Rosemount 708 Wireless Acoustic Transmitter

Rosemount 708 Wireless Acoustic Transmitter

Overview

The Rosemount 708 Wireless Acoustic Transmitter represents Emerson‘s innovative approach to non-intrusive equipment monitoring. Designed for steam traps and pressure relief valves (PRVs), this device utilizes ultrasonic acoustic event detection combined with temperature measurement to deliver real-time condition visibility without process interruption. Unlike traditional manual inspection methods that leave failures undetected for weeks or months, the 708 series provides continuous, automated monitoring that enables annual fuel cost reductions of 10–20 percent.-

The multi-variable transmitter is engineered with a thermocouple and an ultrasonic sensor with peak sensitivity in the 35–45 kHz range, measuring both acoustic amplitude (0–255 counts) and pipe surface temperature (–40 to 260 °C) through a single non-intrusive installation.-27

Model Series and Ordering Configurations

The Rosemount 708 Wireless Acoustic Transmitter is available in multiple complete model configurations, with the full ordering code following the structure 708X1P A1 X X X X X . Below are representative complete model numbers:

Each complete model number encodes specific configuration options including antenna type, power module selection, mounting hardware, and process connection requirements. The 708X1PA1NAHC01WA3WP5 model, for example, integrates the internal antenna (WP option), high-temperature mounting hardware (HC01), and SmartPower power module for extended field life.–38

Complete Technical Specifications

Functional Specifications

The update rate flexibility allows users to optimize between battery life and data granularity. For critical PRV monitoring applications requiring immediate alerting, a 1-second update rate detects valve opening events as quickly as a single second.-

Physical Specifications

The IP66/67 and NEMA 4X ratings ensure reliable operation in washdown environments and outdoor installations exposed to rain, snow, and hose-directed water.-3

Performance Specifications

Temperature Derating Table

The maximum ambient temperature decreases as process temperature increases:

Wireless Output Specifications

Key Features and Advantages

Non-Intrusive External Mounting

The Rosemount 708 Wireless Acoustic Transmitter mounts externally using two stainless steel bands, requiring no cutting into pipes or modification of existing piping configurations. This design enables installation without process shutdown, dramatically reducing deployment costs and downtime.-4-19

Multi-Variable Measurement

A single 708 device provides both acoustic level (0–255 counts) and temperature data simultaneously. The ultrasonic sensor delivers a relative measure of signal amplitude across the spectrum, while the integrated thermocouple measures pipe skin temperature clamped to the foot of the device.-27

SmartPower™ Long-Life Operation

The SmartPower™ solution delivers up to 10-year maintenance-free operation. The power module can be replaced in hazardous areas without removing the transmitter, and the non-rechargeable Lithium-Thionyl Chloride design is intrinsically safe for Class I, Division 1 environments.-4

Self-Organizing WirelessHART® Network

WirelessHART® technology automatically finds and manages optimal communication paths for each device, self-healing around obstacles and interference. The network delivers >99% data reliability and integrates seamlessly into existing host systems, data historians, and energy management software.-4

Rugged Construction

The PBT/PC engineered polymer housing combined with a 316L SST machined waveguide ensures consistent performance in harsh industrial environments, including high-vibration pipelines and extreme temperature conditions.-3

Steam Trap Monitoring Application

Steam traps are critical for energy efficiency, yet annual inspections leave failures undetected for extended periods. A single failed steam trap can cost thousands of dollars annually in wasted energy. The Rosemount 708 continuously monitors both acoustic signature and temperature, providing real-time trap health assessment through optional Steam Trap Monitoring software.-42

How it works: A functioning steam trap produces a distinct acoustic pattern. When a trap fails—either stuck open (wasting steam) or stuck closed (risking water hammer)—the acoustic signature changes immediately. The 708 detects this change within seconds and transmits the alert via WirelessHART®, enabling rapid repair before significant energy loss occurs.–42

Pressure Relief Valve (PRV) Monitoring Application

Manual PRV inspections are time-consuming, imprecise, and cannot detect transient releases. The Rosemount 708 provides continuous, real-time alerts for PRV events, detecting when a valve opens, when it reseats, and the duration of the release. This data enables:

Compliance reporting for environmental agency regulations

Detection of simmering or leaking valves before catastrophic failure

Predictive maintenance scheduling based on actual valve activity

Tamper-proof data logging with timestamped event records

Turbulence generated by a leaky valve is reliably detected using the acoustic transmitter’s 35–45 kHz peak sensitivity band.-27-42

Installation Guidelines

Physical Installation

Locate the 708 on a horizontal section of piping as close as possible to the equipment to be monitored.-

Position the transmitter foot between standoff mounting hardware plates and align.-11

Tighten each mounting screw to 90 in-lb (10.2 N-m).-11

Ensure the power module cover is fully tightened to prevent moisture ingress.-11

Wireless Network Considerations

Install and power the Smart Wireless Gateway first, ensuring proper functionality.-13

Power wireless devices in order of proximity from the Gateway, beginning with the closest.-2

Orient the transmitter with the waveguide horizontal and power module closest to ground for optimal range.-13

Maintain 1 m (3 ft.) clearance from large structures or conductive surfaces.-13

Enable Active Advertising on the Gateway for faster device joining.-13

High-Temperature Applications

For process temperatures exceeding 260 °C (500 °F), high-temperature mounting hardware must be used. The 708 supports process temperatures up to 260 °C standard, with derating for ambient conditions as shown in the Temperature Derating Table.-11

Safety Certifications and Compliance

The Rosemount 708 Wireless Acoustic Transmitter meets the following standards:

Special Conditions for Safe Use: The Rosemount 708 shall only be used with the 701PGNKF Rosemount power module in hazardous locations. The polymer enclosure has surface resistivity greater than one gigaohm; care must be taken during transportation to prevent electrostatic charge build-up.–12

Ordering Information

The complete Rosemount 708 ordering code structure includes:

Example Complete Models:

708X1PA1I2NA00 – Standard configuration with internal antenna

708X1PA1NAHC01WA3WP5 – High-temperature configuration with SmartPower

708X1PA1IMHC02WA3WR3WP5 – Extended configuration with enhanced diagnostics

Warranty Information

Standard warranty: 12–18 months

Extended options: 3-year or 5-year warranties available

Applications Summary

Conclusion

The Rosemount 708 Wireless Acoustic Transmitter delivers continuous, real-time monitoring of steam traps and pressure relief valves through non-intrusive ultrasonic and temperature measurement. With WirelessHART® communication, SmartPower™ 10-year battery life, and robust IP66/67 construction, the 708 series—including complete models 708X1PA1I2NA00, 708X1PA1NAHC01WA3WP5, and 708X1PA1IMHC02WA3WR3WP5—provides a cost-effective solution for improving energy efficiency, reducing maintenance costs, and ensuring environmental compliance. By eliminating manual inspections and providing instant failure alerts, Emerson Rosemount 708 enables dramatic decreases in steam trap failures and annual fuel cost reductions of 10–20 percent.