12
“Something for nothing” hits pay dirt! Joseph D. Gierlach Jr. ~ Vice President, Technical Training and Support TEGG Corporation ~ Pittsburgh, PA ABSTRACT: It has been said by wise men that, “the best things in life are free.” This statement can be very hard to accept in today’s competitive world, and it can be argued that there is nothing left in life that is free. Occasionally, though, we see glimpses of this that can lead to revelations which prevent catastrophe and forge relationships between contractor and customer that will last a lifetime. This paper covers a recent case study in which a simple service led to the discovery of a major deficiency that surely would have resulted in a failure in a large food processing facility. The irony of the story is that the component was not part of the original inventory of components, and the fault was identified simply by taking one extra step out of curiosity. The results are unmistakable, and reinforce the fact that going the extra mile and giving “something for nothing” can and does pay dividends. INTRODUCTION: With the demands on electrical systems and components in the 21 st century, reliability, uptime, reduced operating costs, longevity, and consistency have become paramount considerations. One cannot afford to have an interruption in supply power, let alone the failure or destruction of a component in a system that provides the life blood of any given facility. Interestingly, though, a paradox had developed with respect to maintenance by depending on system performance and reducing allocations in budgets. There is nothing that will last forever without some attention focused on prevention to foster that reliability and performance desired. Insanity has been characterized as “doing the same things over again and expecting different results.” This is a fitting description of some maintenance philosophies where the mentality is that less attention will not contribute to equipment failures or “if it ain’t broke, don’t fix it.” Not all facilities have the resources or contingency plans in place for a “run to failure” operation; however, for those who fit this category, a well administered maintenance program aids in not only lowering operating costs, but increasing the MTBF of components. Doing more for less has become the most common theme throughout the industry, and managers are faced with the challenges of stretching their resources, including budgets and personnel. This can become taxing as the demands grow and possibly lead to shortfalls with unintended consequences. Manufacturing processes of any type, such as metals, plastics, or even food products, require continuous operation that cannot suffer disruption, as this could cause a chain reaction event that could render an entire run or batch useless or scrap. This is

Something for Nothing

Embed Size (px)

DESCRIPTION

Ultrasonido propagado en aire y/o estructuras

Citation preview

  • Something for nothing hits pay dirt!

    Joseph D. Gierlach Jr. ~ Vice President, Technical Training and Support

    TEGG Corporation ~ Pittsburgh, PA

    ABSTRACT:

    It has been said by wise men that, the best things in life are free. This statement can be very

    hard to accept in todays competitive world, and it can be argued that there is nothing left in life

    that is free. Occasionally, though, we see glimpses of this that can lead to revelations which

    prevent catastrophe and forge relationships between contractor and customer that will last a

    lifetime. This paper covers a recent case study in which a simple service led to the discovery of

    a major deficiency that surely would have resulted in a failure in a large food processing

    facility. The irony of the story is that the component was not part of the original inventory of

    components, and the fault was identified simply by taking one extra step out of curiosity. The

    results are unmistakable, and reinforce the fact that going the extra mile and giving something

    for nothing can and does pay dividends.

    INTRODUCTION:

    With the demands on electrical systems and components in the 21st century, reliability, uptime,

    reduced operating costs, longevity, and consistency have become paramount considerations.

    One cannot afford to have an interruption in supply power, let alone the failure or destruction of

    a component in a system that provides the life blood of any given facility. Interestingly, though,

    a paradox had developed with respect to maintenance by depending on system performance

    and reducing allocations in budgets. There is nothing that will last forever without some

    attention focused on prevention to foster that reliability and performance desired. Insanity has

    been characterized as doing the same things over again and expecting different results. This

    is a fitting description of some maintenance philosophies where the mentality is that less

    attention will not contribute to equipment failures or if it aint broke, dont fix it. Not all facilities

    have the resources or contingency plans in place for a run to failure operation; however, for

    those who fit this category, a well administered maintenance program aids in not only lowering

    operating costs, but increasing the MTBF of components.

    Doing more for less has become the most common theme throughout the industry, and

    managers are faced with the challenges of stretching their resources, including budgets and

    personnel. This can become taxing as the demands grow and possibly lead to shortfalls with

    unintended consequences. Manufacturing processes of any type, such as metals, plastics, or

    even food products, require continuous operation that cannot suffer disruption, as this could

    cause a chain reaction event that could render an entire run or batch useless or scrap. This is

  • not a good scenario for the bottom line of any company if the goal is to maximize profit

    margins.

