Cast Trunnion Ball Valve

 

Design Advantages for GZP Casted Trunnion Mounted Ball Valve

① Fire-safe design, ② Antistatic, ③ Anti-blowout stem, ④ DIB or DBB Design ⑤ Low fugitive emission packing, ⑥Seat grease injector or Stem seleant injector , ⑦ Trunnion mounted desgin.

 

Technical data
Design	API 6D, API 608, MSS-SP-72(BS5351),ASME B16.34
Pressures range	ANSI 150 ~ANSI 2500 ,PN10~PN420
Size range	2"-48" / DN50-DN1200
Body Material	A216 WCB	A352 LCB	A217 WC1	A217 WC6	A217 WC9	A217 C5	A351 CF8	A351 CF8M	A351 CF3	A351 CF3M
	NACE MR-01-75/NACE MR-01-03 Special Requirements
Face to face	API 6D, ASME B 16.10,
Fanged RF, FF, RTJ Ends	ASME B16.5, ASME B16.47 (Size 26''~60'')
	BS 4504,
Butt-Weld BW Ends	ASME B16.25 ,DIN 3239,
Temperature range	-196°~ 650°C
Design feature
Construction	Two or Three piece body and Welded body
Port	Full bore and Reduced bore
Ball Type	Solid ball
Stem	Blowout-proof stem, Anti-static,
Seat Sealing	Double Block and Bleed, Double Isolation and Bleed
Valve Operation	Gear, pneumatic, Hydraulic, and Electric actuators.
	Locking devices, extended stem, etc
Fire Safe	API 607, API 6FA
Other design	Anti-static design, automatic pressure relief design, emergency grease injection design, drain valve, anti-corrosion design, anti-sulfur design, etc
Inspection and Test
Visual Inspection	MSS SP-55
Material Inspection	PMI Test----Chemical Analysis
	HB Test---Hardness Test
	UT---Ultrasonic Test
	RT---Radio-graphic Test
	MT---Magnetic Test
	NDT Test Non-destructive
Dimension inspection	According to drawings
Valve Inspection and Test	API 598, API 6D, DIN 3230, EN12266

 

Cavity Pressure Relief Seat

Single Piston Effective (SPE) Design

Pd = Medium Pressure

Pc = Body Cavity Pressure

Ps = Spring Force

The medium pressure "Pd" and the spring force "Ps" push the valve seat against the ball, ensuring tight sealing. When the body cavity pressure "Pc" increases beyond the combined pressure of the medium and spring force, the cavity pressure will push the seat away from the ball, allowing the cavity pressure to release automatically. This design ensures that the ball valve can perform blocking and bleeding functions using medium pressure, known as Double Block and Bleed (DBB Valves).

 

Double Piston Effective (DPE) Design

Similarly, the medium pressure "Pd" and the spring force "Ps" push the valve seat against the ball to ensure tight sealing. However, in this design, when the body cavity pressure reaches its limit, it is released through a body vent bleeder (Safety Valve). As a result, the valve cavity pressure remains smaller than the sum of "Pd" and "Ps". This design ensures that the ball valve provides double isolation and blocking, known as Double Isolation and Block (DIB Valves).

Structure: 2-piece or 3-piece body

It features a high shut-off sealing mechanism and low torque operation.

Provides block and bleed function.

Includes self-cavity pressure relief.

Fire-safe design is incorporated.

Constructed with blow-out proof stem.

Anti-static design is featured.

Equipped with a locking device for lever handle operation.

ISO 5211 actuator mounting is available.

Emergency grease injection is an optional feature.

 

Construction

The primary distinction between floating and trunnion-mounted ball valves lies in their construction. In a floating ball valve, the ball is attached to the stem at only one end, leaving the other end free to float within the valve body. Conversely, in a trunnion-mounted ball valve, the ball is connected to both the stem at one end and a secondary shaft called the trunnion at the other. This setup securely holds the ball, allowing it to rotate only as the stem moves. A visual inspection easily reveals this difference: a trunnion-mounted ball valve will feature an additional shaft at its bottom.

Type of Seats

In floating ball valves, the seats are typically made of elastomeric material. An elastomer is a polymer that exhibits both viscosity and elasticity. This soft material helps cushion the pressure from the onstream that pushes the ball against the seats. The seats in the valve directly manage all the pressure from the upstream and have additional seal rings to handle this pressure effectively. In trunnion-mounted ball valves, the seats are spring-loaded, and any additional pressure is controlled by the stem and the trunnion.

Sealing Function

Both floating and trunnion-mounted ball valves provide shut-off, but they have different sealing functions.

In a closed floating ball valve, the onstream pressure forces the upstream seat and the ball against the downstream seat to form a seal. Conversely, in a trunnion-mounted ball valve, the onstream pressure activates the spring-loaded seats, causing them to move toward the ball and seal the valve.

The primary difference in their sealing functions is that in trunnion-mounted ball valves, the ball has no free movement and can only rotate as the stem moves. In contrast, in floating ball valves, the ball is free to rotate and move sideways.

 

Application

Floating ball valves are better suited for medium and low-pressure applications, typically featuring smaller diameters and providing sealing only from the downstream side. They are suitable for liquids and gases. Trunnion-mounted ball valves are designed for larger, high-pressure applications. The seats move towards the ball, creating a seal on both the upstream and downstream sides, allowing these valves to handle liquids, gases, and slurry mediums effectively.

Added Features

In floating ball valves, the seats require a separate mechanism to release additional pressure, making them unsuitable for high-pressure applications. In contrast, trunnion-mounted ball valves have self-relieving seats that handle any extra pressure without the need for an additional mechanism. Trunnion-mounted ball valves can also feature double block and bleed capabilities, allowing them to be used in critical high-pressure, high-temperature operations.

Conclusion

Floating ball valves have many advantages, such as low flow resistance, simple structure, good sealing performance, and cost-effectiveness for certain sizes and pressures. They are widely used in the oil, gas, and water industries and come in various sizes that can be customized to meet specific needs. Value-added features like oval safety handles, locking devices, easy automation with pneumatic actuators, T-handles, and extended bonnets for insulation can be added to enhance their functionality.

Features of cast trunnion ball valves are as follows:

1) Anti-fire safe design: API 6FA, API607

2) Anti-static device

The static conduction spring is set between the stem and the ball, as well as between the stem and the body. This ensures electricity is conducted to the ground, securing system safety.

3) Anti-blow out design

4) Leak-free body construction

Leak-free body construction The connection between the valve body and bonnet is double sealed with a gasket and O-ring. This design prevents external leakage due to fire, high temperature, shock, and uneven torque during opening or closing.

5) Double block&bleed(DBB)

6) Emergency sealing

7) Automatic body cavity relief

If the body pressure rises abnormally due to unstable factors, the downstream seat of the trunnion ball valve will be pushed by the abnormal pressure, releasing it automatically without damaging the upstream seat's sealing.

8) The valve structure can be either 2 pieces or 3 pieces.

 

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