MRU Retrofit Solution

For many applications that depend on an MRU, it can be very costly to perform a re-calibration, repair, or replacement. We have a solution that greatly simplifies this process while saving cost.

Motion Reference Unit - MRU Retrofit / Upgrade


Many vessels have motion reference units (MRU) installed that need re-calibration and repair. Or maybe they are end-of-life since support and re-calibration services are no longer offered by the original supplier. These older MRUs provide input to many vital systems on board and any fault can create an urgent and critical operational issue for your vessel.

Most MRUs require frequent re-calibration. Re-calibration is a cumbersome process since it involves administration, logistics, installation, configuration, and testing. The overall procedure can be very costly and time consuming. With other MRUs, a normal re-calibration procedure has the following steps.

1. Ship rental / temporary MRU to vessel
2. Install & configure rental / temporary MRU on vessel
3. Ship original MRU to manufacturer for re-calibration or repair
4. Ship calibrated / repaired original MRU back to vessel
5. Install original MRU on vessel again
6. Ship rental / temporary MRU back to manufacturer

Possible customs and export license issues can make this process even more difficult. So, this is not only costly, but the procedure requires 2 installations, rental, 4 shipments, and administration. All this while your vessel is sailing from port to port between countries.

The frequent re-calibration cost and hassle are good reasons to replace old MRUs with Norwegian Subsea MRUs. Even if the old MRUs are not end-of-life yet, there is sound economics in replacing them with our latest generation of MRUs.

So, consider an MRU retrofit solution if your old MRU requires re-calibration or repair.

Our MRU retrofit solution

Norwegian Subsea has a retrofit solution to easily upgrade your end-of-life MRU with a Norwegian Subsea MRU. The process consists of an assessment of your current system, and a guided installation of your new Norwegian Subsea MRU.


To help choosing the best Norwegian Subsea MRU for you, and prepare it for your vessel, we need to know

• Application
• Type of old MRU
• Interface – Mechanical, Electrical, Communication ports & Protocols
• Configuration of old MRU

Especially electrical interface and communication protocols are important for a seamless retrofit process. We can deliver MRUs with pigtail cables, junction boxes with standard connectors for ethernet and serial ports or provide cables with custom connectors and pin out at your end.

The old network or serial port settings for ethernet and RS-232 / RS-485, and output protocol must be known for a plug & play experience. E.g., if you use an industry standard NMEA protocol, a binary protocol, or another custom protocol.

Information in the configuration file of your old MRU can be used to pre-configure your new Norwegian Subsea MRU including settings for remote monitoring points and MRU mounting orientation and location.

Retrofit installation

After retrofit assessment, we can prepare a plug & play solution which consist of

• Pre-configured MRU
• Custom cables & connectors
• Remote support during installation

When the pre-configured MRU arrives, simply swap the old MRU with your new Norwegian Subsea MRU, and it will output data with the desired settings and protocol. Final on-board configuration is limited to a minimum and does not require on-board assistance. We are happy to help you via remote online support if you need help with the installation process.

Typical applications for retrofit solution

Any application that uses a motion reference unit should consider our retrofit solution. But especially applications such as


Dynamic positioning

Helideck motion monitoring

can really benefit from the retrofit solution as you can switch to an affordable MRU that does not require re-calibration.

Offshore construction vessel with helideck.
Helideck motion monitoring.

Benefits of switching to Norwegian Subsea MRUs

For most applications, a Norwegian Subsea MRU does not require re-calibration during its lifetime. This is because our MRUs use the latest generation high-end MEMS sensors that are extremely stable. However, re-calibration and validation of the MRU every 4th year is recommended if the customer requires full product specification in roll & pitch after expiration of a valid calibration certificate.

Some key benefits of our MRUs are

• Do not require re-calibration for most applications
• Very competitive prices
• Plug & play installation
• Very high roll, pitch, and heave accuracy in any sea condition

You can find more information about our MRUs and products here.