The method for judging internal leakage of ball valves

Fixed-shaft ball valves are commonly used on natural gas pipelines. The general inspection methods for them are:

Turn the valve to the fully open or fully closed position and check for any leakage through the discharge port of the valve body. If it can be drained completely, it proves that the seal is good. If pressure is discharged, it can be considered that the valve is leaking. At this time, corresponding treatment should be carried out on the valve. However, it should be emphasized that for GRoVEB-5 and B-7A type ball valves, PBV ball valves, and ROBERTCORT ball valves, inspection can only be carried out in the fully closed position. This is because these types of ball valves have a channel opened on the valve body, which, when fully open, is used to balance the pressure in the pipeline and the valve chamber. But this situation will not occur when all positions are closed.

The handling procedure for internal leakage of ball valves

First, check the limit of the valve to see if adjusting the limit can solve the internal leakage of the valve.

First, inject a certain amount of grease to see if it can stop the leakage. At this time, the injection speed should be slow. Meanwhile, observe the change in the pointer of the pressure gauge at the outlet of the grease injection gun to determine the internal leakage of the valve.

If the leakage cannot be stopped, it may be due to the hardening of the sealing grease injected earlier or the damage of the sealing surface causing internal leakage. It is recommended to inject valve cleaning solution at this time to clean the sealing surface and valve seat of the valve. Generally, soak for half an hour. If possible, soak for several hours or even days. Wait until the solidified substance dissolves before proceeding to the next step. During this process, the movable valve can be opened and closed several times.

④ Re-inject the grease, and intermittently open and close the valve to expel impurities from the rear chamber of the valve seat and the sealing surface.

⑤ Check in the fully closed position. If there is still leakage, inject reinforcing sealing grease and open the valve cavity at the same time to vent. This can create a large pressure difference, which is helpful for sealing. Generally, internal leakage can be solved by injecting reinforcing sealing grease.

If there is still internal leakage, the valve should be repaired or replaced.

Our company's main products include forged steel ball valves, high-temperature ball valves, high-pressure ball valves, American standard ball valves, welded ball valves, and cast steel ball valves. We welcome merchants from all over to come and purchase

    The basic features of cast steel ball valves: Currently, cast steel ball valves can be used in natural gas pipeline lines, oil refining facilities and nuclear industry applications in a short period of time. In addition, in other industries, regardless of large and medium-sized diameters and medium and low pressure fields, cast steel ball valves will also become the dominant valves. Its characteristic is that when referring to the flow rate, the fluctuation of the input pressure causes the fluctuation of the output pressure. The smaller the fluctuation of the output pressure, the better the performance of the pressure reducing valve, and the value of the output pressure being lower than the input pressure basically does not change with the variation of the input pressure. The working principle of cast steel ball valves: The application of cast steel ball valves is increasing year by year. In China, ball valves are used in industries such as petroleum refining, long-distance pipelines, chemical engineering, papermaking, pharmaceuticals, water conservancy, power, municipal services, and steel, playing a crucial role in the national economy. The ball valve can be tightly closed with a 90-degree rotation and a very small torque. The inner cavity of the flat valve body provides a straight-through flow path with very little resistance for the medium. It is generally believed that ball valves are suitable for direct opening and closing, but recent developments have designed ball valves to be used for throttling and flow control. The main features of ball valves are their compact structure and easy maintenance. They are suitable for general working media such as water, solvents, acids and natural gas, and are also applicable to media with harsh working conditions, such as oxygen, hydrogen peroxide, etc. To shorten the delivery time, we have cast steel ball valves in stock with diameters ranging from DN15 to DN250 and pressures from 16 to 25 kilograms. Meanwhile, other cast steel ball valves are also in stock to facilitate purchasing by users from all regions. 

With the development of the valve industry, our valve products also need to adapt to the previous economic situation and keep up with The Times. One of the products is the ball valve, and the forged steel ball valve is among them. Let's take a look at the design of this product below! The material of forged steel ball valves is forged, and the density of the material is much greater than that of cast ones, making it suitable for the manufacturing and processing of high-pressure ball valves. The closing part of the forged steel ball valve is a type of ball valve that opens and closes by rotating the ball around the valve body line. The sealing part is embedded in the stainless steel valve seat, and a spring is provided at the tail end of the metal valve seat. When the sealing surface wears or burns out, Under the action of the spring, the valve seat and the ball are pushed to form a metal seal. It features an automatic pressure relief function. When the medium pressure spring in the valve cavity is preloaded, the valve seat at the outlet end retreats and detaches from the ball, automatically releasing pressure. After pressure relief, the valve seat automatically returns to its original position. It is suitable for general working media such as water, solvents, acids, and natural gas, and also for media with harsh working conditions, such as oxygen and hydrogen peroxide. It has been widely used in various industries. The information is provided by the forged steel ball valve manufacturer . Reproduction is welcome!

