Published at Maintenance Technology April 2004
Ultrasonic Leak Detection Improves Heat Rate
By Terrence O’Hanlon, Reliabilityweb.com
In the competitive electric power generation market, attention must be given to improving condenser operating efficiency. Steam turbines cannot attain their specified performance without an efficient condenser. Tube leaks that affect condenser performance are critical. Most condenser tubes are designed to last at least 30 years. Unfortunately, normal plant operation, changes in water chemistry, and other circumstances often create a shorter life for tubes. Most condensers are overbuilt to allow for a certain percentage of tubes to be plugged when a leak is detected.
In the past, Seminole Electric, headquartered in Tampa, FL, like other utilities, used methods including pasting wet newspapers against tube sheets, spraying thick foam, or using saran wrap to locate condenser tube leaks. These methods were slow, required multiple experienced operators at inconveniencing hours (plants can typically be brought to a partial load only during the midnight shift), and worse, were often ineffective.
By using a ruggedized portable ultrasonic leak detector, Brian Thorp, predictive maintenance (PdM) technician for Seminole Electric, has been able to provide quick leak detection and repair on an aging steam condenser, allowing the utility to provide maximum power during high demand periods.
Ultrasonic technology
Ultrasonic leak detectors work like simple microphones that are sensitive to high-frequency sounds ranging from 20-100 kHz. In comparison, most humans can hear at most 17-19 kHz.
Using a sensitive piezoelectric crystal element as a sensor, minute high-frequency sound waves excite or “flex” the crystal, creating an electrical pulse that is amplified and then heterodyned, or translated, into an audible frequency that the technician can hear through a pair of noise reduction headphones.
As a leak passes from a high pressure to a low pressure, it creates turbulence. The turbulence generates a high- frequency sound component, which is detected by the piezoelectric element, allowing the technician to guide the instrument to the loudest point in order to pinpoint the leak.
Several ultrasonic detectors use parabolic or elliptical reflectors to enhance and concentrate the leak signal, which can be useful when detecting small leaks or scanning at a great distance.
Effects of tube leaks
The condenser is the largest heat exchanger in the condensate/feedwater network. It is located under the steam turbine generator. When the steam exits the turbine, it is passed over cool pipes (cooled by river water) that condense it to liquid water. The purified water is pumped back to the boiler to be heated to steam again. The same purified water is boiled and condensed over and over.
Keeping the condenser tubes from leaking the river water into the steam or clean side of the condenser is a key to achieving optimum performance. Fresh water leaking into the purified system can wreak havoc by causing corrosion throughout the system and can significantly reduce operating life if not rapidly addressed.
Leak detection in condensers
The Seminole Electric plant condensers contain 44,000 one-in. tubes per unit and feature a split design, with eight water boxes or two loops. This allows the plant to isolate one loop or four water boxes while running at a partial load. Isolating a section of the condenser allows Thorp to drain the cooling water and enter the water boxes while the plant is still operating. Because the turbine is still operating, a vacuum is present on the steam side of the condenser tube. This vacuum creates a pressure differential that sucks air into the tube leak site. As the air enters the leak site, it creates a minute turbulence, which generates a high-frequency signal. The ultrasonic leak detector quickly detects and pinpoints leaking tubes, allowing them to be plugged.
Operations know when a leak is severe enough to warrant attention by sensitive sodium parts per billion (ppb) counters in the condensate pump discharge system. The sodium counter display is checked by operators on their rounds.
Ultrasonic leak detection
Seminole originally tried an older airborne ultrasound detector. The unit tested was not designed for the high humidity environment that is present in steam condensers. It soon ceased to function as moisture built up in the circuit but not before what was thought to be a tube leak was heard. Unable to complete the ultrasonic test at that time, the usual time-consuming methods were used to solve the immediate problem; however, the PdM department was convinced it should learn more about high-frequency ultrasonic detectors that were designed for harsh environments.
Thorp’s research led him to SDT North America, Cobourg, ON, where he found the company’s 170M, an instrument that is sealed to IP65 (ensuring it will function in wet environments) and includes a flexible extension wand to extend the reach of the leak detection sensor.
Thorp soon discovered that online steam condensers offer abundant ultrasonic signals to compete with the leak signal. To solve this problem, he holds the instrument a few feet from the tube sheet and scans the entire area. If a noisy area is found it is noted. He then switches to an extended flexible sensor and scans tube to tube. If the sound signal on the digital dBVU meter or sound in the headset does not change from tube to tube, a leak is unlikely. This is particularly true of tubes located on the outer edges of the tube sheet, as these tubes are more likely to have noisy steam flowing over their o.d. surfaces.
