Calling it “safer, faster, and deeper” than dry-ice blasting, Jeff Bause, CEO, Groome Industrial Service Group, introduced participants in the 2021 virtual conference of the Combined Cycle Users Group to KinetiClean HRSG tube cleaning, a patented kinetic shockwave technique widely used in other industries but new to combined cycles. It was developed by Explosive Professionals Inc. (ExPro), a detonation-based cleaning services firm with decades of industry experience.

Only a few weeks after his July 27 CCUG presentation, Bause announced on September 7 that Groome had acquired ExPro, uniting the latter’s patented processes and Groome’s 50-plus-year history in providing premium powerplant services—many identified with the hot-gas path in gas-turbine-powered simple- and combined-cycle plants. ExPro executives Brad McGinnis (President/CEO) and Rod Hall (Executive VP) have transitioned to the Groome team, bringing the skills and expertise honed at the 26-yr-old company to increase the number of critical service options available to owner/operators.

One of the stated competitive advantages of KinetiClean over alternative tube-cleaning techniques is that some of the work involved—such as the placement of detonation (a/k/a det) cord—can be performed while other outage work proceeds in parallel.  Additionally, limited to no scaffolding is required for this process.

KinetiClean is a three-step process. First, the shock waves created by the det cord curtain dislodges deposits from the HRSG’s finned tubes, then compressed air removes any loosened deposits that remain, and finally, the floor of the HRSG is vacuumed clean.

The process begins with the installation of det cord, described as a flexible textile jacket encasing PETN which is an extremely stable powder plastic explosive. Simply, a curtain of det cord, spaced 12 to 18 in. apart between tube bundles, extends the length of the finned tubes to be cleaned (photo montage). Det-cord acing is based on the nature and volume of foulant as determined by ExPro. The det cord curtain is only armed when the blasting caps are introduced.

When the cord detonates along its length at a velocity of about 23,000 ft/sec (optimal for hard deposits), the ensuing shock waves remove debris from tube surfaces and fins. Importantly, no detonation material or tools touch any HRSG internal surfaces.

Next, patented air vestibule machines remove loosened debris that settled on fins below with high volume/high pressure air. The machine is digitally programmable to ensure full tube-bundle coverage. Once all debris has been removed from the fins, vac trucks are utilized to collect the material from the HRSG floor.  The primary focus of this turnkey operation is to mitigate the chance of any opacity issues upon startup.  A typical job takes six to eight 12-hr shifts to complete, meaning the cleaning of an F-class HRSG is a three- or four-day project.

Knowing that the mention of explosives was likely to send palpitations to the collective heart of the audience, Bause included as one of his first slides a record of the industry’s safety and training record—specifically, no reportable incidences, lost time, or fatalities over the last three years, each representing close to 30,000 hours of work. A crew of seven typically does the work, including one licensed blaster.

Bause gave several case studies to wrap up, each exhibiting four to six tons of material removed and a 4- to 5-in.-H2O differential-pressure improvement. During one site’s work, damper repair work was conducted in parallel. Other slides quantify the general benefits of tube cleaning, although few combined-cycle personnel need any convincing on that front.

During the Q&A, attendees learned that 30 minutes following detonation, workers can enter the HRSG; noise levels are not expected to impact neighbors; that the technique is effective at removing ammonium bisulfate deposits; and the technique is not recommended for catalyst cleaning, although the patented air vestibule machine could be adapted for non-scaffold cleaning of the SCR catalyst at some point in the future.

Boiler tube leaks have been plaguing fossil-fired powerplants for decades. HRSGs, especially those which cycle frequently, are no exception. Plants experiencing recurring tube leaks should analyze for root cause and make the necessary modifications. If that’s too expensive, another option is to install a sophisticated acoustic monitoring system (AMS) to at least detect leaks earlier, locate them faster, and repair them at the earliest outage opportunity.

This was the situation presented by Tham Chelvan, Siemens Energy, at HRSG Forum 5 (Sept 24, 2021), hosted by Bob Anderson. A 2 × 1 combined cycle at a government-owned plant in South America with V94.3A gas turbines (supplied by Siemens, along with the controls) and triple-pressure, natural-circulation, drum-type heat-recovery steam generators began to have serious tube leaks three years after commercial operation began at the end of 2009. Because they were detected late in the game, the leaks caused collateral and expensive damage to adjacent tubes as well.