The standard procedure for installing forged steel ball valves

1: Preparations before installation

Open the box to check if the model, pressure and diameter match, and confirm that the valve body has no transportation damage. Before installation, the pipeline must be thoroughly purged to remove welding slag, rust and other debris. Prepare the matching gaskets and bolts, and check that the flange sealing surface is in good condition.

2: Installation direction

Bidirectional sealing has no directional requirements. Install those with flow direction arrows as indicated by the arrows.

3: Position the valve

Place the valve between the two flanges of the pipe and ensure that it is not skewed during alignment. Insert the gasket and alternately tighten the flange bolts symmetrically. Gradually increase the force in 2 to 3 steps to prevent the flange from tilting.

4: Debug after installation

Slowly apply pressure to test the sealing performance of each connection point. Conduct a fully open and fully closed operation test to confirm that the torque is normal and the movement is smooth. Adjust the limit to ensure it is fully closed.

Key points to note

Valves must not bear the weight of the pipeline. Large valves need to be independently supported. Welding connections must be operated by certified welders. During welding, the ball should be fully opened to protect the sealing surface. The hexagonal surface of the valve body is clamped by threaded connection. It is strictly prohibited to clamp the valve stem or actuator. The liquid pipeline is first pressurized and slowly opened to prevent impact.

Safety Tips

Release the pressure and empty the pipeline before installation. Reserve a thermal expansion gap under high-temperature working conditions. The wiring in the explosion-proof area complies with the explosion-proof standards.

What should I do if the operation of the forged steel ball valve is stuck and the torque is too large?

On-site emergency response

First, try to slightly open it in the reverse direction and then close it again. Use the medium to flush out foreign objects. For valves that have not been operated for a long time, the packing gland bolts of the valve stem can be slightly loosened, but be careful not to cause leakage. For those with grease injection valves, inject special grease or cleaning agents. If the electric or pneumatic actuator cannot be driven, check whether the air source pressure or power supply voltage is normal. If the valve is stuck in the middle position and cannot cut off the medium, the bypass pipeline should be switched or the load reduced for handling. Contact the manufacturer for on-site solution. Violent force pulling is strictly prohibited.

Common causes and solutions

The adhesion of the sealing surface is usually due to the coking or crystallization of the medium. It can be softened by soaking in a cleaning agent or by blowing with steam in a half-open state, but it is necessary to confirm the temperature resistance of the material. If the packing is too tight or aged, it will cause high frictional resistance. Loosen the cover bolts and apply grease to solve the problem. Foreign objects getting stuck are mostly caused by welding slag and rust. After repeatedly opening and closing several times to try to wash them away, if they fail to do so, they can only be disassembled for inspection and cleaning. Under high-temperature working conditions, metals expand and seize up. The machine needs to be shut down for cooling before operation. When selecting the type, it is recommended to switch to a metal hard seal structure. If the keyway of the transmission components is worn or the worm gear is stuck, the damaged parts need to be disassembled for inspection and replacement.

Daily preventive measures

Valves that have not been used for a long time should be opened and closed at least once a month to prevent adhesion. Regularly apply grease through the grease injection valve for maintenance. It is recommended to select the actuator torque with a margin of more than 1.3 times the normal value. It is recommended that valves with automatic pressure relief function in the valve cavity be selected for liquid medium pipelines to prevent pressure build-up and jamming.

Safety Reminder

It is strictly prohibited to forcibly pull the valve with the force rod. The breakage of the valve stem or damage to the seal will lead to the scrapping of the valve. Before operation, be aware that the valve cavity may be pressurized. Release the pressure first before proceeding to ensure safety.

When internal or external leakage occurs in forged steel ball valves, standardized diagnostic and handling measures should be taken based on the type, location and working conditions of the leakage.

I. Internal Leakage Treatment

Internal leakage refers to the situation where the medium still leaks from the upstream sealing surface to the downstream when the valve is fully closed.

1. Fault diagnosis and confirmation

Online verification: After closing the valve, open the downstream discharge valve or blowdown valve and observe whether there is a continuous flow of medium.

DBB valve verification: For the double-ball DBB structure, open the middle cavity discharge port and verify the integrity of the upstream and downstream seals respectively.

Eliminate false internal leakage: Confirm whether the valve is truly in the fully closed position, and rule out "not fully closed" caused by limit offset or insufficient torque setting of the electric head.

