Valves overview
Valves play a critical role in industrial operations—including oil and gas, petrochemical, chemical processing, power generation, pharmaceuticals, and plumbing—where they handle a wide range of applications and materials. Because of this diversity, valves are manufactured in many styles to meet specific functional requirements, with common types such as ball valves, gate valves, check valves, butterfly valves, globe valves, plug valves, and safety and relief valves. During operation, valves may experience issues such as internal or external leakage caused by factors like corrosion, erosion, or failure of internal sealing components including seats, O-rings, springs, stems, balls, and more. In other cases, valves may become difficult to operate, with the stem rotating only under heavy force or not at all, indicating an internal problem that requires inspection and repair. Proper valve repair and maintenance are therefore essential and require a solid understanding of valve function and servicing procedures. Before performing any maintenance, it is important to review the maintenance scope, drawings, and applicable standards; relevant standards commonly used in valve repair and testing include API 598, API 6A, API 6D, API 621, API 623, API 624, ASME B16.34, ASME PCC-1, ASME PCC-2, API 527, API 576, ASME Section IX, and other applicable industry standards.
Maintenance tasks include
- Visual inspection
- Operational checks
- Inlet and outlet leak testing
- Seal and gasket inspection
- Lubrication
- Pressure and flow verification
- And some complementary steps
Note: When determining whether to repair or replace a valve, consider both the cost and the expected benefits based on inspection results and applicable standards. In some cases, repair costs may exceed the price of a new valve, making replacement the more economical option. Additionally, time constraints during maintenance or shutdown periods may make it more practical to replace a defective valve rather than repair it.
Note: Before performing any maintenance or repair work, review all relevant technical documents and data sheets, along with the associated drawings, standards, and safety regulations for the valve.
Note: Before removing any valve components, ensure that all internal pressure has been fully relieved and that any gases or liquids have been completely drained from the system. Some valves are equipped with external safety plugs; these must be carefully opened and removed prior to performing any repair or maintenance activities.
Note: This article and proposal provide only a brief introduction; a complete and practical maintenance proposal must be prepared for each specific valve, taking into account all relevant specifications, operating conditions, and requirements.
Work Breakdown Structure (W.B.S) for Valves Repairing
In general, the Work Breakdown Structure (WBS) for different types of valves varies, but many elements remain the same across most valve categories. Therefore, the following section focuses on the WBS components that are commonly shared in valve maintenance and repair.
Note: Use a standard crane for heavy equipment and follow safety regulations
| Item | Job Description |
| 1 | Review the maintenance scope, drawings, technical documents, and applicable standards, followed by depressurization, purging, and shutdown of the system. |
| 2 | Get a work permit |
| 3 | Isolate piping from valve |
| 4 | Disconnect and isolate all instrument devices and electrical cables, ensuring this step is performed by a qualified instrumentation expert. |
| 5 | Drain and vent the system for safety by opening all required drain and vent lines. |
| 6 | Install scaffolding and access platforms (if required) |
| 7 | Remove insulation (if required) |
| 8 | Remove the valve and transport it to the workshop or another designated safe location. Note: Use a standard crane for heavy equipment and follow safety regulations |
| 9 | Actuator, instrument, and electrical components must be removed separately, and this activity must be performed and supervised by a qualified instrumentation specialist. |
| 10 | Separate and remove the gearbox or motor-operated valve (MOV), bonnet, gland bush, and other related components from the valve body. To do this, loosen the bolts, connecting the bonnet to the body and then lift the bonnet out carefully. Note: Before removing the bonnet, mark its installation position on the body to ensure proper reassembly. |
| 11 | Remove all internal components from the valve body. Remove the stem; in most valves, the stem is threaded and engages with the ball, disc, plug, or other closure elements to allow rotation and movement. For major maintenance and repair, the stem should be removed before extracting the discs, balls, or other internal parts. Next, remove the ball, disc, plug, or other closure element from inside the body, followed by the seats and any additional internal components. Note: Before removing each part, mark its orientation and installation position to ensure proper reassembly. After disassembly, thoroughly clean all components and the valve body. For proper inspection and evaluation of valve components, all parts must be thoroughly cleaned. Use the appropriate cleaning materials and methods to achieve the required surface condition in accordance with applicable standards |
