While the subject of this post is specifically cable tray fill, the volume of defects is almost limitless in the photos. As a side note, these are new plants and, in some cases, not to COD.
To start, cable trays are usually limited to 40% of cross-sectional area as the maximum allowable cable fill. There are exceptions to this requirement, but those exceptions did not pertain to the subject plants. There are heat dissipation and overloading concerns with trays that have excess fill.
In one of the plants indicated in these photos a 5kV cable tray collapsed during final stretch of commissioning a power block which caused a 3-4 months setback to the block COD schedule. This is a real example where excess load played a factor in a materially costly event.
In addition, the photos show instances where supports are also missing according to NEMA VE-2, which compounds an overloading condition. Further, there are cables hanging over tray rails, missing and defective grounding, bent and sagging tray rungs, no voltage separation, cable transitions with no drop-out fittings, no code... Read more
Minimal cost but takes some planning and trained crews.
In many cases this condition cannot be repaired short of removing all the cables and starting over.
Where labor and supervision are less skilled, electrical installation quality can be very poor. However, keep in mind that all EPC contracts have codes, standards, and often owner specifications that provide overlapping requirements that mandate this be done properly and that it is verified by contractor QC personnel. But, to no avail.
One aspect seen on almost every developing country project, is the abuse of liquid-tight metal flex. Please note the photos are from NEW plants, and alarmingly in some cases not even to COD.
Flex is designed to be used in locations where there is differential movement between a piece of equipment and conduit feeding a circuit to the equipment. Flex is not intended to be a shortcut device where an electrician does not have the skill to make proper conduit bends.
Far too often, flex is used where it should not be. To put an approximate number on it, easily 50% of flex use should not exist.
In other cases, the proper fittings are not provided on each end, grounding continuity is not assured, excessive flex length is used, leaky installation is... Read more
Costs somewhat more to perform correctly.
The life-cycle ramifications for owners can be significant due to water damage of electrical and I&C devices leading to intermittent system ghost trips and failures.
RTV to Fit
EPR has been in many greenfield plants just prior, or just after COD. Basically, new plants.
Without hesitation, liquid-tight flexible metal conduit (flex) is abused and mis-installed possibly more than any other heavy industrial components, especially in developing regions.
Often labor is not given proper instruction and almost never the proper tools to install this system correctly. This results in fittings that are, at best, hand tight. Consequently, there are grounding concerns even in the best cases where flex appears to be installed correctly, assuming an internally grounded flex is used and the correct fittings. In most cases leaks occur and instead of tightening the fittings, a big smear of RTV is used as a seal. This usually does not work and creates a mess of the install.
In some plants, we have run studies in limited areas intending to be ‘representative’ and found >95% of flex fittings are loose.
For Owners concerned about the longer-term implications of moisture in electrical and instrument equipment, this is not a positive finding.
None. Probably costs more to perform incorrectly.
The cost of repair would seem manageable, but this defect is so pervasive in most plants that cost can be material. However, the O&M cost for an Owner can be even higher due to device mortality.
To get a quick understanding of an EPC Contractors performance, look at a few cable vaults. Contractors that have reasonably competent labor and supervision can typically plan cable pull work and install the requisite raceway and supports in advance of their work. This is more than a nice-to-have, since it is a code requirement, and with good reason because it is intended to greatly reduce cable damage.
In a vault there are a great many details that need attending, like cable voltage separation, grounding issues, cable bend radiuses, combed/groomed/tied cables, water management, and a variety of meaningful details.
The pictures are from a couple large, NEW, greenfield plants in developing countries that were recently completed. It is possible for an Owner to monitor and insist the pictured results are avoided, but it does take engagement and follow-through.
If you see this condition start to develop on your project, it is a strong forward indicator of broad electrical quality and safety concerns. Often this condition can lead to grounding, relay, intermittent instrument faults... Read more
Condition is very difficult to repair, and expensive after-the-fact because usually cable must be replaced with the coincident outages.
Generator Circuit Breaker (Explosion)
The more interesting findings during our assessments are related to poor commissioning practices. These items tend to be more complex than construction defects and typically more serious from a safety, equipment protection, and reliability perspective of the asset.
