September 27, 2023
Dynamic Load Monitoring (UK) Ltd. (DLM) has reminded wind energy stakeholders of the importance of calibrating (and recalibrating) load and equipment monitoring systems.
Calibration is the correlation of the readings of an instrument to check accuracy. Southampton, UK-based DLM is a specialist in the design, manufacture, repair, and calibration of load cells and force monitoring equipment for the wind energy sector. A certificate of calibration is valid for one year; DLM contacts customers when their products are due for recalibration.
Running line monitors (RLMs), saddleback monitors, and load cells are all calibrated by DLM; load cells are calibrated upon their manufacture. Typically, the process is to take a test machine (in-house) or a tensile link (on-site) as the reference load cell, which provides a known reading; when the tensile link or machine shows 10t, for example, the other product is referenced to it.
Cable working gear products themselves don’t get calibrated; it’s not applicable to them. Depending on the product, they may be subjected to a load test, but these products aren’t directly relevant to onsite calibration. RLMs are generally calibrated in-house before they are shipped to the customer but are also calibrated on-site; saddlebacks are always calibrated on-site.
The load reading provided by the RLMs and saddlebacks can be used for a variety of reasons, such as monitoring tension on a subsea cable during the lay process and providing real-time data, which is time-stamped and correlated with a vessel’s GPS and other data. This provides the cable owner with detailed records of what tension was applied during the cable lay.
RLMs and saddlebacks will have an inspection done at the same time as calibration, to check the condition of all parts, such as bearings, connectors, running wheels/rollers, encoders, load cells, etc.
Chris Scrutton, technical director at DLM, said: “Recalibration is especially important on offshore vessels and wind energy sites because there are many ways to damage a subsea cable, a tow line, a winch, or other mission-critical equipment without generating a hazardous incident. It is just as much about asset integrity as safety; the only way to do this is to accurately know the load being applied.”
Calibration, a step-by-step process
Step 1: Visually and functionally inspect the equipment.
Step 2: Apply load to the device, with a known reference.
Step 3: Record the load readings from the device before any adjustment is made.
Step 4: Adjust the load output to bring the output within the specified limits (the limit varies depending on the product/application).
Step 5: Produce a calibration certificate to evidence accuracy.
