Murphy SDB500EX-2 Direct Mounting Temperature Swichgage 100-500F with 1/2 NPT Thermowell - Explosion Proof


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0.91 LBS
Estimated Special Order Ship Date:
Special Order (ships approximately 2-3 Weeks)
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The Murphy Explosion-Proof SDB500EX-2 is a Direct Mounting Temperature Swichgage device that provides an accurate direct-reading gauge with an adjustable limit switch to activate alarms and/or shutdown. A knob on the front of the Swichgage allows you to adjust the limit switch trip point. Pointer movement is actuated by a bi-metallic sensing element. When the indicating pointer on the SDB500EX-2 touches the adjustable contact, a one-wire-to-ground circuit is completed to shut down the equipment and/or actuate audible or visual alarms. Proper relays or Tattletale annunciators (magnetic switches) must be incorporated into the system.

A thermowell (separable socket) is used to facilitate maintenance of a temperature Swichgage and to protect the temperature sensing bulb from extreme amounts of system pressure.

Applications: The most common use of the SDB Series is to monitor gas compressor temperatures. Engine exhaust temperature can also be monitored to indicate over-loading or lean fuel mixtures, or use the SDB to help coordinate loads on twin-engine installations.



  • Easy to Read Dial
  • Bi-Metallic Sensor
  • 100 to 500°F (40 to 260°C)
  • Dials Scaled in Degrees Fahrenheit/Celsius
  • Sand-Cast Aluminum
  • 1/2 NPT Thermowell
  • Explosion-Proof and CSA Listed for Class I, Group C and D Hazardous Locations



  • Murphy Part No.: SDB500EX-2
  • Temperature Ranges: 100 to 500°F (40 to 260°C)
  • Sensing Bulb Material and Size: 304 stainless steel; 1/2 in. dia. x 4 in. (13 x 102 mm) insertion depth
  • Maximum Bulb Pressure: 285 psi (1.97 MPa)[19.7 bar] at 625°F (329°C) NOTE: use of a thermowell is recommended
  • Process Connection: 1/2 NPTF
  • Sensing Element: High torque bi-metal element in heliarc welded stainless steel bulb
  • Contact Rating: 2 A @ 120 VAC
  • Limit Contact Adjustment: By knob through full range
  • Maximum Unit Temperature: 625°F(329°C)
  • Case Material: Sand-cast aluminum
  • Swichgage Accuracy: ± 3% of full scale
  • Wire: 18 AWG (1.0 mm2). See Dimensions for lengths (image #3), reverse side
  • Dial: Black print on stainless steel. Dials are scaled in degrees Fahrenheit and Celsius
  • Shipping Weight: 2 lb. 5 oz. (1.05 kg)
  • Shipping Dimensions: 9 x 5-1/2 x 6 in. (229 x 140 x 152 mm)

Product Condition: NEW

California required Prop65 warning.

WARNING: This product can expose you to chemicals, including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to

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