Byworth Boilers Rise to the Tug Boat Challenge
Phil Carr, Sales Engineer at Yorkshire based Byworth Boilers, received what he described as his most unusual request early last year when the industrial boiler manufacturer was asked to replace the old boiler in the steam tug Challenge.
Challenge is a true national treasure, being the last steam tug to have worked on the Thames, but is best known for the role she played in Operation Dynamo evacuating troops from the Dunkirk beaches in 1940. Thanks to a Heritage Lottery Fund grant of almost £1 million, confirmed last year, Challenge is being completely restored to her former glory.
Phil Carr picks up the story. “ Challenge was originally equipped with a coal fired two pass triple furnace marine `Scotch` type boiler which was later converted to simple pressure jet heavy oil burners. The boiler was very short in length but large in diameter and had, sadly, succumbed to severe sea water corrosion.”
He added.” As you can imagine space in the boiler house is extremely confined so our challenge was to produce a boiler to fit the restricted space and at the same time be arranged in such a manner that tubes could be replaced by withdrawing through the very narrow passageway from engine to boiler room.”
After carefully weighing up the unique complexities of the project the Byworth team designed a special triple pass 1500lb/h and 180psig boiler with twin furnaces and modern electronic digitally controlled pressure jet dual fuel burners suitable for sulphur gas oil and low sulphur intermediate fuel.
The new boiler will produce a maximum continuous rating of 6,800 kg/h and can operate up to 13.8bar.g.
The length of the furnace and the overall length of the boiler determined the flame length and another feature was the incorporation of special XiD tubes, which are exclusive to Byworth in the UK. These unique tubes have internal spiral ribs which increase the turbulence thereby boosting the heat transfer rate. This enhancement of the heat transfer from products of combustion enables the length of the boiler to be reduced considerably compared to a conventional boiler. The turbulence within the XiD tubes also helps the prevention of deposits thus increasing the periods between boiler cleaning.
Energy efficiency also played an important part in the configuration of the new boiler. The precise air/fuel ratio control of the burners and the design of the boiler produce a full load efficiency in excess of 84% gross basis. The boiler is very liberally designed with a heat release rate within the parallel section of the furnace a low 1.29MW/M^3 which compares with rates in excess of 1.6MW/M^3 on many standard `packaged` boilers.
Boiler resistance is also low and the combined effect of these design parameters is low electrical energy to drive the burners coupled with high overall thermal efficiency leading to considerable savings on fuel. Lower NOx levels are also a function of the low furnace heat rates and lower flame temperature.
In addition the burners can be selected to fire independently and under normal conditions they modulate in unison.
In summary Phil described working on the Challenge`s new boiler as an extremely interesting and diverse project that demanded the expertise and skills of experienced engineers from both boiler and combustion design disciplines.
When the renovation is complete the 1931 tug will return to active service as a fully operational, educational and public reminder of the thousands of similar vessels that once thronged Britain`s ports and harbours.
Full details the steam tug Challenge story can be found on www.stchallenge.org
Byworth Boilers, one of the UK`s leading manufacturers of industrial steam and hot water boilers, has been producing quality boilers since 1968. In its Keighley factory the latest manufacturing techniques are combined with time honoured boiler making skills.
The company also has a fleet of over 100 hire boilers and operates a complete servicing, repairs and spare parts service. In addition a comprehensive programme of training courses for boiler operators and plant managers is offered.