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Thu 18 Jan 2018

How does a steam autoclave work?

In this blog, BM Engineering Supplies answers the questions ‘How does a steam autoclave work’ and ‘Is an autoclave a steam steriliser’. We will also highlight how manufacturer ESTS was able to produce a Logiclave LAB300 autoclave that promises impressive running and maintenance cost savings over an average 10-year operating cycle by installing Bürkert UK Type 2000 angle seat steam valves and rotary ball valves.

How does a steam autoclave work?

An autoclave is a pressure chamber used to sterilise equipment and supplies by subjecting them to high-pressure saturated steam at 121°C (249°F) for around 15–20 minutes depending on the size of the load and the contents.

Sterilisation autoclaves are widely used in microbiology, medicine, podiatry, veterinary science, mycology, dentistry, and prosthetics fabrication. They vary in size and function depending on the media to be sterilised.

It is important to ensure that all of the trapped air is removed from the autoclave before activation, as trapped air is a very poor medium for achieving sterility. Steam at 134°C can achieve in three minutes the same sterility that hot air at 160°C can take two hours to achieve.

How does steam sterilisation work?

Once the autoclave chamber is sealed, all the air is removed by pumping in steam to force it out (known as gravity displacement) or by using a simple vacuum pump (known as a pre-vacuum design). Then steam is pumped through the chamber at a pressure that is higher than normal atmospheric pressure, to reach a temperature in the range of 121–140°C (250–284°F).

When the desired temperature is reached, a thermostat kicks in and begins a timer. Steam pumping continues for a minimum of three minutes and a maximum of 15–20 minutes – essentially long enough to kill most microorganisms. The exact sterilising time depends on the contamination level of the items being autoclaved and how the autoclave is loaded.

ESTS autoclaves – Is an autoclave a steam steriliser?

Put simply, yes an autoclave is a steam steriliser.

Autoclave manufacturer ESTS was able to produce a Logiclave type autoclave that potentially saves up to £60,000 in running and maintenance costs (over an average 10-year operating cycle) by installing Bürkert Type 2000 angle seat steam valves and rotary ball valves. The Logiclave LAB300 uses ESTS’ revolutionary flash steam generator and comprises 14 Bürkert valves.

Sterilising conditions are achieved through a combination of pressure cycles and pulsed vacuum to replace air with steam in the chamber. When that cycle starts, a Bürkert stainless steel bodied Type 2000 pneumatically operated angle seat valve opens as an exhaust and closes when a vacuum set point of 100mBar is reached. At this point, steam is injected through another Bürkert angle seat piston valve.

The steam supply valve is a high-temperature unit that includes PPS material for longer seal life in the actuator. The bodies of Bürkert’s latest generation of angle seat valves ensure a compact and reliable end product. Several angle seat valves were also supplied with a male thread, reducing the number of joints and connectors needed to construct the piping circuit and thus reducing inventory purchase costs.

Colin Hartop, ESTS Product Director, said: “All the valves on this machine are from Bürkert. We find them to be a high-quality valve at the right price. We’re limited for space on this footprint, so to get 14 valves on this machine, having the extra small actuator head helps us. The angle seat valves that Bürkert provided are male thread on the outside, which saves us on fittings and saves us on space.”

Answering how does a steam autoclave work?

We hope this blog has been informative in answering the questions ‘How does a steam autoclave work’ and ‘Is an autoclave a steam steriliser’. Feel free to speak to one of BME’s knowledgeable advisers about all your steam equipment requirements today by calling 0141 762 0657 or email sales@bmengineering.co.uk.

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