Valve Maintenance: An Open and Shut Case?
By D. YOUNG, Celeros Flow Technology (Celeros FT), Aberdeen, Scotland
(P&GJ) — Valves are essential pieces of flow control equipment used in applications from water treatment and chemical processing to power generation and offshore platforms. They enable the safe and efficient storage, transportation, production and/or processing of gases and liquids at the desired rate, pressure and temperature—often in harsh and remote environments.
Maintaining valves throughout a plant’s lifetime helps to preserve optimal performance, minimize supply disruptions and reduce environmental impacts; however, it can be challenging. Remote locations, extreme operating conditions and the often-aggressive properties of the fluids being transported can pose specific servicing and maintenance challenges (FIG. 1).
Warning signs
Valves may remain in one position—either open or closed—for most of their service life. While they may not need to operate frequently, regular maintenance is essential because it is undesirable to discover a valve is not functioning properly at a critical moment. Routine inspection, such as actuator/operator testing (including partial stroke), helps identify early warning signs of valve deterioration. Many issues can be detected early without even opening the valve. However, some signs indicate more serious safety and operational risks that may require urgent intervention.
Deterioration of consumables
Parts like O-rings become brittle over time, reducing efficacy and leading to breakages. Visual inspection, which can be undertaken without opening the valve, will reveal telltale signs like cracks and discoloration. The part will also feel hard, rather than pliable, to the touch. Other visual indicators may be external leakage through mating components and joints or gaskets that are visibly damaged or protruding from joints, which can indicate overpressure, improper installation or thermal cycling.
Increased energy consumption
Solids accumulate in the bottom of the valve body over time, particularly in dirty services. Left unchecked, this material will adversely affect valve operation, prevent full gate travel and impact the valve’s functional capability. On electrically actuated valves, torque or thrust requirements increase because the actuator must compensate. Left unresolved, sediment build-up results in higher energy costs.
Actuator or handle resistance
Accumulation of solids may also result in excessive force being required to operate the valve manually or via an actuator. Difficulty operating the valve may also indicate internal friction or mechanical failure.
Scratches and gouges
Scoring to the valve stem indicates internal damage to the stem and packing. The yoke must be removed to confirm the cause, which involves some time and cost, but this is preferable to a full rebuild if the damage is not rectified. Full replacement of the valve’s top works to incorporate a two-piece stem rather than a single piece makes it easier to swap out damaged parts and meet actuation requirements. Whether the valve is welded in or buried, this approach can extend valve life without requiring complete replacement.
Leakage
Valves can leak in different ways and for different reasons. Internal leakage (passing) occurs through the valve itself, typically between the seats and the ball, disc or plug. Causes include seat wear, erosion, corrosion or debris lodging between sealing surfaces. Leaking valves are not cheap to repair, particularly if they are sub-surface and/or weld-in valves that must be repaired in situ during planned outages. If a valve is leaking internally (referred to as passing), it will not shut off completely, posing a potential safety risk. Consequences include product losses, product contamination and environmental damage.
External leakage occurs through the gland packing, flanges or body joints. Packing leakage may result from improper installation, thermal cycling, vibration or packing degradation over time. Flange and joint leaks may be caused by gasket failure, bolt loosening or misalignment during assembly. Packing leakages can be temporarily mitigated by injecting packing compound, but this is not a substitute for identifying the cause of the leakage and proper replacement.
Better leakage prevention
A new way to prevent leaks is the author’s company’s valve packing systemᵃ (shown in FIG. 2), developed to reduce fugitive emissions and provide a safe and efficient sealing solution for valves. This valve packing systemᵃ uses a spring-loaded mechanism to ensure a tight and robust seal even under extreme conditions, eliminating the need for packing tightness intervention during the seal’s lifetime.
It also accommodates slight misalignments or deformations in the valve stem or body, further helping to prevent leaks and reduce the need for frequent maintenance or repair. Simple to retrofit, the valve packing systemᵃ is well suited for critical valves in remote and inaccessible locations that are not used for extended periods. The system is certified to ISO 15848-1 and ISO 15848-2 fugitive emissions type tests and adheres to API 6FA and ISO 10497 valve fire test standards.
Reactive or corrective maintenance
Despite the best-planned maintenance schedule, unexpected valve failures will occur. Reactive or corrective maintenance involves unplanned intervention for emergency repairs. Downtime depends largely on the availability of qualified personnel and replacement parts. Budget constraints, regulatory requirements, operating environments and personnel availability all influence maintenance decisions.
Risk assessments evaluating safety, environmental and financial consequences help determine appropriate maintenance strategies. These decisions should be supported by historical data, reliability analysis and cost-benefit assessments.
Preventative maintenance
A preventative maintenance regime involving planned, routine actions aids compliance and can prevent valve failures or performance degradation. Preventative maintenance is essential to ensure optimal performance, prevent leaks, minimize downtime and extend the lifespan of valves, but what does best practice look like?
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Regular visual inspections should be undertaken to check valves for signs of wear, corrosion or damage. Any leaks around valve seals, flanges and connections must be addressed promptly. Tighten any loose bolts and replace damaged gaskets as part of any maintenance regime.
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Change out consumables (soft goods) whenever the valve is opened as part of regular maintenance schedules. Ideally, maintenance teams should also replace the valve seat, gate and stem as a precaution at 10-yr intervals for good actor valves. Bad actors require earlier intervention to determine and correct the cause of the problem.
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Regular lubrication of all moving parts is good practice. It reduces friction and ensures smooth operation. Lubrication type and frequency will depend on the valve manufacturer, so always check the guidelines. Grease costs less than loss of production.
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Cleaning valves will remove build-up of dirt and debris, while periodically flushing associated pipelines or vessels will help prevent sediment from accumulating and affecting valve performance.
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Periodic testing of valves under actual operating conditions should be performed at regular intervals (either partial or full stroke). This will ensure that the valves open and close smoothly without sticking or excessive force when required.
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Accurate record keeping and retrieval are key to good valve maintenance. Keep maintenance logs detailing all activities—inspection dates, repairs and replacement parts used, including as-found condition—in an electronic database.
Outsourcing maintenance
Retaining comprehensive valve maintenance resources in-house is not always practical. Outsourcing can provide access to specialized expertise, advanced technologies and lifecycle services that improve reliability and environmental performance.
The author’s company services both its own-brand and third-party valves through a global network of service centers, offering lifecycle support, engineered upgrades, inventory management and training programs.
Outsourcing in action
The author’s company resolved a critical valve maintenance issue for a pipeline operator (FIG. 3) after an unexpected failure threatened production schedules. A legacy valve installed in the 1970s required obsolete spare parts that were no longer available. By rapidly engineering modern components to fit the existing valve, the company restored performance within a 12-hr maintenance window—avoiding production losses estimated at $500,000 per day.
Takeaway
Valve maintenance is a complex but essential component of safe, efficient and reliable industrial operations. By combining preventative strategies with expert lifecycle support, operators can reduce risks, enhance performance and ensure long-term asset reliability.
NOTE
ᵃ Celeros Flow Technology’s CFT-Green Valve Packing System
About the Author
DAVID YOUNG is the Valve Aftermarket Development Director at Celeros Flow Technology. His expertise includes the design, manufacture and overhaul of rotating and static equipment, working in both dynamic service environments and original equipment manufacturing. David holds an MEng degree in mechanical engineering and has more than 20 yrs of experience in international technical and managerial roles. He started his career with Celeros FT as an apprentice in the company’s Glasgow factory, which is now the ClydeUnion Pumps brand, rising to be Principal Engineer.