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Buried all-welded ball valve details

2018/12/24 16:27:04

Buried all-welded ball valve details


Double shut-off and discharge: According to API 6D, the medium in the cavity of the valve body can be discharged in the valve closed position.


Path: The valve can be full or reduced (venturi type), and the minimum diameter is as specified in API 6D.


Body structure: There are three types of valve body: welded, split, top mounted, split and welded valve body is side-mounted, three-body forged steel structure, bolted or welded. The valve body of the top mounted valve is a single cast valve body.


Anti-static design: Conductivity between metal parts (such as valve body, ball, support ring, valve stem) isolated by rubber or plastic seals, guaranteed by stainless steel springs, in accordance with BS 5351.


Ball without pressure balance hole: The ball has no pressure balance hole to balance the pressure of the middle cavity when the ball is opened. This can discharge the medium in the cavity of the valve when the valve is fully closed or fully open, without changing the operating conditions. Next, effective inspection and maintenance of the seat and stem seals.


 


Stem anti-fly design: The stem is separated from the ball and is designed for anti-flying according to ASME B16.34 and BS 5351. It has an integral shoulder that is pressed under the bonnet by a self-lubricating thrust bearing.


Double Seal Seat: Each support ring is independently floatable and reasonably designed to be cut off by internal pressure automatic seal (double piston effect). It is a two-way double seal type. This repeated seal design has a double barrier to fluids. The function is to ensure that the downstream seal can also be sealed when the upstream seal fails. The overpressure in the valve cannot be released back into the pipeline. When the medium is liquid, a pressure relief valve needs to be installed at the valve outlet.


Seat: Rubber seat with valve pressure lower than ASME 1500# guarantees double seal of the ball, primary metal seal, secondary soft seal; plastic seat with higher pressure rating, such as nylon or reinforced PTFE, to ensure only The airtight soft seal of the ball; in addition, the double rubber + plastic seat is recommended for use on valves with very low pressure and stainless steel internals without a layer.


Fire protection design: The standard design of all valves meets the requirements of API607/API 6FA/BS 6755: PART 2. For the connection of the inner part and the valve body, without graphite material, the fluororubber (such as VITON) can pass the fire test, and the test proves to be in compliance with the requirements.