Calibrate, check, recalibrate


National Winter Service Research Group (NWSRG) initiatives have highlighted the effect that changes in salt grade, moisture content or supplier have on the spreader’s performance and the importance of calibrating the spreaders to each individual salt pile. Should the salt type change or vary after the initial manufacturer calibration this should result in recalibration.

The proliferation of de-icing materials such as Thawrox 6, Thawrox 6+, Cleveland Potash, Pre Wet, ABP (agricultural bi products) and a host of imported materials only increases the need for all spreaders to be regularly calibrated and checked.

The differing discharge settings used for a different salt grade could result in a significant amount of material – as much as 40% – being wasted, or more importantly less salt being applied.


The weather can also have a major impact on salt stored unprotected outside. Dry weather will obviously reduce the moisture content of the salt in the pile, giving the salt entirely different characteristics if stored for long periods.

At the NWSRG we are continuing to try to find new ways to detail how crucial it is to check this key service and ensure the correct amount of de-icing material is distributed on the roads.

Our Calibration Working Group, consisting of members from the Steering and Technical Advisory Group, are working towards a simple step-by-step guide to walk practitioners through completing a conformity check on the salt quantity and distribution of their vehicles throughout the winter season.

Static distribution and discharge checks, (as pictured), are key to the step-by-step process along with the recording of the results and subsequent recalibration if required.

Calibration and continuous monitoring/checking of winter service vehicles throughout the season are vital for the provision of a good winter service.

If the spreader’s calibration is inaccurate, the information recorded on vital functions such as spread width and discharge rate will also be inaccurate.

If this goes unnoticed throughout the season and is repeated across several vehicles, a completely misleading picture of actual spreading performance will result.

For maximum efficiency, salt should ideally meet the industry standard regarding moisture. This not only helps to prevent the salt from being blown away in the wind but previous research has also shown that salt at the recommended moisture level initiates a more rapid de-icing process.

In controlled experiments carried out at -50C on a 2mm thick ice sheet, 6mm damp salt performed better than 10mm damp salt and both grades performed better with the addition of water. With the growth in popularity of initiatives such as the Code of Practice Guidance, accurate calibration is more important than ever.

New technology enables highway engineers to be updated daily on all aspects of overnight spreading operations.

Salt stockpiles are automatically adjusted and further supplies ordered if stocks are low. But if the vehicles are poorly calibrated the data will be inaccurate.

Cold Comfort 2018, the 27th Annual Winter Maintenance Conference and Exhibition takes place at the Ricoh Arena, Coventry on 16 and 17 May 2018.

Register your interest today at and we will keep you informed with the Early Bird Discount offers and programme updates.

This article appears in the December/January issue of Highways magazine.

Register now for full access

Register just once to get unrestricted, real-time coverage of the issues and challenges facing UK transport and highways engineers.

Full website content includes the latest news, exclusive commentary from leading industry figures and detailed topical analysis of the highways, transportation, environment and place-shaping sectors. Use the link below to register your details for full, free access.

Already a registered? Login

comments powered by Disqus
highways jobs

Definitive Map Manager

Cambridgeshire County Council
£32,825 - £35,401
This role is based within the Highways Service at Cambridgeshire County Council and provides an unusual and... Cambridgeshire
Recuriter: Cambridgeshire County Council

Assistant Engineer

Cambridgeshire County Council
£21,074 - £30,756
A great opportunity for someone looking to start or develop a career in Highways Engineering including the... Cambridgeshire
Recuriter: Cambridgeshire County Council

Head of Strategic Transport

Cheshire East Council
£64,000 - £75,000 + benefits
We’re committed to “working for a brighter future together” – and we expect you to be too! Cheshire
Recuriter: Cheshire East Council

Regeneration Manager

Mole Valley District Council
£52,895 - £57,143 FTE
This is a great career opportunity to specialise in town centre regeneration and repositioning. Dorking, Surrey
Recuriter: Mole Valley District Council

Technical Services Officer (Mechanical)

Kirklees Metropolitan Council
£36,876 - £38,813
This is an exciting and challenging time for Kirklees and we want to expand our team to manage and deliver construction... Kirklees, West Yorkshire
Recuriter: Kirklees Metropolitan Council

Road and Footway Asset Engineer

Kent County Council
£28,925 per annum
An exciting opportunity has arisen to join the Road and Footway Asset Team as an Asset Engineer. Kent
Recuriter: Kent County Council

Head of Waste

Lincolnshire County Council
£65,651 - £70,725
As Head of Waste, you will be commercially focussed and forward-thinking. Lincolnshire
Recuriter: Lincolnshire County Council

Assistant Director

Reading Borough Council
Up to £92k
It’s the ideal time to take the lead on our modernisation agenda, and deliver growth in the trading of our front line services. Reading, Berkshire
Recuriter: Reading Borough Council

Assistant Director – Highways

Lincolnshire County Council
£82,264 - £107,878
Come and lead the future agenda for our highways services. Lincolnshire
Recuriter: Lincolnshire County Council

County Highways Manager

Lincolnshire County Council
£55,503 - £60,578
Seeking a highly motivated leader and an excellent communicator, who has a proven ability to build relationships and trust, leading by example. Lincolnshire
Recuriter: Lincolnshire County Council

Local Highways Manager (East) - Lincolnshire County Council

Lincolnshire County Council
G12 £43,662 - £50,430
Seeking someone who combines excellent technical knowledge with a dedication to the customer. Lincolnshire
Recuriter: Lincolnshire County Council