressure test. back-seat position.This separates the O-ring and packing from the system refrigerant.Remove the packing nut carefully and Bonnet O-ring leaks-Valves 5" (125mm) and larger use then use a wire hook or a small blade screwdriver to remove bonnet O-rings. If a leak is discovered at the bonnet- the packing and O-ring.Take care not to scratch the stem or to-body interface, first bring the pressure in the valve bonnet sealing surfaces.Carefully install the backup washer to zero pressure and check the bonnet bolt torque.The (11/2"-18"orl3mm-450mm only),new lubricated stem O-ring, torque recommendations are provided below. If the leak stem washer,and stem packing.Tighten the packing nut only persists, isolate the valve from the refrigeration system enough to give the handwheel slight turning friction. and disassemble the valve. Check for debris on the surfaces of the bonnet and O-ring groove in the valve VALVE SEAT body.Check for scratches and polish the surfaces.Clean To inspect or replace the valve seat disc, isolate the valve and check the O-ring for cuts, cracks and embedded from the system and safely pump out all refrigerant to zero debris.Check the bonnet and valve surface for flatness. pressure with the stem open at least one turn.Evenly loosen Occasionally, the edge of the bonnet on the valve body all bolts one to two turns.Using a screwdriver,break the seal is struck or dropped which could damage or raise the between the bonnet and valve body,proceeding cautiously sealing surface of the bonnet. This prevents the two to avoid any refrigerant which may still remain inside the sealing surfaces from being completely engaged.Remove valve body.Remove the bonnet bolts and bonnet assembly, the raised edge. Also, if not carefully re-assembled, being careful not to damage the Teflon seat disc surface. If the bonnet may have been slightly askew, preventing the seat surface in the body is marred, it may be possible proper sealing. Before reassembling the valve, clean to repair the seat by polishing with emery paper. the sealing surfaces and O-ring apply suitable grease to the O-ring. Install the bonnet, making sure the stem If the Teflon seat disc is damaged,replace the entire disc is open several turns. Evenly tighten, then torque the assembly 1/2"(13mm)thru 4"(100mm)by first removing the bonnet bolts to the specified value below. Pressure test ball retainer spring, ball bearings and anti-spin O-ring. the valve to check for leaks. Install a new disc assembly including anti-spin O-ring. Alternately, use a lathe to take a 1/64" (0.4 mm) by 45° surface cut on the Teflon seat.The 5" (125mm)thru 18" (450mm)Teflon seats can be replaced by disassembling the disc holder by loosening and removing the disc screws. Replace the Teflon ring, the upper disc O-ring in 10" (250mm) and above, and reassemble the disc. Replace body gasket or O-ring and reassemble bonnet into body using care not to damage Teflon seat surface. Be careful not to pinch the O-ring. If necessary, retain O-ring in O-ring groove by using a suitable O-ring grease. Ensure the stem is opened at least several turns. Hansen assembles valves with bonnet cap screws factory tightened as follows: 1/2" to 11/4" (13mm to 32mm)- 30 ft-Ib(41 Nm);11/2"(40mm)and 2"(50mm)-40 ft-Ib(54 Nm); 21/2" (65mm) and 3" (80mm)-60 ft-Ib (81 Nm); 4" (100mm)- 180 ft-Ib (244 Nm); and 5" to 18" (125mm to 450mm)- 200 ft-Ib(271Nm).Test the valve for leaks before returning it to service. G359d 18 NOV 2019