Truck Scale Calibration Overview

Since 1980, Central Carolina Scale has been providing outstanding weighing equipment and scale repair service for our customers. Our truck scale calibration and inspection service is what our customers depend on to keep their scales accurate and dependable year round.

Most customers choose to have their truck scales checked and calibrated at several predetermined points during the year. We can customize your service based on your needs and requirements. And, by choosing this method of periodic scheduled service; the customer benefits by receiving priority scheduling, reduced labor rates, and discounted parts.

Before our factory trained, state certified scale technicians hit the road, they perform all mandated DOT vehicle inspections. Safety has always been a top priority.

Once our scale technician reaches the job site, the technician will notify the customer. Then the technician blocks off the scale to keep trucks from entering during the inspection and adjustment period. Keep in mind, Central Carolina Scale works with our customers truck traffic to be as accommodating as possible.

truck scale technician

BUILDUP UNDER THE TRUCK SCALE

The next step in a truck scale inspection is to inspect all critical components. Depending on the scale, the technician checks for buildup of dirt, sand, mud and debris underneath the scale. Dirt buildup under the scale platform is often one of the top reasons for scale inaccuracy.

If the scale has bumper bolts, the technician will examine these and adjust if necessary. It’s also a good time to look at any other areas that may need to be addressed periodically such as junction boxes, grounding, rubber t-grip molding, load cell caps, pit cleanliness and more depending on the type of scale. The technician also checks cabling, structural steel, and concrete approach pads.

scale calibration test truck

Next, the scale technician will drive the fully loaded test truck across the scale and check the sections for consistency and accuracy. Weights are recorded and used to assist with adjusting.

certified weight cart

Next, the technician unloads all the certified test weights into a specialized weight cart. This cart is also certified by the state weights and measures department and is traceable to NIST. Then, the technician checks each section of the motor truck scale.

When we mention the word “section” we’re referring to an area of weighbridge which bears on two supporting platform points. Once the section testing of the motor truck scale has been completed, the scale can be adjusted and calibrated if needed.

scale test truck on platform

The technician can once again drive across the sections with the fully loaded test truck which includes the certified weights and certified weight cart. The section weights and the overall weights should be consistent and accurate. The calibration and inspection is now complete.

The technician loads his vehicle and reopens the scale for traffic. Once the technician has moved off the scale and the scale has reopened, the technician completes all the necessary paperwork. The inspection detail report shows both the condition of the scale and components, as well as the as found and as left test results.

Central Carolina Scale has the factory trained technicians, certified test weights, and certified test carts to accurately and thoroughly check your vehicle scales. Give us a call today (919) 776-7737 and we can work with you to customize a service plan that will improve your accuracy and limit downtime.

Concrete Batching: NRMCA, Scale Company, and Calibration

In a concrete batching plant typically all of the ingredients that go into the concrete are measured by weight with certified digital scales. As you can imagine, those scales that are batching and mixing of concrete, need to be calibrated on a regular basis in order to maintain accurate weighing.

At Central Carolina Scale, we have checked and tested ready mixed concrete hopper scales for many years. Over all these years, concrete batching plant calibration procedures have evolved and we have also made changes to adapt to new guidelines and requirements. Whether it’s asphalt plant calibration or concrete batching, we have many years of experience repairing and calibrating these digital scale systems throughout central and eastern North Carolina.

While we don’t sell Command Alkon or Mettler Toledo indicators, we have worked on many systems that include those units. Popular instruments that we offer for sale include the Cardinal 205.

For concrete producers looking to achieve National Ready Mixed Concrete Association (NRMCA) Plant Certification, they need to adhere to the Guidance to Concrete Producers maintaining plant certification. This includes a list of Primary Requirements, Plant Inspector Guide and most importantly to us, the Scale Accuracy Verification guide.

Scale Accuracy Verification
There are some differences in what the scale companies are accustomed to doing in accordance with NIST Handbook 44 and what is required by the NRMCA plant certification and ASTM C94. Some of these differences are described in the Plant Inspector’s Guide.

Minimum quantity of test weights should be at 10% of scale capacity. Aggregate scale capacities will generally govern the minimum amount of test weights required – about 4000 lbs is typically needed. (There may be situations where the plant configuration does not permit the minimum test weights to be used and that has to be verified by the plant inspector).