2. Treatment of internal leakage in floating ball valves

To check for dirt clogging: Try slightly opening the valve by 10% to 20% and then closing it again to use the medium to flush the sealing surface. Repeat 1-2 times. If the internal leakage is eliminated, it is a temporary particle entrapment.

Grease injection auxiliary sealing: If the valve seat is equipped with a grease injection port, inject special emergency sealing grease for valves to temporarily restore the seal and arrange for gas supply to stop and the valve seat to be replaced.

Disassembly and maintenance: If the above measures are ineffective, stop the operation, empty it, and then disassemble the valve to check for damage, scratches or cold flow deformation on the sealing surfaces of the ball and the valve seat. For minor cases, grinding and repair are required; for severe cases, the valve seat and ball need to be replaced.

3. Treatment of internal leakage in fixed ball valves

Online troubleshooting: Open the middle cavity discharge port and determine whether the internal leakage comes from the upstream valve seat or the downstream valve seat. Internal leakage in the upstream valve seat can usually be repaired by online grease injection, while internal leakage in the downstream valve seat needs to be drained and treated later.

Grease injection intervention: Inject sealing grease into the grease injection port of the upstream or downstream valve seat to restore the sealing specific pressure. It is suitable for temporary emergency use of soft-sealed valve seats.

Disassembly and maintenance: When grease injection is ineffective, stop the operation and disassemble. Check whether the valve seat spring has failed, whether the piston effect valve seat is stuck, and whether the sealing surface is eroded. Replace the failed valve seat assembly. Grind or replace the sealing surface of the ball as needed.

4. Verification after maintenance

The bidirectional high-pressure gas seal test is carried out in accordance with API 598. Zero bubbles are the qualified standard.

Ii. Handling of External Leaks

External leakage refers to the escape of the medium from the sealing interface between the valve body and the external environment. The main leakage points are the valve stem packing area, the valvebody connection area, and the grease injection port/discharge port.

The packing of the valve stem is leaking

Symptom: The medium seeps out or spurts out between the valve stem and the stuffing box.

Processing steps

1. Try to tighten the gland: Use a wrench to symmetrically and evenly tighten the packing gland nuts by 1/4 turn each time, and observe whether the leakage decreases. Do not apply pressure on one side to avoid the valve stem getting stuck.

2. Automatic compensation for live load disc spring: If a live load disc spring stuffing box has been configured, confirm whether the disc spring has failed. When the disc spring breaks or the compression amount is exhausted, the disc spring assembly needs to be replaced.

3. Online pressurized grease injection: If the stuffing box is equipped with a grease injection port, inject special sealing grease for valves as a temporary leak sealing measure.

4. Disassembly and replacement of packing: If the above measures are ineffective, remove the gland under safe emptying and pressure relief conditions, take out the old packing, and replace it with PTFE/ graphite braided packing of the same specification. Press it in circle by circle according to the specifications, and lock the gland symmetrically and evenly. Operation under pressure is strictly prohibited.

2. Leakage at the connection of the valve body

Common leakage points of forged steel ball valves: flange gasket between the valve body and the valve cover, sealing surface connection between the valve body and the end.

Processing steps

1. Tighten the bolts: Tighten the flange bolts at the leakage point symmetrically and evenly, and observe the leakage changes.

2. Replace gaskets: If tightening is ineffective, stop the operation to vent and relieve pressure. Disassemble the connection points and replace the graphite wound gasket or PTFE gasket. Before installation, clean the sealing surface, pre-tighten the bolts symmetrically and evenly, and lock them in two steps according to the torque value.

3. Sealing surface damage repair: If there are pits or scratches on the sealing surface, the minor ones will be ground and repaired, while the severe ones will be surfacing and reprocessed.

3. Leakage at the grease injection port/discharge port

Grease injection port: Check if the check valve is faulty and replace the grease injection port.

Discharge port: Check whether the discharge valve itself has failed to seal properly or whether the connecting threads are loose. Tighten or replace the discharge valve.

4. Leakage from the valve body itself

Forged steel valve bodies, due to forging defects or cracks, cause the medium to seep out from the valve body, which is a serious accident hazard.

Treatment method:

Immediately isolate and drain. The valve must not be used any longer.

· Determination of scrapping: In principle, forged steel valve bodies with penetrating cracks or organizational defects should be scrapped directly. Welding repair is not recommended as the heat-affected area may cause changes in the mechanical properties of the material and there is a risk of rupture under high-pressure conditions.