Although a root cause of the leaks was determined, owners considered the recommended modifications too expensive at $3.5-million. So the plant installed a Mistras AMS system instead for about 15% of that investment. Siemens was unable to identify a system comparable to Mistras, Chelvan told CCJ in a follow up conversation.

Basic idea behind the technology is that noise created by tube leaks (distinguishable from other noises inside the boiler—such as attemperator sprays—using sophisticated signal processing) travels through the exhaust gas, hits the inner liner, causing a sounding rod to vibrate. The sensor converts the vibration energy into electrical signals.

Hundreds of fired boilers and feedwater heaters are equipped with AMS these days, but only 20+ HRSGs serving combined-cycle facilities because of the need to filter out ambient noise generated by the gas turbine. Perhaps this latest success will encourage HRSG manufacturers, EPCs, and/or owner/operators to consider AMS as standard for unit monitoring and diagnostics.

According to Chelvan, the AMS was installed in 2016 on both boilers, and since then has successfully early-detected 10 tube leaks, almost all of them in one unit. Chelvan also told CCJ that this facility isn’t as penalized for tube leaks at the wrong time. However, users in the US have said that, because of penalties assessed to sites not available in markets when they are committed, as well as lost revenue, a Mistras system can pay for itself with the first tube leak detected. Plus, because the data collected by the Mistras system are tracked in the company’s central monitoring center, no additional work is required from a time-challenged plant staff.

Chelvan includes numerous slides showing the AMS equipment, installation of sensors, trends pre- and post-leak, and weld repairs made to the tubes, all required viewing if you are contemplating an AMS.  Perhaps of most practical importance is how the sensors (attached to sounding rod wave guides) are arrayed outside the boiler casing and where the amplifier boxes, power boxes, data logger, computer, and monitoring screens are positioned relative to each other (figures). Several slides clearly show how the data are measured, trended, and interpreted.

EPRI touts carbon initiative

A second presentation at the HRSG Forum gave EPRI an opportunity to pitch it’s Low Carbon Resources Initiative (LCRI), billed as an independent assessment of the work going on worldwide to modify gas turbines and duct burners for natural gas/H2/ammonia fuel blends, which could have repercussions for other sub-systems, such as emissions control.

Twenty years ago, few people probably thought that a tube cleaning technique for HRSGs attached to gas-fired turbines would be adapted from those used for solid-fuel boilers. Yet that’s where we are today. Carl Wise, Thompson Industrial Services, and Vince Barreto, PowerPlus Cleaning Systems, showed attendees at the HRSG Forum Supplier Workshop, Oct 7, 2021, that such a system can be elegantly designed and operated even if it’s dislodging and removing tons of material stuck on HRSG tubes.

The technology, originally called PowerWave+ when introduced by GE in 2006 as an online system for solid-fuel boilers, was converted from a sound-wave- to a shock-wave-based process, then acquired by PowerPlus in 2014 and adapted to offline cleaning. Simply, the acoustic driver attached to a sound horn, was replaced with a combustion tube to create a pulsed detonation cleaning device.

PowerPlus calls it Extraction Pressure Impulse Cleaning (EPIC). While the recording of the Forum presentation gives more details about the technology, what you really want to experience are the videos, which show how the device is engineered into a “navigation rig,” temporarily installed in the lanes between the tube bundles, and moved remotely from location to location while a technician monitors the cleaning on a 50-in. screen.

The rig is arranged for the HRSG being cleaned, which can be vertical or horizontal, and can accommodate baffles, which one astute attendee asked about. If sky-climber ports are not available for rig support, they must be added, although Barreto noted he’s only encountered one unit that was not so equipped. Another attendee wondered if the blasts would dislodge material on the ID side of the tube and the answer was “no”; the shock wave energy does not reflect through the tube wall.

Two of the key benefits of this technique over dry-ice blasting and open detonation, say Barreto and Wise, are avoiding scaffolding or sky-climbers and providing the capability to deep clean “every square foot of the heat-transfer surface.” Tube sections are subjected to the shock waves from the lanes on both the upstream and downstream sides.

Several case studies were presented with dramatic total tonnages of material removed, several inches of differential pressure restored, and 1-2 MW of output recovered.

