Honeywell SmartLine GWR Guided Wave Radar Level Transmitter

SmartLine GWR guided wave radar level transmitter (SLG700)

The Honeywell SmartLine GWR is the guided wave radar level transmitter in the SmartLine family, sold as the SLG 700 series. It sends nanosecond radar pulses down a rod, wire or coaxial probe and measures how long the reflection from the liquid surface takes to return (time domain reflectometry). The result is level, volume or interface level on a two-wire, loop-powered 4 to 20 mA signal with HART or FOUNDATION Fieldbus. Seven Star LLC supplies SmartLine GWR transmitters in Oman and the GCC as an independent supplier in Muscat.

The series has two versions: SLG720 for standard pressure and temperature, and SLG726 for high pressure and temperature up to 400 bar and 450 °C, including a saturated-steam compensated version for boiler drums.

SmartLine GWR technical specifications

How SmartLine GWR measures level and interface

A pulse travels along the probe until it meets a change in dielectric constant, which is the product surface. Part of the energy is reflected, and the electronics convert the transit time into distance and then into level, volume or ullage. The method does not depend on density, conductivity or temperature, but the product needs a dielectric constant of at least 1.4.

For two-liquid interface, the transmitter reports both the surface and the interface. The datasheet limits are an upper-medium dielectric constant of at most 9, a lower-medium dielectric constant of at least 10, a difference of at least 8, and an upper layer of at least 7 cm; the measuring accuracy of both is ±3 mm. In high-pressure boilers the SLG726 steam-compensated version uses a reference measurement of the steam dielectric constant, because uncompensated error is about 1 % at 172 °C and 5 % at 250 °C.

SmartLine GWR probes, blocking distances and mounting

Rod probes suit short, clean spans up to 6.3 m, wire probes go to 50 m and tolerate low headroom, and coaxial probes give the strongest signal for low-dielectric products and turbulent tanks. Blocking distances depend on probe and product: for a rod or wire probe in water the minimum upper blocking distance is 9 cm, in oil 7 cm; coax is 5 cm in both. Nozzles should preferably be 150 mm (6 in) wide, at least 50 mm (2 in), and a taller nozzle adds to the upper blocking distance.

For bypass chambers and stilling wells, Honeywell recommends 3 or 4 inch pipe for rod probes and 4 inch for wire probes, with the probe 25 mm (1 in) above the bottom and a centering disk for rigid probes longer than 1 m. The SLG 700 can also be ordered with remote electronics on a 3 m cable.

SmartLine GWR selection and ordering checklist

• SLG720 or SLG726, set by the maximum working pressure (40 bar or 400 bar) and temperature (200 °C or 450 °C).
• Probe type, length and material: rod, wire or coax, in 316L or C-276, with optional FEP coating on SLG720.
• Process connection: NPT (from 3/4 inch), BSP, or flange from DN40 / 1.5 inch, and the O-ring or metal seal material for the temperature.
• Output and housing: HART or FOUNDATION Fieldbus, aluminium or stainless housing, display, remote mounting.
• Dielectric constant of the product, tank dimensions, nozzle height and interface or steam duty.
• Hazardous-area approval, SIL certification and overfill protection requirement.

Installing and commissioning SmartLine GWR

Keep the probe at least 400 mm from tank walls and obstacles for reference accuracy, avoid nozzles wider than 200 mm for single-lead probes, and fit a metal flange over 2 inch / DN50 or a metal plate when the vessel is plastic. Wiring is polarity insensitive, and the electronics are in a dual-compartment housing with replaceable modules. Honeywell offers an online SmartLine Application and Validation Tool so that the tank data can be validated and the transmitter delivered pre-configured, which reduces commissioning time.

Echo curves can be viewed on the local display as stem plots or through the DTM-based field service tool, FDM and Experion PKS. When the probe sits in a nozzle, Honeywell requires a field background measurement to reach the stated blocking distance and upper-zone accuracy.

Typical SmartLine GWR applications in Oman and the GCC

Typical uses are separators, scrubbers and knock-out drums in oil and gas, hydrocarbon storage and day tanks, condensate and chemical tanks, feedwater and deaerator vessels, and boiler drums where the SLG726 handles high pressure and steam. Hot desert conditions and process temperatures are covered by the -40 to 85 °C ambient rating and the metallic-seal options for high temperature.

SLG720 and SLG726 compared

Information to send with a SmartLine GWR RFQ

• Tag list and the version (SLG720 or SLG726) if already known.
• Product, dielectric constant, density, pressure and temperature range.
• Tank type, height, nozzle size and any bypass chamber dimensions.
• Output (HART or Fieldbus), approvals and SIL needs.
• Quantity and delivery location.

Documents and quotation

The Honeywell SLG 700 guided wave radar specification (34-SL-03-03) is attached on this page. It contains the probe tables, blocking distances, approvals and dimensional drawings. Send your application data and we will quote the right SmartLine GWR version.

Seven Star LLC is an independent supplier in Muscat; availability is confirmed per order.