Can you afford not to use "Predictive Maintenance" for water and wastewater assets? |
February 08, 2009 |
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Posted by Steve Carson at February 8, 2009 05:44 AM |
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As asset management of wastewater collection systems and water supply systems has become more important, every utility wants to know the state of their assets.
For some types of assets, making the assesment is very easy - although it might be a sobering one. For example, the assessment of pipes and wells - the civil infrastructure that makes up a significant proportion of the utility's asset base. It's not so hard to figure out whether this asset class needs replacement, even though there is some work in the investigation.
The problem for wastewater utilities is that often the pipe network is 100 years old and so corroded that the whole pipe network needs replacement -and it's the largest asset class in terms of replacement value.
Pumps, Motors and Control Systems
But what about pumps and motors - and control systems?
The question "How do you maintain pumps and motors?" strikes at the heart of this problem. There are really three approaches to the problem:
- "Run to fail", i.e., wait until the pump or motor fails and - usually - race out and fix it or replace it
- Preventive maintenance, i.e., periodic maintenance of a pump or motor to avoid waiting for it to fail
- Predictive maintenance - the utility determines the state of each asset and can plan for servicing or replacement of a pump or motor
The majority of wastewater organizations in the USA have adopted a "run to fail" approach, although usually due to lack of resources and not with the perspective that this is the best way to reduce "whole of life" cost.
A significant proportion have adopted preventive maintenance, although when questioned, they are usually very open about the problem they have in understanding whether they are doing too much maintenance - or too little. Frequently, when we ask the question about their maintenance schedule we get the question back:
"So what does everyone else do?"
The UK, by comparison, has been trying to adopt a much more proactive approach, generally known there as Condition Based Monitoring, which in practice is the same as Predictive Maintenance.
The problem is really one of data, but, like any challenge, there has to be a motivation for doing something different.
Where is the data?
The most typical wastewater collection and water supply systems have very limited data for remote sites.
At a tradeshow a few months ago I was talking to the capital works manager of a wastewater utility with about 30 lift stations. I asked him how he planned his capital works program - how did he decide where to put his resources? His answer:
"It's all based on hours run"
His non-verbal response indicated that he wasn't comfortable with the approach. And when I followed up with a few other questions, he did say that he really felt the organization was flying blind.
However, the problem for this utility, as for so many others - the data just isn't there. The field devices aren't collecting enough data and the SCADA system isn't producing any reports that asset managers, utility directors and operations managers can use for proactive maintenance.
What Predictive Maintenance data can I get?
What is available for pumps, motors and control systems?
- Insulation Resistance of motor windings - leading indicator of 50-80% of motor burn outs in submersible pumps
- Flow - pump flow rates indicate whether impellors need servicing, and total station volume and inflow per station give system wide metrics for capital works
- Pump efficiency - volume per cost of energy, indicates ROI on replacement or servicing of pumps and impellors
- Detailed pump fault data - the respective totals of specific fault conditions provides leading indicators of problems
- Vibration analysis - only usually cost-effective on the larger pumps
All of this data is now easily available in Pump Station Managers - although to get vibration data, of course, you need the sensors. The other data is available from pump station managers without any additional equipment or sensors - view more information on the MultiSmart pump station manager.
The Organization still needs to be reactive!
It's important to understand that adopting predictive maintenance strategies doesn't mean that every failure will be known in advance. Failure of components in a system - regardless of the actual system - is governed by random factors. We see these random factors as statistics! One in one hundred failed! One in one thousand failed!
Statistics and random failure might be the subject for another day, but the important point is you still have to retain a responsive organization for when a pump fails at 2am on Sunday morning.
The Benefit
The benefit you have with condition based monitoring or predictive maintenance is that you can now have a lot more confidence of the state of your assets and you run your maintenance program more proactively and most cost-effectively.
You can say - confidently - that you are not running your pumps and motors into the ground. Or you can say - confidently - that the organization has almost run its assets into the ground! Let's hope it's not this one!
And based on the real state of the system, you can plan the most effective capital works, replacement or servicing program.
I often use the analogy of a business. If you don't know whether you will make a profit or loss this year, your stakeholders won't think you are looking after their interests.
If you are looking after critical infrastructure you don't want to find that 2009 is the year when all of your pumps started failing and your energy costs went up 10%!
Steve Carson
MultiTrode
MultiTrode is the specialist in control and monitoring for lift stations, and also runs a Lift Station Technology Blog
Comments
Having a predictive or preventive maintenance program is a must in my opinion if you want to manage cost and keep downtime to a minimum at best.
Brent King
Posted by: Brent King at February 9, 2009 10:24 AM
I am currently managing wastewater Treatment Works, pumpstations and water reticuation systems in South Africa whereby this system and program can be utilised, please can you forward me additional information with regards to predictive maintenance.
Thank you
Shamin Eswardutt
Senior Technologist
Wastewater
Posted by: Shamin at May 6, 2009 03:15 AM
Please provide me more info about predictive maintenance.
Thanks,
Ricardo Cinco
Posted by: ricardo cinco at August 29, 2009 01:55 AM
Can you advise on the best asset management manual with detailed implementation guidelines
Posted by: Mazunda at September 16, 2009 10:03 AM
I agree with the items you mentioned (vibration, root cause failure analysis and pump performance) are excellent tools but from our experience you are missing so other equally important methods worth mentioning. I what to suggest that can be both cost effective and save $$ while helping to extend the useful life of vital plant equipment. (1)Specific bearing analysis for sign of distress and early warning of failure really works. There are numerous meter available today. (2) Analysis of bearing grease is emerging by using the vacuum siphon of oil analyzer sampler to draw grease from bearing for analysis of wear and the proper greasing program works well and is quite cost effective. (3)Regular infrared hot spot monitoring of electric components and their connection points will uncover the majority of impending electrical faults before they explode. The price for these tools has dropped dramatically. (4) For belted systems, I constantly find that attention to sheave alignment and belt tension not only improves bearing life but prevents both motor and fan bearing premature failures. Now doing what I like to call condition surveys where you quickly get overall vibration velocity rms data in 3 principal directions at each bearing (and on attachments like piping and supports), take bearing noise ratios, record performance data like speed, pressures, flows, amps, spot check temperatures, alignment and belt tension and sample grease or oil wear particle information will not only track the condition of existing machines better but will identify signs of distress before it becomes and unplanned failure. These are also very useful in the acceptance stage of any overhauls, repairs or new installations.
Posted by: Sam Duckworth at July 25, 2010 02:40 PM