Emerson Power & Water Solutions held its 2021 Ovation Users Group conference virtually, focusing on current industry and business trends, projects, and services. Robert Yeager, president of Power & Water Solutions, and Al Eliasen, president of Emerson’s OSI Digital Grid Solutions, highlighted how the 2020 acquisition of Open Systems International Inc helps the company meet the needs of two-way flow on the grid and accommodating power distribution.

Apparently, the one common theme among attendees was that “change is everywhere,” and Emerson experts suggested that lifecycle planning can help owner/operators navigate that change. Emerson’s leaders also reported that more and more customer sites are consolidating their data—pulling data from smaller, remote, separate applications into Ovation.

For more on what transpired at the event, check out these links:

https://www.emersonautomationexperts.com/2021/control-safety-systems/ovation-users-group-balancing-change/

https://www.emersonautomationexperts.com/2021/control-safety-systems/ovation-users-conference-how-collaboration-leads-to-success/

https://www.emersonautomationexperts.com/2021/control-safety-systems/ovation-users-conference-its-a-pleasure-to-be-of-service/

Average length of service of the contractor’s employees and the skill levels of the various tradespeople are important qualification metrics, advises Bill Kitterman, GM, Bremco Inc, a recent addition to the SVI family of companies. He recommends that you ask for and carefully review resumes. Contractors worth considering for your work should have them ready for your review without asking, Kitterman says.

In your evaluation, be sure to differentiate between supervisory personnel and crafts. Length of service, formal training, and work experience of supervisors is particularly important. For example, service time is an indicator of the company’s health, quality of management, job performance, etc. At Bremco, supervisors average more than 15 years of company service; crafts about half that.

Pay particular attention to craft skill levels. What codes are welders qualified to? Does the contractor have millwrights, fitters, iron workers, riggers, etc, on staff? Most HRSG work requires all of these skills. In Kitterman’s experience, the more the owner/operator knows about the contractor’s capabilities and personnel, the smoother the planning process and conduct of the actual job.

Quality assurance. Evaluation of supervisory and craft resources are only one part of the due diligence effort. Perhaps just as important to project success is the support staff responsible for quality assurance and safety.

Your QA audit, in the specific case of HRSG work, should focus on knowledge of ASME and NBIC (National Board of Boiler and Pressure Vessel Inspectors) code requirements, experience in code work, welder qualifications, registering of repairs and work, etc.

The QA department and its procedures are particularly important when work involves repair or changes to boiler pressure parts. A plant manager auditing a specialty contractor for such services wants to verify staff capabilities with respect to weld inspection, familiarity with the code, accessibility of staff code experts to field personnel, availability of QA specialists to monitor repair work, etc. Last thing any owner/operator wants is to slow down or halt a job while waiting for a weld-quality verification or a code interpretation.

Kitterman says Bremco has two QA experts on staff—both certified weld inspectors. Note that some welders also are CWIs. At Bremco, QA staff is responsible for maintaining code stamps (National Board “R,” and ASME “S” and “U” certificates of authorization), promptly answering questions from field personnel regarding what the various codes allow and what they don’t, visiting sites where specialty work—P91/T91 welding, for example—requires their expertise, etc.

A quick read of Bremco’s QA procedures points out that the both the company’s QA manager, and the customer, are empowered to establish hold points on boiler and pressure-vessel work to ensure proper procedures are being implemented. Kitterman notes that trust and collaboration between owner/operator and contractor are cornerstones of a successful project.

Important to investigate is the contractor’s experience in making repairs and modifications similar to the ones you require. Where possible, you want to avoid having contractor personnel “learn” on your project. Part of this effort is a review of weld procedures and qualifications specific to the work at hand.

Project reports. Sometimes overlooked, says Kitterman, is the value of complete, orderly paperwork at the project’s conclusion detailing work procedures followed, welder qualifications, identification of welders with specific welds, materials receipt and test reports, quality-control documentation, applicable drawings, etc. All this, and more, should be archived by the owner/operator in support of required registration of work conducted, as well as for insurance and other purposes.

The diligent contractor will file all applicable paperwork as required by regulatory authorities immediately following job completion. Be sure to check that procedures are in place to make this happen. Using HRSG work as an example, repairs to pressure parts require signoff by an uninvolved third party to verify job integrity. One example: An authorized inspector from an insurance company offering boiler and machinery coverage would supervise a hydro test. Upon successful completion of the test, repair forms and other certifications can be filed with NBIC, state/local jurisdictions, etc.