    CASE STUDY:

    Recently, one such event took place at a bacon processing plant in northeast Ohio. A major

    processor of food products implemented a maintenance agreement with Advanced Electrical

    Testing and Preventative Maintenance, located in Canton, Ohio. Work commenced at the

    facility in June of 2008 and was performed by Jeff Hinton and Jerry Bennett, lead technicians

    who have been performing TEGG services for about a year. The inventory on this particular

    site consisted of 222 components, so there was enough service to keep the technicians on site

    for a couple of weeks, and time would be of the essence.

    Jeff Hinton Jerry Bennett

    Throughout the application of the service, a number of deficiencies were identified and

    documented. A summary of the classes included 19 infrared, 42 electrical, and 1 ultrasonic

    problem. Interestingly, the one ultrasonic class problem just happened to be located within a

    12,470 VAC safety disconnect switch (similar to Figure #1 below) feeding a primary side of a

    main service, oil-filled transformer with a 480 VAC secondary, and this was one of two major

    components that did not make the inventory list. Additionally, this was a parallel service that

    had two identical switches and transformers side by side.

  • Figure #1

    As is typical with higher voltage classes of equipment, there is an inherent danger with opening

    the equipment while energized, so this is not a common practice. Manufacturers will include

    electrical and/or mechanical interlocks to prevent this from taking place; a prudent measure

    given the risks. It is difficult, if not impossible, to perform maintenance on equipment such as

    this without gaining access to the interior section. A more acceptable course of action would be

    to secure a shutdown of the equipment, administer several industry standard tests, install

    properly sized and placed infrared windows, return to service, and then use thermography to

    ascertain operating health.

    Through discussions with the customer contact, Jeff and Jerry were able to get some

    background on the two identical disconnects. The one switch had been rebuilt in 2006, with

    new hardware and terminations. Anyone who works on this type of equipment knows that it is

    an art to properly terminate high voltage cables. Improper installations can and have resulted

    in failures, which is never a pretty sight, is costly, and generally has collateral damage of other

    components.

    Being the conscientious technicians that Jeff and Jerry are by nature, they decided to listen to

    the switches with the ultrasonic probe using both the airborne scanning module and the

    contact attachment. Up on the mezzanine servicing the Main Distribution Panel, there were the

    two switches, one fed by the 12,470 VAC coming in from the utility, and the other tapped from

    the line side of switch number one. The vented bottoms of the enclosures made the use of the

    airborne scanning module elementary.

    The first switch appeared normal as one would expect - very quiet with only ambient and

    competing ultrasound present. The second switch surprised the technicians with respect to

    tonal quality and also intensity. The emission from this device was a very familiar audible

    sound that Jeff and Jerry have heard many times through their training and work in the field. It

    appeared to them to be tracking of some sort, or possibly a mechanical vibration. A thorough

  • visual inspection of the enclosure soon ruled out any loose tags, nameplates, hinges or

    propagating emissions from the transformer that was close by.

    It did not take long to confirm that what they were dealing with was in fact an electrical

    anomaly originating from the interior of the second disconnect safety switch. Jerry quickly

    made several recordings of each switch, as comparisons of similar components are crucial to

    making sound judgment calls. Seeking a second opinion, he also reached out to me through a

    phone call and we discussed his observations. The recordings were sent for analysis, and in

    Figure #2 below are the frequency spectrums of the two switches.

    Figure #2

    The red trace illustrates the first switch in which there were no ultrasonic emissions present.

    The white trace is the recording of the second that clearly has an anomaly. The frequency

    content in between each 60 Hz peak is clearly more evident, the amplitude of the frequency

    peaks are much higher in intensity, and the 60 Hz peaks begin to disappear on the outer part

    of the spectrum, suggesting not corona only, but destructive corona with tracking. Nuisance

    corona in this type of equipment would not be uncommon, however, when the 60 Hz peaks

    start to disappear on the outer portion of the spectrum, this indicates that electrical

    discharges are now taking place, better known as tracking.

    The time domain is even more telling in this example, as it truly illustrates why comparison

    recordings have so much value in identifying problem items. Everyone knows that as we have

    intermittent discharges relative to tracking, there are more inconsistencies in the time domain.

  • One would expect that the characteristic band of white noise would be present; however, the

    amplitude and spacing (more specifically, timing) should be uniform in this tool and recording.

    As evidenced by Figure #3 below, this is clearly not the case.

    Figure #3

    Although we can see that there is an abundance of white noise throughout the recording, the

    excursions that take place suggest no uniformity in spacing at all, which is our tell-tale sign of

    electrical discharges due to the timing of the events. On the non-deficient switch, this becomes

    even more transparent and is illustrated in Figure #4 below.

