Forged Steel Trunnion-mounted Ball Valve Double Block & Bleed (DBB)

Forged Steel Trunnion-mounted Ball Valve Double Block & Bleed

The trunnion mounted ball valve has been designed with two floating seats, which are movable under the pressure of medium. Under the bottom of seats, seat pre-loading springs are positioned to ensure two floating seats attach the ball surface tightly. The ball is fixed by upper and lower trunnions, so the seat rings don’t afford too much flow pressure force when valve is in closed position. During service, pressure of medium pushes the front seat against the ball, forming a bubble tight seal.

Furthermore, the forging material can ensure sufficient rigidity and strength under maximum rated operation pressure, without the inherent flaw of cast. Standard wall thickness of separate body and adaptation of high strength tie bolts are convenient for valve maintenance and sufficient to bear the stress of pipe.

Small operating torque, small deformation on seats, reliable sealing performance, long service life are the main advantage of trunnion mounted ball valve. Trunnion mounted ball valves are widely used in long distance pipeline and normal industrial pipelines that can withstand various kinds of corrosive or noncorrosive flows.

Design Features:

1. Double Block and Bleed (DBB) Function
In the closed position, the spring-loaded seat rings provide a positive seal against pressure from both end of the valve, when the body cavity between the seat surfaces is vented through vent valve and drain valve.

The vent valve could also be used to test for seat tightness. In addition, the deposits down the body cavity could be purged and drained through the bottom bleeding hole to avoid damage to the seats.

2. Low Operating Torque
A trunnion-mounted ball valve has a trunnion-mounted ball and two floating seats, which are movable under the medium pressure. The self-lubricating PTFE seat inserts and sliding bearing could reduce the friction between the seats and the ball to minimum, to achieve lower torque under operating pressure.

3. Emergency Sealing Device
For trunnion-mounted ball valves larger than 6″(DN150), there’re sealant injection devices on stem and seat areas. In case the seat rings or stem O-ring is damaged accidently, the emergency sealant injection through the injection fittings could avoid medium leakage on seat and stem areas. The sealant injection system could also be used for the lubrication of the seats.

4. Fire-safe Design
In case the fire accidently occurs in the pipe and valve, the seat rings, stem O-rings made of PTFE, rubber or other non-metal materials could be burned down under high temperature, causing massive leakage to the valve. The fire-safe seat design is a precaution design between the ball and seat. After the valve seat insert is burned away, the medium pressure and the pre-loaded springs would push the front seat retainer continuously towards the ball to form an auxiliary metal-to-metal sealing, which could effectively reduce valve leakage. In addition, the middle flange sealing gasket is made of metal spiral-wound gasket, which could also ensure sealing under high temperature. The fire-safe design of KOLINK ball valves are approved per API 607.

5. Anti-static Structure
The ball valve is provided with anti-static devices and could form a static channel between the ball and body through the stem, to discharge the static electricity built up due to friction during the operation of the valve, to through the pipeline, avoiding fire or explosion that may be caused by electric spark and ensuring system safety.

6. Reliable seat sealing structure
The pre-loaded springs are positioned to ensure tight seal between 2 floating seats and the ball. In addition, under high pressure, the medium pressure would automatically push the front seat to the ball tightly to ensure reliable seat sealing.

9. Safety Relief Device
As the ball valve is designed with the primary and secondary seat sealing, the middle cavity cannot relief pressure by itself. In this case, the safety relief valve are installed on the body in order to prevent the danger of over-pressure damage inside the valve cavity that may occur due to thermal expansion of medium.

11. Blow-out Proof Stem

The stem is machined with an integral collar at its bottom end, and it is installed from the valve inner cavity, so that the stem is blocked by the valve neck and would not be blown out by the medium even under the abnormal pressure-rising condition in the valve cavity.

Features of Trunnion Mounted Ball Valves:
Trunnion Mounted Ball for low operation torque
Floating Spring Loaded Seat
Double Block and Bleed (DBB)
Split Body, End Entry
2-Piece or 3-piece Body
Full Port for Pigging Operation
Fire Safe to API 607
Antistatic Device
Anti-blowout Stem

Emergency sealant sealing device

Automatic Pressure Relief in Middle Cavity of Valve
Gear Operation or Actuator Available

Optional Direct Mounting to ISO 5211

Optional Locking Device

Optional Stem Extension

Applicable Standards of Trunnion Mounted Ball Valves:

a) Design & Manufacture: API 6D, BS 5351, API 608, ISO 17292, MSS SP-72

b) Fire-safe: API 607, API 6FA
c) Face to Face: API B16.10, API 6D, EN 558, DIN 3202
d) End Connection: ASME B16.5, EN 1092, JIS B2220, ASME B16.25
e) Test and Inspection: API 6D, EN 12266, API 598

Kolink Valve, specializing in manufacture and supply of quality industrial valves, is building up its reputation for quality and economical products in the valve industry.