Dial Temperature Gage

Vapor-Actuated Mechanism | High & Low Limit Contacts | Surface & Panel Mount Options

Industrial · Marine · Oil & Gas

SPL Series 4.5" Dial Temperature Gage with Integrated Limit Contacts

The SPL Series Dial Temperature Gage is a heavy-duty mechanical instrument that combines real-time temperature indication with adjustable high and low limit contacts on a single 4.5-inch (114 mm) dial. Designed for demanding industrial environments, it provides both visual monitoring and automatic electrical switching for alarm activation or equipment shutdown — making it an essential safety instrument for gas compressors, engine cooling systems, heaters, and process applications.

15–350°F Temp Range

4.5in Dial Size

Dual Limit Contacts

600psi Pressure Rating

Key Features

Combined Indication and Limit Switching: The SPL Series integrates both a temperature indicator and adjustable high/low limit contacts into one compact instrument. This eliminates the need for separate switches and gauges, reducing installation complexity and panel space.
Adjustable High and Low Limit Contacts: Both limit contacts are field-adjustable using a fingertip-type knob, allowing operators to set alarm or shutdown thresholds directly on the dial face without any tools — ideal for installations where setpoints need to be changed over time.
Vapor-Actuated Sensing Mechanism: The gage uses a sealed capillary and copper sensing bulb that generates vapor pressure when exposed to heat. This vapor actuates a Bourdon tube, providing accurate, responsive mechanical temperature readings without any electrical power required for indication.
Wide Temperature Coverage: Available in two ranges — 15°F to 250°F (9°C to 121°C) and 130°F to 350°F (54°C to 177°C) — with dual-scale °F and °C dials as standard. This broad coverage makes it suitable for a wide variety of industrial temperature monitoring needs.
Gold-Plated Silver Limit Contacts: The SPDT limit contacts are made with gold-plated silver for superior electrical conductivity and long service life. They feature a self-cleaning wiping motion that maintains reliable continuity even in dusty or contaminated environments.
Multiple Mounting Configurations: Available as the SPLC surface-mount model or the SPLFC panel-mount (round case) model, giving installers the flexibility to suit different equipment layouts. Square case variants are also offered for standard round panel openings.
Start-Up Lockout Override Switch: SPLC models include a built-in toggle switch that bypasses the low temperature contact during equipment start-up — preventing nuisance shutdowns before the system reaches operating temperature. The switch must be manually reset once normal temperature is achieved.
Optional Explosion-Proof and Liquid-Filled Versions: For hazardous area installations, an explosion-proof enclosure option is available rated for Class I, Division I, Groups C and D. A liquid-filled case variant (OS option) provides added resistance to vibration, corrosion, and electrical arc in harsh environments.
Thermowell Compatible for Process Isolation: The gage can be used with optional stainless steel thermowells — rated to 3,000 or 4,000 psi — allowing the sensing bulb to be installed or replaced without interrupting the process connection. This is especially valuable in high-pressure or corrosive media applications.
Flexible Capillary Length Options: Standard capillary length is 5 feet (1.5 m), with options extending up to 30 feet, giving installers the freedom to locate the instrument remotely from the sensing point as required by panel or cabinet layouts.

Applications

Gas Compressor Temperature Monitoring: The SPL Series is widely used on gas compression equipment to monitor discharge or jacket temperatures, with limit contacts configured to alarm or shut down the unit when critical thresholds are reached.
Engine Coolant Temperature Control: Installed on diesel and gas engines to track coolant temperatures in real time, triggering automatic engine shutdown before overheating causes irreversible damage to internal components.
Industrial Heaters and Coolers: Used in heating and cooling systems within process plants to maintain safe operating temperatures, with the limit contacts configured to alert operators or activate control circuits when setpoints are exceeded.
Process Temperature Applications: Suitable for monitoring temperature at any stage of an industrial process — from chemical processing and refining to food and beverage production — wherever mechanical reliability and dual-limit protection are required.
Water Pump Systems: Applied to pump engine temperature circuits where continuous monitoring is needed to prevent pump seizure or thermal damage during long operational cycles in remote or unattended locations.
Marine Engine Monitoring: Suitable for marine diesel engine cooling and auxiliary system temperature supervision, where compact, reliable, and self-powered instruments are preferred over electronic sensor arrays.
Oil & Gas Production Equipment: Used on wellhead and production site engines, separators, and fluid handling equipment where explosion-proof ratings and rugged construction are mandatory for compliance with safety regulations.

