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HS Sensors

Oil and gas: machine vibration monitoring

Oil and gas installations operate continuously, often in hazardous areas and far from maintenance facilities. Vibration monitoring of pumps, compressors and drives makes it possible to detect developing damage before it forces a shutdown of the installation.

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Oil and gas
© Hansford Sensors

What fails most often

An unplanned shutdown of a process installation has consequences beyond lost production: it requires safe shutdown and restart procedures, and a failure of a rotating machine can lead to seal damage and leakage of the process medium. Elevated vibration shortens the life of pump mechanical seals, so vibration monitoring supports reliability as well as process safety and environmental protection.

Ex zones and intrinsically safe circuits

Much of the equipment operates in hazardous areas with explosive gas atmospheres. An intrinsically safe sensor is only one element of the measurement chain: it requires a barrier or isolator in the safe area, a cable with known parameters and circuit documentation, and its marking must match the zone, gas group and temperature class.

Add to this the environmental conditions — outdoor operation, corrosive atmospheres, salt mist at offshore sites, high temperatures — and widely dispersed sites. Compressor stations, pump stations and field installations often operate unattended, so the signal has to reach the DCS or SCADA remotely.

Typical machines

Process, pipeline and injection pumps
cavitation, bearing damage, mechanical looseness
Compressors
unbalance, misalignment, bearing damage
Motors and drives
bearing damage, misalignment, vibration of electromagnetic origin
Gearboxes
gear tooth damage, bearing wear
Air cooler and cooling tower fans
unbalance, bearing damage, mechanical looseness
Plant blowers and fans
unbalance, misalignment, bearing damage

From the machine to the monitoring system

  1. 01Machines in this industry

    Process, pipeline and injection pumps, compressors, motors and drives and others — measuring point on the bearing housing.

  2. HS-104R — Low-power triaxial accelerometer, top exit, PUR cable

    02Sensor

    An IEPE accelerometer or a 4–20 mA sensor converts vibration (and often temperature) into an electrical signal.

    Industrial IEPE accelerometers
  3. HS-AA018 — Inline adaptor

    03Signal

    A cable with the right connector and a junction box carry the signal from many measuring points to the system.

    Cables and connectors
  4. HS-570-60 — Power supply module

    04Monitoring

    PLC, DCS, an online system or a data collector: trends, alarm thresholds and diagnostics before a failure happens.

    Vibration systems and switches

How to choose the measurement

Accelerometers for hazardous areas

The intrinsically safe HS-100I and HS-150I accelerometers, of shear design and with ATEX and IECEx certification, are intended for measurements in Ex zones — see accelerometers for hazardous areas. The documentation for these sensors includes, among other things, a guide to safety barriers and maximum cable length, which helps in designing the measurement chain.

4–20 mA signal to DCS and SCADA

HS-420, with a 4–20 mA output proportional to vibration velocity, integrates directly with PLC, DCS and SCADA systems. In non-hazardous areas the standard version is sufficient, and for Ex zones intrinsically safe 4–20 mA transmitters are available.

Measurement in three axes

Triaxial accelerometers measure vibration in three directions simultaneously from a single mounting point. They are useful where there is little space for sensors and the analysis requires all directions and the phase relationships between them.

Submerged and flooded measurement points

For underwater applications, the manufacturer offers HS-150 accelerometers in versions with an integral cable. The permissible submersion conditions are given in the datasheet, and it is worth discussing the selection before placing an order.

Connections in Ex zones

Measurement circuits from multiple sensors can be brought together in stainless steel intrinsically safe connection boxes, including a version with safety barriers.

Recommended versions

All products for this industry (24)

Product groups for oil and gas

Industry questions

Is an ATEX-certified sensor enough to make the measurement chain intrinsically safe?

No. Intrinsic safety applies to the whole circuit: the sensor, the cable, and the barrier or isolator in the safe area. Their parameters — voltage, current, power, capacitance and inductance — must be compatible with each other. The circuit is selected and documented according to the rules for designing installations in hazardous areas, e.g. to EN 60079-14.

When should I choose a triaxial accelerometer instead of three single-axis ones?

When there is not enough space at the measuring point for several sensors, or when you need simultaneous measurement in three directions and phase comparison. A triaxial sensor reduces the number of mounting points, but it requires three channels in the system and a multi-core cable. In Ex zones, check that the selected triaxial version has the required marking.

Can an accelerometer replace proximity probes on a compressor?

On machines with plain bearings, no. There, protection is based on measuring shaft vibration with proximity probes, and accelerometers on the casing complement it, e.g. with diagnostics of gearboxes and of the rolling-element bearings of auxiliary drives. On machines with rolling-element bearings, however, the accelerometer is the primary diagnostic sensor.

Further reading

Sensor selection for Ex zones

Send us the zone, gas group, temperature class and a description of the measurement chain: barrier, cable length and target system. We will help you select sensors and accessories.

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