Vehicle Weighing Reliable Vehicle Weighing Helps Protect Profits - White Paper Contents 1 The importance of reliable vehicle weighing 2 Enhancing accuracy: microprocessors within load cells 3 Reducing physical threats: innovative product design 4 Considering ROI 5 Summary 6 Additional resources Moving bulk goods or raw materials into or out of a processing facility effectively is critical to plant productivity. As a result, unplanned truck scale downtime can seriously impact the total product output of a processing plant and threaten profit margins. Primary causes of unplanned downtime in traditional truck-scale systems include: • Harsh conditions, including water ingress, damage to load cells, junction boxes, and scale terminals, and lightning-generated surges • Heavy loads and high traffic volume, which con- tribute to issues such as scale drift, and cause de- creased accuracy over time • Rodent and debris damage which can affect the in- tegrity of cables and wiring Many companies believe unplanned downtime to maintain or repair truck scales is unavoidable. How- ever, unplanned scale downtime does not have to be an accepted variable in the productivity equation. Newer scale technologies, such as microprocessor- equipped load cells and systems that eliminate junc- tion boxes, have many advantages over older technology. This paper addresses technology and design advances that help eliminate unplanned downtime such as self-monitoring load cell networks, which keep scales operating and help ensure in-plant pro- ductivity gains are not made in vain.
Transcript
Vehi
cle
Wei
ghin
gReliable Vehicle Weighing
Helps Protect Profits - White Paper
Contents
1 The importance of reliable vehicle weighing
2 Enhancing accuracy: microprocessors within load cells
Moving bulk goods or raw materials into or out of a processing facility effectively is critical to plant productivity. As a result, unplanned truck scale downtime can seriously impact the total product output of a processing plant and threaten profit margins.
Primary causes of unplanned downtime in traditional truck-scale systems include: • Harsh conditions, including water ingress, damage
to load cells, junction boxes, and scale terminals, and lightning-generated surges
• Heavy loads and high traffic volume, which con-tribute to issues such as scale drift, and cause de-creased accuracy over time
• Rodent and debris damage which can affect the in-tegrity of cables and wiring
Many companies believe unplanned downtime to maintain or repair truck scales is unavoidable. How-ever, unplanned scale downtime does not have to be an accepted variable in the productivity equation. Newer scale technologies, such as microprocessor-equipped load cells and systems that eliminate junc-tion boxes, have many advantages over older technology.
This paper addresses technology and design advances that help eliminate unplanned downtime such as self-monitoring load cell networks, which keep scales operating and help ensure in-plant pro-ductivity gains are not made in vain.
2 METTLER TOLEDO - White Paper - Reliable Vehicle Weighing
The crucial reason a truck scale must perform is simple: Every minute a scale weighs inaccurately – or not at all – costs money. Without correct amounts of incoming materials, critical processes are put on hold. Additionally, in-plant productivity gains can be nullified if goods are waiting to be shipped out.
Internal/External Scale Influences
There are many reasons that truck scales can be the Achilles’ heel of a processing or production opera-tion. Scale systems that use conventional analog load cells, hydraulic load cells, sectional controllers, and even digital junction boxes, have weaknesses that can either slow down weighing operations or leave a scale system open to errors or harm from both internal and external factors. The influences that can affect conven-tional strain gauge load cells include:
• Temperature• Voltage variation• Non-linearity• Hysteresis• Creep• Instability• Zero change• Sensitivity change
Many traditional systems use junction boxes which are naturally difficult to seal and deteriorate with time. This leaves them highly susceptible to mois-ture ingress, causing corrosion and damage to the electrical connections inside. Without networked self-diagnostics, such issues may not be discovered for weeks. This can mean the scale is providing inac-curate weights without the operator knowing. Even once an error is noticed, diagnosis is a challenge and can require lengthy inconvenient downtime to trace the cause and correct it. Junction boxes are in fact a lead-ing cause scale system downtime.
Problems such as load cell fluid leaks in a hydraulic system can decrease weighing accuracy and effective-ness, and can also be difficult to troubleshoot. The slower response time of hydraulic load cells can also mean fewer trucks are processed through the line.
