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Valves are the most critical – and most neglected – components in a process plant. A disciplined maintenance program routinely extends service life by 50% or more and prevents the unplanned shutdowns, safety incidents and emissions that cost far more than the upkeep. This guide gives a practical schedule, the "exercise or seize" rule, the failure modes you will actually meet, and when repair stops making sense.
A static valve is a vulnerable valve. Metal surfaces left in contact under pressure can cold-weld; stem packing hardens and adheres; sediment and scale build up in the cavity. Cycling the valve breaks these bonds, flushes debris, and – critically – proves the valve will actually move during an emergency. Frequency by service:
For automated ESD / control valves, use a Partial Stroke Test (PST) – move the valve part-way and return it – to verify function without interrupting the process.
Lubricate stems, bearings and gear operators per the manufacturer schedule (typically every 3–6 months). Match the grease to the service: lithium-based for normal duty, polyurea for high temperature, fluorinated for aggressive chemicals. Never over-lubricate – excess grease attracts abrasive dust and can contaminate soft seats. Stainless valves must avoid chlorine-containing cleaners that cause pitting.
Repair when only the trim (seats, packing, gaskets, disc) is damaged and the body is sound – it is cost-effective and parts are available. Replace when the body has cracks or severe corrosion, repair cost exceeds roughly 60% of a new valve, the model is obsolete with no spares, or it fails repeatedly despite fixes. Keep a valve register with tag number, specification and full maintenance history to make that call on data, not guesswork.
Before any intervention: depressurise and drain the line, isolate with upstream/downstream block valves, confirm zero energy, and apply Lockout/Tagout (LOTO). For actuated valves, disconnect the power (pneumatic / electric / hydraulic). Use a torque wrench and OEM-equivalent parts – never force a stuck valve with a cheater bar, which bends stems and strips gears.
A static valve is a vulnerable valve. General guidance by service: clean / potable water annually; wastewater, slurry or sewage every 3-6 months (sediment settles in the cavity); corrosive chemicals or seawater every 1-3 months; high-temperature steam every 6 months. For automated ESD/control valves use a Partial Stroke Test (PST) so you verify function without shutting the line. Always cycle before a planned shutdown so a stuck valve never surprises you during an emergency.
First tighten the gland nuts evenly (a little at a time, opposite sides like a flange) – over-tightening raises operating torque and can extrude the packing. If leakage continues, the packing is worn or the wrong grade for the service: depressurise, lock out, and repack with a compatible ring set. For fugitive-emission-regulated plants, act when stem emissions exceed the limit per ISO 15848 / EPA Method 21.
No. Gate valves are on/off isolation devices – operated fully open or fully closed. Throttling with a partially open gate exposes the seat edges to high-velocity flow, scoring and eroding the seats until the valve can no longer seal. Use a globe or control valve for throttling duty; keep gates for isolation.
Visual inspection weekly or monthly depending on criticality; operational stroke testing monthly to quarterly; detailed leak and seat checks quarterly to semi-annually; full internal overhaul during annual shutdowns or turnarounds (every 5-10 years for low-criticality block valves, annually for safety-critical ones). Keep a valve register with tag number, spec and maintenance history.