posted in: Technical Insights

Autoclaves are a common piece of medical equipment that appears in our service department. These units require proper maintenance to sterilize equipment properly and allow the unit to work efficiently while ensuring sterility for your medical instruments. In addition to the recommended yearly maintenance, many manuals will recommend weekly maintenance on these units. This can include running additional cycles, using test strips and sterilization indicators to ensure the unit is in good working order.

There are manual and automatic autoclaves; however, they operate similarly. The chamber is filled with water which is then heated by the heating element [1]. The pressure created by the sealed unit allows for high temperatures to be reached [1]. This combination of heat and pressure is able to kill any bacteria that still remains on the instruments when given sufficient time to sterilize [1].

The TRH preventative maintenance for these units includes removing the sides of the unit while a cycle is running to ensure that there are no internal leaks. During this cycle, it ensures the unit is reaching the correct temperatures and pressure. The cycles are also timed to ensure the unit takes the correct amount of time during each part of the cycle. This includes the amount of time to build temperature and pressure and also the amount of time for sterilization. A second cycle is run when the unit is reassembled to ensure that there was no shift of any internal components. This second cycle also allows us to test the unit on two different settings. The preferred settings for testing are the most used cycles and the cycle with the highest temperature. The safety relief valve is also checked to ensure that it is in proper working order. Electrical safety analysis is also performed on these units to ensure that the unit is properly grounded and has the correct, current leakage

When we perform preventative maintenance, we recommend installing a preventative maintenance kit (PM kit). Some items change as some units do not have all of the same components. For example, for a Midmark M11, this kit includes a door gasket, chamber filters and door springs [2]. Each of these items have a specific purpose in the machine and can cause a variety of failures if not properly maintained.

The door gasket allows for the door to properly seal [3]. This allows for the proper building of temperature and pressure. The rubber of a door gasket will become loose and stretch over time [3]. This will result in the door not sealing properly and can cause cycles to fail. The chamber filters prevent any debris from travelling from the chamber to the internal components of the unit [3]. Without proper filters, the buildup can damage the internal valves [3]. Finally, the door spring allows for the door on automatic autoclaves to open properly at the end of a cycle to release the remaining steam [3]. When the spring is worn down or broken, the door may not open properly at this stage; this will prevent the venting of steam [3]. The spring must also be in the correct position to work properly [2].

In addition to the PM kit, there are other important points that should be noted to ensure that autoclaves are well maintained. The most important is that only distilled water is used within these units [3]. This prevents the internal components of the unit from being damaged.

While we recommend replacing the PM kits every year, each unit may require it more frequently or less frequently. This is dependent on how often the unit is used. A unit that is run multiple times daily will require more maintenance than a unit that is only run a few times a month.


Units Typically worked on by TRH Services, in South Western Ontario, including Kitchener, Waterloo, Cambridge, Toronto, London and Hamilton

Manufacturer Model Number
AmscoE10AP (EagleTen)
Barnstead | Lab LineST127330
Barnstead | Lab LineST127335
Midmark CorporationM11
Midmark CorporationM11-001
Midmark CorporationM11-020
Midmark CorporationM11-021
Midmark CorporationM11-022
Midmark CorporationM11-041
Midmark CorporationM11-042
Midmark CorporationM11-Ultraclave
Midmark Corporationm7
Midmark CorporationM7 Speedclave
Midmark CorporationM7-001
Midmark CorporationM7-011
Midmark CorporationM7-022
Midmark CorporationM9
Midmark CorporationM9 Ultraclave
Midmark CorporationM9-022
Midmark CorporationM9D-022
Midmark CorporationM9D-042
Modular Driven Technologies Corp. (MDT)5000
Pelton & Crane Co.Delta Q
Pelton & Crane Co.DELTA XL
Pelton & Crane Co.OCR
Pelton & Crane Co.Omni-Clave OCR
Pelton & Crane Co.Validator 10
RitterM11 Ultraclave
Sanyo Electric Co., Ltd.MAC 1200
SciCanBravo 21V
SciCanStatim 2000
SciCanStatum 5000
SciCanSTATUM 5000 (01-201101)
SciCanStatum 5000 (201103)
SciCanStatum 7000
Tinget AutoclavesSTE-16L-E
TuttnauerEZ11 Plus
Tuttnauer Company Ltd.1730M
Tuttnauer Company Ltd.1730MKV
Tuttnauer Company Ltd.2340EA
Tuttnauer Company Ltd.2340M
Tuttnauer Company Ltd.2540EA
Tuttnauer Company Ltd.2540M
Tuttnauer Company Ltd.3870E
Tuttnauer Company Ltd.3870EA
Tuttnauer Company Ltd.3870M
Tuttnauer Company Ltd.TVET 11E


Written By: Dixon Murphy

Edited By: Tyler Hasenpflug CET



[1] “Steam Sterilization,” Centers for Disease Control and Prevention, 18-Sep-2016. [Online]. Available: [Accessed: 28-Nov-2021].

[2] “Maintenance Kit Check List,” Midmark.Com, 2018. [Online]. Available: [Accessed: 30-Nov-2021].

[3] “M9 / M9D / M11 Self -Contained Steam Sterilizer User Guide,” Midmark.Com, 10-Nov-2018. [Online]. Available: [Accessed: 30-Nov-2021].