Test weights should be certified to be accurate to 0.01% of their indicated load within the last two years. This is typically not a problem with commercial scale companies.

Scale checks should be done through range of use of the scales. Scale companies may only verify it through 50% of the scale capacity.

Up through 50% of the scale capacity, scale checks should be done using a build-up test load using a combination of product and test weights in a process called a substitution loading. Scale increments should not be skipped. In substitution loading, product in the scale should only be to the load previously verified – as close as possible.

Over 50% of the scale capacity, strain test loading is permitted. An unknown quantity of product is charged and the incremental weight indication with the test weights is verified. At least two points should be tested in this portion of the scale – through typical range of use.

Scale accuracy requirements (ASTM C94) is the greater of
● ±0.15% of scale capacity (governs at the lower end)
● ±0.4% of applied test load
● If it’s not accurate the scale has to be adjusted.

Maintenance tolerances in accordance with Handbook 44 are stated on the basis of scale divisions (min grad) but are generally more restrictive than those in C94 that state tolerances based on applied load or scale capacity.

A copy of the scale verification data sheets should be obtained to indicate details of the test loads used, test load increments, load indications and load error. A certificate just indicating a scale is OK is not acceptable.

Definitions of load testing, concrete batching plant calibration format, discussions and numerical examples of the scale accuracy verification are available in the NRMCA Plant Inspector Guide.

concrete batching scale calibration

Batching Plant Calibration Frequency

Accuracy checks of measuring devices (scales, water meters, admixture dispensers and moisture probes) should be performed at least once every 6 months.

State DOTs may have a requirement for these to be performed more frequently. The requirement with the greater frequency governs. Documentation of these verifications should be maintained and made available to the inspector during the plant inspection.

Also, scale accuracy should be verified anytime the plant is moved (portable plants), maintenance activities on the plant impact the weighing systems, or when there is a concern on scale accuracy determined from the batch man operating the batching process or the quality of concrete.

For customers throughout the central part of North Carolina, adhering to the NRMCA requirements can be accomplished with the help of the experienced service technicians of Central Carolina Scale located in Sanford, NC.

We have the trucks to handle these requirements and we have the large certified test weights (and small weights too) needed to accurately test your digital scales.

And we also stock a huge amount of replacement load cells, digital weight indicators, load cell cable, and other scale accessories to keep your batching plant up and going year round.

Contact our service department today (919) 776-7737 or fill out the RFQ button on our website for additional information.

Inspecting and Testing Heavy Duty Truck Scales

At Central Carolina Scale in addition to selling and installing truck scales; we also check, test, adjust, and calibrate truck scales just about every working day of the year. We have factory trained technicians who can troubleshoot even the smallest problem areas like a load cell that might be creeping. We also have certified test weights and a weight cart which allows us to provide the highest level of truck scale service available in North Carolina. When we’re finished doing our scale check, we supply the customer with documentation that shows before and after readings and how much weight we tested the scale with, etc…

However, in quite a few cases, where money changes hands based on scale weight, the state of North Carolina will also check the customer’s truck scale to make sure it is weighing correctly and performing within legal for trade tolerances. The blog post linked below is a field trip that describes a state test in more detail.

The Standards Division checks any scales where “money changes hands.” This would include scales at grocery stores, livestock scales, buffets, agricultural-supply centers, highway patrol weigh stations and scrap metal facilities. Scales are checked on an annual basis or by complaint. The only exception is stockyards, which are checked twice a year.

When consumers bring unwanted appliances, metal debris or even old vehicles to a scrap metal facility the items are generally weighed on a truck scale. At some facilities, this scale can record up to 100,000 pounds of weight. The entire weight of the vehicle, trailer and scrap metal is recorded on the scale. After unloading inside the facility, the consumer then drives the emptied vehicle and trailer back over a scale at the exit and this weight is recorded. The consumer is paid for the difference of the two weights. Depending on the amount of scrap brought in, the amount could be a couple of hundred dollars.
weight cart testing scales

To check a heavy truck scale, Inspector Glenn Farmer uses a six-wheeled, gas-powered, steel test cart. A hydraulic arm is used to fill the cart with certified 1,000-pound and 500-pound weights. For the test, he uses a known weight (the cart plus added weight) and test different quadrants of the scale. A five-section scale would have 18 different test points. There are two different types of truck scales, mechanical and load. To test a mechanical scale, Farmer must move his cart side to side to record weight. To check the accuracy of a load scale, he moves the cart down the center of the scale.

