TL;DR
Autoclave door or penetration seal leakage causes inability to hold cure pressure. Inspect and replace the door seal, check penetration fittings, and verify the seal groove is clean before pressurizing.
What you might see
- cure pressure drops during the hold phase requiring the compressor to compensate
- audible hissing near the door seal during pressurization
- pressure hold test fails during pre-cure checks
- visible wear groove or flat spot on the door seal
Likely causes
Door seal aged or compression-set no longer filling the seal groove
Door seal groove contaminated with resin or debris preventing full contact
Penetration fitting seal failed at a thermocouple or vacuum port
Door locking mechanism under-tightened preventing full seal compression
Required tools
- Replacement door seal (ASC-specified material and size)
- Solvent for seal groove cleaning
- Pressure test gauge (calibrated)
- Penetration fitting wrench set
- LOTO kit
Safety first
- The autoclave is a pressure vessel. All maintenance on seals and penetrations must be performed with zero pressure in the vessel.
- Consult the ASC vessel documentation before changing seal materials or cross-sections. Incorrect seals can fail under cure pressure.
Procedure
- 1
Depressurize the autoclave to zero and confirm zero pressure on the vessel gauge before opening the door.
Warning: Never open the autoclave door with any pressure remaining in the vessel. Verify zero pressure on a calibrated gauge. - 2
Open the door and inspect the door seal in the seal groove. Look for flat spots, cracking, or tears in the elastomer.[1]
- 3
Clean the seal groove thoroughly with a solvent-dampened cloth to remove resin, dust, or debris.
- 4
Replace the door seal with an ASC-specified seal of the correct cross-section and material. Follow the ASC installation procedure for seal splicing or continuous ring installation.[1]
- 5
Inspect each thermocouple and vacuum penetration fitting for seal integrity. Tighten fittings or replace seal washers as needed.
- 6
Close the door and run a low-pressure leak test (typically 20 to 50 psi) before running a full production cure cycle.
Sources
ASC Process Systems ASC Econoclave Composite Autoclave general technical documentation, ASC Process Systems
ASC Econoclave pressure vessel and door seal maintenance documentation (general)
More guides for ASC Process Systems ASC Econoclave
How to diagnose temperature uniformity failure on an ASC Econoclave composite autoclave
Temperature non-uniformity during composite cure causes ply delamination or under-cure. Check thermocouple placement, recirculation fan speed, and door seal integrity before adjusting the cure profile.
How to diagnose vacuum system faults on an ASC Econoclave composite autoclave
Vacuum loss during composite cure can cause voids and delamination in the finished part. Check the vacuum bag integrity first, then inspect the vacuum pump and lines if bag is intact.
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