- #1
intoodeep
- 5
- 0
Hello,
I am hoping someone can set me straight on the following.
Situation:
At one of our power stations, we have a single conveyor which transfers coal from the mine to the power station. This single conveyor travels across two belt weighers mounted approx 5 metres apart. Both are the same model and made and installed by same OEM. Except one is a class 1 ±0.5% and the other is a class 0.5 ±0.25%.
In an effort to try and keep track of what they are doing, I constructed a graph in excel to plot their daily measurements. As I do not know the actual weight of the coal passed across them, except that the same amount goes across both each day. All I have at the end of each day is a measurement from each weigher representing what each weigher claims has passed over it during the day. I determine the difference between the two measurements and covert it to a percentage against one of them. In the ideal world, if both weighers were measuring accurately, both readings would be the same. But given the allowable tolerance of each weigher, in my mind the maximum allowable difference would be ±0.75%, if one was on its upper limit and the other on its lower.
But the thermal performance engineer I work with is telling me that the maximum allowable tolerance is ±0.56%, based on the following √(0.5^2+0.25^2)
Based on what I have read regarding the adding of tolerance/uncertainty, this situation does not fit any example given.
Am I missing something?
Any thoughts most appreciated.
Thank you
I am hoping someone can set me straight on the following.
Situation:
At one of our power stations, we have a single conveyor which transfers coal from the mine to the power station. This single conveyor travels across two belt weighers mounted approx 5 metres apart. Both are the same model and made and installed by same OEM. Except one is a class 1 ±0.5% and the other is a class 0.5 ±0.25%.
In an effort to try and keep track of what they are doing, I constructed a graph in excel to plot their daily measurements. As I do not know the actual weight of the coal passed across them, except that the same amount goes across both each day. All I have at the end of each day is a measurement from each weigher representing what each weigher claims has passed over it during the day. I determine the difference between the two measurements and covert it to a percentage against one of them. In the ideal world, if both weighers were measuring accurately, both readings would be the same. But given the allowable tolerance of each weigher, in my mind the maximum allowable difference would be ±0.75%, if one was on its upper limit and the other on its lower.
But the thermal performance engineer I work with is telling me that the maximum allowable tolerance is ±0.56%, based on the following √(0.5^2+0.25^2)
Based on what I have read regarding the adding of tolerance/uncertainty, this situation does not fit any example given.
Am I missing something?
Any thoughts most appreciated.
Thank you