A safe working environment is one of the few things on which all people agree. Plants and contractors take particular pride in having “no lost-time accidents.” This, of course, doesn’t happen by accident: It takes thorough training, testing, retraining, record-keeping, vigilance, management commitment, etc.

A safety audit is an important part of the plant manager’s due diligence effort. You can get a quick read on a particular company’s commitment to a safe working environment by reviewing its safety manual, suggests Kitterman. It should be a living document—one capable of addressing any and all customer and site-specific safety requirements based upon sound OSHA guidelines. Names and contact information for members of the company’s safety committee should be in evidence. Further, committee members should be a mix of management and craft personnel.

A conscientious contractor will perform an initial job-hazard analysis, continues Kitterman, to address site-specific challenges as well as to incorporate any policies required by the plant owner/operator into the project safety plan. In addition, brief daily meetings for contractor personnel are important for communicating unsafe conditions and changes to the existing safety plan. If you don’t see mention of these actions in a prospective contractor’s safety manual that company may not be your best partner.

Also look for words in the manual that openly encourage all employees to monitor their own safety, as well as those around them, and to be proactive. All employees should be entitled to report any unsafe work condition, without reprisal, and if need be to stop the situation until the area can be made safe.

Next, carefully check safety training records. At a minimum, all field personnel should be current on OSHA-required training. Ideally, the contractor should have someone on staff capable of teaching the standard 10- and 30-hr OSHA courses to employees and also be able to conduct or supervise other required training—such as forklift operation and confined-space working practices. Latter includes training to pass the so-called pulmonary function test, which qualifies workers to use a respirator and work with it.

If your site and/or project have specific safety requirements, verify if contractor personnel are already so trained or will require additional schooling prior to job start.

Review of government and insurance records can offer an objective assessment of the candidate contractor’s safety performance. For example, companies are required to log work-related injuries and illnesses on OSHA 300 forms and maintain that file. The Experience Modification Ratio (EMR) is another index to check.

EMR, an industry factor used in Workers’ Compensation Insurance, is based on an employer’s claim history and determined by the claims paid and reserved in the previous three years along with the audited premiums paid. It is considered a fairly accurate reflector of a company’s safety record, and is often used as a factor for prequalification by during a project’s bidding process. An index of more than 1 is indicative of a poorer-than-average safety record; below 1, better than average.

Audit of general administrative procedures is important, too. Review procedures for purchase and delivery of job materials as well as for documentation archives. You’ll also want to know the contractor’s job-costing procedures—including the development of line-item budgets and schedules.

Keep in mind that a contractor’s ability to continually track project cost is invaluable for on-the-spot evaluation of changes in work scope. Kitterman says Bremco can tell you at 10 a.m. what was spent on your project three hours earlier. Contractor also should have the ability to track job performance by line item so you always know where you stand.

Further, a proactive company culture that supports regular morning and evening progress meetings is important. It helps ensure that schedule impacts (positive or negative) are communicated to both contractor and customer personnel. These meetings guard against the “ah shits” that can adversely impact project cost and schedule. With the proper personnel present, they also are a convenient forum for signoffs on change orders.

Flexibility in invoice format and in providing the backup documentation required by the customer is another subject to discuss.

Siemens Energy Day during the virtual 2021 Combined Cycle Users Group (CCUG) conference gave users plenty to think about to keep their plants “relevant” as renewables continue to claim a larger share of generating capacity. Presentations covered the more immediate options for upgrading, optimizing, weatherizing, and cyber-securing your plant, but also longer-term options like adding green hydrogen capability, battery storage, synchronous condensers, and other equipment for grid stabilization.

Dilshan Canagasaby, head, Integrated Product Solutions, kicked off the day with a few slides underscoring what the Siemens Energy “brand” stands for on the global stage. Then the technical content started flowing. What follows here are the highlights. Readers are urged to contact Canagasaby [link to dilshan.canagasaby@siemens-energy.com] with questions or for deeper discussion on the presentations.

James Loiselle, principal engineer, Integrated Product Solutions, and Anil Peravali, project engineering manager, Plant Solutions Engineering, covered plant assessments for flexibility, upgrades, performance, and operational reliability—such as weatherization (Fig 1).

