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The scope of application of floating ball valve

The scope of application of floating ball valve

The floating ball valve is the initial structure of the development of the ball valve, this structure is characterized by the media pushing the ball, and squeezing on the seal seat to obtain a reliable seal, the media force is proportional to the square of the valve diameter, so when the diameter increases, the pressure level increases, the media force will be large, for example, Class300, NPS 8 floating ball valve, the media force acting on the seat is about 190kN, which will make the seal seat on the This will cause the contact stress on the seal seat to approach the allowable specific pressure of the material and increase the operating torque exponentially. Therefore, the floating ball valve is suitable for NPS 8 or less, pressure class 150, class 300, and class 600 for small diameter NPS2 or less.


Floating ball valve installation and maintenance guidelines:

(1) Precautions

For safety, the following must be observed before the valve is removed or disassembled from the pipeline.

①When disassembling the valve, hands must not touch the inner cavity of the valve. Remotely operated valves can be closed at any time and hurt the operator.

② The medium in the pipeline should be understood and if in doubt, it can be verified with the relevant personnel.

③When contacting the medium, protective clothing or appropriate equipment should be worn in accordance with conventional requirements.

④When the valve and pipeline are relieved of pressure, open the valve before it is taken off the pipeline and empty the pressure that may remain inside the valve so that the valve is in the open position. After removing the valve and before decomposition, place the valve vertically and repeatedly open and close the valve to drain the residual medium.

⑤ Seal Seat and Body Ratings – Safe and proper use of this type of valve depends primarily on the seal seat and body ratings. The ratings on the nameplate should be known. There are many seal seat materials available for this type of valve, some of which are rated at less than the body rating. The overall rating of the body and seal seat also depends on the type of valve, specifications seal seat material, bolt material and stability, the use of the valve operating conditions can not exceed these ratings.


(2) Installation

① Valve is in the open position.

② Valve allows fluid to flow from either side. To ensure good installation, install in accordance with the standard pipeline transmission of the actual situation.

(3) Use flange bolts of corresponding specifications, and tighten the flange bolts in accordance with the gasket manufacturer’s requirements.

④If leakage is found at the valve stem seal during installation, this is due to the large temperature change during valve transportation, and the seal can be restored by simple adjustment of the packing as described in the “Maintenance” section.


(3) Maintenance

① Routine maintenance. Regular inspection is required to ensure that the valve is running well, and routine maintenance includes regular tightening of the gland bolts to compensate for the wear of the valve stem seal.

② Overhaul. Including replacement of seal seat and packing, etc. Repair kits can be purchased and replaced by referring to the “disassembly” and “assembly” methods below.

③Repair kits. Standard repair kits are available, including seal seats, stem seals, and PTFE gaskets.


(4) Disassembly

① Fix the right flange of the ball valve on the bench, and turn the stem to close the ball valve.

②Unscrew the connecting flange nut and remove the left valve body.

③Take out the ball from the inner cavity of the right valve body (pay attention to the ball body not to be bruised).

④Take out the seal seat from the left valve body and the right valve body.

⑤Remove the stem retainer and wrench.

⑥Screw down the gland and two bolts, and remove the positioning block and gland.

⑦Remove the valve stem from the inner cavity of the right valve body

⑧Take out 4 packings (1 upper packing, 2 middle packings, 1 lower packing) from the middle port.

⑨ Remove the gasket from the right valve body.

⑩Remove the thrust gasket from the valve stem and remove the upper bushing from the gland. Check all parts for damage, bruising and corrosion, replace the gasket and damaged, worn or corroded parts, and repair the bruised parts.


(5) Assembly

① All metal parts are cleaned with oil-free cleaning agent.

②Assemble the right valve body and the seal seat on the left valve body.

③Put the stop gasket on the valve stem.

④Fix the right valve body flange down on the bench, put the valve stem from the right valve body cavity into the packing hole, and then put in a group of packing (4 in total).

⑤ Put the upper liner set into the gland, put the gland into the mouth, and pre-tighten the two bolts.

⑥Turn the stem so that the flat body at the end of the stem is in line with the channel, then align the groove on the ball with the flat body of the stem and

Put the ball into the right valve body.

⑦ the gasket will be installed on the right valve body, installed on the left valve body, turn the stem so that the ball is completely in the open position, and then pre-tighten the relative nuts on the connecting flange. Turn the stem to open and close the ball valve several times, so that the ball is in the open position, tighten all the relative nuts on the connecting flange, and then open and close the ball valve several times, in the opening and closing process should feel flexible, no jamming phenomenon. The stem will be installed on the positioning block, card on the shaft with a retaining ring, and the ball valve in the fully open or fully closed state.


(6) with the implementation of the ball valve maintenance use

① Valve part refer to the valve product instruction manual.

② actuator (electric, pneumatic and worm gear drive, etc.) refer to the instructions for use of the actuator.


(7) common valve failure and troubleshooting methods

①Leakage at the right valve body and left valve body. Repair the sealing surface, remove dirt, replace the gasket, and tighten the nut evenly and crosswise.

②Leakage of packing. Tighten the gland bolts or replace the packing (1 upper packing, 2 middle packing, 1 lower packing). Be careful not to cut the edge during installation and tighten the gland bolts evenly.

③The valve stem is not flexible. Loosen the gland bolts, evenly loosen the left and right body connection nuts or thicken the gasket to reduce the preload, and pay attention not to leak.

④Leakage of seal. Evenly and cross-tighten the left and right body connection nuts, increase the preload, or change the sealing seat, gasket and clean the sealing groove.

⑤ When the ball valve can not be screwed, do not set the auxiliary lever on the wrench or other tools hard to wrench, which will damage the stem. If the operation is too laborious to analyze the reasons, some of the valve closing parts of the thermal expansion caused by opening difficulties, then the gland bolts can be loosened, to clear the stem stress and then open, packing is too tight, you can properly relax the packing.

⑥ Ball valves can only be fully open or fully closed with, generally not allowed for regulation and throttling. Ball valve with a wrench, the wrench and the channel parallel to the full open, turn 90 ° for the full closed.

⑦ Seal leakage. Evenly, cross-tighten the left and right body connection nuts, increase the preload, or switch the sealing seat, gasket and clean the sealing groove.

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