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Vaisala Offshore Weather Monitoring Systems: WMT700, WXT530 & HMP155
Reliable Weather Measurement for Offshore and Marine Operations
Offshore weather conditions can change quickly. Wind, rain, humidity, temperature and barometric pressure can affect lifting operations, helicopter movements, vessel approach, work at height, maintenance planning and general platform safety.
The further an operation moves from shore, the less representative a land-based weather station may become. Local measurement at the platform, terminal, vessel or coastal facility gives operators weather information from the conditions that actually affect the site.
A practical offshore weather monitoring system therefore starts with the operational question: which measurements are needed, where should they be taken, and how will the information be used?
Key Weather Parameters for Offshore Monitoring
| Parameter | Why It Matters | Typical Offshore Application |
|---|---|---|
| Wind speed and direction | Shows sustained wind, gusts and changes in wind direction | Crane operations, helidecks, vessel approach, lifting and work-at-height decisions |
| Air temperature | Provides local ambient conditions | Deck operations, equipment monitoring and meteorological reporting |
| Relative humidity | Supports assessment of moisture, condensation and fog-related conditions | Equipment protection, weather monitoring and dew-point assessment |
| Barometric pressure | Provides atmospheric-pressure and pressure-trend information | Weather observation, storm awareness and aviation-related applications |
| Rainfall | Measures precipitation intensity and accumulation | Deck safety, drainage, maintenance and local weather reporting |
WMT700 for Critical Offshore Wind Measurement
Where wind speed and wind direction are critical measurements, the Vaisala WMT700 Ultrasonic Wind Sensor is a strong choice for exposed offshore and marine installations.
The WMT700 measures wind ultrasonically. Unlike conventional cup-and-vane anemometers, there are no rotating cups or mechanical wind vane, reducing the number of conventional moving components exposed to salt, wind and continuous outdoor operation.
The WMT700 family includes several measurement ranges, allowing the sensor to be selected according to the expected wind conditions and the requirements of the application.
- Ultrasonic measurement of horizontal wind speed and direction
- Fast response for rapidly changing wind and gust conditions
- High wind-range options for demanding exposed locations
- Stainless-steel construction for professional outdoor installations
- No conventional rotating cups or wind vane
- Multiple communication and output options for integration with monitoring and control systems
- Heating options for applications where freezing or icing conditions need to be considered
For offshore platforms, helidecks, marine terminals and other locations where wind is an important operational measurement, the WMT700 should normally be considered as a dedicated wind measurement solution rather than treating wind simply as another environmental parameter.
View Vaisala WMT700 Ultrasonic Wind Sensor
WMT700 or WXT530?
The choice between WMT700 and WXT530 depends mainly on the role of the measurement.
| Requirement | Recommended Approach |
|---|---|
| Wind speed and direction are the primary operational measurements | WMT700 |
| High or rapidly changing wind conditions must be monitored | WMT700 |
| Several weather parameters are required from one compact instrument | WXT530 Series |
| Wind, rainfall, pressure, temperature and humidity are required from a compact weather station | WXT530 Series |
| Dedicated meteorological humidity and temperature measurement is required | HMP155 |
WXT530 for Compact Multi-Parameter Weather Monitoring
For sites requiring several weather measurements from one compact instrument, the Vaisala WXT530 Series Multi-Parameter Weather Transmitter provides a practical alternative.
Depending on the selected WXT530 model, measurements can include:
- Wind speed
- Wind direction
- Liquid precipitation
- Barometric pressure
- Air temperature
- Relative humidity
The fully equipped WXT536 combines all six parameters, while other models provide selected combinations. This allows the weather transmitter to be matched to the actual measurement requirement instead of specifying parameters that are not needed.
Its solid-state wind and precipitation measurement also reduces dependence on conventional mechanical wind cups, vanes and tipping mechanisms.
For compact offshore installations, coastal facilities, ports, terminals and general environmental monitoring, WXT530 can provide several important weather parameters from a single instrument.
HMP155 for Dedicated Humidity and Temperature Measurement
Where humidity and temperature require a dedicated meteorological sensor, the Vaisala HMP155 Meteorological Humidity and Temperature Probe can be used as part of the weather-monitoring system.
The HMP155 measures relative humidity across the full 0–100 %RH range and is designed for demanding outdoor meteorological applications.
Correct installation is important. A suitable radiation shield protects the sensor from direct solar heating and precipitation while still allowing representative airflow around the probe.