The presentation included several combined-cycle use cases from customers with different GT frames seeking individual or a combination of the above assessments. One underlying message was that such assessments are good for evaluating the plant operational and design limitations and developing tailored solutions addressing specific market needs and maximizing asset value.

Weatherization is top of mind these days after the catastrophic loss of the Ercot grid in Texas this past February. Loiselle and Peravali gave statistics on this event, including the astonishing one that lack of weatherization and auxiliary system maintenance led to shutdown of 14,000 MW of gas-fired generation in the state.

Fair warning: Most plants’ operating envelope may be unsuitable for extreme weather events, they said. Siemens Energy is issuing a white paper on this topic which addresses the approach to identify site-specific limitations and develop solutions to increase operational reliability during extreme weather.

Continuous monitoring of critical thermodynamic, mechanical, and electrical parameters supports this objective. If your plant is not well-equipped for M&D, Siemens Energy can help, with a diagnostics level of service (limited amount of feedback) and a continuous optimization level of services (regular communication about performance and solutions).

Christopher Bonilha, manager of plant optimization, noted that renewables are expected to account for 50% of generation by 2030 and 67% of decentralized power. He stressed having a multi-year optimization plan, rather than conducting a single plant assessment. That way, you can make the best maintenance decisions continuously to remain in optimal performance.

The presentation includes several individual examples of sustaining top performance accompanied by return-on-investment estimates: Adding HEPA filters to slow GT compressor degradation, tuning for cold weather, changing compressor control logic to avoid a pressure-ratio limit from causing GT unloading, quantifying and validating losses in the HP bypass attemperator, optimizing LP drum-pressure set point, monitoring condenser backpressure for efficiency loss, and optimizing cooling water pump operation.

In response to an audience question, the presenters noted that Siemens Energy performs continuous monitoring for 10,000 MW of customer capacity, although that includes sites where only the GT is monitored.

Galen George, director of business development and marketing, covered startup optimization and cybersecurity (Fig 2). He noted that some customers will start up their units 30 minutes early to meet anything from a 30-min to 3-hr start time. While control mods for faster starts usually mean greater automation, Galen stressed that “control is not taken away from the operator.” For example, the system may tell the operator when to do something, but the operator actually has to do it. In other words, they still have to pay attention.  The slides included a project executed in the USA Midwest that reduced startup times and fuel costs by 50%.

Cybersecurity. George’s cyber-related slides quantified what we all know implicitly: Connected industrial digital devices have increased eight-fold since 2011, which means the “threat environment” has also grown exponentially. Most of the slides were intended to make the case for including an industry expert like Siemens Energy as service providers in your vulnerability management programs.

Audience questions addressed how to back up, save, and test systems (Siemens Energy recommends at least once a day, a function which can be automated, though older units may have manual only); then storing the backup files on a drive within the system, then transferring to long-term storage within the DMZ. Another attendee inquired about wireless devices and mesh networks. George said these are “much more vulnerable” and suggested continuous intrusion monitoring and detection.

Beyond the GT and CC. Jim Badgerow, senior project manager, Expanded Scope Solutions, covered battery solutions to reduce costs and/or add revenue streams. One of the more interesting use cases is to avoid paying demand charges for the electricity needed to frequently start up combined cycles as well as provide black-start capability (Fig 3).

The day concluded with Thorsten Wolf, product manager, plant innovations, presenting on opportunities for green hydrogen and grid stabilization. Main points:

• • Surplus (often “spilled” or wasted) renewable energy can be harnessed to produce and store “green” hydrogen for later use.
  • Hydrogen substitution for methane in natural gas does not lead to a linear reduction in carbon—for example, a 30% hydrogen mix by volume reduces carbon by 10%.
  • Even low percentages of hydrogen may require changeout of carbon steel for hydrogen handling and transport, because of embrittlement risks, in plant fuel handling equipment depending on site-specific variables.
  • Hydrogen storage has many considerations as it has to be compressed to 2400-2600 psig and un-lubricated reciprocal compressors may be necessary.
  • Steam turbine/generators at shut-down fossil plants can be converted into synchronous condensers for grid stability by adding a clutch and other equipment.
  • Siemens Energy is developing static voltage compensator (SVC) technology to respond instantaneously for frequency stabilization.

