Valve Maintenance for Turnaround & Shutdown (TAR) — Selection, Inspection & Replacement

Plant turnarounds (TAR) or scheduled shutdowns are the primary — and often only — window for comprehensive valve maintenance in process industries. A refinery turnaround at a 200,000 bpd unit might involve inspecting, repairing, or replacing 5,000–15,000 valves across all process units during a 4–8 week scheduled outage. Efficient TAR valve management — pre-identifying replacements, pre-ordering in advance, and having a disciplined inspection protocol — directly impacts the schedule and cost of the turnaround.

When to Replace vs. Repair a Valve During Turnaround

• Replace: Gate valves with wire drawing (seat damage from throttling at partial open) — seat lapping is a temporary fix; severely wire-drawn seats require body replacement
• Replace: Ball valves with scratched or pitted ball seats beyond repair tolerance — re-lapping is often uneconomical compared to new valve cost
• Repair: Globe valve packing — standard PTFE or graphite packing replacement is a 30-minute task; no need to replace the entire valve
• Repair: Gate valve backseat — if backseat is sound, replace packing only; if backseat is damaged, decision depends on valve size and remaining service life
• Replace: Any valve showing body wall thinning below minimum ASME B16.34 wall thickness — per corrosion allowance calculations in the inspection records
• Replace: Butterfly valve seat elastomers (EPDM, NBR, PTFE) — elastomers degrade over 5–10 years; seat replacement is economical for large bore valves
• Replace: Safety relief valves exceeding the manufacturer's recommended service interval (typically 5 years for process service; 3 years for sour/corrosive service)

Gate Valve Inspection Checklist During TAR

• Seat leakage test — API 598 seat test at rated pressure; record leakage in cc/min or ml/min
• Backseat test — verify backseat sealing integrity (fully open, pressurize bonnet cavity)
• Body wall thickness measurement — ultrasonic thickness (UT) at body thinning zone
• Stem condition — check for pitting, scoring, thread damage; measure stem diameter
• Packing condition — inspect packing rings, packing box bore, lantern ring
• Wedge/disc condition — visual inspection for wire drawing, erosion, cavitation pitting
• Handwheel and stem nut — check for wear, thread galling, corrosion
• Flange face condition — check for gasket contact face corrosion or damage

Procuring Replacement Valves for Turnaround

TAR valve procurement requires advance planning — 8–16 weeks lead time for engineered valves. Best practice: create a valve replacement list 6 months before turnaround by combining: (1) corrosion history and UT data from the previous inspection; (2) valve maintenance history (number of repackings, seat repairs); (3) valve age and remaining service life estimate; (4) criticality ranking (critical valves on safety-critical lines should be replaced based on age, regardless of apparent condition). Pre-order identified replacements with a 10–15% contingency quantity for valves not identified until the unit is opened.

Valve Packing Replacement Guide

• PTFE packing: standard for ambient-to-200°C service; easy to install; replace every 2–3 TARs or on leakage
• Graphite (Grafoil) packing: mandatory above 260°C; requires re-torque after first thermal cycle
• PTFE/graphite combination: most common for moderate temperature service — PTFE rings at anti-extrusion top and bottom, graphite core rings
• Packing installation: clean packing box bore, install rings with staggered joints (90° offset each ring), tighten follower to spec torque — do not over-compress or valve will be hard to operate
• Live-loading (Belleville springs): recommended for valves in high-temperature cycling service to maintain consistent packing load across thermal cycles