The control panel on a lift station, a wastewater pump house, a wet-process line or a plant next to a rendering operation does not fail all at once. The HMI touch screen starts dropping inputs, a relay sticks, a terminal strip goes green, and one day the pump does not start. The panel gets replaced, the electrician spends a shift on it, and six months later the new one is going the same way. Hydrogen sulfide and humidity are doing exactly what they do to copper and tin, and the enclosure is not keeping them out.
A North Dakota city’s wastewater utility stopped this with an aerosol, an emitter and a gas scavenger per panel, at a cost it put at under one percent of a replacement HMI. Cortec Case History #669 (2019 to 2020) is the source, and a geothermal plant in Cortec Case History #712 (2021) shows the same method holding for years in far worse H2S.
The problem: two to four HMI replacements a year
The utility runs pump houses across a 258-mile sewer system. The air inside them carries hydrogen sulfide, and the panels that house the HMI and pump controls breathe that air. The plant was losing one or two HMI panels every six months. Each replacement cost about 15,000 to 40,000 US dollars in hardware, plus the labor and the pump downtime while it was out.
What they did: seal, mist, emit, scavenge
In April 2019 the treatment staff put a standing program in place for every panel:
- Reduce airflow into the panel. Seal unused knockouts and conduit entries so less corrosive gas gets in and the inhibitor vapor stays in.
- Power down and apply a light mist of ElectriCorr VpCI-239 across the boards, terminals and contacts. It cleans, leaves an ultra-thin corrosion-inhibiting film, and does not change electrical resistance or magnetic or thermal properties.
- Stick one VpCI-111 emitter inside each panel. The emitter releases vapor-phase inhibitor through a breathable membrane and protects up to 11 cubic feet of enclosed volume for up to 24 months.
- Add one H2S scavenger cup per panel to absorb the gas that does get in. (Cortec’s scavenger cup is not something we stock; ask us and we will source it or suggest an equivalent.)
- Inspect on a routine schedule and reapply once a year as needed.
| Before | First year of program | |
|---|---|---|
| HMI failures | 2 to 4 per year | 0 |
| Cost per failure | About 15,000 to 40,000 US dollars plus downtime | None |
| Program cost | Under 1 percent of one replacement |
As of April 2020, one year in, the utility had not lost a single HMI. Cortec’s write-up puts the direct savings in the tens of thousands of dollars and notes the avoided downtime and electrician hours on top of that.
The same method in a geothermal plant
Cortec Case History #712 (2021) is the harder test. A state-owned geothermal generating station in Indonesia sits in hot steam laced with hydrogen sulfide. Three years earlier the plant’s electrical equipment supplier had used the Cortec method on the instrument and electrical panels in one building, and it had held. In 2021 the plant extended the program for another three years, applying it to a second building from the day the panels were installed and re-treating the first. The recipe was identical: ElectriCorr VpCI-239 on exposed instruments and open panels, VpCI-111 emitters and scavenger cups inside closed cabinets. The plant’s reasons for repeating it were that it needed no mechanical work and could be done quickly in the field.
The point for a Midwest reader is that these two cases bracket the range. If the method holds for three-year cycles in geothermal steam, a lift station, a wastewater headworks or a plant with a sour drain is well inside its capability.
How to do this in your plant
- List the panels that fail. Lift stations, headworks MCCs, VFD cabinets near aeration basins, anything downwind of a digester or a rendering line. Note the enclosure volume of each; a typical 24 by 36 by 12 inch panel is about 6 cubic feet.
- Tighten the enclosure. Plug open knockouts, gasket the door, and if the panel has a vent fan, consider whether it needs one. Less exchange with the room air is the single biggest lever.
- Clean and coat. With the panel de-energized, mist ElectriCorr VpCI-239 over boards, terminal strips, relay bases and connectors. It is the outdoor-rated version of Cortec’s electronics cleaner, which is why it is the choice for damp and gassy enclosures. For a shop full of panels, the 5-gallon bulk pail feeds a pump sprayer.
- Size the emitter. One VpCI-111 covers 11 cubic feet; one VpCI-101 covers 1 cubic foot for junction boxes and small instrument housings. Peel, stick, date the label. Our VpCI product selection guide covers emitter sizing and which products are rated for enclosed versus open service.
- Put it on the PM schedule. Inspect at six months, reapply the aerosol and replace emitters at 12 to 24 months depending on how severe the atmosphere is.
- Do the same for spares. A replacement HMI or drive sitting on a stores shelf in the same building is corroding too. Bag it in VpCI-126 film with an emitter and it will be usable when you need it.
Which Cortec products
- ElectriCorr VpCI-239 aerosol, 6-pack: cleaner and corrosion protector for energized-equipment environments that are wet or gassy; the product used in both cases.
- ElectriCorr VpCI-239 bulk, 5-gallon pail: same chemistry for spray application across many panels.
- VpCI-111 emitter: self-stick, 11 cubic feet, up to 24 months; the standard for control panels and MCC sections.
- VpCI-101 emitter: 1 cubic foot, for junction boxes, instrument housings and tool boxes.
- VpCI-126 Blue zip bag: for spare boards, drives and HMIs on the shelf.
We stock ElectriCorr VpCI-239 and the VpCI-111 and VpCI-101 emitters in Elmhurst, Illinois, and can ship a trial quantity for a handful of panels this week. Contact Solvent Recycling Systems with your panel count and sizes and we will put together the kit and a reapplication schedule.
Sources: Cortec Case History #669 (2019 to 2020), Cortec Case History #712 (2021); Cortec product data sheets for ElectriCorr VpCI-239 and VpCI-111.
