On Board Truck Scales

by William Cayce of CLERAL USA ( 22-Feb-2009 )

On-board weighing systems are here to stay for trucks and Trailers.  Affordable and as easy to use as a bathroom scale, on-board truck and trailer scales offer the user many benefits including increased safety, increased revenues, reduced fuel consumption and operational savings.  As a distributor and weighing systems engineer specializing in on-board weighing systems for the past 10 years, I have helped develop several unique on-board weighing solutions with input from operators and several major equipment and vehicle manufacturers.  Operators that have already installed and are using on-board scales are experiencing increased revenues and significant savings in operating costs.  knowing your exact weight at the point of loading reduces costs.  It is simply inefficient not to know your weight at the point of loading.  With diesel fuel prices continuing to increase operators are looking for ways to be more efficient.  Adding an on-board weighing system is one way to increase efficiency.  Why leave under loaded by several thousand pounds or more?  The revenue from the extra cargo that could be added might pay for the increased cost of fuel.   On the flip side,  why leave overloaded and risk the cost of an overload fine or worse contributing to a serious accident resulting in injury or death because you’re overloaded?  Operating savings aside, avoiding one overload fine or accident justifies the cost of the having an on-board scale fitted to your truck.  This technology has arrived,  it has been proven to work and  is here to stay.  On-board scales can be easy to install, easy to use, reliable, accurate and reasonably priced.  Weight is everything in the trucking business and there is simply no reason, with the systems available today, that an on-board scale shouldn't be standard equipment for your truck and or trailer. The savings using an on-board weighing system are significant.   After interviewing many operators hauling various products under different conditions for different industries these savings are considered conservative. Choosing the right on-board weighing system for your needs is crucial.  Things to consider are:  Type of system, cost, ease of installation, accuracy, ease of use, durability, support and serviceability. I will discuss a few. 1.   Type - There are many types of systems that can be fitted to your truck and/or trailer depending on your suspension type.  First, determine your suspension type (air, spring or combination).   Air ride systems generally use devises that accurately measure small changes in air pressure in the suspension system as loads change and convert that pressure to a weight.  Spring ride systems use various methods to measure the deflection (bend) of walking beams, steer axles, trailer axles etc. as loads change and convert that bend to a weight. Systems vary greatly in installation time and difficulty.  A few suspension configurations cannot be fitted with a weighing system and if there is any doubt consult the manufacturer or dealer.  Other types of on-board scales to consider use load cells.  Load cells come in various shapes and sizes and although accurate they are generally significantly more expensive and difficult to install and service. Installing load cells may also require major alterations to your vehicle.  Other things to consider might be the use of a wireless system instead of a system using a standard cab mounted display.  The newer wireless systems now available are convenient to use and worth the added cost.   The operator can monitor the truck's total weight and axle weight distribution using a small hand held meter from anywhere within several hundred feet of the vehicle.  Wireless systems are easier to install because they eliminate the cables that run from the individual air, axle sensors or load cells mounted on the tractor and/or trailer to a display mounted in the cab.  Eliminating these cables also makes it easy to swap multiple tractors and trailers.  Some systems can be easily self installed (air suspension systems) while others require professional installation (load cells).  Contact the scale manufacturer or dealer and ask a few questions based on your suspension type (air or spring) and your individual requirements.  Most are happy to help. 2.   Cost - Prices range from less than $1000 (suspension mounted air systems) to over $10,000 (some load cell based systems).  Installation time and costs vary greatly depending on the type of system.   Generally systems mounted to the axles and/or suspensions are less expensive and easier to install.  Consult your manufacturer or dealer. 3.   Ease of Installation - Systems vary greatly as already discussed.  Consult your manufacturer or dealer. 4.   Accuracy - Most manufacturers advertise accuracy within +/- 1% of your gross vehicle weight which is the industry standard.  Accuracy will vary slightly load to load, repeatability within reason all things equal, is important.  Environmental conditions, temp., altitude, uneven terrain, sloping ground,  will also cause small fluctuations.  Variables like amount of fuel (full, empty), the presence of ice, changes in installed or carried equipment.... will also effect weights.  Be aware of these factors (the scale will help to see these).  Some of these variables can be compensated for by updating the calibration of the scale periodically (usually an easy process) and zeroing (usually involves pressing a button when empty but not available on some systems).  The bottom line is that the scale installed on your vehicle is a tool and subject to variations like any scale, bathroom or otherwise,  however, based on how and where it's used, 0ver all, +/- 1% accuracy is realistic for most systems.  Watch for unexplained erratic weight fluctuations high and low as this may be a sign of problems with the scale and/or suspension system or be an indication of some other maintenance issue not related directly to the scale.  Calibration for most systems is a simple process and usually involves a few trips to a certified weigh station to get an empty weight and loaded weight for your truck and/or trailer.  The weights obtained from the certified weigh station are entered into the scale by the operator using a series of easy key strokes (a step-by-step manual is usually included).  The scale uses the entered empty and loaded weights as a reference and computes all future weights based these initial numbers .  Once calibrated the scale should only require infrequent periodic adjustments. In my mind the benefits of installing an on-board scale far out weigh the costs of installing and maintaining the system.  So why are there not more systems in use?  I'm not quite sure but will chalk it up to the general lack of awareness by operators of the on-board weighing industry and it's products even though some on-board scale manufacturing companies have been around for decades.  What I am sure of is that those who are currently using on-board weighing systems are operating more efficiently and being rewarded with increased revenues and operational savings.  I'm also quite sure that it is just a matter of time before on-board scales become an industry standard.  Try one or several, I don't think you will be disappointed.