The Standards Division uses National Institute of Standards and Technology guidelines to determine tolerance levels on the scales. A tolerance level is the amount of weight a scale is allowed to vary. For a scale that can measure more than 25,000 pounds of weight, the tolerance level would be 60 pounds. A scale that does not pass inspection must be pulled out of service until the facility fixes the problem. “Many times the issue is debris buildup in the crevices of the scale,” Farmer said. “Pine straw, cans and other debris can cause the scale not to weigh correctly.

Our advice to the company is to power wash or use an air hose to clean the area around the scale.” If the scale is still recording incorrect weights after cleaning, the facility may call a scale calibration company to fix the problem. Some facilities will have a representative from their scale company go along with the standards inspector on the day of their inspection. This means that most problems can be fixed immediately, and the facility doesn’t have to endure a prolonged shutdown of a scale if problems are found.

This was a nice write up about testing scales and how important it is to keep your scales weighing accurately. It’s always a good idea to keep your scales clean and weighing as accurate as possible, year round. One easy way to do that is to contact us at (919) 776-7737 and set up a maintenance schedule for your scales. You’ll save money and you will have accurate scales with the regular scale checks.

Save Thousands of Dollars By Just Having Your Truck Scale Calibrated Regularly

Over time, truck scale accuracy can change due to a variety of issues, mostly usage and wear and tear. When you’re looking at a truck scale, accuracy is very important to your business because the value of the product you are transporting affects your bottom line and correlates to the weight you see displayed on the scale indicator. It can also be a safety concern as well, since truck weights must be in compliance with federal safety regulations.

truck scale calibration

You might think that a small issue doesn’t mean too much but the truth is that just small inaccuracies on a truck scale that is used regularly can accumulate to large costs for your company over time.

See the example below.

WEIGHMENTS PER DAY: 100
SCALE ERROR: 10 LB
PRICE PER POUND OF YOUR PRODUCT: $0.50
DAILY LOSS: $500
YEARLY LOSS: $150,000

As you can see from the example above, small errors can add up very quickly.

So, you might be thinking, but my scale was calibrated when it was installed, I should be good, right?

Well, the initial installation, does not guarantee continued accuracy. When a truck scale is first installed, it is tested by the scale company and the state weights and measures, both using certified test weights. This is done to ensure the scale’s accuracy as well protect the scale buyer, seller, and the scale installation company. At this point, the scale is certified and ready for everyday use.

However, the scale will need to be checked and adjusted at least a couple of times a year at a minimum. As you can see from the example above, just a few pounds of errors can cost your company a lot of money.

It’s important to remember, scale calibration does not lock in forever. It is dependent on several factors such as frequency of use, weather, gravity, electrical currents etc…. can throw off the accuracy of a measurement device.

The main point of this article is this. A truck scale should be periodically tested and adjusted if necessary. A commercial scale company, like Central Carolina Scale can check your truck scale on a regular basis or if you currently have a scale that has been “tagged out” by the state of North Carolina, CCS can check, test, and adjust your scale and get it back to weighing accurately. Give the service department a call at (919) 776-7737.

Regular Scale Maintenance & Calibration Can Increase Accuracy & Reduce Downtime

We’ve been checking, testing and adjusting scales for a long time. And over the years of calibrating scales you learn a few things and pick up on a few nuggets of wisdom regarding scales and how to keep them working year round. Scales are precision instruments that need to be maintained on a fairly regular basis in order to ensure accuracy and reliability. Your scale accuracy can influence your profitability greatly. There are lots of examples, everything from ingredients used in a recipe for batching to recycling metal or aluminum. Every ounce counts and a scale that isn’t accurate can cost you, or your customer. Of course, if your scale breaks down, you’re going to be down for potentially several hours depending on the service and replacement parts needed. The bottom line is, Scales are important and need to be maintained.