Iii. Acceptance of the processed standards

Test method for acceptance criteria of leakage types

Internal leakage zero bubble API 598, bidirectional 1.1 times design pressure gas seal

For the shell with no visible leakage, conduct a water pressure strength test at 1.5 times the design pressure, and visually inspect the valve stem packing area

Low dissipation (optional) ≤50 ppmv ISO 15848-1, helium leak detection

Iv. Record and Traceability

The time of leakage occurrence, location, diagnosis process, handling measures and post-repair test data should be entered into the valve maintenance file and incorporated into the full life cycle management. For valves with repeated leakage, it is necessary to trace whether the design selection, materials or operating conditions exceed the original design boundaries.

A detailed introduction to the standard opening and closing operation procedures of forged steel ball valves

I. Preparations Before Operation

Inspection items and requirements

Valve status confirmation: Confirm that the valve is currently in the fully open or fully closed position and observe the position indicator or limit pointer

Visual inspection: There should be no external leakage, rust or mechanical damage at the valve body, valve stem, packing gland and flange connection

Operating space: There are no obstacles around the handle or handwheel, and the operator's position is stable

Pipeline status: Ensure that the pressure difference between the upstream and downstream is within the allowable operating range. It is strictly prohibited to force operation under a huge pressure difference before and after the valve

Actuator (if any) : Confirm that the air source/power supply is normal, the set air pressure of the filter pressure reducing valve is correct, and the lubrication system is normal

Ii. Manual Operation Process

Handle operation

Open the valve

Confirm that the valve is currently in the closed position (with the handle perpendicular to the pipe axis).

Hold the handle with one or both hands and apply the torque steadily.

Rotate the handle counterclockwise by 90° until it is parallel to the pipe axis.

Observe the position indicator to confirm that the valve is fully open.

Check that there is no leakage at the valve stem and packing.

Close the valve

Confirm that the valve is currently in the open position (with the handle parallel to the pipe axis).

Rotate the handle clockwise by 90° until it is perpendicular to the pipe axis.

Stop applying force after the handle is in place. Do not forcibly rotate over the position.

Observe the position indicator to confirm that the valve is fully closed.

Lock the handle (if equipped with a locking device) to prevent misoperation.

Worm gear operation

Open the valve

Confirm that the position indicator of the worm gear box points to "CLOSED".

Turn the handwheel smoothly and rotate it in the valve opening direction marked on the worm gear box.

Keep rotating until the position indicator points to "OPEN" and the handwheel cannot continue to rotate in the same direction.

Turn the handwheel in the reverse direction by 1/4 to 1/2 turns to release the meshing stress of the worm and prevent thermal expansion and jamming.

Close the valve

Confirm that the position indicator points to "OPEN".

Turn the handwheel smoothly in the direction of valve closing marked on the worm gear box.

Keep rotating until the position indicator points to "CLOSED", and stop when the handwheel torque increases significantly.

Rotate in the reverse direction by 1/4 to 1/2 turns to release the stress.

Lock the handwheel (if equipped with a locking device).

Key Warning

The use of extension rods is strictly prohibited: The designed torque of the worm gear box has already matched the valve requirements. Extension rods can cause overload of the worm gear, pitting on the tooth surface, and broken teeth.

Excessive reverse rotation of the handwheel is strictly prohibited: Rotation is only used to release the meshing stress of the worm. Excessive rotation will cause the ball to deviate from the fully closed position, resulting in internal leakage.

Iii. Pneumatic Operation Process

Remote activation

The DCS/PLC issues the start command.

When the solenoid valve is energized, compressed air enters the open side of the cylinder.

The piston drives the transmission mechanism to rotate the ball to the fully open position.

The limit switch feeds back a "fully open" signal to the central control room.

Confirm that the valve action time complies with the design requirements.

Remote shutdown

The DCS/PLC issues a shutdown command.

When the solenoid valve loses power, the cylinder opens and exhausts on the side.

Single-acting spring return or double-acting reverse gas supply can push the ball to the fully closed position.

The limit switch feeds back a "fully off" signal to the central control room.

On-site manual emergency response

Cut off the gas supply and confirm that the actuator has been depressurized.

Disengage the clutch between the pneumatic actuator and the worm gear box (if equipped).

Manually open and close the valve according to the worm gear operation process.

After the operation is completed, reset the clutch and restore the air supply.

Iv. Electric Operation Process

Remote activation

The DCS issues an activation command.

The contactor is engaged, and the motor starts to rotate in the forward direction.

The valve stem is driven by the reduction mechanism, and the ball rotates to the fully open position.

When the limit switch or electronic torque detection is in place, the power supply to the motor is automatically cut off.

The position transmitter feeds back a "fully open" signal to the central control room.

