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PRODUCT OVERVIEW

The FW Murphy LM500-TF (part number 15700836) is a Genuine Murphy Lube Level Maintainer with Test Feature designed to automatically maintain the crankcase oil level of engines, pumps, and compressors of any size. Adjusted to the correct running oil level, the LM500-TF replenishes oil from an external supply tank as it is consumed — eliminating the need for manual checking and refilling between maintenance intervals. When the supply oil is depleted and the crankcase oil level continues to fall, the built-in low-level snap-action switch triggers an alarm or shutdown signal to protect the equipment. The "-TF" designation indicates the Test Feature: a single push-button that confirms both the float and switch are operating correctly without requiring disassembly or separate test equipment.

HOW IT WORKS

The LM500-TF operates on a simple, reliable float-and-valve principle. As the crankcase oil level drops during normal engine operation, the stainless steel float drops with it, opening the Thumb-Valve. Oil flows from the external supply tank, through the LM500-TF, and into the crankcase. When the correct oil level is restored, the float rises and closes the Thumb-Valve, stopping oil flow. The Thumb-Valve is non-clogging and provides a positive, leak-free seal — no screens, needles, or small orifices to obstruct.

If the supply tank runs dry and the crankcase oil level continues to fall below the normal operating range, the Form C (3-wire) snap-action low-level switch activates at approximately 1/4 in. (6 mm) from the bottom of the low zone. This switch triggers an alarm and/or shuts down the equipment, preventing operation without adequate lubrication. The Form C contact (SPDT, three-wire) allows the switch to be wired as a closed-loop system with a controller or annunciator, providing a fault-sensitive circuit that will trip on either a contact failure or a genuine low-level condition — a significant safety advantage over simple N.O. or N.C. switch wiring.

The Test Feature allows a single push-button press to simulate a low-level condition, verifying that both the float mechanism and the electrical switch are functioning correctly during routine maintenance checks. This eliminates the uncertainty of not knowing whether the switch would operate in an actual low-oil event.

CAUTION: Holding the test button for a prolonged period of time could cause crankcase overfill. Press and release promptly.

KEY BENEFITS

The LM500-TF eliminates one of the most common causes of engine damage and premature failure in stationary industrial equipment: running low on crankcase oil between maintenance visits. In unmanned or remotely monitored applications — natural gas compression sites, pipeline stations, agricultural irrigation pumps, generator sets — oil consumption between service intervals is a real operational risk, and the LM500-TF directly addresses it by providing continuous automatic replenishment from a customer-supplied tank.

The direct mount (DM) capability allows the LM500-TF to mount directly to the engine or compressor crankcase without requiring a separate mounting bracket or standpipe for many standard installations. Three oil outlet connection points (two side, one bottom) provide installation flexibility to match the crankcase drain location. A removable screen on the oil inlet fitting prevents debris from the supply tank from entering the system.

The clear "Frog Eye" polycarbonate lens and high-contrast white-on-green dial allow the current oil level and condition to be visually checked at a glance without shutting down the engine — a practical maintenance advantage on operating equipment. The UV-stabilized, heat-resistant lens material is rated for continuous service up to 250°F (121°C) ambient temperature.

SPECIFICATIONS

Part Number: 15700836

Model: LM500-TF

Type: Lube Level Maintainer with Test Feature

Float Material: 304 Stainless Steel

Case: Die-Cast Aluminum

Lens: Clear "Frog Eye" Polycarbonate; UV and Heat Stabilized; High Impact

Dial: White Background, Solid Green Band for Normal Level Indication

Switch Type: Form C (3-Wire SPDT) Snap-Action Low-Level Switch

Valve: Thumb-Valve™, Viton Seal Material, Non-Clogging

Wire Leads: 18 AWG x 14 in. ± 2 in. (355 mm)

Conduit Connection: 1/2 in. Female (Top)

Crankcase Balance Breather Connection: 1/2 NPTF (Top)

Oil Inlet Connection: 1/2 NPTF with Removable Screen (Side)