One case involved an "explosion" of a generator circuit breaker. The event took place about one year after COD, destroyed the GCB and damaged an F-class turbine generator (both stator and rotor).
The Event: During a unit start the operator was at the elevated GCB panel. The generator field breaker was closed, so the generator exciter was energized. The operator inadvertently pushed the earthing switch button which activated. The earthing switches are NOT designed to be activated when the generator/exciter is energized. The switch exploded (vaporized) with the GCB housing being damaged and opened like a tin can. The operator was shielded from bolts and other shrapnel, but luckily did not fall from the platform.
Background: The GCB vendor provided a set of dry contacts on each earthing... Read more
Possibly only a time savings, but doubtful.
Unit was out of service for 6 months. New breaker, rewound stator and rotor, recommissioning of unit... All-in costs between contractor, owner, an insurance company was about $8mm.
Electrical Zip(less) Ties
Recently EPR evaluated a facility, which among other difficulty, suffered from a condition that is unusual but serious in that essentially all the nylon cable (zip) ties were defective. While the zip tie is a wonderful time saving and usually effective component widely used to affix electrical cables, it must remain unaffected by its environment to remain durable over time.
In this instance, the plant was less than two years old and located in a high UV zone. This defect was so severe that gently touching the installed tie would cause a brittle failure. The plant was littered with failed zip ties that had fallen from tray systems and cable installations.
One supplier used by the contractor indicated in the technical literature that the ties are compliant with NEC, meaning Nylon, UV, weather, seawater, and oil resistant type from Panduit /T&B or equivalent. However, those ties have failed almost universally. While some cursory research was performed on the ties, it is not clear exactly why the ties were brittle and failing, but they certainly all needed replacing. The real... Read more
Negligible material savings.
Contractor: Somewhat time consuming, especially in an operational plant. Owner: Outage events and unpredicatablity are hard to quantify, but even a single lost generation day is expensive.
Faked Electrical Ductbank
There are several important reasons to concrete encase underground raceway (rigid and PVC conduit) that carry power and control cables.
At a newly completed powerplant, the EPC Contract clearly stated: “All underground cables are installed in underground duct bank consisting of concrete encased duct: Hard polyethylene or rigid galvanized steel conduits as per ANSI C 80.1.” It goes further with detail but does not allow direct bury cables and articulates a minimum depth of cover. Engineering understood the implications and cascaded the contract/code requirements into the construction drawing details, which were available to the construction team.
Upon casual observation, the ductbank risers (concrete exposed above grade) did not appear "correct". Detailed investigation revealed there was effectively no ductbank. In some cases, rigid conduit was inserted into soil, perhaps 24” deep and then simply ended, leaving a direct bury cable condition. In other cases, groups of conduit were encased in concrete risers, giving the “impression” a ductbank existed. However, upon removing 6” of adjacent... Read more
Certainly, some marginal cost was saved, as well as, sometime early in the project. Almost certainly not a critical path activity (No LD savings).
Owner: Unpredictable unit operation. At ~$35,000/day finding/repairing cable problems is costly. Contractor: Full remedy would cost millions.
Galvanized Hardware (Or Not)
When a plant is built in a moist, heavily polluted, and/or salt laden environment, corrosion protection is a serious consideration. At a minimum, hot dipped galvanized hardware (nuts, bolts, washers, clips, etc.) is usually specified for outdoor service.
In a recently visited new facility, aggressive corrosion was exhibited almost universally on the hardware. What was discovered is that wherever galvanized was specified, electro-galvanized, electroplated zinc, or zinc plated, (different terms, same thing) was substituted by the contractor. This results in a 3 to 12 micron coating that gives it a much lower degree of corrosion protection than hot dipped galvanized with an 85 to 90 micron layer of zinc. IEC indicates these coatings degrade (in this environment) at 4-8 microns/year. It's then easy to see why there is so much aggressive corrosion and advancing stages of metal loss after only a couple years.
In the rare cases where hot dipped galvanized was provided, it seemed to perform well.
Marginal material cost savings; No labor savings.
Contractor: Substantial cost (Labor/Material) to replace fasteners in bulk. Owner: Fasteners failing is significant. Electrical system risks increase over time.