When selecting or upgrading your weighing operation, there are many advantages to a hydraulic truck scale, including the fact that they are extremely accurate in high-capacity applications.
By Steve Hosp
Today’s hydraulic truck scales combine state-of-the-art electronics with virtually indestructible hydraulic load cells for a weighing system with no electronics in the scale platform—the area of greatest potential problems and failures. The design of a hydraulic truck scale allows the weight signals from the load cells via pressure transducers to be totalized and converted to a single data signal, which, in turn, is sent to the indicator for viewing and further system processing by the operator.
When selecting or upgrading your weighing operation, there are many advantages to a hydraulic truck scale, including the fact that hydraulic scales are considered to be extremely accurate in high-capacity applications, and have several advantages over a traditional truck scale using analog strain gauge or digital load cell technology.
Hydraulic Truck Scales are Immune to Lightning Strikes and Power Surges
In locations subject to lightning strikes and power surges, hydraulic truck scales are superior to both digital and analog scales due to the fact that the load cells used in hydraulic truck scales are immune to damage resulting from lightning strikes or power surges—also called transient voltages. Unlike traditional truck scales using digital or analog strain gauge load cells that require power in the scale, hydraulic load cells have neither strain gauges nor wiring and absolutely no power in the scale making them unaffected by lightning strikes and power grid changes—the main source of power surges and one of the most common reasons for load cell failures.
Hydraulic truck scales use hydraulic tubing from the load cells and are terminated at the scale totalizer by a non-conducting rubber line. This creates a barrier of protection, preventing lightning from traveling into the scale house where your digital weight display is located.
Hydraulic Truck Scales are Immune to Water and High-Pressure Washdown
If your weighing operation is in an area that frequently floods and the scale is continuously submerged in water for an extended period, then a hydraulic scale will prevent your operation from coming to a standstill until the water recedes and damaging the weighing components in the scale. Hydraulic truck scales use hermetically sealed load cells that are welded together and then pressure tested to ensure there are no leaks. By keeping the hydraulic fluid inside of the load cell, water is kept out preventing damage that would shut down a traditional truck scale using digital or analog strain gauge load cells.
Another benefit to a hydraulic truck scale is that the scale’s weighing components will not be damaged by the high-pressure wash-down that is routinely performed on scales used in the solid waste industry to remove dirt and grime and by steam cleaning ice and snow from the scale in the winter.
Hydraulic Truck Scales Operate Over a Wide Range Of Temperatures
Extreme temperatures can affect a traditional truck scale’s circuit boxes and cause problems with the load cells. Fortunately, there are no electronic components in hydraulic truck scales, allowing them to operate over a wide range of temperatures. Instead of using electronic components, hydraulic truck scales have load cells that use aircraft-quality hydraulic fluid. This type of hydraulic fluid allows a hydraulic truck scale to continue to operate accurately and efficiently in environments with temperatures as low as -65oF (-54oC) and up to 275oF (135oC) resulting in a truck scale that will never stop working because of weather extremes.
Some Hydraulic Truck Scales Offer the Same Advantages as a Digital Truck Scale
Digital truck scales can display weight data from each load cell and can alert the scale operator or service technician of a potential problem before the scale weights are affected. Some hydraulic truck scales are available with the same type of load cell controllers that perform the same functions as found in digital truck scales. These controllers digitize each hydraulic load cell output independently, allowing the operator or technician to view the outputs of each load cell. Software is also available to alert the operator when an excessive shift in the no-load output of one or more cells is detected prior to affecting the accuracy of the scale. Another feature of a hydraulic truck scale with this type of load cell controller is the ability to perform quick and easy calibration.
Hydraulic Truck Scales are Safe to Operate in Hazardous Areas
Hydraulic truck scales are ideal for grain elevators, chemical plants, or any hazardous environments where explosive materials are present and where a spark could potentially set off an explosion. Furthermore, hydraulic truck scales are a safer alternative in an operation with a pit-type scale, where fuel or other flammable materials leaking from a vehicle and collecting in the scale pit can be ignited.
Traditional truck scales using analog or digital load cells must take extra precautions and use barrier strips to limit the energy to the scale or explosion-proof enclosures to contain the explosion. Those steps are not necessary when you use a hydraulic truck scale. Because hydraulic truck scales contain no electrical circuitry, there are no electrical currents and, therefore, do not have a chance of an explosion-causing spark when used in an explosive atmosphere.
With all the components that require power located in the scale house and absolutely no power and electronics in the scale itself and using only hydraulic fluid for the weighing elements in the scale, hydraulic truck scales are inherently safe and highly recommended for hazardous environments.
Hydraulic Truck Scales Perform Well in Operations Subject to Shock Loading
In any operation, there will be times the scale is subjected to shock loading or vibration. Hydraulic truck scales perform well when this happens due to the design of the load cells. Both analog and digital load cells use a steel spring element to sense the load. Applying a shock load, even one less than the capacity of the load cell, can and will cause permanent damage to the load cell rendering it unusable. Hydraulic truck scale load cells, on the other hand, act much like a shock absorber on your automobile, dissipating the shock load or vibration in the hydraulic fluid and preventing damage to the scale, resulting in costly downtime.
Hydraulic Truck Scales Meet the Same Legal and Metrology Standards
Scales used in commerce, where money is exchanged based on scale weight, must have a National Type Evaluation Program Certificate (NTEP) to verify that they comply with the requirements for use in trade. Just like their digital counterparts, today’s hydraulic truck scales have been thoroughly evaluated and comply with the National Institute of Standards and Technology (NIST) Handbook 44 requirements for Class IIIL scales for use in commerce.
The Technology in Hydraulic Truck Scales has a Long History of Use
The technology used in hydraulic truck scales has a long history of being used in scales, much longer than either the strain gauge or digital technology used in traditional truck scales. Although hydraulic truck scales have not been as popular as the less expensive traditional truck scale, when the costs of ownership including repairs are figured in, the hydraulic truck scale is clearly less expensive to own and maintain.
Hydraulic Truck Scales Offer the Lowest Maintenance Cost
Hydraulic truck scales are easy to maintain as there are very few moving parts and it is easy to spot any leakages so, therefore, easy to know if there are any maintenance issues. With virtually no moving parts, the life expectancy of a hydraulic truck scale can be as much as 30, 40, or more years.
Most manufacturers of hydraulic truck scales offer a lifetime warranty on the primary components (the hydraulic load cells) against damage from voltage surges (lightning) and water damage—the two most common reasons for the failure of strain gauge and digital load cells. With a lifetime warranty on the primary components of the hydraulic truck scale, components that are waterproof, shockproof, explosion-proof, and resistant to both caustic and corrosive environments, you will never have out-of-your-own-pocket expenses to replace these due to damage or malfunction. | WA
Steve Hosp has been a Technical Writer for Cardinal Scale Manufacturing Co. for more than 27 years writing technical and operation manuals, instructions, and articles for products ranging from precision balances to railroad track and truck scales. He can be reached at e-mail at [email protected].