If a significant signal change occurs, a leak is suspected. If the leak is in the tube, the difference will be heard at the tube opening. If the noise level is heard on the tube sheet, the area is blocked to eliminate reflected noise. A concentrator cone with an opening of 1/8 in. is placed on the flexible extended sensor and is held almost on the tube sheet surface. It is then moved around the tube to tube sheet fit or the plug previously installed in the tube. During this process the small area of the 1 in. tube that is leaking can be pinpointed and repaired.
After using the ultrasonic detector for a while, Thorp attended a 21/2 day Level 1 training course. He returned from that training confident that he would expand the use of the ultrasonic detector to detecting problems with coal conveyors, bearings, compressed air leaks, and other problems that commonly occur in a power generating station.
Benefits
Seminole Electric realized several intangible savings from improvements in water cleanliness and reliability related to the ultrasonic leak detection project. Reduced water chemical cleanings mean reduced costs and a reduction in tube leakage also means less corrosion.
Also, working in water boxes at operating power plants can be unpleasant, with an ambient temperature of 100-105 F and a 99.99 percent relative humidity. Using ultrasonic leak detectors has allowed Seminole’s maintenance personnel to get into the water box, find the leak, and get out quickly.
Thorp reports a quick return on investment for the ultrasonic detector and has attracted the attention and support of top company management based on the results to date.
His advice to others considering ultrasound is to use as many technologies as are available to solve problems, as no one technology can supply all the answers. He is confident that ultrasound will remain an important inspection tool for Seminole Electric.
Terrence O’Hanlon, CMRP, is the publisher of Reliabilityweb.com., P.O. Box 07070, Ft. Myers, FL 33919; (239) 985-0317
SEMINOLE ELECTRIC
Seminole Electric is a generation and transmission cooperative headquartered in Tampa, FL. It provides bulk supplies of electricity and wholesale energy services to 10 cooperatives located throughout peninsular Florida. More than 1.5 million individuals and businesses in 45 counties rely on Seminole and its members for electric service. Seminole’s primary generating facility is located on the St. Johns River in Putnam County, FL, about 50 miles south of Jacksonville. This 1300 MW station has two 650 MW generating units. The plant’s water hyperbolic cooling towers (450 ft tall and 400 ft across) and 675 ft stack are visible from miles away. This plant generates electric energy from coal. Its output is distributed across transmission lines to Seminole’s member distribution systems that, in turn, deliver electricity to individuals and businesses—about 10 percent of Florida’s population.
So far most of what people focus on in their plants is failure and the culture has been focused on such.Everthing is about fixing equipment before it fails, why not prevent failure from the start as Deming states, by not putting the defect into the process. Is anyperson using the Six Sigma methodology to focus on eliminating failure? Proven method and I imagine should increase EVA quicker than anything else out there.
Answer:
In response to your question regarding is anyone using six-sigma methodology in the field of reliability. The answer is yes, there are a few proven tools that work as you suggest to identify and eliminate failures before they occur. Most popular would be Reliability Centered Maintenance (RCM) and Failure Modes and Effects Analysis. RCM was designed to be used in the design phase of a process and looks to develop a maintenance strategy for a process or piece of equipment based on the failure modes, effects and consequences of each component that makes up a system. RCM can also be used on existing equipment where there is no maintenance strategy or the maintenance strategy is ineffective. In looking at each component, RCM looks to develop a strategy that predicts, prevents, eliminates or reduces the consequences of each failure mode. The traditional methodology is structured and takes some discipline but produces a highly effective and thorough product. There are some abbreviated RCM products that are not that effective, so make sure you to ask for traditional RCM should you be interested.
FMEA is similar to RCM but does not look to build a strategy. It is used in the design phase of a project to build failure relationships.
My company provides instruction, facilitation, and mentoring of both products, Good luck with your reliability efforts!
Douglas J. Plucknette
Tel: 585-349-7245.
I have been in maintenance for 12 years and I have not herd of Asset CARE as mentioned in the Coors ad. Is this a generic term or is this a program that can be followed? If so, any information on it would be helpful.
Answer:
Asset CARE is a term being used in many different ways around manufacturing companies. The Asset Care position at Coors is one that has overall responsibility for the physical assets (manufacturing equipment) including developing a maintenance strategy (predictive, preventive, failure-finding) assessing spare parts, consolidating equipment, and developing equipment hierarchy.
Coors does have a plan for Asset CARE, the focus is on lowering operating and maintenance cost through increased reliability and standardization across company sites.
I have heard the term at other companies but it is used in a more generic terms in reference to maintenance groups.
Coors is a member of PEMCO, these are non competing companies that share information on maintenance strategies so they may be willing to share more information than I can in this note. If you would like more information, contact Mike Kopcha at 303-277-3870.
