Rosemount TankRadar Rex RTG 3950 Radar Level Gauge

Rosemount TankRadar Rex RTG 3950 Radar Tank Level Gauge

The Rosemount TankRadar Rex RTG 3950 is a custody-transfer non-contact radar level gauge designed specifically for still-pipe installations on floating roof tanks, crude storage units, and refined hydrocarbon product terminals. Operating on high-precision Frequency Modulated Continuous Wave (FMCW) radar architecture with an integrated digital reference oscillator and internal thermal compensation, the RTG 3950 delivers instrumental accuracy of ±0.5 mm (±5/256 in.) with a maximum operational deviation well within OIML R85 custody transfer tolerances.

The RTG 3950 addresses the common problem of heavy crude wax buildup, rust, scale, and pipe deformation using proprietary Low Loss Mode circular wave propagation. Unlike standard horn or coaxial radar devices where wall roughness degrades signal-to-noise ratio, the RTG 3950 array focuses the microwave energy centrally within the guide pipe, concentrating signal strength downward toward the liquid surface. The unit mounts directly to standard 5-inch to 12-inch slotted or unslotted still-pipes without taking the storage tank out of service.

Model Details

• Base Model Series: Rosemount TankRadar Rex 3900 Series
• Transmitter Model: RTG 3950 (Still-pipe Array Antenna Gauge)
• Standard Manufacturer Part Number (MPN) Configuration Structure:
  • RTG3950-F-[Size]-[Supply]-[Bus]-[Card]-[Pressure] (Fixed Flange Version)
  • RTG3950-I-[Size]-[Supply]-[Bus]-[Card]-[Pressure] (Inclined Version with Integrated Hand-Dip / Sampling Hatch)
• Typical MPN Examples:
  • RTG3950-F-08-AC-TRL2-TIC-P1 (8-inch fixed still-pipe, 100–240 VAC, TRL/2 bus, Transmitter Interface Card)
  • RTG3950-I-10-DC-PBP-TMC-P2 (10-inch hinged hatch version, 24 VDC, Profibus-DP, Temperature Multiplexer Card)
• Transmitter Head Electronic Spares:
  • Transmitter Interface Card (TIC): Ref 109200E / TIC-REX
  • Temperature Multiplexer Card (TMC): Ref 109210E / TMC-REX
  • Motherboard / Processing Unit: REX-CPU-3900

Features

1. Patented Low Loss Mode Wave Propagation: Concentrates circular wave radar energy down the center axis of the pipe, reducing reflection losses from internal scale, paraffin wax, rust, and slot perforations by up to 100 times over standard microwave designs.
2. Fiscal Custody Transfer Measurement: Provides ±0.5 mm instrument precision via ~10 GHz FMCW digital reference tracking, meeting international legal metrology standards (OIML R85, API MPMS Chapter 3.1B, ISO 4266).
3. Hinged Inclined Hatch Option: Available in an inclined antenna arrangement with a full-bore verification port, permitting direct physical hand-dips, ullage verification, and product sampling through the gauge column without breaking the atmospheric seal.
4. Multi-Drop Bus & Emulation Protocols: Direct native support for Emerson TRL/2 2-wire field communication, Modbus RTU, Profibus-DP, Foundation Fieldbus, and onboard emulation modes for legacy third-party gauging buses (e.g., Enraf GPU, Whessoe, Varec).
5. Functional Safety (SIL 2): Engineered and tested according to IEC 61508 criteria to support safety-instrumented systems (SIS) and certified TÜV high-level overfill prevention requirements.

Applications

• Crude Oil Floating Roof Tanks (EFRT): Tank gauge installations subject to heavy wax accumulation, pipe scaling, and mechanical pipe eccentricities.
• Finished Hydrocarbon Storage: Gasoline, diesel, aviation kerosene, jet fuel, and blendstocks with or without internal floating covers (IFR).
• Chemical Terminal Inventory: Petrochemical storage requiring corrosion-resistant wetted parts (AISI 316L, PPS) and vapor containment.
• Pipeline Terminals & Marine Depots: Fast-turnaround custody transfer, batch dispatch, and automated inventory balancing.
• Overfill Protection Loops: SIL 2 critical high-level shutdown loops and independent tank safety architecture.

Frequently Asked Questions

Can the Rosemount RTG 3950 be installed on a tank that is currently in operation?

Yes. The RTG 3950 is specifically engineered for retrofitting onto existing 5″ to 12″ still-pipes without opening the storage tank to atmosphere or degassing. The lower flange section bolts directly onto standard ANSI or DIN matching pipe flanges, allowing installation while hydrocarbons remain stored inside.

What is the primary operational advantage of “Low Loss Mode” over standard radar level gauges?

In conventional non-contact radars, corrosion scale, heavy crude deposits, and slots inside a guide pipe cause signal attenuation, phase distortion, and false structural reflections. The RTG 3950 Low Loss Mode uses a specialized array configuration that propagates circular microwave patterns, which direct the signal field down the center of the column. This maintains custody transfer precision even in heavily scaled pipes.

Can the RTG 3950 emulate older or third-party tank gauging protocols?

Yes. In addition to native Rosemount TRL/2 and Modbus communication, the transmitter’s processing electronics can emulate legacy proprietary protocols from vendors such as Enraf, Whessoe, Varec, and L&J. This simplifies replacement of legacy mechanical servo or older radar transmitters without replacing existing field cabling or central DCS communication interface cards.

How are multi-spot temperature measurements integrated into the level measurement?

The RTG 3950 can be ordered with an internal intrinsically safe Temperature Multiplexer Card (TMC) or paired externally via TRL/2 bus with a Rosemount DAU 2100. This allows up to 14 or 16 Pt100 temperature spots to be measured and averaged alongside level data for precise API net volume calculations.

What maintenance is required on the RTG 3950?

Because the gauge is a non-contact, solid-state radar device with no moving mechanical parts, routine maintenance is minimal. Periodic inspections should confirm that the electronics desiccant cartridge is active (blue), the flameproof cover O-rings are lubricated, and on inclined models, that the hinged hatch gasket maintains a gas-tight seal when closed.