Imagine putting your turbine back together after an outage only to find that you’ve lost 8 MW because the clearances were grossly out of spec. Or adding three days to the outage because someone didn’t check the capacity of the bearing repair shop. Or losing time because the lifting and laydown plan that worked flawlessly for a dozen previous outages isn’t effective for the current one because the scope expanded and laydown area was lost.

These and other situations can be avoided, said Greg McAuley, CTO, Turbine Repair & Support (TRS) Services, during an Oct 5, 2021 webinar, “Five ways to make or break your turbine outages,” by having an independent expert, a/k/a/ technical field advisor (TFA), help develop and implement the outage plan. In every step of the plan, McAuley advocates, “Ask what could go wrong and develop contingencies and options.”

Whose specs are referenced when the document says, “all clearances within spec”? Does the contractor provide evidence of experience in meeting the schedule? What do you do when you have an incapable crew onsite? Are the pre-bid work scopes vague and incomplete? Are you putting too much trust in what the OEM is telling you?

Make sure your plan follows a checklist and guidelines that are customized for your site, and accommodate current adverse factors (Covid, supply-chain issues, etc) which can affect parts and service availability, timing, delivery, etc. Don’t rely on “generic” checklists from the OEMs or assume that the upcoming outage will go just like the last one.

See contingency planning checklists in the sidebar for gas-turbine compressor and turbine sections, plus generators. McAuley also has developed checklists for safety, craft labor and engineering, logistics, etc. To get your copy, write gmcauley@trsglobal.com.

But even the best plan may get thrown out when the battle begins, so the saying goes. McAuley embraced the analogy of a football team’s offense built around a quarterback who gets injured during the first game of the season. That’s when it really helps to have someone onboard with deep outage experience and a network of resources to develop options on the fly.

In response to the question, “What controllable items unexpectedly extend outages in your experience?” McAuley gave the example of a contractor team which did not fully understand LOTO procedures; when the site had to unexpectedly turn the turbine lube-oil system back on to roll the rotor, the outage was prolonged an extra shift to train the team on those procedures.

Outage planning and implementing is aggravated today, McAuley notes, because sites push outages as long as possible, then take them all on top of each other, stressing all the OEMs and services firms.

McAuley began his presentation with a safety minute, but ended by cautioning that during recent work at a site, he observed that only 50% of the outage team was wearing safety glasses.

Contingency planning checklists

Compressor section

Inspection scope
Borescope service provider
Do we have the labor to assist?
Blending service provider
Thrust-bearing shim-grinding resource
Spare rotor availability
How do we deal with shim migration?
Blade/vane availability
Bleed-valve scope and who is responsible
What if I can’t remove all my borescope plugs?
Dry ice and/or heating resources for stator-vane removal
Vane pinning resources

Turbine section

Consumable hardware availability
What to do if my clearances are too tight or loose?
Exhaust static or flex seals
Exhaust cylinder or diffuser cracking: Weld procedures and welders
Spare rotor availability
Parts don’t fit
Parts found contaminated
Interstage-seal field-alignment issues (Siemens units)
Blending service provider
Bucket sequence chart availability
Fuel-nozzle flow-test results
Non-capital-parts condition

Generators

Test work scope
Test and inspection service provider
What if my field megger is low or grounded?
Wedge, blocking, and ties
Cooler gaskets
Cooler leaks
Alignment jacking fixtures
Bearing availability and repair resource

With winter just over the horizon, the roundtable on winterization at the 2021 conference of the Combined Cycle Users Group was perfectly timed. There are still a few weeks, depending on your plant’s location, to implement best practices shared by colleagues from Woodbridge Energy Center, Dogwood Energy, and others.

By virtue of its location and importance to the grid, Woodbridge, a 2 × 1 7FA.05-powered combined cycle located outdoors in the Northeast, has heat-trace experience beyond that of many others in the industry. Engineering Manager Mike Armstrong represented his plant in the roundtable.

What follows are details on Woodbridge’s heat-trace initiatives, some of which were not discussed during the roundtable because of time constraints.

Get off on the right foot. Plant personnel learned during commissioning, and afterwards, that poor installation practices coupled with the lack of documentation made it difficult to troubleshoot the heat-trace system. This required staff to spend roughly 60 man-hours per week identifying and fixing issues with heat-trace circuits not functioning as designed. The poor performance of the heat-trace system jeopardized reliability and operability by allowing critical instruments and equipment to freeze-up.

