High pressure vacuum to lift evacuated soil on a mobile evacuator is supplied by two pairs of blower units from Air Control Industries. The blowers replace units from another manufacturer which were not robust enough for the task.
Vac-Ex of Doncaster designs and builds mobile "Vacuum excavators" that provide fast, efficient excavation without the risk of damaging buried utility services, such as pipes and cables. Employing a high pressure air and a powerful vacuum system, operators of Vac-Ex's MOD-EX 5000C lorry mounted excavator are able to excavate and remove hole/trench material in a fraction of the time normally required. Further, the excavation is left clean for easy access to any utility that might need servicing.
The excavation is performed using an air lance that delivers 180 CFM of air at pressures up to 100psi/8bar from an onboard Compair compressor. Once the earth has been loosened it is sucked-up (wet or dry) via a 125/180mm hose and fed into an integral 1.2m3 skip using a powerful vacuum system.
Energy efficient vacuum system
The high-pressure vacuum required to up-lift the excavated soil is provided by two pairs of special blower units supplied by ACI. The blower heads are normally used in ACI's EP10 blower and driven by an electric motor (7.5, 11 or 15kW). For this application, however, each pair of blowers is belt driven by a dedicated 50hp Lombardini diesel engine. 
Because there are two separate vacuum units the level of vacuum can be reduced for light duties, which is more energy efficient than some alternative systems that employ single drive units. It also permits work to continue even if one power unit goes down.
The ACI blowers replace ones from another manufacturer that were not robust enough for this arduous job and also cost more. Much of the MOD-EX 5000C's overall enhanced reliability results from the fact that ACI's blower impeller shafts are mounted on a two-bearing assembly whereas the previous unit only employed a single bearing. ACI's dual bearing configuration serves to reduce stress which enhances durability and reliability, thereby minimising the risk of downtime and ensuring greater operating efficiency.
"The ACI blowers are robust and reliable which helps to ensure our MOD-EX 5000C mobile excavators can be deployed across the country with confidence," says William Bell, technical director. "ACI has been flexible, too, by providing us with just the blower heads, which has avoided the need to provide an electrical power supply. The blowers are ideal for our needs and help to keep the MOD-EX 5000C compact and easy to maintain."