Sunday 11th Apr, 2021

Realising safer, faster, and more accurate tank scale calibration

Manually calibrating large tanks is often difficult and has the potential to put workers at risk. That’s why Mettler-Toledo Ltd has developed a cost-effective, fast and reliable calibration method.


Tanks, hoppers and related vessels are likely critical tools in a bulk handling operation. Turning these workhorses into active scales can significantly improve inventory management, filling, batching and mixing. These weight-based process solutions can be particularly attractive for operations that require higher dispensing accuracy.

But according to Jim Lambros, Standard Industrial Product Manager (Australia and New Zealand) at Mettler-Toledo Ltd, historically the effort to calibrate a large tank scale has been nothing short of Herculean.

“From gathering a series of heavy test-weights to substituting vessel contents, the process can risk both worker safety and tank contamination,” Lambros says.

“To add insult to injury, the purified water used in the process must be disposed of properly, resulting in waste-handling fees. Plus, a tank can be out of commission for days.

“Factors such as these have historically caused plant managers to put off calibration for tank scales as long as possible – sometimes to the detriment of product quality or even worker safety. But not anymore.”

A new method of tank-scale calibration, known as RapidCal, is replacing traditional calibration methods around the world.

Created by Mettler-Toledo Ltd, RapidCal offers an economical tank-scale calibration method that uses no test weights and eliminates the expensive and risky process of material substitution. The process has provided stability to a producer of bulk materials used in agribusiness and chemicals, which formerly used hectic calibration exercises.

Based on a consultation with Mettler-Toledo Ltd specialists, the company installed the anchor points required to perform the innovative calibration on 25 pre-selected tanks. Today, the complete calibration service for all these tank scales is performed using RapidCal, reducing a process that used to take more than 30 hours per tank to just two.

Lambros says that even without doing the detailed math, it’s clear this development has significantly reduced the amount of time each scale is offline, resulting in productivity improvements that cover the costs of calibration activities – and then some.

“The company has also been able to fully outsource the calibration procedure while ensuring traceability. Plant management no longer contemplates skipping calibration activities,” Lambros says.

“The result is higher product quality and more accurate shipments. And, because the RapidCal process is standardised, the company is looking to expand use of this highly effective technology to its other major processing centres.”

RapidCal works by applying downward force using hydraulics attached to the outside of the tank and the load cell, eliminating the need to transport heavy test weights or go through the expensive process of draining and cleaning tanks for material substitution. It has been developed through years of applied experience in metrology and weighing that Mettler-Toledo Ltd gained through serving the bulk materials market.

Calibrations are accurate to 0.1 per cent for vessels ranging from one to 32 tonnes. Process traceability to both internal and external quality standards is assured by Mettler-Toledo Ltd technology and service technicians. Piping effects are automatically compensated for as well. Regular recalibrations are included as part of the quality system established for the producer.

Lambros says that because of the sheer volumes most bulk material handlers deal with, management may delay improvements because current system limitations are known, understood, and compensated for.

“However, in cases such as RapidCal when relatively straightforward activities can yield significant improvements in accuracy, uptime and productivity, any risk is almost certainly outweighed by the potential benefits,” Lambros said.

“Overall, the partnership between internal personnel, the company’s third-party engineering firm, and Mettler-Toledo Ltd’s metrology experts has added up to much more than the sum of each individual part.

“The end result? A calibration process that has improved worker safety, reduced downtime, and enhanced process quality far beyond what management originally thought possible in an almost textbook definition of true process improvement.”