Another significant issue for traditional scale systems is lightning. A lightning strike can put an unprotected vehicle scale out of service in an instant. Some scale companies provide warranties for lightning strikes, but when one occurs, you are still faced with consider-able downtime during a repair or replacement. Over the years, lightning protection systems have been de-veloped, but even so, not all are created equal. Many manufacturers claim to offer lightning protection, but have not actually tested their systems to evaluate ef-fectiveness.
The Cost of Weighing Errors
Because conventional scale systems cannot alert operators to the above issues or compensate for their influence, they can continue to produce undetected weighing errors. In fact, the errors can often exceed the limits established for certified legal-for-trade appli-cations. The more vehicles that are weighed, the more the losses add up.
Perhaps even worse, customer complaints may be the first indicator that a scale is in trouble. Of course, a manufacturer never wants outside entities such as a customers, auditors, or regulatory bodies to be the ones who bring inconsistent weighing results or other quality control issues to the foreground. A scale’s performance can not only affect profit and productivity, but an organization’s reputation as well.
1 The importance of reliable vehicle weighing
3 METTLER TOLEDO - White Paper - Reliable Vehicle Weighing
Innovative technology can provide the first-line de-fense against costly weighing errors.
The place to start may be to replace any analog load cells with load cells that are equipped with on-board microprocessors that transmit strong digital signals and provide self-diagnostics.
Microprocessors within each load cell can provide computing power to help assure a manufacturer that a vehicle scale is working properly. They can alert scale operators to performance indicators and potential problems. Often this allows potential problems to be prevented through routine maintenance, or allows a user to pinpoint the source of an immediate problem for quick intervention and correction.
Monitoring Weighing Performance
The key to increasing a load cell’s weighing accuracy is reducing the effect of internal and external influence factors. A load cell that incorporates digital signal processing technology can monitor and greatly re-duce the affects of internal and external influences on weighing accuracy. This process is known as digital compensation. With on-board microprocessors and advanced software, each load cell can correct or alert
Operators are alerted to problems instantly so they can be fixed. This saves time and scores of potentially inaccurate inbound or outbound truckloads.
Scheduling Maintenance
Through the use of advanced digital load cell technol-ogy, diagnostic log files record performance trends and help predict problems before they occur. These internal preventative maintenance systems alert super-visors about issues on the screen of the scale terminal, or via email or text message.
This allows maintenance to be scheduled when it is most convenient. Time-consuming troubleshoot-ing and parts swapping are replaced by prevention and detailed data analysis. Unplanned downtime is avoided and operating costs are reduced.
2 Enhancing accuracy and uptime: microprocessing within load cells
While enhanced load cell technology can help make critical gains in reliability, the physical design of the load cell system can also help ensure costly un-planned downtime is avoided. Several important con-siderations for the weighing system’s physical design follow..
Heavy-Duty Stainless Construction
Heavy-duty, corrosion-resistant stainless steel helps resist damage in abusive or corrosive environments. Critical weighing electronics are now being protected like never before within hermetically sealed, IP68/IP69K watertight systems. A fully welded enclosure and watertight connectors can ensure that flooding will not impact a company’s maintenance budget.
Junction boxes – which contain sensitive electronics easily affected by moisture – are wired by hand in the field during a complex installation process on tradi-tional scales. They are a common cause of vehicle scale failures because the electronics are not protected from environmental elements by a permanent seal. Newer digital systems do not require a junction box or complex wiring by hand, greatly simplifying the instal-lation process and future maintenance. Electronics in newer systems can be housed within the laser welded stainless steel load cell enclosure.
Eliminating all junction boxes means fewer compo-nents that could be damaged through water ingress or lightning strike as well. Junction box removal reduces the number of connections in a vehicle scale by at least 25% compared to systems with junction boxes.
Junction box removal reduces the number of connec-tions in a vehicle scale by at least 25% compared to systems with junction boxes. Eliminating all junction boxes also means there are fewer components that could be damaged through water ingress or a light-ning strike.
