Expanding Gate Valve Maintenance: Troubleshooting Leakage and Operation Issues

Supporting Long-Term Functional Performance

The functional reliability of any mechanical equipment is supported by an approach that includes periodic observation and considered care. For valves in critical service, understanding their operational characteristics and potential performance shifts contributes to system availability and safety. This article outlines practices for the maintenance of expanding gate valves and provides insights into addressing some situations that may be encountered during their service life.

Practices for Sustained Operational Readiness

A structured approach to care can help in identifying potential issues before they affect system operation. These practices focus on observation and routine servicing.

Cyclical Operational Checks

Periodically exercising the valve through a full open and close cycle is a recommended practice for valves that are normally left in a static position for extended periods. This helps prevent the accumulation of deposits that might impede movement and ensures that the operating mechanism remains free. For valves in standby service, a quarterly or semi-annual cycle is often suggested, depending on the service conditions.

External Observation and Leakage Monitoring

A simple yet effective practice involves regular visual inspections of the valve. This includes checking for signs of external corrosion, inspecting the condition of the stem threads on manual operators, and monitoring for any evidence of leakage from the stem packing or the body/bonnet connections. Early identification of minor leaks from the stem packing often allows for adjustment while the valve is in service.

Addressing Specific Operational Observations

Despite a robust design, situations may arise where the valve does not perform as expected.

If a valve becomes progressively more difficult to operate, it may indicate the presence of foreign material within the valve body or an issue with the stem threads. A procedure involving partial stroking and flushing, if possible, can sometimes clear debris. For manually operated valves, inspecting, cleaning, and lubricating the stem threads can restore smooth operation. If high torque persists, internal inspection may be necessary.

A common indicator of seat leakage is the inability to maintain pressure in an isolated section of pipe. For expanding gate valves, this can result from damage to the gate or seat sealing surfaces or from an obstruction preventing the gate from fully expanding. Some valve designs incorporate a sealant injection system that can be used to introduce a compatible sealant into the seat area, which can temporarily restore sealing capability until a permanent repair can be scheduled.

Guidance for Internal Inspection and Component Care

When a valve is removed from the line or system isolation allows for internal work, a thorough inspection can be performed.

Internal Cleaning and Examination

The internal cavity should be carefully cleaned to remove all process residue and debris. The gate, seats, wedge, and stem should be examined for signs of erosion, corrosion, or scoring. Light surface marks may not affect performance, but significant deformation or pitting on the sealing surfaces typically requires component replacement or specialized repair.

Seat and Seal Replacement

Replacing the seat rings and other seals is a standard repair procedure. It is important to use replacement parts that conform to the original valve's design specifications to ensure proper fit and function. Following the manufacturer's assembly procedures, including recommended torques for seat retainers and bonnet bolts, is necessary for restoring the valve's pressure-containing integrity.

A systematic approach to the care of expanding gate valves, combining regular observation with a clear process for addressing functional observations, contributes to their reliable operation over time. Keeping records of maintenance activities and any performance observations provides valuable historical data for planning future inspections and turnarounds. This proactive stance supports the overall operational readiness of the piping system in which these valves are installed.