Warrick Conductivity Sensors in Medical Instrument Sterilizers


Sterilization in a hospital, dental or any medical environment is extremely critical for patient safety.  To kill any bacteria and viruses from being used on the previous patient, the medical instruments must be brought up to very high temperatures.  This is vital to ensure patient safety and to prevent the spread of diseases.  This sterilization is typically via a very high temperature steam spray along with specially formulated chemicals to ensure that all microorganisms, spores, fungi, etc. are eliminated, leaving the instrument sterile and ready for use.

In order to create the high temperature steam, a small condensing boiler is used.  In order for the boil to operate correctly it needs level sensors to measure the water depth.  As steam is used on the medical equipment the water level will decrease and therefore will need refilling.  The level sensors and control board will sense this loss of water and activate a pump or a valve to refill the tank.  This is critical to the safe operation of the boiler/sterilizer as loss of water can result in over pressurizing of the tank and/or cause a fire.

Challenge: Finding a reliable and repeatable level sensor and control relay that can withstand the high temperatures and pressure of a sterilization process

Traditional level sensors have a difficult time staying within specification when it comes to high temperature and pressure found in these sterilizers.  These elevated specifications can cause materials to swell and cause premature failures.  

Solution:  Warrick 3H Conductivity Probes and Series DF Relay

warrick 2
Gems’ 3H probe is constructed of premium materials including 316 stainless-steel and PTFE.  This ensures a maximum temperature rating of 406°F at 250 PSI, easily handling the sterilizer requirements.  With a 3/8” NPT or 5/8” straight thread (UNF or UNEF) the 3H conductivity probe is compatible with most port fittings.  The 3H probe can be field cut or ordered at the desired length from Gems, providing specific lengths for each boiler’s design.

When paired with one of Warrick’s highly configurable conductivity relays, it’s a match made in sterilizer heaven.  Specifically, the Series 26 and Series DF relay are UL approved to meet the CSD1 requirement to be used as a boiler low water cutoff.  Safety is critical for boiler water level indication, so both relays meet the requirement for built-in redundancy in the control circuitry.   The Series DF (Dual Function) builds on the specifications of the Series 26 with the added feature of pump control. As mentioned earlier, not only is low water cutoff critical, but so is the feedwater control to refill the boiler. This dual relay feature of the Series DF saves crucial space in cabinets and simplifies the controls into one relay.       

Additional Sensors used in Medical Instrument Sterilizers: 

  • Series 3L Probes: Similar to the 3H probe but with 1/8” NPT mounting
  • Series 3R Probes:  Similar to 3H probes but connect a Warrick fitting  
  • Series 16 Relay: Controller for boiler feedwater