The HAT/RA-LP (reverse-acting heat actuated trap valve with leak port) is a cooling water control valve designed to automatically and continuously maintain a constant temperature in liquid cooling systems. Since it is what we classify as reverse-acting, the valve will open on rising temperatures.

At start-up, the valve is closed except for its “control leakage”, which allows a small amount of flow through the valve so that the temperature control actuator can sense the changing fluid temperature upstream in the system.

As the fluid temperature increases to within the operating range of the HAT/RA-LP, the thermal actuator modulates the valve open. If the fluid temperature is above the valve’s set point, the valve will continue to modulate open allowing additional fluid discharge.

As the outlet temperature falls, the cooling water control valve then modulates toward the closed position, reducing flow. This modulating action maintains a relatively constant fluid temperature even as operating conditions vary.

Typical Applications

cooling water control valve

HAT/RA-LP valves are ideal for maintaining cooling temperatures in water-cooled compressors,
die-casting equipment, engines, water-cooled heat exchangers, welding equipment, electrical equipment, and molding equipment.

Design Features

  • Exclusive self-actuating Thermoloid® blend paraffin wax actuator
  • Corrosion-resistant – long service life
  • Compact low mass – fast response
  • Operates in narrow temperature band
  • Stainless steel body, fittings, spring, and plug
  • Ram-type plug for reliable shut-off
  • Leak port (LP) senses changing upstream temperature


  • Self-operating – no external power source required
  • Maintains constant discharge temperatures
  • Improves system efficiency
  • Unaffected by pressure variations
  • Conserves water
  • Easy installation




144 - 202X02 - XXX

1/2” HAT/RA-LP B-Port 1/4 GPM

144 - 212X02 - XXX

1/2” HAT/RA-LP B-Port, all SS 1/4 GPM

144 - 302X02 - XXX

1/2” HAT/RA-LP C-Port, 1/4 GPM

144 - 312X02 - XXX

1/2” HAT/RA-LP C-Port, all SS 1/4 GPM

145 - 502X02 - XXX

3/4” HAT/RA-LP D-Port 1/4 GPM

145 - 502X03 - XXX

3/4” HAT/RA-LP D-Port 1 GPM

145 - 512X02 - XXX

3/4” HAT/RA-LP D-Port, all SS 1/4 GPM

145 - 512X03 - XXX

3/4” HAT/RA-LP D-Port, all SS 1 GPM


  1. Full open temperatures “XXX” available: 040°F, 045°F, 050°F, 060°F, 070°F, 075°F, 085°F, 095°F, 100°F, 105°F, 110°F, 115°F, 120°F, 125°F, 130°F, 140°F, 150°F, 160°F, 170°F, 175°F, 180°F, 190°F, 200°F, and 210°F
    1. Closing temperature is typically 10°F below the opening temperature
  2. Leak port flow rate specifications:
    1. All 144 Series (B and C-Port) leak flow rates at 60 PSIG (4.1 BAR)
    2. All 145 Series (D-Port) leak flow rates at 40 PSIG (2.8 BAR)
  3. Seal material compatibility:
    1. EPDM – air, water, steam, ketones, and synthetic hydraulic oils
    2. Viton – air, fuel, oil, gas, petroleum-based hydraulic oils
  4. Replace singular “X” with 1 for EPDM body seals; 2 for Viton body seals


  • Sizes: ½”, ¾”
  • Maximum Operating Pressure for B Port: 200 PSIG (13.8 BAR)
  • Maximum Operating Pressure for C Port: 150 PSIG (10.3 BAR)
  • Maximum Operating Pressure for D Port: 70 PSIG (4.8 BAR)
  • Maximum Temperature: 150°F (66°C) over set-point – limit 300°F (149°C)


HAT/RA-LP Product Sheet
HAT/RA-LP Installation and Maintenance Instructions
Instrument and Process Temperature Control Brochure