Investing in a weighbridge?
Selection guide to help you decide on Pitless or Pit type installation depending on your site.
A weighbridge is an important piece of equipment in any industry vertical where inwards or outwards transaction of material is done through road vehicles and based on weight. Being a capital asset requiring substantial investment, it is important to know technicalities before purchasing one.
The monetary investment in procuring a weighbridge broadly consists of three parts.
- Cost of purchasing the weighbridge equipment
- Cost of civil foundation for installing the weighbridge
- Cost of maintaining the weighbridge
Purchase & maintenance costs depend on factors like size, capacity, usage, instrumentation specification, features, quality & brand. The cost of civil foundation depends on the type of installation of weighbridge.
The electronic* weighbridges can be categorised on basis of type of installation:
- Pit mounted weighbridge
- Pitless weighbridge (also known as Surface mounted)
a. With dedicated foundation for permanent use
b. With alternate foundation for non-permanent (Portable) use
Pit mounted weighbridge:
- Weighbridge platform top is flush with floor level
- Requires a pit to accommodate height of weighbridge structure
- Requires headroom space for maintenance access by service personnel
- Takes up less floor area, more suitable for smaller spaces
- Easier access to weighbridge platform as no ramps are required
- High cost of civil foundation (typical pit depth 1.2~1.5m)
- Pit is prone to waterlogging & debris accumulation
- Additional cost of pump & periodic cleaning of pit
- Civil cost is wasted if weighbridge is required to be relocated later
Pitless weighbridge (Surface mounted):
- Pitless weighbridge is above the road surface level
- Does not require a pit for installation
- Requires sloped ramps to enable vehicles to access the weighbridge
- Cost of civil foundation is lower than pit type
- Easy to clean & maintain as no pit is involved
- Possible to relocate economically with special type of foundation
- Requires more space & turning radius due to presence of ramps
- Higher the deck height, longer will be the length of ramps.
- Steep slope of ramps or improper design can cause unwanted shock loads
Portable Pitless Weighbridge:
- ‘Portable’ or ‘Mobile’ weighbridge is a sub-type of pitless weighbridge
- It is in fact semi-portable and not freely portable like bench or platform scales
- Requires a foundation, re-installation, re-calibration & stamping to relocate
- Uses alternate design of foundation like existing RCC floor or transportable RCC blocks to save civil costs
What should you consider when deciding?
- Pitless weighbridge is the preferable option, unless space is a constraint
- Compact, low height deck structures are better as they need lesser ramp length
- Common structural design for pit/pitless weighbridge gives flexibility of options
- Pit/pitless decision has no relation with accuracy of weighbridge, which depends on load cells used
- Both pit/pitless require a good foundation having load bearing capacity as specified in the ‘Plan of foundation’ drawings provided by the weighbridge supplier
Avery Weigh-Tronix offers weighbridges with compact & modular, low-height deck structures, common for pit or pitless installation. The use indigenously manufactured & repairable T302X/T301X high accuracy load cells, certified as per global OIML-R60 standards for C5/C6 accuracy class.
*This article specifically covers electronic road vehicle weighbridges and not the mechanical (lever-based structure with dial/steelyard indication) or electro-mechanical (lever-based structure with single load cell) types as these are obsolete technologies not relevant in current scenario.