SECTION I
Specifications for Valves for Transformers
1.0 SCOPE
1.1 This section covers specification for valves for transformers. This part specification does not purport to include all necessary provision of a contract. For general requirements reference shall be made to other sections of the Transformer Manual.
2.0 GENERAL
2.1 All valves in oil line shall be suitable for continuous operation with transformer oil (IS : 335) at 1000C.
2.2 Gland packing/ gasket material shall be of teflon rope/nitrile rubber. In case of GM/CI (gum metal/cast iron) gate and globe valves, gland packing preferably of teflon rope shall be used to prevent oil seepage through gland. Asbestos or graphite (gun metal/cast IM M) packing material shall not be used as they are not compatible with hot transformer oil.
2.3 Inside surface of valves shall be clean and valve ends shall be suitably blanked at the time of despatch. Machined and flange surfaces shall be suitably protected against rusting and transit damage. Butterfly and radiator valves shall be covered in polythene bags before packing for despatch.
2.4 After testing, inside surface of all C.I. valves coming in contact with transformer oil shall be applied with one coat of oil resisting paint/ varnish.
Inside surface of all valves in water lines shall be applied with two coats of paint conforming to IS: 9862, two coats of black Japan conforming to Type B of IS: 341 or any other suitable water resistant compound.
Unless specified otherwise by the purchaser, outside surface of all valves with ferrous body shall be painted with two coats of red oxide zinc chromate primer followed by two coats of full gloss finishing paint conforming to IS: 2932 and of shade matching with the transformer body or shade no. 631 of IS: 5.
Outside surface of all valves with non ferrous body shall be painted with one coat of etch primer followed by two coats of red oxide zinc chromate primer followed by two coats of full gloss finishing paint conforming to IS: 2932 and of shade matching with the transformer body or shade no. 631 of IS: 5.
Outside surface of all valves with non ferrous body shall be painted with one coat of etch primer followed by two coats of red oxide zinc chromate primer followed by two coats of full gloss finishing paint conforming to IS: 2932 and of shade matching with the transformer body or shade no. 631 of IS: 5.
After testing, inside surface of all C.I. valves coming in contact with transformer oil shall be applied with one coat of oil resisting paint/varnish. Inside surface of all valves in water lines shall be applied with two coasts of pant conforming to IS : 9862 or two coats of black Japan conforming to Type B of IS : 341. Outside surface of the valves shall be painted with two
coats of red oxide zinc chromate primer followed by two coats of full gloss finishing paint conforming to IS : 2932 and of distinct different shade (631 of IS – 5) to that of main tank surface.
2.5 All hardwares used may be electro-galvanized.
3.0 SIZE OF THE VALVE AND VALVE FLANGES
3.1 The size of the valve and valve flanges shall be as per Table 1. All flanges shall be drilled at off-centres.
3.2 Recommended size of the valves for drain, filter, sampling and air release applications shall be per Table 2.
Table 1
Nominal size of Diameter of Diameter of No. of Bolt Diameter of
valve (nominal flange bolt circle bolts size bolt hole
pipe bore) mm mm mm mm
4.1.1 15 mm valves used for oil sampling or air release shall be made of gunmetal gate valve (screw down stop) type generally conforming to class 1 of IS : 778 with inside screw stem. The oil sampling valve shall have provision to fix 15 mm PVC pipe.
4.1.2 The flanges shall be either drilled as per Table 1 (of this specification) or screwed as explained in Table 2 of IS : 778.
4.1.3 Preferred dimensions shall be as per Table 3.
Table 3
Size of valve Face to face dimension Thickness of flange mm mm mm
15 (Screwed) 57 — 15 (Flanged) 72 6.6 4.1.4 Tests
(a) Pressure tests : Body ..15 kg/cm2 Seat .. 10 kg/cm2 Duration .. 2 minutes
(b) Seepage test in open condition : Test pressure.. 2 kg/cm2
Duration .. 12 hrs.
Note : Transformer oil (IS : 335) or water at ambient temperature shall be used for pressure and oil seepage tests.
4.2 Gunmetal Gate Valves
4.2.1 25 mm valves used for oil filtering, oil drainage or in Buchholz pipe shall be gunmetal gate (screw down step) type generally conforming to class 1 of IS : 778) with inside screw stem.
4.2.2 The flanges shall be drilled as per Table 1.
4.2.3 Preferred dimensions shall be as per Table 4.
Table 4
Size of valve Face to face dimension Thickness of flange mm mm mm
25 (flanged) 90 8.0 4.2.4 Tests as per clause 3.1.4
4.3 Cast Iron Taper Plug Valves
4.3.1 50 mm, 80 mm and 100 mm C.I. taper plug or gate valves may be used for oil filtering, oil draining.