Remote shutdown

The DCS issues a shutdown command.

The motor starts in reverse.

When the sphere rotates to the fully closed position, the torque switch automatically cuts off the power upon detecting the set torque.

Feed back the "all off" signal to the central control room.

On-site operation

Switch the actuator control mode to "LOCAL/LOCAL".

Operate through the "OPEN/CLOSE" button on the in-place panel.

Observe the local position indicator to confirm that it is in place.

After the operation is completed, switch back to "REMOTE".

Special precautions for electric operation

Torque protection: The turning torque value of the electric actuator has been set at the factory. During operation, it is strictly prohibited to increase it without authorization, otherwise the valve seat sealing surface will be damaged.

Overheat protection: The continuous opening and closing times of the S2 duty motor are limited. Frequent operation and overheating will trigger thermal protection and automatically shut down.

Emergency power failure: Valve position retention when power is cut off. In case of emergency shutdown, the handwheel should be used for manual operation.

V. Safety Warnings

Prohibited items and consequences

It is prohibited to forcibly open the sealing surface under full pressure difference to avoid erosion damage. Excessive torque may cause the valve stem to break

Do not use the extension rod or strike the handle to deform the valve stem, break the worm gear or crush the sealing surface

Excessive reverse rotation is prohibited for the ball to shift to the fully closed position, which may cause internal leakage of the valve

It is prohibited to adjust the limit bolts at will. If the limit fails, the ball will be out of position or not closed properly

It is strictly prohibited to disassemble the packing gland under pressure as the medium may spray out and cause personal injury

Vi. Inspection after operation

Confirm that the position indicator is consistent with the actual valve status.

Check that there is no external leakage at the valve stem packing and the valve body connection.

Check that there is no leakage in the air path of the pneumatic actuator and the oil level of the three-piece oil mist lubricator is normal.

Check that the operating current of the electric actuator is within the normal range, and there is no abnormal vibration or noise.

Record the operation time, operator and valve status, and incorporate them into the operation log.

The deformation chamber of the valve seat plate spring has poor sealing performance, resulting in silicon powder entering the deformation chamber of the valve seat plate spring, causing the plate spring to be blocked and fail. After that, the ball valve is locked by the valve seat and cannot be opened and closed well.

2. Silicon powder enters the middle chamber between the valve body and the ball during valve opening and closing, causing the ball to lock and preventing the valve from opening and closing smoothly. But the reason for this requires a working condition, which is that the silicon powder can only bond inside the cavity when it is moist. And silicon powder will not cause this kind of locking in dry or fluid conditions. If the silicon powder causes lock up in dry or fluid conditions, it means that the silicon powder has entered the deformation chamber of the valve seat plate spring.

Solution to the above two methods of causing forged steel ball valves to lock up:

The 1 Kezhong valve adopts a fully "O" - shaped sphere, double seat, and plate spring loading structure. The seat seal is designed as a wide face knife structure, which can remove the silicon powder adhered to the sphere during valve opening and closing, and has self cutting self-cleaning function. The plate spring adopts a double graphite sealing structure, which not only seals the valve, but also seals the plate spring. The medium will not enter the deformation chamber of the plate spring, so that the plate spring will not be blocked or fail, and can meet the requirements of long-term use.

2. In the special situation where the valve cavity is blocked by damp silicon powder and cannot be opened or closed, we generally recommend that customers strengthen the drying effect of silicon powder or use the V-shaped hemispherical valve introduced by Kezhong Valve to solve this blockage problem.

1. Suitable wrenches should be used when operating manual valves. It is strictly prohibited to use large wrenches for small valves and small wrenches for large valves. It is also strictly prohibited to add force rods to the wrench for operation.

2. When operating the valve, stand on the side of the valve handwheel. It is strictly prohibited to operate in the direction of the valve stem to prevent the medium in the pipeline from leaking and spraying out from the valve disc root, which may cause injury.

3. Use a wrench to operate the manual door. Before operation, the wrench and valve handwheel must be securely fastened to prevent slipping and injury. (Especially when standing on a potentially slippery ground)

4. The operation should be carried out with arm strength, and it is strictly prohibited to rely on body weight to prevent the wrench from slipping and falling.

5. When operating valves in acid and alkali pipelines, if there is a possibility of system leakage or direct contact with acid and alkali, labor protection equipment must be worn to prevent acid and alkali injuries, and a dedicated person must be assigned to supervise and take preventive measures.

6. All steam and water sampling valves must be operated manually, and the use of wrenches is strictly prohibited. Gloves should be worn during operation to prevent burns. If there is a leak, fire-resistant clothing should be worn.