Fully Welded Ball Valves

What is a fully welded ball valve?

Fully welded ball valve is a switch type control valve. The valve body adopts the form of all welding, which is not easy to produce deformation and aging resistance.

The sleeve of the fully welded ball valve is a short joint welded at both ends of the valve and a transition section added at both ends of the ball valve, which is used to weld with the submarine pipeline terminal or the pipeline on the underwater manifold. In order to prevent damage to the seal of the fully welded ball valve body during sleeve welding, the sleeve welding of the ball valve is generally required to be completed before leaving the factory, and in order to facilitate subsequent welding with the pipeline, The sleeve shall be made of the same material as the pipeline. The length of the sleeve shall ensure that the heat generated during welding with the pipeline will not affect the sealing performance of the fully welded ball valve. The sleeve shall be welded to the valve body before the inspection of the fully welded ball valve. The signal pressure tapping point of the pneumatic-hydraulic actuator and the opening of the power air source shall be on the sleeve.

Structural features of fully welded ball valve

• 1. The full welded ball valve body is forged from high-quality materials, the ball is installed on the side, and the middle flange and neck are connected by full welding;
• 2. A soft sealing structure and a hard sealing structure are respectively arranged between the valve seat and the ball rod;
• 3. The valve stem is of blowout prevention design, which can prevent the valve stem from spraying out of the valve body due to improper operation;
• 4. All have fire and anti-static devices;
• 5. Emergency sealing grease injection inlet is designed at the valve seat seal and valve stem seal, and each grease injection orifice is equipped with a grease injection valve and an embedded one-way valve;
• 6. The connecting plate can be matched with various driving devices. The driving device includes: handle, worm gear, electric, pneumatic, gas-liquid linkage, electro-hydraulic linkage, etc;
• 7. The position adjustment is convenient. St ball valve provides a special “positioning groove”, which is very easy and accurate to find the full opening and closing of the ball valve. Facilitate the adjustment of actuator limit device;
• 8. Buried design: the valve and valve stem installed underground shall be lengthened according to the needs of the project for ground operation.

Code for design of fully welded ball valves

• Design standard: API 6D, GB/T 19672, GB/T 12237;
• Structure length: API 6D, ASME B16.10, GB/T 12221;
• Flange connection standards: ASME B16.5, ASME b16.47, GB/T 9113, JB/T 79, HG/T 20592;
• Butt welding connection standard: ASME B16.25, GB/T 12234;
• Fire protection requirements: API 6FA, API 607;
• Pressure test: API 6D, API 598, GB/T 13927, GB/T 26480.

Features of fully welded ball valve

All welded ball valves are characterized by high strength, light weight, compact structure, zero leakage and long service life.

Advantages of fully welded ball valve

• 1. Integral welded ball valve, no external leakage, etc.
• 2. Since the valve seat is composed of carbonized Teflon sealing ring and coffee spring, it has strong adaptability to the changes of pressure and temperature, and will not produce any slip within the marked pressure and temperature range.
• 3. The machining process of the sphere is tracked and detected by an advanced computer detector, so the machining accuracy of the sphere is high.
• 4. As the material of valve body is the same as that of pipeline, there will be no uneven stress, no deformation due to earthquake and vehicle passing through the ground, and the pipeline is resistant to aging.
• 5. The seal ring body is made of cptfe with a content of 25% carbon (carbon), ensuring no leakage (0%).
• 6. The directly buried welded ball valve can be directly buried underground without building a high and large valve well. It only needs to set a small shallow well on the ground, which greatly saves construction cost and engineering time.
• 7. The length of the valve body and the height of the valve stem can be adjusted according to the construction and design requirements of the pipeline.
• 8. The machining accuracy of the sphere is very precise, the operation is light, and there is no bad interference.
• 9. The use of advanced raw materials can ensure the pressure above PN25.

