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Condition Assessment - Frequently Asked Questions
By Jonathan Morris is a Senior Asset Management Consultant with Opus International Consultants Limited.
What is condition assessment?
Many people talk about Condition Assessment, but there is little agreement on what it actually means. This article is intended to answer some common questions and give you some ideas of how to get better information about your system.
NAMS defines Condition Monitoring in their Infrastructure Management Manual as...
“Continuous or periodic inspection, assessment, measurement and interpretation of the resultant data, to indicate the condition of a specific component so as to determine the need for some preventive or remedial action”.
But NAMS does not define condition assessment, so we can make our own definition:
“Condition assessment is how you determine the present state of a system or component“
In simple terms, it is a way of checking if a system or component has changed in service.
This is all very well, but checking things takes time and costs money - and it usually means taking your system out of service that often isn’t very popular.
Why should I do condition assessment?
Almost all systems deteriorate with age or with use. Often performance hardly changes until deterioration is well advanced, so by the time you see a problem you have little time to react. The figure shows a typical theoretical plot of how failure rate changes with time as a result of deterioration. This kind of slow onset followed by rapid acceleration is also seen in real systems.
So you do condition assessment because it gives you advance warning of problems so that you have time to act - and because if you don’t do it you will either get in-service failures or have to replace things before they need it.
It’s also important to remember that you don’t do condition assessment when you don’t need to – like when it is as much work to check the condition as to fix a problem, or when failures aren’t related to condition.
Theoretical plot showing how break rate changes with time for a DN100 AC pipe undergoing constant deterioration.
The break rate hardly changes for a considerable time even though the pipes continue to deteriorate.
By the time the break rate from deterioration rises above the background rate (from ground movements, interference and other external factors) enough to notice, there can be little time left to react.
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When should I do condition assessment?
If you do have to shut your system down, you can choose when to do it so that it causes the least amount of trouble and so that you can get everything ready to make it as quick and easy as possible.
Having said that, the best way to collect samples is while you’re doing other jobs – repairs, new connections, renewals, upsizing – anything that allows you a free chance to get at the system. Most of the samples you collect will still be useful months later as long as you collect some basic information on where and when you collected them. There will always be a need for some targeted sampling to fill in the blanks, but this will provide the best return for your money and with minimal disturbance to your system.
Who should do condition assessment?
That depends on what you’re trying to do.
Your operators and contractors see the system every day, so they can give you a lot of useful information. It’s a great way to keep up with what’s going on in your system, but you have to ask them things they know about. Far too many engineers ask contractors and operators for information that they don’t have and can’t get and don’t explain what they are looking for. So the engineers get a mix of inconsistent information, incomplete information or (worst of all) people will fill in the forms just to keep their engineers happy. It might pay to train up your contractors and operators (and engineers) to get consistent gradings and to check that your forms only ask for information that they do have access to.
Some engineers and consultants can pull together information from the contractors and operators with system performance information to make a useful assessment, but usually don’t have access to specialist testing equipment or lack the time and experience to make detailed assessments. There are some special cases - Health and Safety issues related to handling AC pipes require specialist testing facilities, which are few and far between, so you have no choice but to use specialists for this.
Condition specialists are not that common and are expensive, but will be able to understand what is really going on and relate it to what you want to do with your system. Even the best can only look at a limited part of the system. The better ones will have proven methods of extending what they do find to other parts of the system – this is where the contractors’ and operators’ information and input from your engineers provides extra confidence in what’s really going on in the rest of your system.
What about Non-destructive testing?
Non-destructive testing (NDT) describes any way of getting information without damaging the system you are inspecting. There are many different types of non-destructive tests - simple non-destructive tests include looking and listening, and more sophisticated tests that need special equipment and specialist operators like ultrasonic testing, X-ray imaging or electromagnetic tests for metals. Some tests that cause only a very small amount of damage can also be considered as non-destructive tests.
Many non-destructive tests cause a lot of disruption even though they don’t cause any actual damage - they require pieces of pipe to be cut out, flow turned off or pressure reduced. NDT can also be expensive, or require a lot of interpretation.
Remember that non-destructive testing is just one way of getting information – and there might be a better, cheaper or easier way to get what you need.
What should I do with condition information?
Too often, condition assessment is done in isolation and the condition report ends up sitting on a shelf gathering dust. You could have got just as much information and saved yourself some money by sending your consultant half the fee to do nothing! (I always have time for this type of work - my contact details are at the bottom of the page).
You really need to think about this when asking “Why?” and “When?” In simple terms, you should identify what you need to know and when, then design a sampling strategy to get enough information at a reasonable cost and with minimal disturbance to system operation. Consider who will be using it, so that reporting and outputs are readily interpreted and understood.
How do I do condition assessment?
There are no national standards, or codes of practice for gathering condition data – this is not so surprising given that there isn’t even a definition. It is hard enough finding examples of best practice and most of these are from industries that have nothing to do with water.
The most important thing with condition assessment is to decide what you want to know and what you will do with the information you get. Once you (and possibly your specialist consultant) have done this, you will be able to set realistic budgets and information gathering targets, which makes success more likely.
Dr Jonathan Morris is a Chartered Materials Engineer with a doctorate in non-destructive testing and over 20 years of materials evaluation experience, which includes fifteen years doing condition assessment of networked services and industrial plant. Jonathan is a Senior Asset Management Consultant with Opus and is based at the Environmental Training Centre in Lower Hutt.
For further information on industry training on water industry training course and opportunities, whether existing courses or development of specialist training materials, please contact Jonathan Mackey, NZWETA Manager, on 0800 699 382, or nzweta@nzweta.co.nz.
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