Regular service and calibration from a factory trained service technician is important. We have seen examples in the past where companies realized that they need regular maintenance on their scales, but to save money they would choose a different company who didn’t have factory training on the actual scales the company owned. As fate would have it, the scale broke and their technician spent large amounts of time trying to troubleshoot the problem, which was difficult since he didn’t have factory training on this particular brand. CCS was contacted and the scale was repaired and working within a couple of hours.

scale technician calibrating a gse digital weight indicator

Another example is a company who buys/sells based on the weight of items loaded on their trucks. With most truck scales we recommend at least a semi-annual check and calibration but the customer felt the costs were not worthwhile for their business and they wanted to go with a call as needed model. Over the course of the year they noticed that their truck weights seemed to be off, so they called CCS to check and calibrate their truck scales. Their scales were off by several graduations and the customer had been losing what turned out to be hundreds of dollars in profits per truck over the past several weeks. At that point, the customer was very interested in discussing a quarterly scale check and calibration. Continue reading

Weight Tolerances

Recently, I was informed of a situation that involved a digital infant scale and a “test weight” also known as a 5 pound consumer barbell weight. Apparently, the barbell weight was used to check the digital scale and it was thought that the scale had not been calibrated correctly due to a scale readout of 5.2 lbs.

Actually, consumer barbell weights like those used in the above scenario are manufactured to tolerances between +/-1% and +/-7%, a significant range of tolerance as compared to NIST certified test weights. Using a consumer barbell weight with a wider manufacturing accepted tolerance than the scale may result in a scale display reading that seems inaccurate. A +/-5% tolerance on a 5 pound consumer barbell weight means the weight can weigh from 4.75 lb to 5.25 lb and still be sold as a 5 pound weight. Compare that to a 5 pound NIST Class F weight which is manufactured and adjusted to within +/-230 mg tolerance. In the example above, the user contesting the calibration accuracy of the digital scale checked their consumer barbell weight again, this time on a certified Legal for Trade scale and found that it weighed 5.2 pounds, meaning the digital scale was correct.

We recommend using NIST certified Class F Sealed manufactured test weights in most applications to check or calibrate medical scales and industrial scales.

Truck Scale Spring Maintenance Is Important!

Summer will be here before you know it and if you haven’t had your truck scale tested and inspected lately now is the time. The changing of the seasons brings us warm weather, but it also brings running water to truck scale pits and foundations. If left unmaintained, the mud and debris can wreak havoc on truck scale operations and accuracy. We recommend completing the following steps to ensure your scale is up and running in time for the busy summer season. You, the scale owner, can actually do quite a few of the steps below.

Take a walk around the perimeter of your scale. Examine the entire deck, scale pit, foundation and approaches for any major structural or surface problems. If you see any foundation deterioration be sure to fix it right away. Any deck and approach repair is not merely cosmetic; those issues can have a negative effect on the scales performance. Flaking rust and crumbling concrete falling into the pit will add maintenance costs now, but in the future they will reduce the scales’ usefulness.

We’ve been servicing truck scales for a long time and the most common cause of incorrect weighments is debris under the scale (or in the pit) binding movement. Clean all dirt from each component. Remember, even though most scales these days are electronic, they still have moving parts underneath. Load cells still need to be able to deflect through their capacity range.

To cut down on any future debris problems, it’s a good idea to invest in flexible T-Grip or T-Strip rubber molding. These moldings, while being flexible enough to work with the movement of the scale, will keep debris from causing problems and eventual damage to the scale. Depending on the scale design, the molding might only be necessary to cover the end gaps where the trucks enter and exit the scale. Scales weighing open trucks or messy operations will also need side molding to protect against spillage falling into the pit. Continue reading

Scale Calibration Frequency: How Often Should I Calibrate my Digital Scale?

We’ve actually covered the subject of how often to calibrate a scale before but it’s always a good idea to remind customers just how important the accuracy of their scales can be. We get this question fairly often so today with the help of Doran Scales we’ll take another look at why it’s important to have your scales calibrated on a regular basis by a trained scale technician.