Hope this is what you were looking for!
Douglas J. Plucknette, President
Reliability Solutions
Reliability Terms
1. Active Repair Time – That portion of the downtime during which one or more maintainers are working on the equipment or system to affect a repair. This time includes preparation time, fault-correction time, and final checkout time for the equipment system, and perhaps other downtime subdivisions, as required in special cases.
2. Achievable Availability -- The probability that a system is operating satisfactorily at any point after the start of operation, when operated under stated conditions when the times considered are operating time, active repair time, logistic time, administrative time, and preventive maintenance time.
3. Administrative Time – That portion of the downtime not included under active repair and logistic downtime, but required to make decisions about maintenance crews, etc.
4. Availability – The percent of time that equipment is mechanically able to perform its required function.
5. Corrective Maintenance – Maintenance activities required to place equipment back into its required operating state.
6. Design Adequacy – The probability that a system will successfully accomplish its mission, given that it is operating within design specifications, and accomplish all the design-to objectives.
7. Downtime – The total time during which the system is not in acceptable operating condition. Downtime can be subdivided into a number of categories such as active repair time, logistic time, and administrative time.
8. Failure – The loss of equipments ability to perform its required function. Does not require the equipment to be inoperable.
9. Failure Effects – The physical manifestations of the loss of required function. Includes such items as equipment downtime, loss of quality, injuries, damage to other equipment and surroundings, and environmental impacts.
10. Free Time – Time during which operational use of the system is not required, but for which the system is operationally ready.
11. Intrinsic Availability – The probability that a system is operating satisfactorily at any point after the start of operation, when operated under stated conditions when the only times considered are operating time, and active repair time.
12. Logistic Time – That portion of the downtime during which repair is delayed solely because of the necessity for waiting for a replacement part or other subdivision of the equipment or system, for acquisition of required tools, additional maintenance personnel, diagnostic equipment, etc.
13. Maintainability – The probability that, when maintenance action is initiated under stated conditions, a failed system will be returned to operating condition after a specified downtime.
14. MTBF – Mean Time Between Failures. Applicable to repairable systems.
15. MTTF – Mean Time To Failure. Applicable to non-repairable systems.
16. MTTR – Mean Time To Repair. The average time it takes to perform corrective maintenance on a system.
17. Operational Availability -- The probability that a system is operating satisfactorily at any point after the start of operation, during normal plant operations.
18. Reliability (R) – The probability that a system will perform satisfactorily for a given period of time under stated conditions.
19. Repairability -- The probability that a failed system will be returned to operable condition within a specified repair time. Ease of access to critical components improves repairability.
20. Storage Time – Time during which the system is assumed to be in operable condition, but is not required for use.
21. Unreliability (Q) – The complement of Reliability.
Published at The Manufacturer April 2004
R. Michael Donovan says that Total Productive Maintenance is essential for truly achieving lean operations
Why should a senior level executive be concerned with Total Productive Maintenance (TPM)? First and foremost, doing TPM effectively can significantly impact the income statement and balance sheet by increasing production throughput, increasing customer service, lowering inventory buffers and decreasing cycle times. Second, and very important, running a manufacturing company necessitates the creation of a very safe and pleasant work environment. To do this you must have machines, equipment and tooling operating in such a way that you create and maintain safe working conditions for the benefit of all.
Total Productive Maintenance is the systematic approach to combining preventative maintenance, total quality control and total employee involvement to create a culture where operators and support staff are educated and cooperate as full partners to assure that machines, equipment and tooling operates so that production is never interrupted and safety is assured.
This is an interesting web site I found.
It actaully functions just like a books as you turn virtual pages.
There is a great deal of useful information here.
Click here to access ASSET MANAGEMENT FOR UTILITIES
There are 100,000 Power Transformers in America, and they are beginning to fail. The results can be catastrophic. What can we do about it?
If it ain't broke, don't fix it
In the old days, the expression in business circles was "if it ain't broke, don't fix it". Later, in the era of re-engineering the corporation, that expression morphed to "if it ain't broke, fix it!”
Fact is both expressions are useful. When it comes to power transformers, what one wants to avoid - is "fixing" an unbroken multi-million dollar piece of equipment. It’s costly. It also introduces new risks. However, when a transformer fails, the results can be and often are catastrophic -financially, environmentally, and socially. Sometimes people get hurt, and sometimes, even worse.
So the problem is distinguishing broken from unbroken.
Published at Refinery Technology Online
OEE Reports - Automated Capturing & Recording of Availability Data
Moving Beyond Manual Data Collection & Manual Data Compilation
By Bob Giese, President of VersaCall Technologies Inc.
