Case Study: Vacuum Pressure Vessel for Ceramic Coating Technology — Toshiba Industries, Japan
The Client
GC Logicals was engaged by a specialist design house operating at the cutting edge of ceramic coating technology, based in the Oxford-Cambridge Arc — one of the UK’s most innovative technology corridors. The end client was Toshiba Industries, Japan. The project demanded a level of precision, compliance, and documentation control that left no margin for error.
The Challenge
The scope centred on a complex 316L stainless steel pressure vessel — 2,600mm in length and 1,400mm in diameter — designed and built to exacting standards for use as a vacuum vessel in a ceramic coating application.
The design presented several significant technical challenges simultaneously:
Double-skinned dished ends — each end of the vessel featured an inner dished head of 10mm thickness and an outer dished head of 5mm, with the void between them forming a water cooling system. The geometry and the welding sequence required careful planning to maintain dimensional integrity and ensure full water-tightness.
Spiral-fluted water jacket — the vessel body incorporated a 3mm water jacket with spiral fluting to control the water cooling pathway around the vessel shell. Welding in this area demanded precision to maintain the integrity of the cooling circuit without distortion.
Vacuum service leak rate requirements — as a vacuum vessel, all sealing faces and O-ring grooves were subject to a strict surface finish requirement of Ra 0.2. This is an exceptionally fine machining tolerance. A specialist tooling provider was consulted to confirm correct tooling selection, a surface roughness checker was procured to verify compliance, and a dedicated machining quality plan was drafted, reviewed with the machine shop, and formally issued before any machining commenced.
The vessel was designed in accordance with PD5500 and all welding was carried out in accordance with BS EN ISO 15614 and BS EN ISO 9606.
The GC Logicals Approach
Welding Compliance
A full weld mapping, PQR and WQR gap analysis was carried out at the outset. The review identified that existing Welding Procedure Qualifications covered the majority of the scope, with one additional PQR required for small bore fillet welds. This was developed and qualified before fabrication commenced, ensuring full procedural coverage across every weld on the vessel.
Manufacturing Path Development
A detailed manufacturing path was developed incorporating formal Hold Points and Witness Points at every critical stage of fabrication, machining, and testing. This gave the client full visibility and control throughout the programme without disrupting the production schedule.
NDT Sourcing & Control
All non-destructive testing was sourced, controlled, and managed by GC Logicals:
- Dye Penetrant Inspection (DPI) — carried out in-house
- Radiographic Testing (RT) — applied to all vessel seams
- Ultrasonic Testing (UT) — applied to thick section welds
Works Procedures
A full suite of works procedures was generated and issued for client approval, covering DPI, RT, UT, Hydrostatic Testing, Visual Inspection, Vacuum Leak Testing, and Weighing. Every procedure was returned Code A — Approved Without Comment by the client. First time, no exceptions.
Testing & Verification
Hydrostatic testing was carried out on all water jackets and the vessel itself Vacuum Leak Testing demonstrated a Maximum Leak Rate of 7×10⁻³ mbar l/s — meeting the specified requirement All surface finishes on sealing faces and O-ring grooves were verified against the Ra 0.2 requirement prior to final inspection
The Outcome
The vessel was manufactured, tested, documented, and delivered on time and within budget to the satisfaction of both the design house client and Toshiba Industries, Japan.
Every weld was traceable. Every test was witnessed and documented. Every procedure was approved without comment. The project is a benchmark example of what rigorous compliance management, practical engineering knowledge, and methodical project control delivers in a high-stakes, high-precision manufacturing environment.
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