Valve Disassembly and Inspection Procedures

Systematic disassembly and thorough inspection of valves during maintenance shutdowns maximizes the information gained and ensures correct restoration of valve function. Following documented procedures protects personnel and equipment.

Pre-Disassembly Steps

• Confirm valve has been properly isolated, depressurized, and drained

• Verify safety isolation (lockout/tagout) is in place

• Review valve data sheet and maintenance records before opening

• Photograph valve in-situ, especially actuator and position indicator orientation

• Prepare clean work area with appropriate tooling and replacement parts

Disassembly Sequence

Disassembly should proceed in the reverse order of assembly. For a typical gate or globe valve: remove actuator if present, remove handwheel, remove packing gland and packing, remove bonnet bolting, lift bonnet, extract stem and gate/disc assembly, then remove seats if replaceable.

Inspection Points

• Stem: check for corrosion, erosion, scoring, and straightness; measure diameter for wear

• Seats: inspect for erosion, corrosion, wire-drawing, and pitting; check seating surface finish

• Gate/disc: inspect seating surfaces, examine for cracks or deformation

• Bonnet gasket surface: inspect for corrosion and damage to seating area

• Packing chamber: check for erosion, corrosion, and dimensional conformance

• Body cavity: inspect for scale buildup, corrosion pitting, and erosion patterns

Dimensional Checks

Critical dimensions including stem diameter, seat bore, and body wall thickness should be measured and compared against original drawings and acceptance criteria. Significant wear or corrosion loss requires engineering evaluation before return to service.

Documentation

All inspection findings should be documented on a maintenance report form with photographs. Condition codes (Good, Satisfactory, Degraded, Unacceptable) should be assigned to each component. Recommendations for repair, replacement, or continued service should be stated clearly.