Feedwater / Access planning
Leave room for the handwheel, stem and yoke
A valve module must cover the intended hot surfaces without obstructing operation or service. Bore size alone cannot define the required opening.
Open the equipment studyConstruction
Identify how the valve moves
Handwheel and stem
Record whether the stem rises, rotates or remains enclosed. Show both travel limits on the coverage drawing. Reserve the operating space for the handwheel and any fitted position indicator. Do not treat gate, globe and quarter-turn ball valves as one geometry.
Bonnet and yoke
Distinguish the pressure-containing bonnet from the support around the stem or actuator. Their permitted insulation boundaries can differ. Manufacturer instructions are model-specific: ARI STEVI 405/460 instructions describe separate actuator and bonnet work. They do not identify or approve the valve in this render.
Module layout
Preserve service routes
Openings that have a purpose
Show access to the packing area, identification plate and fasteners needed for service. Mark module seams and the direction each section is removed. Do not turn an unverified clearance into a universal millimetre value. An exposed moving part may still require a separate burn-risk assessment.
Do not test by changing the live process
A designer should use drawings and an authorised maintenance inspection to confirm travel and removal space. Do not operate an in-service valve merely to check a module. Dismantling requires the site isolation procedure and the applicable manufacturer instructions.
Calculation
Separate covered and exposed surfaces
Flange and bonnet hardware
Include bolts, studs and nuts only where present. Record exposed heads, nuts and shank lengths at each joint. Keep their temperatures and coverage status with the area record. Do not assume that every bolt is at fluid temperature or multiply a generic bolt pack by DN.
A useful handoff
Supply the valve model, dimensional source, open and closed envelopes, covered surface inventory and excluded hot surfaces. The calculation should retain losses from parts left exposed. A good module fit does not prove the assumed thermal area, and a low calculated temperature does not prove free movement.
Asked about access
Questions.
Answers distinguish modelled heat-loss estimates from equipment selection and service guidance.
Can DN determine handwheel clearance?
No. DN describes nominal bore, not the handwheel envelope, stem travel or bonnet construction. Use the exact valve drawing and operating instructions.
Do exposed bolts disappear from the insulated calculation?
No. Record exposed fasteners and other uncovered hot surfaces separately. Avoid counting hardware twice when an area model already includes it.
This is an insulation planning checklist, not a maintenance procedure or OEM installation approval. Use the exact equipment manual and site safety controls.
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