Pressure reaction capability covers manufacturing processes run above atmospheric pressure, either because the reaction chemistry requires it or because a gaseous reactant needs to be kept in solution. Pressure vessels in the UK are subject to specific safety regulation given the stored-energy risk they represent.
Key points
- The Pressure Systems Safety Regulations 2000 (PSSR) cover the safe design and use of pressure systems in UK workplaces, enforced by the HSE.
- PSSR aims to prevent serious injury from the hazard of stored energy if a pressure system or its components fail.
- Qualifying pressure systems require a Written Scheme of Examination (WSE), produced and periodically checked by a competent person.
- Pressure reaction capability often works alongside temperature-controlled manufacturing for combined pressure and temperature processes.
What This Capability Involves
A manufacturer with pressure reaction capability operates pressure-rated reactors and associated pipework, with a current Written Scheme of Examination in place and regular inspection by a competent person, as required under PSSR.
When You Need This Capability
You need a manufacturer with this capability if your reaction chemistry requires operation above atmospheric pressure, or if a gaseous reactant must be kept dissolved in the reaction mixture under pressure - see reaction chemistry and polymerisation for related processes.
Regulatory Considerations
PSSR requires a Written Scheme of Examination for qualifying pressure systems, produced by a competent person, along with regular examination to confirm the system remains safe to operate. Confirm with a prospective manufacturer that their pressure equipment has a current, valid WSE and examination record before committing to a process that requires pressure reaction capability.
A Certified Asset, Not an Operating Choice
Pressure vessels are designed, manufactured and certified to defined standards, and are subject to a written scheme of examination and periodic inspection by a competent person. A vessel is rated for a specific maximum working pressure and temperature, and operating outside that rating is not a matter of judgement.
The practical consequence is that pressure capability cannot be added for a project. A manufacturer either holds rated vessels of the right size with valid inspection, or they do not - which makes this one of the more decisive filters in a search. Confirm the rating and the vessel size together, since a suitably rated vessel of the wrong capacity is no more useful than an unrated one.
Why Processes Run Under Pressure
Pressure serves several purposes. It allows a solvent to be heated above its normal boiling point, giving faster reaction without loss of solvent. It is necessary for reactions involving gases, keeping them in contact with the reaction mixture. And it can improve selectivity or yield where the chemistry favours it.
Pressure work brings additional requirements around relief systems, controlled venting and emergency procedures, since a runaway exothermic reaction in a closed vessel raises pressure as well as temperature. A manufacturer experienced in this will discuss relief provision and thermal assessment as routine parts of process design.
Questions to Ask a Manufacturer
- What pressure rating and vessel capacity do you have available for our process?
- Is your Written Scheme of Examination current, and when was your last inspection?
- What experience do you have with our specific pressure reaction chemistry?
- How do you monitor and control pressure throughout a batch?
Related Pages
Frequently Asked Questions
Does every reactor need a Written Scheme of Examination?
Only qualifying pressure systems under PSSR - not all equipment falls under this requirement, but pressure-rated reaction vessels typically do. Confirm the specific status of the equipment being used for your process.
Can a manufacturer without pressure reaction capability still support our project?
Not for the pressure step itself - if your chemistry genuinely requires above-atmospheric pressure, you'll need a manufacturer with the specific vessel rating and PSSR compliance in place, though other steps in your process may not require this.
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Search the DirectoryLast reviewed: August 2026. Regulation and guidance change — verify anything you rely on against the primary source. Tell us if something here is out of date.