Features

"BOS" brand BELLOW SEAL GLOBE AND GATE VALVES are preferred by Nuclear, Space, Chemicals, Petro Chemicals, Fertilizers and Synthetic industries, to handle various hazardous fluids and gases. The valves are available from 1/2" NB to 24" NB and above and can be used for pressure over 400 bar and temperature above 450 deg. C. End connection can be either threaded or welded or flanged type to suit operating requirements. These valve are produced in varieties of material of construction i.e. Cast Carbon Steel Construction such as WCB / LCB / LCC, Cast Stainless Steel (CF8 / CF-8M / CF-8C), Alloy 20, Hastelloy-C, Forged Carbon Steel, Forged Stainless Steel etc. Additional safety is provided with stuffing box.

Valves with Bellow Seal construction is a high-tech product introduced by us, which eliminates leakage through gland packing absolutely and valve spindle is sealed with Stainless Steel, Inconnel 625, Hastelloy-C 276 Bellow in multiply construction. Bellow is welded with valve spindle / plug at the lower collar at the lower side and stainless steel collar at the upper side. This stainless steel collar is held in between the body and bonnet joints and glands are sealed to have Absolute Zero-Leakage. These Metallic Bellows can with - stand high temperature and pressure also. Bellow is in Normal Position when the valve is CLOSED and Compressed when the valve is in OPEN position. Bellow assembly inside the valve is developed indigenously by us and are capable of offering minimum cycle life of opening and closing of 20,000 cycles.

Comparison Between Bellow Seal & Traditional Valves

BELLOW SEAL VALVES PISTON VALVES CONVENTIONAL VALVES
Primary stem seal Metallic Bellow Piston ring Gland Packing
Secondary stem seal Gland Packing None None
Stem Leakage Not Possible since MetallicBellows are designed to last several thousand cycles Occurs as soon as the rings (which are made of gasket mtl)wear out. Very common. Due to friction between stem occurs withina few cycles no matter which make valve or qualityof gland packing.
Packing Replacement Not applicable Rings need to be changed frequently Packing needs to be replaced very often
Replacement Cost Not applicable Very high High
Media Loss Zero Loss. As the isolationis by metallic bellows ,leakage (in ppm) is not possible. Large in case of leaks Considerable amount through gland leakages. Normally large amount when leakage remains unattended.
Equipment Downtime Nil Very high for replacing rings Very high for replacing gland packing
Maintenance Cost Nil High as rings need to be changed at least once in six months Very High.Gland packing needs to be replaced / repacked often.This cost along with equipment down time, man hoursspent etc. is very high.
Valve Life High- in years Low Very Low - in months. Due to leakage through gland, certainparts erode, making the valve irreparable after some months.
Safety Can be used safely for almostany media Can be used for limited medialike steam, hot water Highly unsafe when the media is hazardous/poisonous
Cost Comparatively higher initiallybut lowest total cost ofownership High compared to the benefitsviz a viz problems Initially low but very high after some years if cost of packing,down time, man-hours spent, number of valves replaced etc.are taken in to account.
Cast Bellow Seal Globe Valve
Forged Bellow Seal Globe Valve

 
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