Pressure vessels

Guidance on pressure vessels.

Policy Framework: Arrangements

The use of pressure vessels is covered by Section 15 of the University Health and Safety Policy, Framework: Arrangements document. The following information must be considered in conjunction with this section of the Framework.

Code of Practice

General guidance

A ‘Pressure System’ is a system comprising one or more pressure vessels of rigid construction, any associated pipework and protective and measuring devices, or the pipework with its protective devices to which a transportable pressure receptacle is, or is intended to be, connected and which contains or is liable to contain a relevant fluid, but does not include a transportable pressure receptacle (gas cylinder). ‘Pipework’ means a pipe or system of pipes together with associated valves, pumps, compressors and other pressure containing components and includes a hose or bellows but does not include a pipeline or any protective devices.

A ‘relevant fluid’ means –

1. steam (at any pressure);
2. any fluid or mixture of fluids which is at a pressure greater than 0.5 bar (7.25 psi) above atmospheric pressure, and which fluid or mixture of fluids is-
   1. a gas, or
   2. a liquid which would have a vapour pressure greater than 0.5 bar above atmospheric pressure when in equilibrium with its vapour at either the actual temperature of the liquid or 17.5 degrees Celsius; or (c) a gas dissolved under pressure in a solvent contained in a porous substance at ambient temperature and which could be released from the solvent without the application of heat. ‘Pipeline’ means a pipe or system of pipes used for the conveyance of relevant fluid across the boundaries of premises, together with any apparatus for inducing or facilitating the flow of relevant fluid through, or through a part of, the pipe or system, and any valves, valve chambers, pumps, compressors and similar works which are annexed to, or incorporated in the course of, the pipe or system.

The University Safety, Health and Wellbeing Committee reviewed and authorised the publication of the Pressure Vessels guidance document, written by by Steven Gourlay, Technical Support Officer, School of Engineering and Richard Fincham, Senior Engineer (Pressure Systems) Zurich Engineering as a corporate guidance document which must be adhered to as much as possible.

Pressure Vessels guidance

Legal requirements

Registration and Written Scheme of Examination

The main Regulations that cover pressure equipment and pressure vessels are the Pressure Equipment Regulations (PER) 2016 and the Pressure Systems Safety Regulations (PSSR) 2000.

One of the main requirements of the Regulations is that a ‘Written Scheme of Examination’ is drawn up by a ‘Competent Person’ for any pressure system and that that system then be examined annually and maintained in accordance with the Written Scheme of Examination. In this University the Competent Person who undertakes annual examinations and produces Written Schemes is the engineer supplied by the University’s engineering insurers. The onus to ensure that a system is maintained in accordance with the Written Scheme of Examination lies with the individual School or Support Unit. Therefore all autoclaves and other pressure vessels (such as air receivers, boilers, calorifiers, pressure cookers and other gas pressure vessels, such as gas cylinders owned by schools) must be notified to the University's Engineering Insurers.

In order to ensure that a Written Scheme of Examination is drawn up for any pressure system that a School may have, details must be passed to the Insurance Office at: insurance@ed.ac.uk. Notification of newly installed equipment is required before it is brought into use, so that the requirements of the Pressure Systems Safety Regulations may be complied with.

Details required are;

• Name of School or Support Unit
• Contact name/telephone number
• Description of equipment (e.g. air receiver)
• Manufacturers name
• Serial number of item (usually found on a plate affixed to the equipment)
• Exact location of equipment (e.g. room 29 Joseph Black Building, Kings Buildings)

The following pressurised systems are likely to require a written Scheme of Examination:

• A compressed air receiver and the associated pipework, where the product of the pressure in bars multiplied by the internal capacity in litres of the receiver is equal to or greater than 250 bar litres;
• A steam sterilising autoclave and associated pipework and protective devices
• A steam boiler and associated pipework and protective devices;
• A pressure cooker
• A gas loaded hydraulic accumulator
• A vapour compression refrigeration system where the installed power exceeds 25kW
• The components of self-contained breathing apparatus (BA) but excluding the gas cylinder
• A fixed LPG storage, system supplying heating for the workplace

The following systems are unlikely to require a Written Scheme of Examination;

• An office hot water urn
• A machine tool hydraulic system
• A pneumatic cylinder in a compressed air system
• A portable compressed air system and associated pipework where the product of the pressure in bars multiplied by the internal capacity of the receiver is less than 250 bar litres
• Any ‘pipeline’ and its protective devices in which the pressure does not exceed 2 bar above atmospheric pressure
• A portable fire extinguisher with a working pressure below 25bar at 60oC and having a total mass not exceeding 23 Kg
• A portable LPG cylinder
• A tyre used on a vehicle

If you are unsure as to whether a particular system requires a Written Scheme of Examination report the details to the Insurance Office who will pass the details to the Competent Person to make that decision.

Statutory inspections

The University's Engineering Insurers hold a register of all notified pieces of equipment and will inspect each item at the statutorily required interval. Agreed approach for School/Department managed equipment is as follows;

• It is the School/Department’s responsibility to ensure that all equipment is made available for the statutory inspections and records updated as required, via Crimson reporting system.
• It is the School/Department’s responsibility to ensure that all reports are checked and take any necessary action.  Again this should be recorded in Crimson.
• The School should notify the Insurance Manager, of all new users so that they can be added to the system.  
• Training in the use of the Crimson portal is available by contacting the Insurance Office or via the self-enrol monthly Crimson webinar for training on the system (enrolment can be done from the home page of the Zurich Engineering website). 
• All School contacts should be given guidance notes (published at https://uoe.sharepoint.com/sites/FinanceSpecialistServices/SitePages/Engineering-%26-Inspections.aspx – refreshed late 2021 and published early 2022).

Safe use guidance

Safe working pressure

The safe working pressure (SWP), as indicated on the insurance certificate, must be clearly marked on each item of equipment, and these limits must never be exceeded under any circumstances. All pressure vessels should be cleaned out regularly, and residues which might cause corrosion should be removed. Maintenance of all pressure vessels must be arranged so that a competent engineer inspects each item of equipment frequently.

The manufacturer's instructions must always be closely followed, and the various safety interlocks must never be tampered with or over-ridden. Older autoclaves which do not have interlocked doors or lids should be fitted with an appropriate device which will prevent the chamber being opened when residual steam or boiling water are present.

Compressed air supplies

Never direct a compressed air supply at yourself or at any other person; a high pressure jet of air can maim or kill. Do not use compressed air for cleaning purposes unless there is no alternative. Where it is essential, use suitable eye protection to offset the effects of flying swarf and dirt particles.

Autoclaves

Further guidance on use of autoclaves in a biological lab is available in the Biological agent risk assessment (9.8.2 Autoclaving) and the Genetically modified organism risk assessment (9.8.2 Autoclaving).