The historical debate of which type of steam sterilizer door is better – sliding or hinged – has largely been settled in favor of the sliding door for a variety of significant safety, simplicity, convenience and maintenance reasons.

Hinged doors are only advantageous in a situation where an older hinged door sterilizer must be replaced and the building layout physically cannot accommodate the sliding door type. In these cases, the end user owner must replace “like for like” and purchase a hinged access door sterilizer even though the sliding door would be preferable.

Due to the extensive sterilizer service experience of PRIMUS’ founder, Ron Thompson, and the extreme difficulties and costs he and other Castle (now part of Getinge) service technicians encountered in the field servicing hinged door units, the company chose to manufacture only sliding door sterilizers from its inception nearly twenty-five years ago.

Sliding door sterilizers have proven to be a great benefit to end users due to their simplicity, safety, convenience, and low maintenance costs.

Hinged Door Designs

The traditional hinged (or radial arm) door consists of a series of locking arms (bolts) radiating from the center of the door. When the door is swung closed, a wheel at the center of the door is turned to extend and engage the bolts into locks distributed around the chamber opening.

The locking action also provides pressure to seal the door gasket. A typical design for a radial arm-door includes 200 – 300 moving parts, making maintenance and adjustment a constant maintenance task.

Door adjustment and maintenance is critical to prevent a calamitous event (see the examples discussed below).

Another type swing-door has a “lift, swing-close, drop” action, and the reverse to open the door. This design has fewer parts than the radial arm door, but still has the inherent disadvantages of all swing doors, specifically:

  • The operator is exposed to the hot surface of the door and potential burns on completion of every cycle. Facilities must go to extreme lengths to protect their operators from burns by writing comprehensive procedures and protocols when using hinged door sterilizers. Numerous facilities have had to file Workers Compensation claims because of injuries associated with this type of sterilizer.
  • The door gasket is fully exposed and subject to damage from loading equipment. A significant problem exists when loading carts and transfer carriages are used. The space in front of the door must be kept clear. Carts or other objects must be cleared away before the door can be opened.
  • Hinged door repairs and overhauls require special maintenance expertise and experience.
  • Search Google with one of the following inputs – “Faulty Autoclave Operations” or “Autoclave Hinged Door Failure” – and the search will list a document from a major university that is entitled “Lab Lesson Learned.” In this document the author describes and illustrates the problems that occur when there is a failure to follow established procedures. Two hinged door sterilizer incidents were cited:
    • In April 2010, an incorrect application of the closing and seating procedure resulted in a broken door that had to be replaced.
    • In April 2011, a similar failure resulted in pin breakage and door replacement.
    • In each one of these cases, the door had to be re-fabricated, taking six weeks and costing over $10,000 per door!

Sliding Door Design

Sliding door designs were introduced to eliminate the many design and operating problems inherent to swinging doors. The smaller PRIMUS vessels employ a vertically sliding door and the larger units, a horizontally sliding door.

The sliding door is locked into a “picture frame” around the full perimeter of the head ring, thus providing an inherently secure design. This simple, fast-acting, and safe design is trouble-free requiring little, if any, maintenance.

  • On vertically operating models, a single dynamically balanced counterweight offers smooth fingertip opening and closing of the door. (An automatically operating door is offered as a loading convenience when both hands are needed or for considerations of aseptic techniques).
  • The horizontal sliding doors on the larger PRIMUS sterilizers are pneumatically actuated and operated by depressing the Open/Close button on the control panel. To open, press and release the button. To close, press and hold until the door is closed.
  • Release of the button during closing ceases closing and returns the door to the open position.
  • In both vertical and horizontal versions, the door opens behind a protective panel, thus shielding the operator from hot surfaces.
  • The floor area in front of the sterilizer remains free to store carts until ready for loading. There is always ready access to the chamber for loading and unloading.
  • Sliding door designs are simple and relatively easy to work on as the few component parts are visible and readily accessible.


While it is true that some laboratory remodeling jobs are less expensive upfront to simply replace a hinged door sterilizer with another hinged door sterilizer, it is smart money in the long haul to transition to sliding door sterilizers, if at all possible. Many times, it only takes a little imagination and a few thousand more dollars to design the room to capture all the myriad sliding door benefits discussed above.

PRIMUS will help Dealers and Independent Sales Representatives in any way possible when the “hinged door dilemma” is encountered in the field.

Have a question or having difficulties? Talk to Dave Schall, our PRIMUS sterilizer expert who is here to assist you anytime at 877.679.7800 extension 1212 or email at dschall@spire-is.com.

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