Honeywell STAW84L Wireless Absolute Pressure Transmitter

Honeywell STAW84L wireless absolute pressure transmitter: scope of the model

The STAW84L is the absolute pressure transmitter in the Honeywell SmartLine Wireless range. Absolute pressure is measured against a perfect vacuum rather than against the atmosphere, so the reading does not move with weather or with the altitude of the site. Typical uses are vacuum service, distillation columns, condenser and ejector monitoring, and any application where barometric drift would corrupt a gauge reading. The STAW84L covers 0 to 500 psia (0 to 35 barA) in an in-line body, and delivers the value over an ISA100.11a-ready 2.4 GHz radio instead of a signal cable. Seven Star LLC supplies the STAW84L in Oman and the GCC as an independent supplier in Muscat.

The model code is short because the datasheet lists a single range: STAW84L means wireless (W), absolute (A), 500 psia class (84) and in-line (L) construction. Other options such as wetted materials, fill fluid, antenna and calibration are chosen from the model selection guide.

STAW84L technical specifications

Values apply at the datasheet reference conditions of 25 °C, 10 to 55 % relative humidity and a 316L stainless barrier diaphragm.

Why an absolute measurement matters, and how the STAW84L delivers it

A gauge transmitter vents one side of its sensor to the atmosphere, so its reading rises and falls by a few millibar with the weather and by a larger amount on a high-altitude site. An absolute transmitter instead references a sealed vacuum. For a process running at 50 or 100 mbar absolute, a gauge instrument would waste much of its resolution and lose accuracy to atmospheric swing. The STAW84L uses the same piezoresistive meter-body technology as the wired SmartLine ST 800 and ST 700 absolute versions, with temperature compensation built onto the sensor chip.

The wireless electronics then scale the value, apply any filter you configure and publish it at a rate between half a second and sixty minutes. The datasheet notes that the device can sit in a mesh or a star topology on the same network. Choose star operation when the pressure feeds a loop that needs predictable timing.

STAW84L in the SmartLine Wireless family and OneWireless network

The transmitter is a field device on a Honeywell OneWireless network, which uses a Wireless Device Manager as gateway and one or more Field Device Access Points as access points and routers. The manufacturer states that SmartLine Wireless transmitters join existing OneWireless networks and interoperate with XYR 6000 devices and other ISA100 compliant products. Related wireless models you may need on the same job include the STGW800 gauge pressure series, the STDW800 differential pressure series, the STFW828 flange mounted level transmitter, the STIW400 temperature transmitter and the STUW750 universal I/O transmitter. They share antennas, batteries and brackets, so one spares kit covers several tags.

Selecting an STAW84L

• Confirm the pressure is absolute. If the process is above atmospheric and a gauge reading is acceptable, the STGW800 range may cover the need; for vacuum or tight low-pressure control the STAW84L is the correct measurement basis.
• Range and span. The upper limit is 500 psia with a minimum span of 5 psia. A narrow span on a high URL loses some accuracy per the datasheet formula, so verify the operating window before ordering.
• Wetted parts. Select 316L stainless steel or Hastelloy C-276 for the diaphragm according to corrosion data for the fluid, including any chlorides in seawater-cooled systems.
• Fill fluid. Silicone oil suits general service; CTFE is the inert choice where oxygen or strong oxidisers are present.
• Network release. Pick the OneWireless release option that matches the existing network (R2xx or R3xx).

Antenna, power and battery planning

The integral 4 dBi antenna gives a nominal 350 m line-of-sight range to an access point. Where the transmitter sits among vessels and structural steel, remote 8 dBi omnidirectional or 14 dBi parabolic antennas can be specified with cables up to 10 m and a surge arrester. Batteries are generic 3.6 V lithium thionyl chloride D cells from approved makers (Xeno Energy, Eagle Picher and Tadiran models are listed), and the compartment is intrinsically safe. A 24 VDC supply is also available. Longer publish intervals extend battery life, so use the slowest rate that still satisfies the monitoring or control requirement.

Installation, commissioning and maintenance of the STAW84L

• Mount with the antenna vertical on a 2 inch pipe or on a wall using the optional angle or flat bracket in zinc-plated carbon steel or stainless steel.
• Provision the device onto the network using either the infrared interface and a handheld, or the over-the-air method. Each transmitter carries a unique encrypted key from the factory.
• For vacuum service fit an isolation or manifold arrangement that allows the process to be shut off and the reference checked without disturbing the measurement.
• Perform a zero check against a known vacuum or absolute reference at commissioning, and repeat during shutdowns. Ordered options include a custom calibration to your range and an overpressure leak-test certificate.
• Keep the vent and drain plugs sealed. Firmware updates are pushed over the wireless network by the device manager.

Typical STAW84L applications in Oman and the GCC

Absolute pressure transmitters are widely used in multi-stage flash and multi-effect desalination units, where condenser and brine heater vacuum levels indicate performance. Refineries and gas-processing plants use them on vacuum columns, steam-ejector systems and surge-vessel monitoring, and petrochemical units use them on reactor and dryer vacuum lines. The wireless version helps when a measurement is needed on an existing unit and cabling would require shutdown work. In hot coastal sites, shade the housing from direct sun and apply the stainless steel housing option in salt-laden atmospheres.

Information to send with an STAW84L RFQ

• Operating, minimum and maximum absolute pressure and the calibrated range.
• Process fluid and temperature, including steam or condensate exposure.
• Diaphragm material, fill fluid and housing material.
• Hazardous-area classification and required approval scheme.
• OneWireless release, antenna option, destination country for the radio power setting.
• Battery or 24 VDC supply, bracket type, tag text, quantity.

Documents and quotation for the STAW84L

A datasheet for the STAW84L is attached on this page, including the model selection guide and hazardous-location approvals table.

Send us the model number and your instrument list and we will confirm availability and lead time for the quotation.