    Figure #4

  • This is the more atypical time domain spectrum of a properly functioning electrical component

    of this type. There is minimal content throughout the recording period, with the minor

    exceptions of two excursions that represent an adjustment of the instruments contact module

    for positioning purposes. The above represents what one expects to hear when applying the

    ultrasonic instrument in the electrical arena, notwithstanding the obvious items such as

    transformers, contactors, and variable speed drives, to mention a few.

    By comparing these two recordings, it became even more evident that something was taking

    place in the second switch that could be nothing short of imminent failure. Action had to be

    taken as soon as possible with this discovery.

    After consulting the customer contact and presenting the exculpatory evidence and findings,

    the recommendation was made that a shutdown should be scheduled to open the switch to

    investigate the suspicions related to the destructive corona. The customer agreed, and a plan

    was devised to secure this outage on July 4, 2008. As this was a holiday weekend, everything

    came at a premium, so our analysis had to prove correct.

    Jerry and Jeff made preparations over the next week by securing all the parts for this particular

    switch that might be needed - tools, temporary grounding clusters, lock-out / tag-out items, and

    a coordinated plan with plant personnel and the utility supply to ensure a smooth and safe

    transition to the de-energized service.

    Finally the day arrived and work began early that morning. After working with plant staff to

    secure the removal of source power, verify the absence of power, and lock out all the

    applicable components, it was now time to open the suspect switch. All were curious as to

    what would be revealed, as this remained a hypothesis based solely on the recording and

    spectral analysis until now. In a matter of moments, it was crystal clear that our diagnosis was

    right on target. The visual inspection quickly uncovered two major deficiencies that could have

    never been identified while in operation and undoubtedly would have failed at some point.

    First, the A and B phase knife contacts on the line side of the switch were only seated into the

    clip approximately , barely making contact for the size of the service. This contributes to

    high resistance connections which produces additive levels of thermal energy; however, one

    could not see this without opening the door (not a recommended protocol due to the voltage

    potential) or the benefit of infrared windows (not installed at this site). Absent this observation,

    the switch would have more than likely remained in service, continued to deteriorate, and

    ultimately experienced a failure due to this. Line side knife contacts are seen in Figure #5

    below.

  • Figure #5

    Full Switch View Close Up of A & B Phase

    You can see by the close-up view above that the left (A Phase) contact is not seated properly

    compared to the right (B Phase) contact knife. Comparative ductor measurements indicated a

    deviation that was simply not within the acceptable limits, so the technicians exercised the

    switch blades four (4) times before the knives would seat properly, assuring good, low

    resistance connections. Cleaning, burnishing, lubrication, and a retest of the contacts verified

    that the repair actions were successful, with all values now within tolerances.

    This was not, however, the source of the ultrasonic emissions identified and recorded two

    short weeks ago which predicated the outage and maintenance efforts. The source was close

    by, though, and did not take long to deduce the course of action. The conductors in this switch

    were cotton jacketed SRML type insulation which connected the load side of the switch to the

    pin bushings of the service transformers. The conductors were all routed through a dielectric,

    mica board to allow for securing the wires and provide separation of magnetic fields.

    The white, powdery residue that is typical of the nitric acid formed when destructive corona

    releases nitrates into the oxygen was clearly present on these conductors and mica board.

    Nitric acid both degrades and destroys electrical insulation and insulators, allowing discharges

    along the insulator path that ultimately seek a path to ground and cause a flashover. This can

    be seen below in Figure #6.

  • Figure #6

    This left no doubt that insulation breakdown had occurred and the integrity was compromised,

    setting the stage for an explosion to eventually manifest. A failure of these conductors surely

    would not be contained to this area and would initiate a chain reaction that would impact not

    only the conductors, but the switch itself, the service transformer, and possibly the downstream

    components supplied by this transformer due to their close proximity.

    Repair work continued, and the load side conductors were removed to measure the length of

    the replacement runs. Further evidence of the discovery and heating effects (suggesting

    current flow to ground) can be seen below in Figure #7.

    Figure #7

    Insulation Breakdown

    Nitric Acid Residue

  • The conductors were extremely difficult to remove from the mica board due to swelling of the

    insulation and effects of the nitrates and heat! Evidence of thermal heating was apparent on

    the conductors; however, this would have NEVER been identified with even the best of the

    infrared cameras on the market, as there were no IR windows installed on this equipment.

    Indirect measurements of temperature and thermal energy can be very misleading, as the

    source energy can be hundreds or even thousands of degrees higher than what a camera

    would detect on the outside of equipment such as this.