What is the value of the product to be weighed on the scale?
If the product being weighed is very expensive, there is value in regular and periodic inspection and calibration. For example if the product costs $10 a pound and on an average day 1,000 pounds of product is weighed on the scale, the total value is $10,000. Let’s assume the scale is out of tolerance by 0.5%; that discrepancy would be $50 per day, $250 per week, and $1,000 per month. Obviously, eliminating this error would save a tremendous amount of money and more than pay for the calibration services.

Is it a legal-for-trade application?
If you buy or sell product based upon weight using your scale, it will need to be inspected and certified by the State or local Weights and Measures Department at the time of or shortly after installation. If a scale is tested and found to be out of tolerance or if products in the field are found to not meet the stated weight, Weights and Measure can condemn the scales so that they cannot be used until recalibrated, and literally shut your production down.

How many weighments per day and at what % of scale capacity?
Generally speaking, with time and use scales can start to lose accuracy. It may be a tiny error but over months and years it can grow to unacceptable levels. Think of it in these terms: when you buy a new car, you can expect that the wheel alignment will be exactly accurate. When this same car has 75,000 or 100,000 miles on it, the wheel alignment may need to be adjusted due to normal wear and tear. The same idea is true with your scale. Regular calibration of heavily used scales will correct any accuracy errors that will normally occur with this type of use.

Are the scales frequently moved around in your facility or from one location to another?
Doran scales are designed to be portable, in the sense that they do not require a permanent installation location. However, many times when scales are moved, they are handled incorrectly, resulting in damage that can affect the calibration and accuracy of the unit. If your scales are constantly being moved around in your facility or moved from one location to another, regular calibration will help keep them accurate and reveal any damage that may have occurred when they have been moved.

Continue reading

Wrestling Scale Certification

Each year customers at middle school, high schools, and colleges contact our scale company looking to purchase certified digital scales to use for their wrestling team or sometimes they just simply want to get their old scale checked and certified. Most of the time the process is pretty simple. However, occasionally the customer is not certain about what rules or regulations they need to follow to weigh a wrestler. So, before you purchase a scale or have one certified, it might be a good idea to check with your athletic conference or sanctioning body or perhaps you have some type of “rule book” to make certain what rules you need to follow. For example, one rule that we have been told is that some states require schools to use a NTEP legal for trade scale (with CoC#) for weighing wrestlers.

certified wrestling scaleWhen it comes to actually certifying the scales, it is usually a good idea to get your wrestling scale certified annually. Generally, when we calibrate and certify the scale we normally look over the scale and make sure it appears to be functioning correctly. If something appears broken or missing such as a leveling foot, we might mention that on the paperwork or even recommend you purchase a replacement. We make sure the display is working correctly and showing all the digits and decimal point correctly. We also like to make sure the platform is solid. Also, if your scale has a rechargeable battery inside you might want to try charging it up and using it a few days before your scale check up to make sure it’s Continue reading

Do you carry any other type, that are less…

We were recently invited to provide a written quote on a 5’x5′ floor scale at a metal recycling center in North Carolina. When we sent the customer a quote for a quality set of floor scales, he replied back with the statement.

Do you carry any other type, that are less. In other words (brand x) scales are around 500.00 and I told (co-worker) that we could buy almost 3 for the price of 1 and if one breaks down we would have a back up.

Of course our first comment would be, it might be a good idea to buy two or three of them so you have a system that works! Seriously, if you’ve read any of our blog posts in the past, then you know our philosophy when it comes to floor scale systems. You can always find a set of scales at a cheaper price. Lets face it, in today’s world doesn’t that almost apply to just about any product? There is always somebody down the street willing to sell something a little cheaper. And often times if they can import a bunch of junk that has serious QC issues and sell them to unsuspecting customers who are simply looking to get a good deal, then that is what they will do.

That is why we focus on providing you a set of platform scales that we have confidence in.  The other note worth mentioning is the scale he was “comparing” our scale to wasn’t even legal for trade. The main point of this entry is, give us a call or send us an email and we can provide you with a quote for a weighing scale that we feel will meet your needs. If you have a budgeted price in mind, be sure to let us know that too. Often times when something costs a lot less than other similar products, there is a reason.