Woodbridge was constructed by a single EPC contractor with multiple equipment suppliers. Design of the heat-trace system was subcontracted to a reputable supplier while installation was handled by the EPC contractor’s craft electricians, who had little or no experience with heat-trace equipment.

The various scope-of-supply boundaries and types of heat tracing proved problematic. Many field changes were required to complete the installation—changes performed without the knowledge of the designer and poorly documented.

Heat tracing was designed to maintain an equipment temperature of 40F at an ambient of -8F. The heat-trace supplier implemented the use of microprocessor-based temperature control and monitoring panels which required other new equipment—including various temperature sensors, new alarm capability, DCS integration, self-testing circuit cards, and programmable RTD outputs.

The lack of qualified oversite from the heat-trace designer during equipment installation and in preparing documentation of as-built conditions proved challenging for the plant operator once it took possession of the facility.

The first step in fixing the problem was to bring back the original heat-trace designer to audit the entire system and identify and correct any deficiencies. This required all 612 individual circuits to be reviewed to ensure the correct materials were used along with the correct installation practices. Next, all the documentation was updated to reflect as-built conditions. This information and a thorough review ensured the system was designed and installed as originally intended.

With the proper installation and operational techniques identified for the new technology, the plant operator developed a heat-trace guide to provide a laymen’s approach to better understanding of equipment and operational requirements. In the guide, details which had been segregated because of scope breaks are included in one location, eliminating the need for multiple sources of documentation. The guide is written in plain language and includes pictures of installed equipment to better acclimate the reader and facilitate troubleshooting.

Success. Using the original design team to identify and fix the installation issues the heat-trace system achieved its specified objectives. System performance now is aligned with the original design intent, ensuring safe and reliable operation of plant equipment during times of inclement weather.

Upon release of the guide, personnel were immediately able to reference site-specific information for heat-trace issues in a timely manner. Today, only about 10 man-hours per week are required to properly troubleshoot system issues, down from the 60 mentioned earlier. The guide also helped personnel identify equipment improperly installed, before it adversely impacted heat-trace performance.  

More ideas. One or more of the following best practices pertaining to the development/design, and construction/startup of a plant-wide heat-trace system also may have value at your facility:

Development/design.

• • Add smart-panel amp indication on each circuit as well as a light to visually indicate that the circuit is energized. This makes it easier for operators to walk down the system, verifying that the heat tracing is on and working when it should be.
  • Have your engineer do a detailed evaluation of all vendor equipment (gas and steam turbines, HRSGs, etc) requiring heat tracing and make sure that the information is clearly presented to the heat-trace system supplier.
  • The mechanical engineer responsible for the heat-trace design scope should be the same person who reviews the vendor’s design isometrics. The field engineer may not necessarily understand the mechanical properties of the piping system and may miss things that should be included in the isometric drawings. In addition, the mechanical engineer is better positioned to be aware of potential piping changes needed.
  • Since the heat-trace design usually is not complete until late in the project, the necessary conduit cannot be installed until very late in the schedule. You can benefit by moving a large portion of this work forward. For example, run small (12 in.) cable trays in areas known to require heat tracing (finger racks, main racks, bottom of HRSG, etc); once the heat-trace design is finalized and power connection devices are located, only short pieces of conduit from the tray to the devices are needed.

Construction/startup.

• • Ensure that compressor bleed-valve actuators and inlet-filter differential-pressure instruments are heat-traced and insulated properly for adequate freeze protection.
  • Coordinate with the instrumentation fitters to make sure that when cutting back the heated tube bundles they leave at least 3 ft of heat-trace cable on both ends. When they cut the heated tube bundles short, there is not always enough cable to reach the power connection kit inside the heated enclosure, or to trace the root valve. This results in having to relocate power-connection kits and add jumpers to accommodate.
  • Ideally, start the heat-trace crew when the piping discipline is at least 65% complete. Prior to this, the pipe systems generally are not complete (missing valves, permanent supports not installed, etc) which creates rework for heat-trace crews. This will allow a large runway ahead of the heat-trace crew, increasing productivity. Impact upon the project completion schedule and weather conditions may override this.
  • When installing the rubber boots in the termination kits, the leads tend to bunch up at the bottom and touch. If there’s a ground fault during commissioning, 80% of the time it’s likely to be in the rubber-boot connection.
  • Perform a thorough heat-trace audit each summer to identify and address any issues before the cold weather sets in.