ACC Fin-Fans Cleaned in Just One Day
Rapid mobilisation saves refinery $100,000s
Summary
A number of ACC 'fin-fans' each containing 225 tubes, serving the coker unit, were costing the refinery around $20,000 per day each - and rising - as a result of their reduced efficiency. Local cleaning firms were unable to unblock the tubes or clean the polymerised effluent from within the 12 metre-long tubes. The exchangers were on the refinery's critical path, so cleaning had to be completed within a scheduled shutdown. Tube Tech was only given one week before the start to plan and cost the job, then mobilise to site. The refinery itself had traditionally allowed six days to clean each ACC unit, with limited success. Initially contracted to clean two units, with the possibility of a third, Tube Tech in fact completely cleaned not two but four totally blocked units back to full production standard within the shutdown period.
Background
The refinery of BP Refining & Petrochemicals (BP RP) is a major supplier of olefins in northwest Europe. The petrochemical plants are operated jointly by Deutsche BP and its partner, the Venezuelan oil company PdVSA. Supplies come predominantly from the oil-refining facilities of Ruhr Oel. The total annual capacity of the petrochemicals plants amounts to 4.9 million tonnes. BP RP is the biggest supplier of ethylene in the wholesale market. It is also market leader in sales of cyclohexane.
Problem
A number of ACC fin-fans serving the coker unit at BP RP's refinery had become blocked with a material that consisted of an elastic, cured polymer, similar to bathroom sealant. The deposit was pliable but tough and was resistant to jetting pressures up to 750 Bar/10kpsi. Once cooled, the deposit tended to harden to a brittle, glass-like consistency. Each unit contained 225 x 10 metre carbon steel tubes, terminated by 328mm-deep header boxes. The reduced efficiency of the ACC fin-fans was estimated to be costing the refinery around $20,000 per day for each unit. As the exchangers were on the refinery's critical path, they could only be taken down for maintenance during a scheduled shutdown. Each unit had previously taken six days to clean, so this time it was important to reduce time significantly. There was an additional hazard for the cleaning team of aromatic solvent left behind by a previous cleaning attempt.
Solution
With only a week's notice to plan the project, prepare a quotation and get all necessary equipment assembled and shipped to site, Tube Tech moved with well-practised speed: within 24 hours, MD Mike Watson had flown to Germany from a Texas Tower (VCFE) cleaning project in Saudi Arabia and the company's technical specialist and contracts administrator were there to meet him.
The nature and extent of the fouling in the ACCs, which normally handle E3 reformate, was revealed by careful investigation. Tube Tech always tries to take at least three alternative cleaning systems to site; as this was to be an emergency mobilisation, it was doubly important that all scenarios were covered. The fouling to be removed from the tubes was a gooey and putty-like substance, which included the remains of catalytic (PCA) material. The effluent was potentially carcinogenic and would therefore require the operators to wear half-BA suits in the washdown area.
Once on site, cleaning proceeded as planned, with two methods being employed to clean both the headers and tubes of the ACC units. It is very common for traditional technology to clean the tubes but the waste ends up in the header boxes; Tube Tech ensured that all deposits were extracted at source. The first method was based on the well-established SafeTrackT system, while the second utilised a newly-developed HydrolanceT - a hydraulically-driven rotary lance which employs a hydraulically-powered reaming principle with simultaneous pump pressure of 30-52kpsi water. The Hydrolance applied a high-torque rotary action within the tube, with water pressure to clean the various consistencies of deposit encountered.
Despite the sticky nature of the effluent, which constantly threatened to glue the jetting lances in the tubes, both systems progressed better than expected. In fact, the cleaning went so well, that the two ACC units Tube Tech had been contracted to clean were completed quickly enough for the client to ask for a third, then a fourth unit to be cleaned as well. All four units were completely cleaned to inspection standard within the shutdown.
Tube Tech Comment
Tube Tech MD and Technical Director, Mike Watson, commented: "This is an excellent example of the kind of rapid mobilisation that makes Tube Tech one of the most responsive and effective companies in the field. In this case, we mobilised to site at very short notice, as the client wanted time to review our technical approach and approve our quotation. In the most serious emergency, however, where getting to site is more important than knowing the cost in advance, we can mobilise to sites in Europe within 24 hours and within 12 in the UK itself."
Client Comment
The Shutdown Manager, commented: "Cleaning these important fin-fan units has always been a problem for us, both in getting them cleaned in the time available and to the required standard, using our usual local contractors. This time we had a situation where the decision to clean the units was not made until very late in the planning for the shutdown as our replacements had been delayed. As it has been taking six days to clean just one unit and we wanted to clean at least two, we knew we had to look for an alternative service provider and we found Tube Tech International. Tube Tech quickly came to the refinery to assess the problem and prepared an acceptable quotation so that we were able to get them on site in just one week. The cleaning went exceptionally well - and so quickly that we were able to get them to clean not two ACCs, but four. We had been planning to order some new ones, so badly were they blocked, but Tube Tech was able to clean all four to a much higher standard than we have seen before, so we have made some really great savings. If we had known about Tube Tech before, the savings could have been even greater, as we could have avoided ordering new ACCs."
Clients can be contacted via Tube Tech for references.
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