Serpentine W.H.R.U (waste heat recovery unit/hot oil heater) cleaned mechanically, in-situ, on offshore oil platform
First in-situ clean of WHRU (hot oil heater) completed with safety and environmental considerations in mind
Summary
The tubes on a serpentine Waste Heat Recovery Unit (W.H.R.U./hot oil heater) on the offshore platform were showing signs of becoming constricted with hard carbon deposits. This was a similar situation to a problem that occurred with its sister unit in 2004, where the operator also wanted a safe and cost-effective clean.
Challenge
- There has never been an effective conventional means of removing this type of fouling from within serpentine or coiled heat exchangers.
- Previous methods had included
- simply bypassing the fouled unit – hardly ideal
- doing nothing and accepting the increasingly inefficient burning of fuel
- removing/cutting off the bends to allow straight access to all tubes for cleaning
- replacing the complete unit.
- None of methods were satisfactory, as bypassing results in higher operating costs, while cutting bends off is not only time-consuming but sufficient access for welding cannot be guaranteed and is in any case best avoided in-situ.
- Replacing the unit is not only expensive, but also entails a six-month manufacturing lead time.
- Other major considerations for the Tube Tech team were safety and, in accordance with the platform operator’s ISO 14000 accreditation, the need to keep waste contained and to a bare minimum.
- Logistically, due to the transportation limitations of getting equipment out to the North Sea location, Tube Tech’s technical and organisational skills had to be first class returning to base for any forgotten equipment was not an option.
Solution
- To achieve the cost-effectiveness that the client required, Tube Tech actually cleaned the WHRU in-situ on the platform.
- Mindful of safety and environmental considerations a system of rotary turbine cleaning heads was developed and these were delivered by an insertion tool custom-designed to negotiate multiple bends.
- To keep waste volume to a minimum a calculated burst of water was used and collected.
- Tube Tech’s expertise was key to the operation’s success because, during 2004, a companion WHRU (hot oil heater) had been removed from the platform and successfully unblocked and cleaned at Tube Tech’s UK headquarters.
- With the benefit of this previous onshore experience Tube Tech was able to suggest that the second WHRU (hot oil heater) could actually be cleaned just as effectively in-situ on the platform, thereby avoiding huge costs and logistical headaches.
- The work would be followed by a complete internal tube inspection of the coiled pipes within the WHRU (hot oil heater).
- The WHRU (hot oil heater) was returned to peak performance by Tube Tech who saved the client substantial time and money as a result of the cleaning and inspection being carried out in-situ.
- A clean and efficient waste heat recovery unit (WHRU) generates immediate benefits as a result of lower operating costs and emissions.
- Tube Tech’s unconventional approach, which allowed the job to be completed in just a few days, also meant that the hazardous operation of removing the unit from the platform and returning it after cleaning – normally a three-week process – was not necessary.
Tube Tech Comment
Scott Donson, Technical Sales Manager: “We were very confident, having cleaned the WHRU onshore at our onshore facility, that we could execute a successful in-situ and on-time cleaning contract for the client. We had to study previous performance and experience data, so as to ensure all tools and equipment needed were transported out to the platform, as we could not return for additional resources once mobilised. I foresee our next challenge being to clean a waste heat recovery unit on-line, something we’ve successfully achieved already with flare line and furnace decoking projects.”
Clients can be contacted via Tube Tech for references.
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