The L971 Series crankcase level switch is a float-operated instrument that continuously monitors lubricating oil level inside a compressor crankcase. When the oil level drops to a preset low-level threshold, the falling float trips an internal SPDT snap-switch — instantly triggering an alarm output or initiating a compressor shutdown to prevent lubrication failure and mechanical damage. Housed in an explosion-proof aluminum enclosure rated IP66, the L971 is engineered for demanding industrial and hazardous-area compressor installations.
The L971 Series crankcase level switch offers a reliable, low-maintenance solution for protecting industrial compressors against the hazards of low lubricating oil. By using a buoyant float mechanism coupled to a precision SPDT snap-switch, it provides a direct, automatic response to falling crankcase oil levels — without requiring external power, programmable controllers, or complex instrumentation. Its explosion-proof construction and certified hazardous-location ratings make it equally suited for indoor compressor rooms and outdoor upstream gas compression installations. Backed by a two-year limited warranty and designed for minimal installation downtime, the L971 delivers long-term compressor protection that procurement teams and field engineers can depend on.
All specifications listed below apply to the L971 Series in standard and L971-C configurations. Parameters are provided for engineering reference and procurement evaluation.
| Parameter | Specification |
|---|---|
| Switch Type | SPDT Snap-Switch |
| Switch Contact Rating | 4 A @ 250 VAC |
| Operating Temperature Range | -15 to 275°F (-26 to 135°C) |
| Maximum Working Pressure | 30 psi (206 kPa / 2.06 bar) |
| Process Connection | ½ NPT |
| Conduit Connection (Electrical) | ½ NPT |
| Wire | 18 AWG (0.75 mm²) |
| Enclosure Material | Aluminum (Explosion-Proof) |
| Mounting Adaptor Material | Brass |
| Float Material – Standard (L971) | Rigid Polyurethane Foam |
| Float Material – L971-C Configuration | 304 Stainless Steel (optional) |
| Other Wetted Parts | 303, 304 and 316 Stainless Steel |
| O-Ring Seals | Viton and Buna |
| Enclosure / Ingress Protection Rating | IP66 per IEC 60529 |
| Hazardous Location Rating | UL and CSA Listed – Class I, Groups C & D; Class II, Groups F & G |
| Shipping Weight | 1 lb. 10 oz. (0.7 kg) |
| Shipping Dimensions | 8⅓ × 4¼ × 4½ in. (210 × 108 × 114 mm) |
| Warranty | Two-Year Limited |
The L971 Series operates on a straightforward float-and-switch principle. A rigid float is mounted on an adjustable arm inside the compressor crankcase via the inspection plate opening. Under normal operating conditions, the crankcase oil level is sufficient to keep the float buoyant in its upper resting position — holding the internal snap-switch in its untripped state.
As the lubricating oil level in the crankcase gradually depletes — whether through consumption, leakage, or failure to replenish — the float descends with the falling oil surface. Once the float reaches the predetermined low-level position, it actuates the internal SPDT snap-switch mechanism. This snap action produces a decisive, clean contact transition: the normally open circuit closes and the normally closed circuit opens, sending an immediate electrical signal to the connected control circuit.
Depending on how the output wiring is configured, this switching event can trigger an audible or visual alarm to alert the operator, or it can directly interrupt a shutdown circuit to stop the compressor before lubrication failure causes bearing or cylinder damage. Once crankcase oil is replenished and the level rises sufficiently to lift the float back to its normal operating position, the snap-switch resets automatically — returning the unit to its monitoring state without manual intervention.
The L971 Series monitors lubricating oil level inside a compressor crankcase. When oil drops to the preset low-level threshold, the float falls and trips the internal SPDT snap-switch, triggering an alarm or initiating a compressor shutdown to prevent lubrication failure and mechanical damage. The switch resets automatically once the oil level is restored.
The L971 is purpose-designed for Ingersoll-Rand Type 30, Type 40, and ESH compressor models. It can also be adapted to other compressor types that feature an inspection plate located below the normal operating oil level — making it a versatile choice for mixed compressor fleets across industrial facilities.
Yes. The L971 Series carries UL and CSA hazardous location listings for Class I, Groups C and D and Class II, Groups F and G. The enclosure is also rated IP66 per IEC 60529, providing protection against dust ingress and high-pressure water jets — making it suitable for demanding outdoor compressor installations and classified-area environments.
The standard L971 configuration uses a rigid polyurethane foam float. The L971-C variant offers a 304 stainless steel float as an alternative, suited to applications where a more chemically resistant or mechanically durable float material is needed — for example, in high-temperature crankcase environments or where the lubricant formulation may be aggressive to foam materials.
Yes. The SPDT snap-switch provides both normally open and normally closed contacts, allowing the output to feed an alarm annunciator and a shutdown relay in the same control circuit — depending on how the wiring is configured. This enables a staged response: an alarm alerts the operator first, with a shutdown occurring only if the condition is not corrected, or both actions can occur simultaneously if the circuit is wired accordingly.
The L971 mounts through the compressor's existing inspection plate opening using a brass adaptor and a ½ NPT process connection. Electrical wiring is routed through a separate ½ NPT conduit entry using the pre-terminated 18 AWG wire. The self-contained design requires no external sensing lines, transmitters, or additional control hardware — allowing installation to be completed quickly with minimal compressor downtime.
Our engineers will recommend the right L971 Series configuration for your compressor application, send you the full technical datasheet, and provide a competitive quote.
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