Honeywell Enraf 977 TSI Tank Side Indicator LCD Display

Honeywell Enraf 977 TSI Tank Side Indicator LCD Display

The Honeywell Enraf 977 TSI (Tank Side Indicator) is a specialized, intrinsically safe ground-level digital readout unit engineered for industrial storage tanks and marine terminal gauging installations. Mounted at eye level along tank walls, pipe stands, or access walkways, the 977 TSI eliminates the operational safety risk of routine tank climbing by relaying critical real-time level, temperature, status, and alarm data directly from tank-top instrumentation.

Operating on a two-wire intrinsically safe loop connected directly to host Honeywell Enraf level gauges, the 977 TSI extracts its operational power while simultaneously demodulating high-integrity digital data via Bell 202 Frequency Shift Keying (FSK) superimposed on the power conductors. Built in a rugged, marine-grade chromated and polyurethane-coated cast aluminum housing rated to IP65 / NEMA 4, the unit withstands extreme terminal, offshore, and petrochemical atmospheres. The display incorporates a high-contrast 2-line by 16-character alphanumeric LCD optimized for direct sunlight legibility and low-temperature operation.

Typical Manufacturer Part Numbers (MPN)

• 977-U-0-0-A-S-S-A: Standard display, wall mount, PG16, ATEX.
• 977-U-0-0-B-S-N-F: Keypad display, wall mount, ¾” NPT, FM approved.
• 977-U-0-0-B-B-G-A: Keypad display, 2″ pipe bracket, M20x1.5, ATEX.
• 0977.000 / 0977.800 series: Base assembly identification codes.

Key Features

1. Parasitic 2-Wire Bus Powering: Draws operational power directly from the host level gauge’s intrinsically safe barrier circuit, eliminating local mains cabling, conduit runs, or external power supplies.
2. Superimposed Bell 202 FSK Data Link: Digital telemetry modulates directly over the 2-wire DC loop using standard audio-frequency shift keying, maintaining noise immunity over distances up to 250 meters (820 feet).
3. High-Contrast 2×16 Alphanumeric LCD: Formatted for clear readout of level engineering units (mm, m, ft, in, 1/16th), average product temperature (°C, °F), vapour temperature, density, and diagnostic error codes.
4. Optional 4-Key Hazardous-Area Keypad: Version ‘B’ incorporates optical/capacitive navigation keys (Left, Right, Up, Down) for entering PIN-protected engineer functions, displacer calibration cycles, and dip-mode routines from ground level.
5. Offshore-Grade Environmental Enclosure: Heavy-duty coated cast aluminum body with IP65 / NEMA 4 ingress protection and full ATEX/IECEx Zone 1 / FM Class I Div 1 explosion-proof intrinsically safe compliance.

Equipment Compatibility

• Honeywell Enraf 854 ATG (Advanced Technology Gauge): Direct compatibility when populated with the XPU-2/i.s. processor board.
• Honeywell Enraf 854 XTG (eXchange Technology Gauge): Serves as primary local indicator for blind XTG units when equipped with the XPU-2/i.s. board.
• Honeywell Enraf SmartRadar Series 970, 971, and 973: Direct 2-wire interface via internal ICU_IS2 (Interface & Communication Unit) board.
• Enraf 873 SmartRadar Control Units: Compatible via field I.S. transmission modules.
• Legacy Systems: Adaptable across legacy Enraf servo lines fitted with verified intrinsically safe FSK output boards.

Applications

• Bulk Liquid Hydrocarbon Terminals: Atmospheric storage tanks, floating roof tanks, and fixed cone roof fuel storage farms.
• Refinery Tank Farms: Feedstock surge tanks, intermediate slop tanks, and finished product blending tanks.
• Chemical & Petrochemical Processing: Toxic or volatile chemical storage where climbing tanks for manual reading is strictly restricted.
• Custody Transfer Terminals: Fiscal metering inventory checkpoints requiring certified local ground readouts for port customs verification.

Frequently Asked Questions

Does the Honeywell Enraf 977 TSI require a separate 24V DC power cable?

No. The 977 TSI is a fully bus-powered instrument. It receives its operating current directly over the two-wire communication cable connected to the intrinsically safe port of the host level gauge (such as the 854 ATG or SmartRadar).

Can I install the 977 TSI on a blind Honeywell Enraf 854 XTG gauge?

Yes. The 854 XTG is a blind servo gauge without an integrated local display. Installing a 977 TSI at ground level is the standard industry method to monitor levels and operate the gauge locally, provided the XTG is equipped with an XPU-2/i.s. board.

What is the maximum cable distance allowed between the gauge and the 977 indicator?

While Honeywell recommends an installation within 50 meters (164 feet) for optimum line maintenance, the certified physical transmission limit is up to 250 meters (820 feet) using low-capacitance shielded twisted-pair cabling.

How do I clean and service the optical keys on the Version B keypad?

Because the keypad uses non-penetrating optical sensors through the front window, keep the face clean of grease, heavy crude deposits, and salt encrustation using a soft cloth dampened with mild soapy water or isopropyl alcohol. Avoid abrasive scrubbers that score the poly window.

Is the 977 TSI suitable for marine tanker deck installation?

Yes. With its chromated, polyurethane-coated aluminum enclosure and IP65 rating, it withstands marine saline decks. Ensure the housing cable entry is oriented facing downward with a certified IP66/68 cable gland and drip loop to prevent water tracking along the cable jacket.