Mobile drill rig uses electric drive for fume-free operation
A new type of drilling rig, developed with the help of electric motor company Exico, can be used indoors without the risk of filling the building with diesel exhaust fumes.
Planning the redevelopment of London’s New Covent Garden fruit, vegetable and flower market has required a comprehensive geological survey to be commissioned, right down to a depth of 50m. So a specialist drilling company was brought in to collect soil and rock samples from multiple deep drillings across the 57 acre site.
New Covent Garden market, in Nine Elms on the south side of the River Thames, has been in operation since 1974 when the old site was closed to make way for retail and leisure businesses. It is home to the 200-plus independent traders that supply London with nearly all of its fruit, vegetables and flowers.
The redevelopment of New Covent Garden is scheduled to take 10 years and cost £2bn. It will see the market facilities modernised to make them more efficient and free up 20 acres of land for nearly 3,000 homes and 115,000 sq ft of commercial accommodation. There are several equally ambitious building projects nearby, including the new US Embassy and the long-awaited redevelopment of the redundant Battersea Power Station into a cutting edge mixed use facility.
Jerry Hodek of Exico explains that the geological survey has to be thorough and requires many of the exploratory bores to be drilled inside existing buildings. This work was undertaken by D.J. Drilling Ltd, a specialist company that does a lot of work in London and the South East, as well as further afield. Based on the Isle of Wight, the company offer a number of services beyond general drilling, including dynamic probing for land quality assessments, window sampling to assess soil variation across a site and comprehensive site investigations
Normally the drilling rigs used by geological surveyors are driven by diesel engines.
“This is fine if you are working out of doors and the exhaust fumes can dissipate on the wind,” says Jerry.
“However, if you attempt to use such equipment indoors the fumes quickly cause problems. It becomes necessary to use ducting and fans to extract the fumes. This can cause delays to the schedule, add costs and is often difficult to achieve.”
With so many holes to be drilled across the New Covent Garden site a solution was required that would effectively overcome the fume problem yet be quick to set up and easy to operate, and an electric motor drive provided the answer.
“The electric motor is fitted onto the rig in place of the diesel engine,” explains Jerry. “This can be driven from a three phase mains supply or a mobile diesel generator located outside the building, where fume build up is not a problem.”
In fact the motor that Exico supplied is a four pole 18.5kW 400/690V 50Hz machine, fitted with an integral inverter to turn it into a variable speed unit. The inverter, made by Kostal was also supplied by Exico.
Kostal’s Inveor inverters are designed to be mounted directly onto the motors they are controlling, in place of the motor’s usual terminal box. Normally inverters are located in a separate, remote control cabinet, but this would be an impractical configuration for portable equipment such as on-site drilling rigs.
“Motor mounted inverters are subjected to significant levels of vibration and heat,” says Jerry. “The Kostal units are built to be so robust that they can cope with the vibration and also have a large heat sink, which in this case we have augmented with a cooling fan to provide a constant airflow over the unit.”
The variable speed, electrically driven drilling rig is proving its worth on the New Covent Garden project, reliably drilling bores to precise depths and helping the surveyors keep to a strict schedule.