| 12 | Perform a Visual inspection for corrosion, erosion, dents, cracks, buckling, bending, holes, and any other signs of damage. Conduct additional tests as required: • Ultrasonic Thickness Testing (UTM) • Magnetic Particle Inspection (MPI) • Dye Penetrant Testing (PT) • X-ray Testing • and more |
| 13 | Prepare inspection report based on standards. |
| 14 | Replace the defective and damaged parts. All nonmetal sealing and rings must be replaced All Activity must comply with standards. Note: The list of spare parts for each valve can be found in the technical documents and drawing data sheets. Note: All spare parts must meet certified standards. Their dimensions, material composition, and manufacturing methods must be reviewed and verified against the applicable standards and technical documents. |
| 15 | Fill dented or corroded areas with weld material and restore them to their original dimensions. Grind or machine the repaired surfaces as needed to match the specifications in the drawings and original dimensions. This step must be carried out in accordance with applicable standards and technical documents. |
| 16 | Install the springs, rings, O-rings, gaskets, discs, seats, and other required components on the valve body according to the drawings and technical documents. Install the internal parts, such as the ball or plug, inside the valve in accordance with the standards, drawings, and technical documentation. All tolerances and clearances must be checked and verified against the technical requirements. Install the stem onto the ball or plug before placing the ball or plug inside the valve body. Install the gearbox or motor-operated valve (MOV) on top of the valve. Fill the gearbox with the appropriate standard grease. Note: before installing the parts inside of body valve, inject the lubrication and grease, Anti-seize compound and etc. to assist the standard operation of valve. Note: For control valves and MOVs, ensure that after the mechanical valve has been repaired, the actuator and all associated accessories are installed in accordance with the applicable standards. This step must be performed and supervised by a qualified instrumentation specialist. |
| 17 | Test the valve in accordance with the applicable standards. This testing includes both internal and external leakage tests to ensure the valve operates properly without leakage. For external leakage verification, the valve must be tested to confirm the integrity of the bonnet, stem seals, safety plugs, drain plugs, and other external sealing points. A standard valve test bench must be used for this procedure. The test conditions including pressure, duration, and medium, must fully comply with the requirements specified in the relevant standards. Note: Based on some standards, for some valves the internal leakage can exist, but this leakage is limited to a few drops per minute. |
| 18 | Install the certified valve on piping system. Use the new gasket for jointing to the piping. Use the certified crane for lifting valve and putting it on its location. |
Material Requirements for Valve Maintenance
During the repair of valves, sometimes defective parts must be replaced with new ones. Here is the list of materials that are used for valve maintenance and repair. All materials must be standard and must meet safety and technical regulations.
| Item | Specification |
| 1 | Valve spare parts such as balls (plugs, gates, etc.), seats, rings, seals, gaskets, springs, packings (graphite, PTFE, etc.), glands, bushes and sleeves, stems, stud bolts and nuts, gearboxes, MOVs, and others. Note: The spare‑parts list for each valve can be found in the technical documentation and the associated drawing data sheets. Note: all spare parts must be certified standard. Dimensions and material composition and type of manufacturing must consider and check with standards and technical documents. |
| 2 | Flanges (if required) |
| 3 | Gaskets |
| 4 | Stud bolts and nuts |
| 5 | Pipe coating materials |
| 6 | Paint cleaner |
| 7 | WD-40 and other lubricant |
| 8 | Anti-seize compound |
| 9 | Grease |
| 10 | Additional materials as required |
Tools Requirements for Valve Maintenance
Repairing the valves requires the use of special tools that support performing maintenance in accordance with standards and help reduce overall costs. Moreover, using these specialized tools saves time and improves the quality of maintenance.
Here is a list of some of the tools used for valve repair.
Note: all tools must be standard and met safety and technical regulation
| Item | Specification |
| 1 | valve testing equipment |
| 2 | Hand wrenches in various sizes |
| 3 | Hydraulic or pneumatic tools and wrenches |
| 4 | Flange jacks |
| 5 | Standard and certified Crane for heavy valves and spools (if required) |
| 6 | Lifting belts |
| 7 | Hydraulic flange spreader |
| 8 | Hammers (iron, brass, and Teflon) |
| 9 | Air compressor |
| 10 | Blind Flange for testing the valve |
| 11 | A test flange is used for testing the valve, and it includes a hole that serves as a connection point for hydraulic or pneumatic equipment. |
| 11 | Tools for Grinding and machining the valve parts |
| 12 | Additional tools as required |
