For PRIMUS steam sterilizers that use pneumatic valves (sold as an option), airflow to the valves is controlled by Humphrey Products brand 3-way direct-acting solenoid valves. The valves used by PRIMUS are stackable.

Humphrey Products brand solenoid valves have historically provided PRIMUS end users with excellent reliability in the field. The pressure-balanced poppet, coupled with a direct-acting operating principle, provides a simple, compact, and highly functional design.

The cutaway below shows the valve components. The solenoid is on top and the valve is below. PRIMUS always uses “Normally Closed” (solenoid de-energized) Humphrey valves in all applications. In this configuration, the compressed air supply is connected to the IN port. OUT is the cylinder port.

When the solenoid is energized, it overcomes spring tension and the piston moves to allow compressed air to pass through the valve. When the solenoid is de-energized, the spring returns the piston back to its normally closed position and the compressed air flow stops.

Specifications of the PRIMUS Humphrey Valve

  • 1/8 orifice – 10 CFM at 100 psig
  • 3-way operation
  • Two positions – spring return
  • Pressure rating: 0 to 125 psig
  • Voltage – 120/50-60
  • Normally closed
  • Quiet operation with no AC hum
  • Non-locking manual override is standard
  • Fast cycling – 600 cpm
  • Mount in any position – stack one or more valves using end plate assembly
  • All coils are standard with DIN connectors
  • All AC coils are rated for 50/60 Hz
  • Valve assemblies are “hi-pot” tested at 1750 VAC for one second
  • All coils conform to Class B insulation systems
  • Seal Material – Buna N elastomers
  • Body Material – Aluminum
  • Lubrication – Not required, factory pre-lubed
  • Filtration – 40 micron recommended
  • Port Size – 1/8 inch
  • Power Consumption – 4.5 Watts
  • Ambient Temperature Range – 32º – 125º F
  • Weight – 0.26 ounce
  • Estimated Valve Life – 20 million cycles, depending on the application

Compressed Air Safety, Quality, and Usage

Safety – Don’t Take Chances!

Compressed air is an extremely powerful medium. Always take maximum precautions when handling any component of a compressed air system.

Never attempt to construct, replace, operate, or service any component of a compressed air system unless you have been specifically and properly trained to do so.

Always disconnect the supply air and exhaust the air system before attempting to remove or service a component of that system.

Failure to heed these warnings could result in SERIOUS, EVEN FATAL, PERSONAL INJURY.

Compressed Air Quality

An often overlooked aspect of equipment maintenance and care involves the quality of compressed air.

Poor quality compressed air can result in a decrease in equipment uptime, as well as decreased system performance throughout a facility. The expected mean-time-between-failure (MTBF) for critical components, such as pneumatic valves, is greatly reduced when water droplets form in compressed air feed lines.

To help troubleshoot a potential compressed air quality problem, the following represent tell-tale signs of poor quality compressed air supply:

  • Visible moisture in the regulator bowl
  • Water droplets forming on the clear regulator bowl wall
  • Regulator bowl filling with water

Compressed Air Contaminants

Compressed air contaminants can be in the form of solids, liquids, or vapors. Contaminants can enter a compressed air system at the compressor intake or can be introduced into the air stream by the system itself.


The environment in which an air compressor is located should also be considered. A hot, steamy room is not ideal. The air quality entering a compressor is essentially equivalent to the quality exiting the unit.

Air compressors should be located in the best HVAC-controlled environment possible – typically 70°F, with <50% relative humidity.

Most facilities have qualified HVAC technicians on staff who can determine the location best suited for this often-overlooked aspect of equipment care and maintenance.

Lubricant-free rotary screw and reciprocating compressors usually have higher initial costs, lower efficiency, and higher maintenance costs than lubricant-injected compressors. However, the additional separation, filtration, and drying equipment required by lubricant-injected compressors will generally cause some reduction in system efficiency, particularly if the system is not properly maintained.


If a valve fails to function when electrical power is supplied, take the following actions:

  1. Check valve function using manual override. If the valve functions by manual actuation, proceed to Steps 2 and 3. If the valve does not function, proceed to Step 4.
  2. Check line voltage to determine compliance with the valve’s electrical rating.
  3. Check the valve for an inoperable (open) coil, measuring milliamps per the Humphrey Electrical Specification Chart for 301 Series valves (available online at www.humphrey-products.com).
  4. Check that the air supply has been delivered in adequate volume and pressure for proper functioning of the device. Ensure that there are no blockages due to air line contamination or defective/blocked fittings.

New NEMA 4 Humphrey Valve

Beginning in October 2012, PRIMUS began offering NEMA 4 Humphrey valves (315 Series) as an option with new steam sterilizers. The new valve is not compatible with existing PRIMUS valves as it is slightly larger. Again, the new NEMA 4 valves are not suitable as aftermarket parts for currently installed PRIMUS sterilizers.

About Humphrey Products

Humphrey Products was formed as a business in 1901 and is headquartered in Kalamazoo, Michigan. Humphrey Products is both ISO 9001:2008 and ISO 13485:2003 registered.

The Company employs over 200 American workers in their Michigan factories and serves pneumatic products markets around the world. Commendably, 96% of Humphrey Product’s suppliers are from the USA.

Each Humphrey valve is fully tested before leaving the Michigan factory to ensure the valve’s conformance to specification.

All valves have a one year warranty from the date of manufacture due to defects in workmanship and/or materials

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.

Visit us at spire-is.com

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