DP Fuel Tank Services - tank cleaning, Guernsey, black oil, large tank, Vale power station, Channel Islands, MC Integ, UK
While the natural habitat of DP Fuel Tank Services, tank cleaning and decommissioning specialists, is existing and former service stations across the UK, its distinctive orange livery is increasingly being seen on large tank farms as far afield as the Falklands.
One of its largest single tank cleaning jobs has recently been completed on a massive 4,500m3 heavy oil tank, owned by Guernsey Electricity, the sole supplier of electricity to the second largest Channel Island and wholly owned by the States of Guernsey.
After 25 years of solid service, the cavernous tank at the company’s Vale power station needed some maintenance; but before any welding could be done, the tank had to be made safe, all the fuel oil had to be completely removed and the residue cleaned from the 14m-high circular wall; a process that also allowed the wall to be checked for any corrosion – a common problem with heated tanks, especially those sited near to the sea.
To do this, design consultancy and project management company MC Integ called in the specialists from DP FTS.
When in use, the tank is heated to 40ºC to keep the oil from solidifying. An external out-flow heater then raises it still further to 50ºC so it can be pumped around the system.
Says DP Fuel Tank Services supervisor Clive Johnson:”When we first inspected the job, the oil was still liquid. By the time the project was awarded, the temperature had fallen considerably and the oil had turned to the consistency of heavy treacle – almost like tarmac. “As the tank had been drained down to a minimum level of about 300mm deep, which was below the heating elements, re-heating the oil was not an option, so we had to call in a Supervac tanker from the UK, which had a vacuum pump strong enough to remove the remaining oil.”
Once the tanker had done its job, which took four days, the DP FTS team went into the tank in full personal protection equipment and cleaned the floor and walls, up to a height of 2m. The next step was to erect scaffolding so the remainder of the wall could be reached.
“Every inch had to be scraped clean and then washed down with cleaning agent,“ said Clive, “so the wall could be checked and welded where necessary.”
Says John Frost, managing director of MC Integ: “We chose DP FTS to clean the tank, largely on the recommendation of our client Guernsey Electricity, which had used them successfully on previous contracts.
“DP FTS is a very professional outfit. Its people are willing to turn their hands to anything they are asked to do. Considering this is an expensive cleaning job they have performed very, very well.”
There are eight of the huge tanks at Vale, storing heavy oil, which is used to generate power for the whole island.
An undersea cable link to Jersey and France was completed in 2001, which supplies 50-80% of the island’s electricity and could satisfy the island’s full power requirements for nine months of the year. The rest is generated locally at Vale. Local electricity production is also stepped up if world economic fluctuations mean this is more cost effective than buying power from France.