Double door/pass-through type autoclaves

Lee Oakley examines the issues around specifying, design and installation of a double door/pass-through-type autoclaves for clean room and containment applications.

Brunel University based in Uxbridge, Middlesex, UK, needed a new pass-through autoclave for their new CAT III containment laboratory suite to be installed within the Heinz Wolf building. This would provide a Centre for Infection, Immunity and Disease Mechanisms, and a School of Health Sciences with a CAT II and CAT III Research Facility.

The company contracted to source the autoclave based on the Brunel brief was Cleanroom Design and Construction Limited (CDC) based in Stourbridge. As CDC have considerable experience in the type of laboratories Brunel University require they were chosen as the specialist contractor to design and build the turnkey, laboratory containment facility from start to finish. This included: the demolition and alteration to the building structure; the selection of the pass-through autoclave and other laboratory capital equipment and furniture; the organisation of the full commissioning and validation of all the capital equipment they sourced for the containment suite.

According to Nick Henley, CDC's Contracts Director, Priorclave's already proven track record with Brunel University had secured them as the preferred supplier of the laboratory autoclave in the new containment suite.

Pass-through or double entry autoclaves are used in relatively small numbers and require, often complicated, building work as part of the installation process. For this reason double entry units are considered, to some extent, bespoke and create degrees of flexibility which raises additional points for consideration. Such points for example may include the application - clean room or containment, the direction of workflow, door swing profile, thermocouple entry ports etc.

Logistics in delivery

Prior to quotation is an on-site survey to locate the services after which final manufacture would require the full details of the proposed locations and operation routes. However, while Priorclave met with Dr Anthony Tsolaki of Brunel University to discuss the requirements of the autoclave and the best options to suit, it was impossible to do a full site survey as the would-be laboratory was a building site with no walls. Nevertheless, the Priorclave representative was able to walk the route from entry into the building to the laboratory. The route required the use of a goods lift and passing through single doorways as narrow as 900mm, then through another laboratory whose entrance lay between a sink and a bench. There are many obstacles just waiting to create difficulties and if these can be anticipated at the site survey then corrective measures during manufacture and at the point of delivery can minimise or even eliminate costly and nasty surprises.

Performance characteristics

Dr Tsolaki explained that the autoclave needed to be electrically heated or have its own separate steam generator as there was no on-site steam available. Due to the nature of the cycles the autoclave would fulfil, it would also need a vacuum facility, a printer and an exhaust filtration system for the containment of any hazardous pathogens. It was also noted that the hardness of the water around Uxbridge would require the installation of a water softener.

At this point Priorclave needed to specify the autoclave by using room drawings. After deciding on a 350L capacity version, Priorclave submitted drawings to CDC with the autoclave in-situ and various changes were made by CDC to accommodate the unit. One of the main problems of pass-through autoclaves is space inside the machine to house the workings. The more options on the autoclave the more space is required beneath the chamber to fit them - on a pass-through autoclave there is a wall taking up valuable space. For this reason as well as cost, Priorclave opted for elements within the chamber rather than supply an autoclave with a separate steam generator. The former uses less power as the autoclave is switched on only when in use while a separate steam generator would be kept on all day, even when the autoclave is not in use.

In the case of Brunel University, their application of this autoclave was for containment purposes. It is used for the de-contamination of material prior to its release from the containment suite which would be hazardous material. Both ends of the autoclave were required to be isolated and were sealed at the point of passing through the wall by means of a bulkhead. The integrity of the containment was improved by an air pressure differential between the rooms in which the autoclave is located. It is an essential requirement of BS2646 that double ended autoclaves have interlocks to prevent both doors being open at the same time as this would obviously breach the integrity of the site. The interlock must also be present to prevent the door at the unloading end from being opened until the sterilisation cycle has been successfully completed and the load is safe to pass into the unloading end. It is also a requirement of BS2646 that it is not possible to release the loading door until the unloading door has been opened and subsequently closed and locked. However in this instance Brunel wanted the ability to open either door as long as the autoclave had finished and it was safe to do so. An added benefit, enabled by a programmable key lock facility, was the ability to use the autoclave as a single door autoclave at any end.

As Brunel's autoclave was a containment suite autoclave, most of it was located within the unloading room with just the door section of the autoclave protruding into the containment area. This allowed the majority of the maintenance tasks to be completed without the need for an engineer to enter the containment area or for the area to be decontaminated and temporarily disabled. CDC were instructed to install the drains and services at this end, thus minimising the number of pipes and wires etc that need to pass through the wall or bulkhead.

A printer is essential to produce a permanent record of each autoclave cycle, whether an integral part of the autoclave system or a separate and independent chart recorder device. It is normally desirable for the operator unloading the autoclave to be able to examine the record before opening the autoclave. For this reason and the fact that it is often not permissible to remove a paper record from a containment area, the printer was put on the non-containment end of the autoclave.

Priorclave designed and built the autoclave to the specifications requested by CDC and the end users at Brunel University and was delivered by a chosen delivery company who specialise in this type of project and who are used to handling equipment such as this and others that Priorclave manufacture.

Engineers were available on-site to take delivery just in case any difficulties were encountered. The engineers installed and commissioned the autoclave over a couple of days and end users were given instructions on using the equipment. When the Brunel personnel were proficient, Priorclave engineers returned to Brunel University to test the autoclave with the actual loads and made adjustments to the autoclave and software to ensure optimum performance. Performance Testing was done to UKAS accreditation and a full report and certification was given to the University on completion.

The autoclave is now serviced on a regular basis as stated in the extended warranty purchased within the purchase order.

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Lee Oakley is Product Manager, Priorclave Ltd, Woolwich, London, UK.

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