Oil Outlet Connections: 2 x 3/4 NPTF (Side) + 1 x 3/4 NPTF (Bottom)

Maximum Inlet Pressure: 9.50 psi / 25 ft. oil head pressure

Maximum Differential: 2 in. (51 mm) between running and stopped

Maximum Ambient Temperature: 250°F (121°C)

Switch Activation: Approximately 1/4 in. (6 mm) from bottom of low zone

Direct Mount (DM) Compatible: Yes

Overall Dimensions: 6-9/16 in. (H) x 6-3/16 in. (W) x 3-1/2 in. (D)

Shipping Dimensions: 9.5 (W) x 7.5 (D) x 11 in. (H)

Shipping Weight: 3 lbs. 7 oz. (1.57 kg)

Hazardous Area: Not rated for hazardous areas as a standalone device. For hazardous area use, must be connected to a Murphy controller approved for hazardous areas with non-incendive or intrinsically safe digital input circuits.

Warranty: 2 Years Limited

California Prop 65: Warning Applies

PART NUMBER FAMILY — FW MURPHY LM500 SERIES LUBE LEVEL MAINTAINERS

LM500 (15700835) — Standard Lube Level Maintainer, No Test Feature

LM500-TF (15700836) — Lube Level Maintainer with Test Feature (this part)

LM500-PM (15700841) — Lube Level Maintainer with Pipe Mount

LM500-TF-UB — Lube Level Maintainer with Test Feature and Universal Bracket

Optional Mounting Accessories:

Hose Kit (15000355) — Flexible hose kit for LM500 oil outlet connections

Fitting Kit (15000943) — Fitting kit for LM500 installation

Pipe Bracket — For 7/8 in. pipe mounting

Universal Flange Bracket — For base or oil pan mounting (two mounting methods)

Related Murphy Lube Level Products:

LM300 Series (LM300, LM301, LM301-A, LM301-EX, LM302, LM302-EX, LM303, LM303-EX, LM304, LM305, LM305-EX) — Smaller capacity lube level maintainer family

APPLICATIONS

The FW Murphy LM500-TF is designed for any stationary engine, pump, or compressor application requiring automatic crankcase oil level maintenance and low-level protection. Confirmed applications include:

Natural Gas Compression: Compressor skids and engine-driven compressors at well sites, gathering systems, and pipeline stations

Oil and Gas Production: Wellhead pump engines, artificial lift systems

Power Generation: Stationary generator sets and standby power applications

Agricultural and Irrigation: Large irrigation pump engines with extended operating cycles between maintenance visits

Industrial Engines: Stationary engines driving fans, blowers, process equipment, and utility machinery

Marine: Inboard engine oil level maintenance (confirmed application per marine distributor)

Construction and Mining: Engine-driven equipment with demanding oil consumption cycles

ALTERNATE SPELLINGS / PART NUMBER CROSS-REFERENCE

This product is manufactured by FW Murphy (Murphy by Enovation Controls) and may be searched under the following brand name variations:

This product is listed under part number 15700836 and model number LM500-TF and may also be searched or referenced as:

The standard version without the test feature is LM500, part number 15700835, also referenced as 15700835 and LM500.

The pipe-mount version is LM500-PM, part number 15700841, also referenced as LM500PM.

ABOUT FW MURPHY

FW Murphy, now operating as FW Murphy Production Controls — a brand of Enovation Controls, an IDEX Corporation company — has more than 85 years of experience designing and manufacturing engine management, protection, and control systems for the natural gas compression, oil and gas, marine, and industrial engine markets. Murphy's product portfolio spans Swichgage pressure and temperature instruments, the Selectronic Tattletale annunciator series, magnetic switches, lube level maintainers, vibration switches, electronic engine controllers, ignition systems, and full compressor panel control systems. FW Murphy Production Controls is headquartered in Rosenberg, Texas, and its products are recognized globally across oil field, gas compression, power generation, marine, and industrial engine applications.