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The HST (High Sample Temperature) automatic water shut-off valve is used to sense the sample temperature after the sample cooler. Under normal conditions, the valve is wide open so the sample fluid passes through the valve. The valve’s internal thermal actuator is always sensing the fluid temperature and if the temperature exceeds the valve’s set point, the HST will close to protect expensive and delicate analyzers and other instruments downstream from over-temperature damage.

The HST will only open again once the sample temperature falls back below the valve’s set-point. Low coolant flow, total loss of cooling water, or unusually high sample temperatures are typical reasons why the HST self-operating protective device should be considered for your high-water temperature shut-off system.

Typical Applications

Excessively hot samples can cause damage to expensive and sensitive hardware and electronics. For process analyzers and similar instrumentation, it is important to assure that the process sample fluids are always below the maximum allowable temperature for such instruments.

Sample coolers are commonly used to reduce sample temperatures to acceptable limits. In the event of a loss of cooling fluid to the sample cooler, or if the desired sample temperature is exceeded for any reason, the HST temperature shut-off valve will close to prevent equipment damage.


Design Features

  • Exclusive self-actuating Thermoloid® blend wax thermal actuator
  • Ram-type plug provides tight shutoff
  • Operating temperatures unaffected by variable inlet pressures
  • Wide choice of temperature set-points available
  • Corrosion-resistant – all stainless-steel construction


  • Self-operating – no external power source required
  • Automatically controls flow based on fluid temperature
  • Protects expensive and delicate sample analyzers
  • Automatically resets when sample cools
  • Superior value vs. more expensive electric valves
  • Easy installation




1/2” HST (Kalrez® Seals)


1/2” HST-XXX-S6-X


  1. Available in special materials eg. Monel, Inconel, duplex stainless steel, etc.
  2. Body rating: 3000 PSIG at 600°F
  3. Full open temperatures “XXX” available: 100°F, 105°F, 115°F, 120°F, 125°F, 130°F, 140°F, 170°F, 185°F (Other temperatures are available)
  4. Seal material compatibility:
    1. EPDM – air, water, steam, ketones, and synthetic hydraulic oils.
    2. Viton® – air, fuel, oil, gas and petroleum-based hydraulic oils
    3. Kalrez® – Special order option


  • Size: ½”
  • Maximum Operating Pressure: 3000 PSIG (207 BAR)
  • Maximum Temperature: 300°F (149°C)


HST Product Sheet
HST Installation and Maintenance Instructions
Instrument and Process Temperature Control Brochure

Filter Panel

HST (High Sample Temperature)

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