A hermetically sealed ten load cell
network with no junction boxes
Double-Shielded Cables
Traditional load cell cables use a polyurethane jacket over the conductor wires. These cables are easily cut or damaged in rugged environments. Newer systems use stainless steel cables, which ideally are double-shielded. This prevents physical wear, rodent damage, electromagnetic interference, and also provide integral protection against lightning strikes.
Quick-Release Connectors
Rapid and secure connectivity is critical during routine maintenance. Quick-connect IP68 watertight load cell cables enhance connectivity and allow operators to get a scale back in service quickly. These watertight connector styles have been pioneered in the harshest military and medical applications where electronics performance can literally be a matter of life-and-death.
Breach Detection
In addition to heavy-duty, hermetically sealed enclo-sures, a built-in breach detection system can alert an operator to accidental load cell puncture or tampering. Even the smallest of holes can allow humidity into the load cell, which typically leads to weighing errors and failures. Unlike a conventional load cell, systems with built-in breach detection allow for identification and replacement of damaged components before moisture ingress causes real problems.
Lightning Strike Protection
A lightning strike can put a vehicle scale out of service in an instant. Even if a warranty or insurance policy covers repair costs, a manufacturer still faces the cost of business lost every day the scale is not operating during the logistics of a repair or replacement. This makes high-quality integrated lightning strike protec-tion a significant long-term value-added feature.
5 METTLER TOLEDO - White Paper - Reliable Vehicle Weighing
Real lightning damage prevention systems exist. Mod-ern lightning protection can shield an entire vehicle scale system including load cells, cables, and termi-nal. Internal on-board surge protectors redirect voltage surges away from sensitive electronics, creating a bar-rier of protection. Single-point grounding keeps scales up and running in circumstances where electrical damage would previously have knocked a scale out of operation.
The average lightning strike is 30k amperes, but can be higher. Ideally, a built-in lightning surge protection system should withstand up to a 40k amp surge, as tested by International Electrotechnical Commission IEC62305-1. Ideally, a built-in lightning surge protection sys-tem should withstand up to an 80k amp surge, as tested by International Electrotechnical Commission IEC62305-1.
Laboratory lightning testing
In a particularly high-volume situation, avoiding just one day of downtime can offset the cost of a new vehi-cle scale system. The elimination of unplanned service events can result in significant savings and productiv-ity increases that continue to add up over the life of a reliable, fully supported vehicle scale solution.
A METTLER TOLEDO weighing expert can help assess the real impact downtime is making on a company’s vehicle weighing system and suggest an appropriate alternative or existing scale modification. A modern upgrade should pay for itself in both low- and high-volume operations in less than 12 months – and sometimes in as few as one or two months.
4 Considering ROI
No matter how excellent in-plant operations are, pro-cessing gains can be lost when goods cannot flow into or out of a production facility due to unplanned truck scale downtime.
Truck scales face risks inherent to all weighing sys-tems, as well as unique risks such as water damage and lightning strikes because of their outdoor nature. A lightning strike can knock out an unprotected vehicle scale and water ingress can short out wiring in poorly sealed junction boxes.
Analog scales cannot alert operators to these issues. However, a fully digital scale equipped with micro-processor-based digital signal processing technology can:• assure proper operation• alert users to potential problems for quick interven-
tion• self-diagnose and correct for many issues• provide highly accurate weighing under a variety of
Please review the following resources for additional information on vehicle scale solutions.
• White Paper: Digital Compensation in POWERCELL Load Cells – www.mt.com/global/en/home/supportive_content/product_information.VEH_comp.twoColEd.html
• METTLER TOLEDO POWERCELL – www.mt.com/POWERCELL
6 Additional resources
Certain digital load cells also simplify installation and reduce failures because no junction boxes, analog-to-digital converter boxes, or gathering cards are required.
Physical design features such as hermetically sealed load cells, junction-box elimination, quick-release/rodent-proof connectors and cables, breach detection, and lightning strike protection can help ensure day-
in, day-out operation. These features, coupled with networked self-diagnostics can drastically increase reliability and longevity, while reducing overall mainte-nance requirements. Upgrading an existing vehicle scale with new ad-vanced weighing electronics can offer a rapid financial payback, thanks to greater uptime. A system that incorporates these important innovations can offer peace of mind when it comes to your truck scale.