Disadvantages of fully welded ball valve

Because the movement between the ball and the valve seat of the ball valve has the function of wiping, the ball valve can be suitable for media with suspended particles. However, solids with wear particles will damage the surface of soft seal valve seat and ball. For media with long and ductile fiber materials, problems will also occur when using fully welded ball valve because these fibers are wound on the ball.

Design features of fully welded ball valve

• 1. Full welding of valve body connection;
• 2. Forged valve body and ball;
• 3. Support plate fixed ball structure;
• 4. Full bore or reduced bore design;
• 5. Fire protection design;
• 6. Anti static function, in line with API6D standard;
• 7. Double cut-off and discharge (DBB) function;
• 8. The valve stem is detachable and anti blow out structure design;
• 9. Emergency sealing system is set at the sealing position of valve stem and valve seat;
• 10. Floating double valve seat and multi-stage sealing valve seat structure;
• 11. Automatic pressure relief function of middle chamber;
• 12. Corrosion resistant, low friction, self-lubricating bearing;
• 13. ISO 5211 standard connecting flange.

Relevant standards

• ASME B16.34: flanged, threaded and welded valves
• API 6D: pipeline valves
• ISO 17292: steel ball valves for industrial use
• ASME B16.10 face to face and end-to-end dimensions of valves;
• Inspection and test of API 598 valves;
• ISO5208: pressure test of industrial valves.

Difference between welded ball valve and fully welded ball valve

What is the difference between welded ball valve and fully welded ball valve? The connection mode is different. There are also welded valves with compact structure and can withstand high pressure. The fully welded ball valve is mainly used as the flow direction switch for cutting, distributing and changing in the pipeline. The unique floating ball design is adopted to make the sealing ring tightly press on the floating ball, and the pressure in the pipeline ensures that the inside and outside of the valve are completely sealed. The ball valve with integral welded structure is called fully welded ball valve.
The performance stability of fully welded ball valve can not be achieved by ordinary cast steel ball valve, and its service life is much longer than that of cast steel ball valve. All welded ball valve is widely used in urban gas, urban heating, petrochemical industry, shipbuilding, steel, pressure regulating station, power plant and other pipeline equipment. The welded ball valve will not have external leakage. Because the valve seat is composed of carbonized Teflon sealing ring and coffee spring, it has strong adaptability to the changes of pressure and temperature, and there will be no leakage within the marked pressure and temperature range. The processing process of the sphere is tracked and detected by an advanced computer detector, so that the processing accuracy of the sphere is high. As the valve body material is the same as the pipe material, there will be uneven stress, no deformation due to earthquake and vehicles passing through the ground, and the pipe is resistant to aging. When the operating mechanism and connecting plate of the existing fully welded ball valve are removed for maintenance and replacement, the upper valve rod is easy to pop up, and there are potential safety hazards.
Compared with the general ball valve, the fully welded ball valve has strong adaptability to the changes of pressure and temperature because the valve seat is composed of carbon Teflon sealing ring and disc spring. The fully welded ball valve will not produce any slip within the marked pressure and temperature range.

Why use fully welded ball valves?

• 1. The installation mode of fully welded ball valve is different from other ball valves. All welded ball valves can be directly buried underground. This installation method saves a lot of manpower and material resources, does not need to build additional wells, and can freely adjust the length of the valve rod. At the same time, directly buried underground can also eliminate most of the hazards from the environment, making the fully welded ball valve durable.
• 2. The material of the valve body of the fully welded ball valve is the same as that of the pipeline, so that the valve can be evenly divided with the pipeline when under pressure, there is no uneven stress, and there will be no deformation or even damage due to the application of external force.
• 3. Ordinary ball valves need to be installed in a fixed direction, while fully welded ball valves are two-way sealed and can be installed freely. When the pressure rises, the self pressure relief function can be enabled to balance the pressure and achieve the effect of zero leakage.
• 4. According to different working conditions, the fully welded ball valve can be designed into a fireproof or even anti-static structure, and the welding method can make its effect play well.

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