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Risk based maintenance - better results for less effort

Friday, May 11, 2012

Having a "risk based" maintenance plan can give you better equipment performance than a "proactive" maintenance strategy, but with less cost and effort, says Andy Scott, global business director for RMBI (reliability-based mechanical integrity) at Lloyd's Register.

"Risk based" maintenance could be better understood as a "right maintenance right time" maintenance, where you use the best knowledge available, including expert advice and data analytics, to work out the best time to do a certain task, he said.

"Proactive" maintenance is usually understood to mean maintenance using reliability centred maintenance and condition based monitoring tools, to assess the condition of equipment using a range of factors, such as vibration and noise.

The problem with proactive / condition based monitoring is that systems to monitor equipment can be costly and highly complex. "Are the crew and maintenance team up to the task of keeping them current? History shows that perhaps they're not," he said.

Mr Scott classifies maintenance in 4 groups - reactive (fix it when it breaks), preventative (replace items according to a schedule hopefully before they break), proactive (try to monitor the condition of items to see when they are going to break) and risk based (when you try to manage how much risk you are taking).

It is still common for maintenance plans to be time based (replacing certain items after a certain number of hours). This can be nonsense when you consider that one rig might trip (raise and lower drill pipe) millions of feet more than another, and they both replace parts at the same time intervals, Mr Scott said.

Risk based maintenance

The company believes that a good risk based maintenance plan can help reduce the number of inspections you need to make by 50 per cent, and improve reliability by up to 80 per cent.

A risk based maintenance approach can be a great help in reducing non productive time for drilling rigs, he said. "We believe 60 per cent of NPT can be related to maintenance, and we can save 50 per cent of it," he said.

"What we try to achieve is informed decision making, balancing the right level of risk against, asset performance," said Mr Scott. "We build dynamic risk profiles for each asset based on a wide range of criteria including integrity and business drivers."

Lloyd's Register has gathered 15 years of data about the performance of different pieces of equipment, which is important when calculating risk.


The company has developed its own software, called "Capstone RBMI", to help operators of heavy equipment put together a risk based maintenance plan.

The Capstone RBMI software can help put together a risk based inspection (RBI) plan for rotating equipment, and can enable companies to put together a maintenance program for all of their equipment.

Risk based inspection software has been around for many years for fixed equipment, but it has not been made available for rotating equipment before, he said.

Rotating equipment has more complicated components and more varied damage mechanisms than fixed equipment, he says.

Capstone RBMI runs a screening process across all pieces of equipment in the plant. It works out which assets are most critical (ie cause the most problems if they fail), and prioritises maintenance tasks accordingly.

The software puts together a custom preventative maintenance and corrective maintenance task plan, and can be used to record failure information, and promote continuous improvement of the overall system.

Associated Companies
» Lloyd’s Register
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