The most reliable way is by live load test. In some places such a test is very simple, such as straight off the back of a truck onto the conveyor. In other plants, it is impossible to perform a live load test.

When you cannot do a live load test, you have to use engineering assessments of the quality of the weighing system.

If you want to send me some details I can do some calculations for you. ■

Dear Sir,

We have introdued check weighing system in TATA STEEL PLANT, Jamshedpur for checking the accuracy of belt scale.

Regards.

A.Banerjee ■

Dear Mr. Rekhawar,

The system in TATA STEEL is that weigh feeder draws the material from the bin & fed the same to a conveyor provided with belt scale. We took a taping from the same conveyor for feeding the material into a bin (know capacity) mounted on calibrated load-cell.

Regards.

A.Banerjee ■

We used to calibrate by using roller chains as known load on the idler frame. This was done on belt weighers mounted on inclined as well as horizontal conveyors. ■

Dear Mr. Vinayak,

That is for calibartion of load -cell.. After calibration how one can check the result given by belt scale is in order?

Regards.

A.Banerjee ■

Dear Mr.Banerjee

With out droptest, the belt weigher is possible to cross check by using the chain weight or per meter material sample.

ensure the practical belt speed m/s.

If your are using chain weight cross calculate the per meter weight of chain. with respect to measuring zone distance, Calculate the effective load on the load cell in the form of Kg/m.

Based on these two reference (Kg/m & m/s) calculate the TPH, then compare the calculated TPH with indication TPH on the weigh scale.

Then u calculate the error and compensate the same with possible available methods.

Regards

S.Ethiraj ■

Dear Sir,

The only way to assertain the accuracy of the belt scale is by Drop test. Merrick has conducted a detailed study and arrived at the following conclusion:

Material test is the only best way.

Second best is Chain test. The difference between Chain test and Material test is around 3-5%.

Third & crude test ( Calibration of only Load Cells) is using the test weights. The difference between Tast weight calibration & material test may vary from 5-10%.

Only to check the repeatability one may use the following formula:

Tonnes/ Revolution = Belt Load X Belt Length / 1000.

Sundar ■

Dear Mr Sundar,

may i ask what are the acceptable errors on a belt weigher based on the numbers you have mentioned? we are using a weightometer on a conveyor belt for weighing our ores.

and how about acceptable errors on a belt when weighing cu/zn concentrates?

thanks in advance

andrew ■