Introduction
Overall Equipment Effectiveness (OEE) continues to gain acceptance as an effective method to measure production floor performance. Capturing and recording accurate production floor information is critical for producing reliable OEE Reports.
Reaping the Rewards of Remote Monitoring and Diagnostics
Proactive monitoring of rotating equipment and control systems can increase plant efficiency and reduce unplanned downtime, and operating and maintenance costs.
As manufacturers look for new ways and tools to help them do more with less, forward-looking companies are turning to innovative monitoring and diagnostics tools that can dramatically improve existing Maintenance, Repair, and Operation (MRO) programs. Often referred to as “remote-monitoring and diagnostic systems,” such technologies help cut overall production costs, improve quality, minimize downtime, and increase operational efficiency.
Thanks to the Internet, new intelligent monitoring tools, and high-speed plant floor and telecommunications networks, manufacturers can now collect and analyze data from every corner of a plant. This means they have the ability to monitor and protect the health of plant assets — even from remote, offsite locations. Progressive manufacturers realize that capturing, analyzing and effectively using condition and operating information from machines can significantly reduce — and even prevent — unplanned downtime. And, it lets managers make informed production decisions. In short, remote-monitoring systems can provide an important strategic and competitive advantage that can improve profitability.
Read the full story at Metal Producing & Process
Originally Published in Maintenance Technology January 2002
By Terrence O'Hanlon
Welcome to the first of what we expect will be many columns designed to map some of the most productive areas of the information superhighway to help you increase maintenance and reliability productivity in your organization.
You are probably spending more and more time online and we want to make that time more useful. This month we will start with a subject that is important to all of us—reliability strategies.
Before I started writing this column, I visited www.altavista.com, one of the most popular search engines, and searched for "reliability centered maintenance." I got 8,300,412 web pages that contained references to my search term. I quickly repeated the search at www.google.com. The results were a little better, returning only 31,200 sites. No one has time to personally index that many web pages to see if they contain useful information.
Web references, such as those published in MAINTENANCE TECHNOLOGY and links on trusted web sites, are often good places to begin a search. There are many sites that can help you learn more about approaches to reliability such as Reliability Centered Maintenance (RCM).
Reliability centered maintenance
RCM was developed to address the needs of the aviation industry as super jumbo jets such as the 747 were introduced. Industrial companies have been embracing the concepts of RCM over the past decade, many with great success.
Pioneers such as John Moubray and Anthony "Mac" Smith can be credited with moving RCM concepts into the maintenance mainstream. As more people learned about the benefits of RCM, it was inevitable that new versions and adaptations would be introduced. You now can find Reliability Centered Maintenance, Streamlined Reliability Centered Maintenance, PM Optimization, and other reliability strategies each being practiced in any number of ways.
A few hours spent learning about these approaches and their differences can lead you to a better decision when choosing an approach to increase your operational reliability.
Helpful sites
Even if you do not plan on implementing a total reliability program, the following web sites can provide ideas and inspiration you can put to use today:
www.aladon.co.uk—This is John Moubray's official site that includes a brief explanation of RCM, RCM2, and the new SAE Standard for RCM. It also contains a paper titled "Maintenance Management—A New Paradigm" that will change the way you think about maintenance.
www.athoscorp.com—This site is maintained by Athos Corp. and contains more detail regarding RCM, RCM2, and the SAE Standard including a well-assembled "Frequently Asked Questions" section.
www.pmoptimisation.com.au—This site contains good information and downloads for those seeking an alternative approach to reliability called PM Optimization. The site is maintained in Australia where reliability in remote locations is mandatory.
www.rcm-1.com—This site offers free multimedia online reliability training with more than 25 programs. There is one section dedicated to maintenance and reliability strategies. Registration and a Windows or Real Media player are required.
www.reliability.com—This is the Reliability Center web site. You may know the Reliability Center for its work with root cause analysis; however, the PROACT System is a total approach to reliability. The site has a massive reference library for your online use.
www.reliability.com.au—This is another Australian site that allows you to submit past failures on a machine for a free online reliability analysis. There is also a good selection of articles and reference material.
www.smrp.org—This is the site for the Society for Maintenance & Reliability Professionals (SMRP). It includes a virtual library as well as an active reliability discussion forum to ask and answer questions.
Sites such as MAINTENANCE TECHNOLOGY and Reliabilityweb.com contain archives of articles and other useful links to RCM resources.
Please let us know what you think of this new column and what subjects you would like covered in the future. E-mail your comments and suggestions to me.
Terrence E. O'Hanlon is the publisher of Reliabilityweb.com, the solution-oriented asset reliability web site for the plant maintenance community. He has spent the past 20 years as a business leader in the condition monitoring market.