What’s the bellows seal gate valve?

Bellows Seal Gate Valve was invented to meet strict requirements of tightness and severe working conditions.

except for the conventional packing assembly as all the gate valve,the bellows seal gate valve also has a bellow packing device.

it’s completely different approach to packing is a device called a bellows seal,an accordion-like metal tube fastened to the valve stem and to the bonnet,forming a leak-proof seal with negligible friction and the bellows seal is able to stretch and compress with a sliding stem’s linear motion.As the bellows is an uninterrupted metal tube, there is no place at all for leaks to develop.

The port on the extended bonnet serves as a point of connection for process fluid leak detection sensors, to sound an alarm and/or take action in the event of a ruptured bellows.When the bellows seal breaks, the sensor will detect the leak and the standard packing assembly will maintain a reasonable seal until repairs are made on the valve.Bellows has a limited service life, which means the possibility of a rupture is likely. This is why a conventional packing assembly is always included in a bellows-equipped bonnet.

The accordion-shaped bellows is contained and protected inside the thick metal tube.One end of the bellows is welded to the valve stem, and the other end is welded to the protective tube. With the wide flange of the tube firmly clamped in the bonnet of the valve, a leak-free seal exists.

Bellows have a limited service life, which means the possibility of a rupture is likely. This is why a conventional packing assembly is always included in a bellows-equipped bonnet.So the bellows seal is an extra packing sealing for the gate valves,it’s suitable for some severe working conditions.

Main features of the bellows seal gate valve?

In particular chemical processes the fluids in the pipes are often toxic, radioactive and hazardous. Bellows seal gate valves are used to prevent leakage of any toxic chemical to the atmosphere. Body material can be selected from all available materials,The bellow can be supplied in different materials like 316Ti, 321, C276 or Alloy 625.

• 1).Metal bellows seals the moving stem and increases durability of packed stem seal valves.
• 2).Bellows monitoring port (optional): A plug can be connected with the space above the bellows to monitor performance.
• 3).Two secondary stem seals: a) Backseat in open position; b) Graphite packing.
• 4).for Bellows seal gate valve, its key components metal bellows,the lower end and valve stem are automatic rolling welded,and the upper end and the protection tube are automatic roll welded as well. A metal barrier is formed between the stem at its point of entry through the pressure boundary and the process fluid within the valve,to eliminate stem leakage;
• 5).Bellow-sealed valves are usually leak tested using a mass spectrometer to detect leakage rates below 1x10E-06 std.cc/sec.Double sealing design (bellows seal and stem packing) if the bellows fail, valve stem packing will also avoid leakage,and in conformity with international tightness standards;
• 6).Bellow-sealed bonnets are backed up with a standard stem packing set and a leakage monitoring port between the bellows and the packing in order to prevent catastrophic release of hazardous fluid in the event of a bellows leak.
• 7).Not as the tradtional grease screw only for the stem thread,A grease nipple is designed on the valve bonnet,we may lubricate lubricate the stem,nut and bushing directly,through the grease nipple;
• 8).Ergonomically designed handwheel, longer service life, easy to operate, safer and more reliable;

Specifications of the bellows seal gate valve?

• (1)  On request: faced with Stellite   – Monel   – Hastelloy   – other materials
• (2)  On request: faced with Stellite   – Monel   – Hastelloy   – other materials
• (3)  On request: 18 Cr – Monel  - Hastelloy    – other materials
• (4)  On request: Nodular Iron – Nitronic 60
• (5)  On request: PTFE – other materials

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Applications of Bellows seal gate valves

This kind of  Bellows Seal Gate Valve is widely utilized in pipeline with liquid & other fluids,especially for the fluids toxic,radioactive and hazardous 

• Petrol/oil
• Chemical/Petrochemical
• The pharmaceutical industry
• Power and Utilities
• Fertiliser industry