Power generation
The hardest place to protect a pipe is inside a power plant.
Congested underground, no lay-down space, and every buried line bonded to a copper earthing grid that competes for the same current. Plant piping corrodes for reasons a pipeline design never has to account for — and it does it inside the fence, under a running unit, where excavating to find out is the most expensive answer available. Then it has to be proved again every year, one test point at a time.
Where we work
Fig. 3 — Inside the fence
Current from everywhere, dug by water.
Fire water, fuel gas and circulating water all run beneath a plant, and all of them are bonded to the station ground grid. Anodes are distributed along the runs rather than concentrated in one bed, each one placed in a hydro-excavated hole so nothing mechanical ever goes near a pipe that has not been exposed first — and the design has to feed the grid as well as the steel, or the rectifier reads healthy while the pipe does not.
Why plant work is its own problem
Four things that make a plant unlike a pipeline.
A cathodic protection system designed the way a cross-country line is designed will under-protect a plant, and the instruments will not say so. These are the reasons.
Everything is bonded to the ground grid
Safety earthing ties every structure in the plant to a large copper grid. That grid is an excellent conductor and it sits in the same soil as your steel, so it takes protective current that was meant for the pipe and it forms a galvanic couple with it. Current demand at a plant runs far above what the buried footage alone would suggest.
- Current requirement testing on the bonded system, not the pipe in isolation
- Copper-to-steel coupling assessed rather than assumed
You cannot dig the way you would outside the fence
The records never match the ground, so any machine put into a plant yard is a machine that might find a live fuel gas line the hard way. Excavation is done by hydrovac — pressurised water and vacuum, no cutting edge — which exposes what is actually there before anything is committed to. Anodes then go into hydro-excavated holes distributed along the runs. A deep bed is the exception, for the site that genuinely justifies bringing a driller in.
- Hydro excavation and potholing to expose existing services
- Distributed anode placement on a header back to the rectifier
- Deep bed design and commissioning where the site calls for it
Many structures, one system, different metals
Fire water loops, fuel gas, circulating water, condensate returns, tank farms and duct banks all share the ground beneath a plant. They were installed at different times, in different metals, under different coatings, often by different contractors, and the records rarely agree with what is actually down there.
- Continuity and isolation established by measurement
- As-built correction where the drawings are wrong
Interference, and no shutdown to test in
Switchyards induce AC on buried steel, adjacent DC systems throw stray current, and structures bonded in one place and isolated in another carry current they were never meant to. All of it has to be surveyed with the unit running, because nobody takes a plant offline for a corrosion survey.
- Interference and stray current studies
- Interrupted surveys on a live plant
Annual testing
A hundred test points, and the ground has moved since the last visit.
A plant survey is not a walk around with a meter. A large station can carry well over a hundred test points, and every year a number of them are not where the drawing says they are — paved over, buried under fill during a turnaround, sheared off by a truck, or removed by somebody who did not know what it was. Finding them is the work. Reading them is the easy part.
Finding the ones that are no longer there
We reconcile the previous survey against the as-builts before anybody mobilises, so the crew arrives with a list of what should exist and where it was last read — not a hunch and a site map. What is missing then gets tracked down rather than written off.
- Pipe and cable locating to trace the run and pick up leads that no longer surface
- Hydrovac to expose a buried station, which is then raised, marked and left findable
- GPS position recorded for every point located, including the ones not on any drawing
- Anything genuinely unrecoverable is reported as not found, with what was tried — not quietly dropped out of the table
What gets recorded at each one
Every station is read the same way, in the same order, with the rectifiers interrupted — because a number taken a different way next year is not a comparison, it is a new number.
- On and instant-off structure-to-soil potential, current interrupted
- Anode and shunt current, bond current, isolation kit performance
- AC potential where switchyard induction is in play
- Photograph of the station, its condition and the reading being taken
A report you can argue with
Every point in a table with this year set against last year, so what comes back is a trend rather than a snapshot. A single column of readings tells you almost nothing; the same column two years running tells you where the coating is going.
- Point-by-point comparison against the previous survey, deltas flagged
- Deficiencies assessed against AMPP SP0169 and prioritised by consequence
- Photo documentation tied to the station it belongs to
- A corrected as-built the plant keeps — so a hundred points is still a hundred points next year
A test point that did not get read is a length of pipe with no data behind it, and it stays that way until somebody digs. That is the part of an annual survey that gets quietly skipped, and it is the reason plant records drift until nobody trusts them.
Scope
Design, build and prove it, under one licence.
Most plants deal with an engineer who writes the design, a contractor who installs it, and a third party who tests it — and when the readings disappoint, each points at the others. We do all three, so the number at the end belongs to whoever produced it.
Assess what is there
Most plants already have some cathodic protection, installed years ago and inherited by people who did not commission it. The first job is establishing what exists, what it is connected to and whether it is doing anything.
- Structure-to-soil potential survey, current interrupted
- Rectifier, anode bed and reference cell condition
- Continuity, isolation and interference testing
- Soil resistivity and corrosivity
- Findings against AMPP SP0169, with a scope of work
Design the system
Current requirement measured on the bonded system, anode sizing and placement against a stated design life, and a monitoring scheme that will still tell the truth in ten years.
- Design under an AMPP Cathodic Protection Specialist (CP4)
- Current requirement testing on the live plant
- Distributed anode design, and deep bed where it is warranted
- Rectifier and controller sizing and specification
- Isolation, bonding and test station scheme
- Plans, specifications and construction documents
Install it and keep it honest
Licensed installation, commissioned with the readings recorded, then tested every year against the same criteria so the record actually shows a trend rather than a series of unrelated visits.
- Hydrovac excavation and anode installation
- Rectifiers, junction boxes and test stations
- Commissioning record with as-built anode positions
- Test station location, repair and raising where they have been lost
- Annual survey and compliance reporting
- Components supplied from our own catalog
Record
Plants do not hand this work to people who have not done it.
One of the largest independent power producers in the United States relies on us to protect the buried piping inside its plants, at sites across the country — the same scope, plant after plant, which is the only real test of whether an approach travels. We work combined-cycle and cogeneration stations, geothermal, and nuclear generating stations.
What that looks like in practice