Everything you wanted to know about Vacuum Excavation but were afraid to ask.
6th Jan 2022
What is vac ex?
Vacuum excavation or vac ex is a relatively new means of tackling excavation. Basically, it is using air technology to generate suction which can then be used to dig out material. Compressed air is used to break-up the ground before the machine vacuums it away.
The vac ex is used with an operative using an air hose. The air blows all the earth from around the live utilities and the vac ex sucks up all the soil without damaging the pipework.
The vac ex works through high volume air flow, like a giant vacuum cleaner, creating a stream of air 44,000m3/h. The suction hose can be moved hydraulically with a power arm helping to prevent manual handling injuries.
The operative is able to direct the intake nozzle via remote control, giving them full control of the excavation whilst they remain at a safe distance.
Sounds like it could be messy
Actually, it significantly reduces spoil and dust because all of the extracted material is sucked directly into sealed collection chambers on the lorry. The vacuum system means that a great deal of the dust which would normally go into the air during digging is captured too so vac ex is particularly suitable for using in confined spaces.
Aren’t they limited to an area immediately adjacent to the lorry?
Quite the opposite. Extended reach hoses mean that vac ex is an ideal way to reach difficult to access sites up to 45 metres from the machine. It also offers better health and safety performance because there is much less operational danger than with traditional plant. Vac ex also produce much less dust than conventional digging.
Does the size of the machines limit where they can be used?
The required space for operation is about a third less than that required by a mini digger. Also because it is effectively a standalone solution there is no need for other equipment on site – and because it collects material as it goes along sites are cleaner, clearer and safer.
Is it expensive?
No. In practice (and assuming it is not a tiny job) vac ex will almost always work out cheaper than traditional excavation methods. Compared with manual excavation or using a digger it is very cost and time efficient. To provide some context, consider a job requiring the excavation of 25m3 of heavy soil from around cables and pipes. Digging it out by hand will work out more than 70 percent more expensive than vac ex on a cost per cubic metre basis.
It also massively reduces the risk of service strikes. The average service strike costs around £30,000 but can run into millions of pounds. Because there is no physical tool in the ground the chance of damage to existing services is minimal and, most importantly, reduces the chance of anyone paying the highest price of all.
Is it dangerous?
When using any plant or equipment it is important that the operatives are properly trained but the risk of physical injury while using vac ex is very small indeed – especially when compared with hand or machine digging.
First, operative safety is improved because there is a big reduction in manual handling and, when it is necessary, hydraulic power arms improve the equipment’s manoeuvrability.
Second, because the extension tube is made from relatively “soft” polyethylene there’s little danger of damaging existing utilities and it provides insulation while working in high-risk areas. Overall there’s a 60 percent reduction in the amount of utility damage compared to traditional methods.
Can it only be used on already broken or loose ground?
Vac ex is entirely suitable for a wide variety of ground conditions and materials. In one hour it can dig out 10m3 of heavy soil from around buried cables and pipes, as much as 60m3 of sandy soil or remove a pretty incredible 180m3 of water. Compare that with manual excavation which would typically see an experienced labourer able to dig about 1m3 from around buried services in the same time.
Sounds great for exposing utilities but otherwise it’s applications are pretty restricted?
In fact its incredibly versatile. Vac ex can be deployed in tunnel building; trenching and pipelaying; waste transfer and disposal; installing new utilities in and around existing services; building renovations; tree root renovations; site cleaning; and in disaster and emergency situations.
What about the environment?
Vacuum excavations’ environmental performance is arguably one of its biggest assets. It causes less physical damage to existing flora because it can remove the ground between trees and shrubs without damaging root systems.
As a self-contained, standalone solution there is no requirement for other machines on site so the fuel requirement and the carbon footprint are reduced.
The size of the excavation is up a third smaller which can mean less impact on traffic and, because excavated material is collected in a sealed chamber it means the site and the air is much cleaner.
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