    The new conductors were cut to length, mica board cleaned of all residue that could contribute

    to a path for current flow to ground, all connections were tightened and torqued to

    specifications, and the entire service completed on a July 4th holiday with the customer close

    by to witness the efforts. Once the repair and replacement of the conductors was completed,

    the final checks with a ductor were performed to ensure that good, solid electrical connections

    were present to minimize the heating effects of the passive points. Figures #8, #9, and #10

    show the end result as a marked difference from what was found.

    Figure #8

  • Figure #9

    Figure #10

    Upon completion of this final task, the procedure to restore the utility supply was initiated. Plant

    personnel worked with Jerry and Jeff to return the two switches and transformers to service

    and get the normal loads back online.

  • Once this became a reality, one final task remained, which was to verify the repairs under

    normal loads with the ultraprobe. With guarded anticipation, the rescan of the units was

    conducted and the results were as one would expect. Jerry characterized what he determined

    by saying, it is quiet as a church mouse.

    This is the ultimate validation of both the repairs that were performed, as well as the initial

    diagnosis with the ultraprobe. Although the units were not part of the preliminary inventory, the

    discovery of the ultrasonic emission and subsequent analysis with the spectralyzer software

    indicated a major problem that needed attention. When presented to the customer, the

    evidence had to be convincing, as it was on a sight unseen basis. The proof became the final

    product.

    SUMMARY:

    Maximizing both uptime and equipment longevity have become more important than ever, and

    facilities need to have a multi-pronged approach to maintaining components. To accomplish

    this requires not just a good plan and execution of that plan, but taking advantage of every

    single tool available to aid in good, solid, and precise identification of problem areas. One must

    also have competent, forward-thinking personnel applying service and maintenance with the

    propensity to not only think outside the proverbial box, but take extra steps along the way that

    sometimes uncover hidden time bombs. That was certainly the case in this example.

    Jerry and Jeff could have easily performed their duties on just the components contained in the

    inventory and gone home. In between tasks, the conscientious nature of the technicians shone

    through by their taking a listen to nearby items. The ultrasound is a routine service in many

    cases, and going through the motions with complacency setting in can be common. It was

    anything but routine in this example. When one is expecting to hear NOTHING and something

    different transpires, it raises your ears very quickly. You cannot take for granted that

    equipment that should be silent will always be that way. Anything can take place, and todays

    stresses on systems foster an atmosphere conducive to deficiencies, particularly on equipment

    that typically lacks maintenance.

    Budget dollars should be spent wisely in all cases to maximize return and service. Escalating

    costs of products, services, and commodities have impacted organizations from coast to coast,

    causing shifts in planning strategies that typically result in cuts of maintenance budgets. This

    looks good on the balance sheet, but the ramifications of such decisions are seldom taken into

    consideration.

  • What is the cost of reduced maintenance frequency or total inaction? Reducing operating costs

    and retaining capital is a must for any business to redeem margins, realize planning goals and

    remain solvent. The short-term savings can be literally wiped out with the failure of one major

    component in the electrical system, leading to expenditures of hundreds or thousands of times

    more than was initially saved. The adage of you never have enough money to do it right the

    first time, but always have enough to do it again certainly comes to mind when a malfunction

    or failure occurs.

    Planning should include the most critical items that service any facility. This includes not only

    contingency plans if something does in fact fail, but a proactive mindset to maintain these

    items in the most cost-effective manner and achieve the desired results of equipment service

    for many years. Using all the available tools, technology, and test equipment is the first step in

    assuring this outcome. Utilizing service organizations that routinely go the extra mile while

    servicing items does not hurt the cause either. In closing, expect the unexpected with electrical

    equipment. You never know what will be uncovered even with the most mundane of tasks, and

    the pay dirt realized comes in the form of a lasting relationship for years to come as

    customers get something for nothing.

    ACKNOWLEDGEMENTS

    The author wishes to thank UE Systems, Inc. and Advanced Electrical Testing and Preventative Maintenance for

    contributions to this article. We also thank our TEGG customers for giving us the chance to perform inspections

    during scheduled maintenance agreements with the intent of gathering information for this paper.

    Contributors

    Jeff Hinton Lead Technician - Advanced Electrical Testing and Preventative Maintenance, Canton, OH

    Jerry Bennett Technician - Advanced Electrical Testing and Preventative Maintenance, Canton, OH

    Mark Goodman UE Systems, Inc.

    Alan Bandes UE Systems, Inc.

    Doug Waetjen UE Systems, Inc.