The very frequent operation of the valve may lead to slight leakages through gland packing. Tighten the eye bolt nuts equally on both sides to stop the leakage. This sequence should be repeated a few more times. After a period of time you may have to add one or two more glands packing in the stuffing box. To add the gland packing rotates the hand wheel in anti-clockwise direction in full open position. All gate and globe valves are provided with back seating arrangement in full open position. Remove the eye bolt nuts, lift the gland bush and gland flange in upward direction and add the required nos. of gland packing.
Change of Gland Packing:
When the valve is kept in service or in the store for considerably long time, as the gland packing is in compressed position for a long time, it loses its compressibility and becomes hard. It does not hold the pressure even after further tightening. At this stage there is no alternative than to replace the old packing with a new one.
The method of replacing gland packing is similar as described in 3 (a). Old gland packing should be removed by using angular scriber and replaced with new packing of correct size having open ends placed 180 with each other.
If the valve is installed in running pipeline, then precautions must be taken during replacement of gland packing under pressure. There should not be any leakage through gland when valve is in back seat position. In many cases back seat portion of spindle and bush get damaged due to hard foreign particles entering the pipeline and coming in contact with seat surface and back seat area during operation of valve.
It is not advisable to change the gland packing if some leakage is observed in gland packing when valve is in back seat position. In such cases valve should be dismantled and back seat should be repaired.
Cleanliness and lubrication of spindle:
The spindle above gland packing area is always exposed to open atmosphere where a lot of dust and adverse weather conditions can damage the surface of spindle. For smooth operation of valve, threaded portion of spindle must be protected from dust and proper lubrication must be provided periodically. Grease should be applied by grease gun through the grease nipples provided for lubrication of yoke sleeve collar.
Normal life of the valve is designed for years together but there are some factors, which reduce the life of valve considerably. Improper storage, contamination of hard particles in the pipeline and lack of periodic maintenance can cause reduction in valve life considerably.
Dismantling and Servicing Instructions for Gate Valves:
Loosen the body/bonnet joint stud/nuts and remove from body, loosen the eye bolt nuts, rotate the hand wheel in clockwise direction. Wedge will come down to closed position. Further rotate the hand wheel in same direction, bonnet assembly will rise in upward direction. Continue the same till spindle comes out of threaded portion of yoke sleeve. Lift the bonnet assembly to separate it from body. Hold the spindle portion above body with left hand and pull it upward by hammering gently on topside of body surface beyond gasket area. The spindle along with wedge will come out of body. Observe the condition of seat portion and interior portion of body.
Clean body interior portion and seat surface thoroughly with suitable cleaning liquid check up for any scratches on seat ring surfaces. Minor scratches should be removed by lapping with emery paste with the help of body seat lapping fixture.
If the scratches are deep which cannot be removed by lapping, further machining may be required. Threaded seat rings are machined with ‘Right Hand’ threading and can be removed from body with the help of lugs provided. Where seat rings are seal welded to the body, complete body should be loaded on machine for further rectification.
Similarly minor scratches on wedge surface should be removed by lapping with emery paste. Deep scratches should be removed by machining and lapping. In case wedge surface is heavily damaged the entire seat surface should be machined and machining and lapping should follow one layer of hard facing weld deposition as per body size.
Remove old gland packing from bonnet stuffing box. Clean the bonnet surface from inside; lap the degree surface of back seat bush with the help of suitable fixture or by spindle itself. Clean threaded portion of the spindle. Polish the non-threaded portion of spindle on lathe machine or grind if possible. Clean threaded portion of yoke sleeve and apply grease with the help of grease gun through grease nipple provided on the bonnet top.
Change the body bonnet joint gasket and assemble the valve. Put new gland packing of required size and quality into the stuffing box with open end 180 with respect to each other. Tighten eyebolt nut equally on both sides. Lubricate the spindle-threading portion and operate the valve 2/3 times.
Routine maintenance consists of retightening the seat glands to compensate for seat and packing wear.
With no pressure in the valve, use the following procedure.
Dismantling and Servicing Instructions for Check Valves:
Open the cover plate by removing body-cover stud/nuts. Open two bracket bolts and take out assembly of hinge, bracket and disc. Separate the disc by removing split pin and disc nut. Clean the interior portion of body with cleaning liquid. Check the condition of seat ring surface. Rectification of seat surface is same as specified in Gate and Globe Valve
After lapping disc & seat ring, assemble the hinge/bracket/disc assembly as before and also replace the old gasket. Assemble the cover plate on body and ensure that disc assembly sits properly on seat ring and is also free to move inside body.
Ball valve can be installed with flow in either direction.