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

Advantages:

Takes up less floor area, more suitable for smaller spaces
Easier access to weighbridge platform as no ramps are required

Disadvantages:

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

Advantages:

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

Disadvantages:

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.}