Blocked Horizontal ACC Fin-Fan Cleared of Raw Synthetic Rubber
The headers and 258 tubes on an 8.4 ton, 9.5 x 2.4 metre horizontal fin-fan unit at this UK petrochemical plant had become progressively blocked with raw synthetic rubber, used in the manufacture of tubeless tyres. The unit was shipped to Tube Tech’s UK operations centre, where it was successfully cleaned using a high-pressure jetting system with a special side-firing lance head. Before and after bore scope inspection showed that the unit was completely unblocked and all tubes were clear. Two more units are scheduled to be cleaned.
The UK operation of this multinational oil company produces a variety of hydrocarbon-based raw material products for industry at its refinery on the south coast of England.
The headers and 258 tubes on a 9.5 x 2.4 metre horizontal fin-fan unit at this UK petrochemical plant had become progressively blocked with raw synthetic rubber, used in the manufacture of tubeless tyres. Toxic and corrosive hexane gas, a by-product of the manufacturing process, was also present and a potential obstacle to cleaning. The header boxes and a large proportion of the 12m long tubes were seriously obstructed by the deposits, which resembled large, resilient, clumps of rubber that only extremely hard pressure from a knife blade could penetrate.
As the unit had already been taken out of service, it was shipped to Tube Tech’s UK operations centre for cleaning. On arrival, a heavy-duty crane was deployed to offload the 8.4 ton unit into a safe working position. Tube Tech selected a high-pressure system to negotiate the confines of both the 2500 x 250 x 300mm header boxes. The cleaning head and lances were locked off inside the headers to ensure the cleaning head could not accidentally exit the tubes while under extreme pressure and thereby put the operator at risk “ a hazard of more traditional high pressure jetting systems.
The unit was thoroughly cleaned by shredding the deposits and extracting the resulting particles via the numerous 1.25 BSP threaded access holes located on each header. Full inspection was later carried out using a range of endoscopes and CCTV cameras to confirm cleanliness had been achieved, all in under three days. The waste was collected into a specific area and transferred to IBC waste containers, for eventual return to the client in sealed 45 gallon hazchem transportation drums for proper disposal.
Tube Tech Comments:
Tube Tech Technical Sales: “The job went completely to plan and was finished ahead of the client’s schedule. We maintained constant communication with the client, so he was able to plan-in the return and re-commissioning of this unit. Having successfully cleaned one unit, we have been advised that there are a further two units being considered for cleaning by us.”
Tube Tech MD, Mike Watson, added: “Demand for polymers has been rising rapidly in recent times. A middle eastern company, for instance, is building fourteen new petrochemical plants, largely in response to the increasing demand. In Europe, several refineries have experienced near identical problems in quick succession from fin-fan exchangers becoming blocked with polymers. My guess is that companies may well be trying to save money by using existing plant to make these new products, for which they weren’t originally designed. Either the design deficiency is leading to the excessive fouling we are now seeing or there is accidental carry-over due to temperature differentials, product expansion or flow rates. In other markets, it can be cheaper to build new plants than change existing components.”
“We wanted as much deposit as possible removed from the tube bores and the headers, in the shortest time period available, using the quickest and safest method. We needed the unit restored to production standard performance, with a good passageway to ensure the header boxes were clear.”
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