Description

Emerson EPRO PR9268/303-000 Electrodynamic Velocity Sensor

The Emerson EPRO PR9268/303-000 is a high-precision electrodynamic absolute vibration transducer engineered for critical turbomachinery protection applications. It measures structural casing vibration—specifically bearing housing absolute vibration—across steam turbines, gas turbines, hydro turbines, axial compressors, and large industrial fans.

Utilizing a rugged moving-coil mass-spring design, this seismic sensor generates its own primary measurement voltage without requiring an external power source. The analog signal interfaces directly with machinery protection architectures such as the AMS 6500 or MMS 6000 systems.

Technical Specifications

Commercial and Logistics Status

• Condition: New Original (Factory Sealed) or New Surplus available.

• Warranty: 12-month standard industrial warranty from the date of shipment.

• Availability: In stock and ready for immediate global dispatch.

• Lead Time: 1 to 2 business days for order processing; 3 to 5 business days for global air freight via DHL, FedEx, or UPS.

• Pricing Note: Prices are indicative and fluctuate based on specific hazardous area certification suffixes and global inventory levels. Contact our procurement team for a firm, formal quotation.

Field Application and API 670 Implementation

The PR9268 series complies with the casing vibration monitoring mandates defined in the API 670 standard for machinery protection. It translates the physical velocity vectors of structural elements into a linear, low-impedance AC voltage output proportional to the velocity of the machine casing.

       +--------------------------------------------------------+
       |             Machine Bearing Housing / Case             |
       +--------------------------------------------------------+
                                  || (Mechanical Vibration Coupling)
       +--------------------------------------------------------+
       |         PR9268/303-000 Electrodynamic Sensor           |
       |  - Moving-Coil/Permanent Magnet Mass-Spring System     |
       +--------------------------------------------------------+
                                  || (AC Voltage Output: 17.5 mV/mm/s)
       +--------------------------------------------------------+
       |   Armored PTFE Cable / Optional ATEX Barrier Block     |
       +--------------------------------------------------------+
                                  ||
       +--------------------------------------------------------+
       |  MMS 6120 / AMS 6500 Case Piezoelectric/Seismic Module|
       |  - Core Data: True RMS Velocity (mm/s or in/s)         |
       +--------------------------------------------------------+

Because the output signal is generated by a physical mechanical mass suspended by springs within a permanent magnetic field, the sensor boasts a low source impedance. This makes the analog transmission highly resilient against electromagnetic interference (EMI) and radio-frequency interference (RFI) across long cable distances from the turbine deck to the control room rack.

Technical and Field Constraints

Frequency Response Boundaries

The PR9268/303-000 features a natural frequency calibrated to 4.5 Hz.

• Low-End Limits: Measurement accuracy falls off sharply below 14 Hz due to phase shifts and rapid attenuation characteristics inherent to the internal mass-spring arrangement. Do not rely on this transducer for machines running under 840 RPM.

• High-End Limits: Beyond 1,000 Hz, structural resonances within the internal housing spring-assembly can distort amplitude readings. For high-speed gearboxes or aerodynamic blade pass analysis, complement this unit with a high-frequency piezoelectric accelerometer.

Transverse Sensitivity

The transverse sensitivity of this sensor is constrained to $< 0.1$ at 80 Hz (less than 10% of the main-axis sensitivity). However, off-axis acceleration forces exceeding 2g can introduce mechanical friction or premature wear of the coiled wire suspension. Ensure the mounting surface is machined completely flat and exactly perpendicular to the intended measurement vector.

Hazardous Area Installations

When installing this sensor within explosive environments (Class I Div 1, or ATEX Zone 1/2):

Explosive Environment Mandate: The PR9268/303-000 must be wired through a certified intrinsically safe zener barrier or galvanic isolator in accordance with the loop schematic before entering the data acquisition module. Review the model code prefix on the physical label to ensure the specific unit possesses the required regional approvals (e.g., ATEX/IECEx).

Frequently Asked Questions

Can the PR9268/303-000 be mounted in any orientation?

Yes, the “303” sequence corresponds to an omnidirectional or universal variant that allows flexible mounting positions without losing the internal alignment of the moving coil assembly. However, you must verify the exact alignment configuration against your specific installation drawing before applying final torque. For fixed vertical-only configurations, the specialized PR9268/201 series is typically specified.

What causes a sudden loss of signal or zero voltage output during a running test?

If the machine is actively vibrating but the output shows 0 mV, perform a static loop continuity check. Disconnect the sensor cable at the junction box and measure the DC resistance across the signal pins. The internal coil should read approximately 1,723 $\Omega$ at 20 °C. A reading of infinity ($\infty$) indicates an open circuit, usually caused by a snapped internal suspension wire or a severed field cable. A reading near 0 $\Omega$ indicates a short circuit within the terminal plug or the internal coil winding.

Is a separate pre-amplifier or transmitter required for this sensor?

No. Unlike high-impedance piezoelectric accelerometers that require external charge amplifiers or IEPE power sources, electrodynamic sensors generate a low-impedance voltage output entirely on their own. The raw signal can be wired directly to any standard industrial vibration monitor configured for a seismic velocity input.