A Weighty Problem

In today's recycling and solid waste industry, uptime is of utmost importance. Many facilities experience long lines at the weighing scale, and so they place a premium on getting trucks in and out quickly. However, have you ever stopped to think about how much you could be losing per truck? by Mike Wilkinson When a waste or recycling facility places a scale into service the manufacturer will have assured the customer that it is capable of holding to accurate tolerances. Further to this, in the U.S. the State Weights & Measures Department will certify that it meets the necessary regulatory requirements. However, external variables and real-world issues can knock the scale out of calibration, potentially costing the facility a lot of money. A simple error of one 20 pound (9kg) increment can lead to $30,000 in annual product loss! This is a real example and is based on a product with a value of $0.05 per pound and a duty cycle of 100 weighings per day. There is no better reason to implement the following best practices. CALIBRATION & INSPECTION AGREEMENT The simplest step is to implement a calibration and inspection agreement with the service provider. Depending on the requirements and type of weighing device, inspection costs can be as low as $500 annually, depending on the frequency required to assure accurate weighing and to reduce the risk of loss due to an inaccurate scales. Compared to the potential losses this is a worthwhile investment. But how often should a scale be inspected? For most scales a minimum of two inspections per year is recommended, but the sort of heavy traffic which waste and recycling and solid waste facilities experience can easily justify more frequent verification, inspection, and service. However, to determine the optimum inspection schedule it is important to consult the service provider. And what should you look for in a service provider? Investigate the longevity of the company. How long have they been in business? Do they know the industry? Do they have solutions for the challenges that your business faces? Another good check point is to compare the services provided among service providers. The number one priority is to make sure the scale is accurate by testing with certified weights that are traceable to a Federal standard. The servicing company should be able to produce documentation of the test weights' traceability. The electronic and mechanical components should also be inspected to ensure there is no wear or issues looming that could result in inaccuracies or unexpected downtime. After inspection it is important that the service company provides a written evaluation of the inspection and reviews the condition with the customer. This is by far the simplest and most economical way to avoid inaccuracies and unexpected downtime. KEEP THE FOUNDATION CLEAN Recycling and solid waste operations can generate a lot of debris. Be sure to regularly remove the build-up to avoid scale inaccuracies. A pressure sprayer is a fast and easy way to clear debris and keep the scale and foundation free of build-up. However, be sure that the junction boxes, electronics, and load cells are properly rated to withstand pressure washing - otherwise you may cause damage. PERFORM YOUR OWN INSPECTION Inspect for anomalies. A properly operating scale is dependent on every component working together. Inspect the weighbridge for damage or signs of wear and corrosion. Examine the junction boxes inside and out. Do they show signs of damage, corrosion, or moisture entry? Module connection hardware should be intact and not damaged Check the load cells for damage, corrosion, and signs of moisture entry into the enclosure and the cable entry gland. Liquid is a good conductor and can easily short the electronics if allowed to enter the sensing element area Some manufacturers feature quick disconnect style load cell cables. Be sure to inspect these connections frequently as they are responsible for a significant number of avoidable failures This is also a good time to inspect the wiring for damage. Exposed conductors cause communication errors when wet and are usually the culprit of erratic performance Your scale's paint system isn't just for good looks. It's a critical barrier against scale corrosion on the weighbridge steel. Be sure to reapply if you expect maximum life from the weighbridge steel If your scale has cover plates, inspect the connection hardware and make sure they are there, functional, and are not packed with mud and debris Grease the load cell cups at recommended intervals. Some manufacturers incorporate zerk type fittings allowing grease application without the need to physically separate the load cell components Inspect concrete for signs of failure. Address these issues as soon as possible. Left unchecked, they will only get worse and will cause larger-and more costly-problems. MAKE ADJUSTMENTS Weighbridges expand and contract slightly at different times of the year. This is natural. thermal expansion requires attention and readjustments. The checking system keeps the weighbridge in place as it naturally rocks and moves from traffic. Too small a gap in the checking can cause binding and weighing errors. Too much gap in the allows excessive movement, up to and including a scale tipping, as wekk as unnecessary wear to other components. It is vital to ensure that the scale is accurate by testing with certified weights KEEP YOUR SCALE GROUNDED Today's truck scales use sophisticated electronics. A securely grounded scale is a basic defense from lightning and power surges. Be sure that the scale is connected to the manufacturer's specified grounding system and that there are no interruptions in this system Transient voltage seeks the easiest path to ground. If your scale isn't grounded through a ground rod connection, it surely is grounded through other components. Disrupting the ground connection shunts power surges to other places, such as load cells and electronics. Damaged here will cost thousands to repair Also, keep in mind that while the scale is designed to move slightly with traffic, abusive and aggressive entrance and exiting of traffic accelerates wear. Again, taxing the scale means more wear and more dollars spent in repairs. ACCESSORIES Many scale manufacturers offer accessories to promote traffic discipline while entering and exiting your scale. Traffic signals and guide post kits help can manage traffic flow and truck speed very effectively for a small investment. Other accessories developed from real-world experience can also help to prevent issues and selecting the right ones can pay dividends. Riser plates elevate the weighbridge, reducing the risk of debris accumulation and providing clearance for cleaning and inspection. Another useful accessory can be load cell boots. Exposed to debris, weather, moisture, and even product that has migrated below the deck, the load cells operate in the worst environment possible. Load cell boots act like a protective glove and prevent debris from accumulating. Steel and EPDM rubber belting accessories can also help keep things clean. At each end of the scale there is a small gap between the scale and foundation. This gap is a great place for dirt, debris and product to fall under the scale and accumulate. Installing T-belting along this gap between the scale and foundation wall is a good step to preventing this accumulation. CONCLUSION You may be thinking: "These steps sound great, but I just don't have the time for my scale to be out of service six times a year." This is entirely understandable. To keep your inspections frequent without too much downtime, consider switching to a digital scale. A typical scale has eight to 10 load cells. If it's an analog setup, it could take four to six hours to calibrate the scale correctly. Whereas with a digital system, we can see the performance of each individual load cell on the instrument screen. With that ease of access, you're talking minutes to half an hour for recalibration." In the end, how you implement these best practices is up to you. You can partner with a qualified service provider to manage these tasks, or you can go it alone. One thing is certain - neglecting your scale costs you profit. Mike Wilkinson is heavy capacity product manager at Fairbanks Scales