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FW Murphy OPL Series High Quality Pressure Swichgages®

Written by
The MurCal Blogster
Published on
May 12, 2023 at 2:10:01 PM PDT May 12, 2023 at 2:10:01 PM PDTth, May 12, 2023 at 2:10:01 PM PDT

A Little History


“FW Murphy” is the result of one man's search for reliable and high quality engine protection along with customer focus and innovative ideas. 

While Frank W. "Pat" Murphy (brother of MurCal’s founder Art Murphy) was a sales manager for a major equipment distributor in the 1930's, he found that his customers' main complaint was "burned up" engines, so he decided to develop a simpler yet more effective "Safety Switch." Pat's idea, later renamed the Swichgage®, was to combine an indicating gage with a switch that would stop the engine when low oil pressure or high coolant temperature existed. It was a simple design, easy to understand – and it worked well.

Over the past 75+ years FW Murphy developed hundreds of products that monitor and control compressors, pumps, generators, and more. Pressure, temperature, liquid level, overspeed, time, and vibration are monitored by these industrial operation control systems. They cover it all, from simple start/stop operation to sophisticated automation systems. Many of their products and systems carry major international authority approvals.


The OPL-series


The OPL-series pressure gage instruments are combination pressure indicating gages with adjustable low and high limit switches. Limit switches can be wired directly to electric pilot circuits to operate alarms, shutdown or the start/stop of engines and electric motors. 

Surface mount or panel mount enclosure is available for most versions. 

All versions feature a 4-1/2 in. (114 mm) dial for easy viewing. Adjustable limit switches are accessible from the front of the gage. Limit contacts have self-cleaning motion to enhance electrical continuity.


Specifications


Case: Die cast aluminum; weatherproof.

Contact Ratings:

OPLC and OPLFC - 1 SPDT; Center off; 2A, 30 VDC / 0.1 A, 125 VAC pilot duty

OPLBP - SPDT dry relay contacts; 10A, 125 VAC

Dial: 4-1/2 in. (114 mm) white on black, dual scaled psi /kPa

Gage Accuracy: 2-1-2 ±2% for the first and last quarters of the scale, the middle half is ±1%.

Geared Movement: 302 and 304 stainless steel.

Lens: Optically clear polycarbonate.

Pointer: High visibility with a pointer calibration hub.

Process Connection: Available in 1/4 NPT and 1/2 NPT.

Sensing Element: Select from bronze or 316 stainless steel bourdon tube.

Models Available 


OPLC and OPLFC gage instruments have high and low limit contacts to monitor, alarm or shut down. The OPLC has a flanged case. A method to override the low-limit contact for a start-up is provided on OPLC models. This is a Surface mount aluminum case with Start/Run switch for low contact override

Complete with alarms, shutdowns and start-stop circuits, the OPLC products are suitable for engines or electric motors with appropriate magnetic switch or transformer relay assembly. 

OPLFC can be direct or panel mounted. OPLFG gage indication-only pressure instrument is similar to OPLFC models, without switch (limit) contacts.

Both the OPLFC and OPLFG products come will OPLC features except the low limit contact lockout. For these, operators effect lock out externally through the control circuit. The OPLFC is typically used in control panels for compressors, pumps. 


OPLBP is a version of the OPLC featuring pilot duty limit switches connected to an internal latching control relay for on/off control directly or through a motor starter.

-OS and -ES options include oil sealed and environment sealed case for corrosive environments, feature a panel mount case or screw directly into the process.


45APE and 45APEF are versions of the OPLC Series featuring 2 snap-acting SPDT switches instead of the pointer-type contacts.

The OPLBP is specifically designed for start-stop operation of engines and electric motors.

These units do not include low contact lockout.



MurCal experts help oil industry professionals find the products for their unique applications. Reach out today!

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