dynamically inclined

Intelligent Stability Technology – MOSIS

Tymor’s MOSIS (Measurement of Stability in Service) is a unique onboard system which monitors the stability of your vessel during operation. In many regions, MOSIS is an industry approved ‘in-service’ method of compliance with statutory regulations. It has the significant advantage of removing non-productive, costly downtime associated with inshore inclining tests. Instead, the technology conducts tests and gathers data while the vessel is in operation, keeping you moving forward safely, efficiently and productively.

MOSIS – Measurement of stability in service

The short video below explains how to measure stability with no impact on operations.

What is MOSIS?

MOSIS (Measurement of Stability in Service) is a unique system for monitoring the stability of a vessel or floating structure while in operation.

Using MOSIS to replace a traditional inshore inclining test can meet statutory regulations whilst removing the non-productive downtime of taking the vessel out of service for a traditional inclining test.

MOSIS delivers accurate, current and relevant data, reflecting the vessel’s current load and weight distribution, which is a unique advantage of this technology.

The system consists of onboard software and hardware used to measure the vertical centre of gravity (VCG) and hydrostatic (displacement) stability in variable conditions without any impact to normal operations.


MOSIS regularly carries out the equivalent of an inclining test during vessel operations. The results of the tests are used to monitor and track the vertical centre of gravity (“VCG”) over time, allowing action to be taken to prevent an issue from emerging. It has proven HSE and cost benefits and improves operational efficiency. There is, to our knowledge, no other field-proven and industry regulator accepted system available. The MOSIS system was verified in an independent review commissioned by the Health and Safety Executive, with the conclusion below.

The ability to conduct a multitude of tests allied with their statistical analysis can enable prediction of the most probable values of the Lightship data to lesser uncertainties than might be attained in a single conventional inclining test. It also has the important benefit of tracking and measuring stability regularly, enabling long term weight and VCG growth to be monitored.

UK Health and Safety Executive - An Assessment of the MOSIS System

What are the features of MOSIS?

  • No downtime or interrruption to operations.
  • High-quality, reliable data.
  • Can meet regulatory Class requirements to replace inshore inclining tests.
  • More frequent and accurate tracking of the vessel’s VCG and weight characteristics.
  • Data captured during operation, under real and changeable conditions.
  • Multiple data sets captured in real-time demonstrating a time-lapsed profile.
  • Tracks the additions of lightweight, deadweight and variations in load.
  • More accurate measurement of ‘variable deck load’.
  • Can input to the vessel’s manitenance system and discrepencies in instrumentation.
  • Maximises and optimises equipment loading during transit and static operations.

Take the stress out of stability

economic and efficiency benefits

The ability for the owner or operator of a vessel to understand its stability and continue earning revenue instead of returning to a sheltered port for an inclining test is a major benefit.

For example, in the oil and gas sector, floating production units are difficult to bring inshore once they are deployed and drilling units are under significant contract pressures to reduce costs.

In the defence sector, the ability to assess your vessel’s stability and know whether you can, in the event of damage, maintain your effectiveness in battle, or need to withdraw, or as a last resort abandon ship, is a critical part of the decision making process.

For commercial shipping and other sectors, the ability to safely maximise cargo-carrying capacity delivers significant value. This can be achieved with an accurate knowledge of VCG from MOSIS and Tymor’s specialists can provide clients with vessel optimisation analysis, advice and support.

Safety and Risk Benefits

The safety benefits of using accurate and current stability information cannot be underestimated. With MOSIS, the vessel will be operating with an up to date vertical centre of gravity calculation, rather than one which was estimated a number of years previously, with perhaps a different loading distribution.

If equipment has been added and removed from a vessel since the original inclining test, although on aggregate it may result in a similar weight, the centre of gravity may have changed, impacting on how the vessel behaves.

MOSIS delivers frequent and accurate tracking of the vessel’s VCG and weight characteristics during operation. With data captured under real-time, changeable conditions it provides a better picture of safe operating parameters.

With time-lapsed trends and developing patterns becoming evident, the mariner has greater data upon which to base safety decisions and take actions earlier, eliminating risk.

MOSIS also provides an early indication of reduction in cargo carrying capacity, tracking the changes to lightweight and deadweight and optimising equipment loading during transit and operations.

A technical overview

Read a more in-depth overview of the MOSIS technology.

MOSIS stability container ship