Technical Specifications

Precision-engineered mechanical temperature gages offering dual-limit contact protection for industrial and marine applications. All specifications are subject to change; contact us for the latest data.

Parameter	Specification
Dial Size	4.5 in (114 mm) diameter; white on black, dual scale °F and °C standard
Case Material	Die-cast aluminum; available in surface-mount (SPLC) or panel-mount round case (SPLFC)
Temperature Ranges	15°F to 250°F (9°C to 121°C) and 130°F to 350°F (54°C to 177°C)
Accuracy – First 1/3 of Range	±8°F / ±4°C
Accuracy – Middle 1/3 of Range	±2°F / ±1°C
Accuracy – Upper 1/3 of Range	±2°F / ±1°C (15–250°F range); ±3°F / ±1.5°C (130–350°F range)
Capillary	PVC-armored copper tube; standard length 5 ft (1.5 m); optional: 10, 15, 20, 25, 30 ft
Sensing Bulb	Copper bulb; OD 0.5 in (13 mm); length 7 in (178 mm)
Minimum Bulb Insertion	5 in (127 mm) for 15–250°F range; 2.5 in (64 mm) for 130–350°F range
Process Connection	½ NPT compression fitting
Pressure Rating	600 psi (4.1 MPa / 41 bar)
Overrange Limit	Do not exceed 10% above full-scale range
Limit Contacts (SPLC & SPLFC)	1-SPDT, center off; pilot-duty; 2 A @ 30 V DC / 0.1 A @ 125 V AC; gold-plated silver
Dry Relay Contact (BP Models)	10 A @ 28 V DC or 10 A @ 120 V AC
Wire Connections – Surface Mount	½ NPT conduit entry with terminal block
Wire Connections – Panel Mount	18 AWG (1.0 mm²) wire leads, 9 in (229 mm) long
Shipping Weight – Standard	Approx. 8 lb (3.6 kg)
Shipping Weight – Explosion-Proof	Approx. 22 lb (10 kg)
Shipping Dimensions – Standard	16 × 11 × 5.5 in (406 × 279 × 140 mm)
Shipping Dimensions – Explosion-Proof	12 × 12 × 9 in (305 × 305 × 229 mm)
Explosion-Proof Option (EX)	Class I, Division I, Groups C and D; gage enclosed within explosion-proof housing
Liquid-Filled Option (OS)	Filled case for resistance to corrosion, vibration, and electrical arc
Stainless Steel Armor Option (S)	Stainless steel capillary, armor, and sensing bulb in place of standard copper/PVC
Thermowell Compatibility	Stainless steel thermowells available (304 and 316 SS); rated 3,000–4,000 psi @ 300°F

Technical FAQ

Common Questions Answered

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The SPLC is a surface-mount version with a square die-cast aluminum case and a ½ NPT conduit entry for terminal block wiring. The SPLFC is functionally identical but housed in a round case designed for standard panel cutout mounting, making it ideal for control panels and enclosures. Square-case variants with round panel compatibility are also available.

Yes. Both the high and low limit contacts are fully field-adjustable. Each contact has a fingertip-type knob that can be turned by hand to set the desired trigger point anywhere on the dial scale. No tools or recalibration are required, making it straightforward to adapt setpoints to changing operating conditions.

No external power is needed for temperature indication. The gage operates entirely on the vapor pressure generated within its sealed capillary system. Power is only required for the limit contact circuit itself — the pilot-duty contacts switch the external circuit provided by the control system or alarm panel.

Yes. The EX option provides an explosion-proof enclosure rated for Class I, Division I, Groups C and D locations per NEC classifications. This version is suitable for areas where flammable gases or vapors may be present, such as gas processing plants, refineries, and offshore platforms. Contact us to verify certification requirements for your specific location.

A thermowell is recommended for high-pressure process connections (available rated to 3,000 or 4,000 psi), corrosive media that could damage the copper sensing bulb, or applications where the bulb needs to be inspected or replaced without shutting down the process. Thermowells are available in 304 and 316 stainless steel to suit different corrosion resistance requirements.

Standard capillary length is 5 feet (1.5 m), with options available up to 30 feet in 5-foot increments. Longer capillary runs allow the gage to be mounted remotely from the sensing point, which is useful for panels located away from the process. In general, longer capillary lengths can be slightly more susceptible to ambient temperature effects, so consider this when selecting length for precision-critical installations.