Piping, particularly hot services (Steam, Feedwater, Condensate), are engineered systems. The stresses induced on the piping, fittings, and valves are controlled through purposeful routing, hanger locations, and hangar properties. This is very important to the longevity of system components. Thermal cycles and other transients accumulate stress-induced damage with time leading to failure, if incorrectly installed. Plant reliability and personnel safety are dependent on proper implementation of the engineer's design.
Given their status as “engineered components” it is really hard to reconcile the lack of attention-to-detail observed in the installation of supports/hangers in many recently inspected plants. In some cases, the contractors have been so sloppy as to not even finish installing the required supports/hangers.
After a support/hanger is installed, the contractor must also follow up to assure it's correctly setup (commissioned). Usually, this necessitates a QC step to assure the installation is correct, followed by documented verification of the “hot settings”, and then... Read more
Contractor: No savings; hangers usually purchased; lost/not installed.
Contractor: Usually not very costly. Owner: Can be costly, because of the outages caused by even small piping failures/leaks.
Steam Vents at Platform
EPR observed that steam safety valves had lifted at some period in the past during a load transient. The energy from an un-silenced steam release at 1,000F is violent and typically includes a powerful supersonic noise wave. Debris still remains impaled on nearby structural steel and equipment from the force of the previous steam discharge.
A serious safety concern is that a personnel access platform is above and adjacent to the five (5) vent stacks. If any personnel would have been located on the platform during a release, they would have no doubt been seriously injured and burned. The owner's operators are exposed to a serious risk until this condition is resolved.
This safety problem persists because of a failure of engineering, piping construction, and the contractors commissioning team to resolve the issue prior to COD.
This is a very dangerous design and all 5 relief valve vents need to be extended above the structure or vented away from the access area.
Minimal cost to extend the vent stacks to a safe elevation.
Owner: Potential O&M personnel injury or fatality with associated costs. Contractor: Minimal cost to extend the vent stacks to a safe elevation.
Dirt... and Fuel Gas
As background, one critical system in a power plant is fuel gas. Typically, every system is cleaned to a condition that is nearly spotless. This is especially true of fuel gas because it feeds the turbines and duct burners. EPR evaluated a plant that was physically very large. The fuel gas header was 1.5+ miles long, inside the plant downstream of the supplier custody-filters. The system changed elevations, had countless fittings, and pipe size changes. Clearly, this is a difficult system configuration to clean well for an inexperienced crew.
Prior to EPR being involved, roughly 50 warranty claims were raised against the EPC contractor that enumerated roughly 300+ failures of valves, flame scanners, regulators, and really anything in the system with a seat or rubber O-ring. The EPC contractor refused to address the issue on-the-whole with a proper RCA (root-cause analysis), instead dealing with each item as if unrelated.
The attached photographs tell the story. This system is so full of dirt and contamination that it's not defensible to indicate proper, or perhaps any, commissioning... Read more
No Savings. Contractor went through "motions" of cleaning system, just didn't!
Just in terms of Owner down-time for needless repairs this is millions of $'s. Parts, labor, etc...
In a Middle East plant inspected, recurring problems with the process drain system was discovered. It originated from a design flaw where the desalination units had to be blown down more robustly than anticipated to achieve proper conductivity in the steam cycle. To compound the process control difficulty, the drain material selected by the EPC contractor was PVC, which simply cannot stand elevated temperatures.
PVC is interesting because unlike may materials it's strength simply disappears once the working fluid gets to about 140F. It also shrinks axially when it undergoes heating and cooling cycles. For condensate drains to be routed to sumps which feed an underground network of PVC piping material is certainly a high-risk proposition.
After a bit of excavation and diagnosis, it was confirmed that the process water overflow of the sumps was from collapsed drain lines, piping that pulled away from the sumps, and other similar failures.
The only permanent remedy is to replace the PVC with a material that can withstand condensate temperatures of 212F.
This is an engineering... Read more
There was minor savings, amont unknown.
Once repair costs under Warranty considered, this was costly for the Contractor.
Often field quality suffers from a lack of oversight; quality control, supervision, or owner involvement. Sometimes a contractor and owner set out to assure their interests are protected, but it fails anyway.
Using a large international source inspection firm tends to be where problems arise. Those firms use local inspectors to keep costs down by limiting travel. However, local inspectors are often the same people that visit particular shops and due to familiarity, a relationship develops which compromises the effectiveness of the shop inspection. Instances exist in remote areas where inspectors are relatives of shop owners. The main take-away, is that inspections by ineffective, conflicted, or technically limited personnel with no personal connection to your project is wrought with peril.
The opinion of the author is that if an inspection is worth performing by an owner, send your own people, or an inspector well known and hired directly. It will be more cost than outsourcing with a large international inspection firm, but it will be worth it.
At one facility, the contractor... Read more
$150k +/- and wasted time.