4.3.2 Valves shall be self-lubricating, short pattern type, provided with valve operating wrenches. The lubricant used shall be compatible with transformer oil (IS : 335) at 1000C.
4.3.3 Preferred dimensions shall be as per Table 5.
Table 5
Size of valve Face to face dimension Thickness of flange mm mm mm
50 178 (7”) 19 80 203(8”) 19 100 229 (9”) 22 4.3.4 Tests
(a) Pressure tests Body ..15 kg/cm2 Seat ..10 kg/cm2 Duration ..2 minutes
(b) Seepage test in open condition Test pressure..2 kg/cm2 Duration ..12 hrs.
Note: Transformer oil (IS : 335) at ambient temperature shall be used for pressure and seepage tests.
4.4 C.I. Gate Valves
4.4.1 50 mm, 80 mm, 100 mm, 150 mm, 200 mm and 250 mm, C.I. gate valves may be used in cooling water pipe lines.
4.4.2 C.I. gate valve shall generally conform to class PNI of IS : 780 double flanged, inside screw, non-rising spindle, Solid wedge gate and with screwed (inside screw type or bolted bonnet, Gunmetal trim material, teflon rope gland packings and nitrile rubber gaskets. The valves shall be provided with open and shut indicator.
4.4.3 Preferred dimensions shall be as per Table 6.
Table 6
Size of valve Preferred face to face dimension Thinckness of flange mm mm mm 50 215 16 80 230 18 100 255 20 150 280 22 200 318 25 250 355 26 4.4.4 Hydrostatic Pressure Tests
Body ..15 kg/cm2 for 5 minutes Seat ..10 kg/cm2 for 2 minutes
4.5 C.I. Check Valves
4.5.1 100 mm, 150 mm, 200 mm, and 250 mm C.I. check valves may be used in oil pipe lines of forced oil cooled transformers to avoid reverse flow and/or cross flow of oil where required.
4.5.2 C.I. Check valves shall be of horizontal swing check type genrally conforming to IS : 5312 (Part I), without bypass arrangement. The weight of the swing (flap) shall be such that full opening is available at a minimum oil velocity of 1.0 m/s at a pressure of 1.5 kg/cm2. The pressure drop through the valve shall be less than 0.3 m of oil column (0.026 kg/cm2) with normal flow rates. The above requirement should be proved by calculations if test facilities not available.
4.5.3 Preferred dimensions shall be as per Table 7.
Table 7
4.6.1 Cast iron butterfly valves shall be of the nominal sizes; 50, 80, 100, 150, 200 and 250 mm. These valves are used in oil pipe lines such as Buchholz relay pipe lines and as shut off valves between transformer main tank and cooler tank.
4.6.2 The body and cap of butterfly valves shall be made from any of the seven grades of grey iron casting conforming to IS : 210 except grade FG 150 and the disc shaft and stop pin shall be made from mild steel conforming to Fe 410-WA of IS : 2062 disc and body of the valve shall be in direct contact without any sealing ring. Valve is operated by a spanner and provision shall be given for locking in open/closed position. ‘OPEN’, ‘CLOSE’ markings on the body and an arrow mark on the tap for position indication shall be provided. To indicate the disc position in the cap removed condition, some suitable marking on the spindle head shall also be provided.
4.6.3 Preferred dimensions shall be as per Table 8.
Table 8
4.6.4 Tests
The valves shall be tested with transformer oil at 1.5 kg/cm2 with the assembled valve in closed/open position, the leakage shall n ot be more than as specified below:
(i) Leakage through body when pressure is applied for thirty minutes Nil (ii) Leakage around top spindle with cap fitted on Nil (iii) Leakage around top spindle when cap is removed
for 50, 80 and 100 mm valves-2 drops per minute (max.) for 150, 200 and 250 mm valves-8 drops per minute (max.) (iv) Leakage past diaphragm in closed position –
for 50, 80 and 100 mm valves-6 drops per minute (max.) for 150, 200 and 250 mm valves-6 cc per minute (max.) 4.7 Radiator Valves
4.7.1 Radiator valves shall be of 80 or 100 mm size 4.7.2 Construction same as per clause 4.6.2 4.7.3 Preferred dimensions shall be as per Table 9.
Table 9
Size of Size of Diameter of No. of Bolt hole Face to Thickness of valve flange bolt bolt size face flange square A/F circle dimension mm mm mm mm mm mm 80 150 160 4 18 40 16 100 180 180 4 18 40 16 4.7.4 Tests : Same as per clause 4.6.4