Once you’ve made the decision to install a weighbridge, the next step is choosing between a pit-mounted or a surface-mounted one.
It’s a decision where you need to consider many different factors to ensure that your investment delivers value for money and that it performs optimally under all conditions.
It’s worth outlining the basic differences between the two types before delving any deeper into the how you should go about choosing which one is best-suited to your situation.
As the name suggests, surface-mounted weighbridges (also sometimes referred to as above-ground weighbridges) sit on top of the ground whereas pit-mounted weighbridges are flush with the road with the load cells etc housed in an excavated area underneath.
Now let’s look at some of the important considerations when choosing between the two types.
1. The size of the area where the weighbridge is to be installed.
Pit-mounted weighbridges take-up significantly less surface area and don’t need on and off ramps or guide rails, so they’re the right choice in severely confined areas or where a smaller footprint is required.
Surface-mounted weighbridges require the addition of entry and exit ramps and clear spaces on either sides of the weighbridge deck. These requirements, plus the turning circle needed for vehicles to access the weighbridge, dictate the need for a considerably larger surface area. When a surface-mounted weighbridge is installed in an area that is too small, the ramps have to be steep which can result in problems with traction and vehicles slipping.
Above-ground weighbridges are a more cost-effective option, as they don’t require much site preparation and are easy to install. On the other hand, a pit-mounted weighbridge necessitates civil and foundation work including excavation and reinforcing, with their attendant costs.
Installation costs can also escalate if a pit-mounted weighbridge interferes with underground services such as sewerage, power cables, telecommunication services etc, so before you make any decisions, it’s important to obtain a site survey which shows where such services are located.
3. How will the weighbridge be used?
What volume of vehicles will be using the weighbridge? Will the vehicles be weighed during loading by forklifts? How long are the vehicles that need to be weighed? Is the weighbridge going to be a permanent installation or will it be moved at some stage?
These are all crucial questions because pit-mounted and surface-mounted weighbridges met different criteria. Pit-mounted weighbridges are ideal for shared weighing and where vehicles are weighed whilst they’re being loaded, while surface-mounted ones are often chosen for temporary installations or when the bridge needs to be relocated.
4. Site conditions
The physical location of the weighbridge and the environmental conditions are also important selection criteria. Good ventilation and effective drainage is crucial especially with a pit-mounted weighbridge because the performance of the load cells will be compromised if they are submerged for any length of time, so you need to look at the water table and the surface water drainage system.
Surface-mounted weighbridges are generally recommended where there is an issue with water logging, where there are hazardous gases around and where the ground is rocky.
To help you make the right choice of weighbridge in terms of budget, usage, site conditions and your unique vehicle weighing needs, it’s really worthwhile discussing your options with the team at AccuWeigh where you’ll benefit from their extensive experience (over 1 000 weighbridge installations throughout Australasia), extensive range of weighbridges for sale and comprehensive service and support.