For very humid environments, warmed-probe configurations can also be considered where appropriate. The complete humidity and ambient-temperature measurement arrangement should be selected together.
Dedicated Barometric Pressure Measurement
Some offshore monitoring systems require barometric pressure as an independent measurement rather than as part of a compact multi-parameter transmitter.
For these applications, a dedicated transmitter such as the Vaisala PTB110 Analogue Barometric Pressure Transmitter can be integrated with the weather-monitoring or data-acquisition system.
The final choice between integrated and dedicated pressure measurement depends on the required accuracy, redundancy, system architecture and applicable project specification.
Wind Measurement on a Fixed Platform and a Moving Vessel Is Different
A wind sensor mounted on a fixed offshore platform measures wind relative to a stationary structure.
On a moving vessel, however, the measured wind is affected by vessel speed and heading. This is normally referred to as relative or apparent wind.
To calculate true wind, the receiving system must combine correctly synchronised wind information with vessel heading and speed. More demanding marine applications may also require suitable motion information.
| Reported Value | Meaning |
|---|---|
| Relative wind | Wind speed and direction measured relative to the vessel or structure |
| True wind | Calculated wind after accounting for vessel heading and movement |
| Motion-corrected wind | Wind calculation using additional movement and position information where required |
Sensor Location Is Critical Offshore
Even a high-performance wind sensor can produce misleading operational information when installed in a poor location.
Large offshore structures create complex airflow. Cranes, flare structures, exhausts, masts, helideck screens, handrails and nearby equipment can all create turbulence or wind shadows.
A practical installation review should therefore consider:
- Positioning the wind sensor away from major obstructions where practical
- Prevailing wind directions and structural wake zones
- Crane booms and other equipment that can move through the measurement area
- Hot exhaust and ventilation discharge
- Accessibility for inspection and maintenance
- Cable routing and mechanical protection
- Lightning and surge protection requirements
- Corrosion-resistant mounting arrangements
- Safe access for future servicing
Temperature and humidity probes should also be kept away from hot exhaust, ventilation outlets and surfaces heated strongly by sunlight.
Salt, Spray and Maintenance Should Be Considered from the Start
Offshore installations expose instruments, connectors, cables and mounting hardware to conditions that may be very different from an inland weather station.
Routine inspection should consider:
- Salt deposits on sensors and mounting structures
- Corrosion around fasteners and brackets
- Cable and connector condition
- Damage to protective filters
- Blocked radiation shields
- Birds, insects or other physical obstruction
- Sensor alignment and mounting security
- Condition of surge-protection and grounding arrangements
The maintenance plan should match the actual exposure of the site rather than relying only on a fixed calendar interval.
Choosing the Right Offshore Weather Instruments
There is no single weather-station configuration that is correct for every offshore project.
A platform that primarily needs reliable wind information may be best served by a WMT700 with separate sensors for other parameters. A compact installation may favour WXT530. A project requiring dedicated meteorological humidity and temperature measurement may add HMP155.
| Measurement Need | Instrument to Consider |
|---|---|
| Dedicated offshore wind speed and direction | Vaisala WMT700 |
| Compact multi-parameter weather monitoring | Vaisala WXT530 Series |
| Dedicated meteorological humidity and temperature | Vaisala HMP155 |
| Dedicated barometric pressure | Vaisala PTB110 |
Offshore Weather Monitoring Support in Malaysia
Seacom Process Instruments supplies and supports weather measurement instruments for offshore platforms, marine terminals, ports, coastal facilities, helidecks, industrial sites and other demanding outdoor applications in Malaysia.
Our team can assist with selection of WMT700, WXT530, HMP155 and barometric-pressure instruments, together with mounting, power supply, heating, cabling, communication and data-acquisition requirements.
When discussing an offshore weather-monitoring project, it is useful to provide:
- Site type — platform, vessel, terminal, port, helideck or coastal facility
- Fixed or moving installation
- Required weather parameters
- Expected maximum wind speed
- Required outputs or communication protocol
- Receiving PLC, SCADA, data logger or monitoring system
- Power supply available at the measurement point
- Cable distance
- Mounting location
- Environmental and hazardous-area requirements
- Applicable marine, aviation or operator specification
Selecting the instrument is only one part of a reliable offshore weather system. Correct location, installation and system integration are equally important to obtaining measurements that operators can trust.
Ask Seacom about offshore weather monitoring
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