Because pumps and control valves have specified features and uses, it is essential to install flow instruments where the design data recommends. By doing so, you can be confident that your readings will be both reliable and accurate
However, it’s important to keep in mind that many different factors affect an instrument’s accuracy and precision. In this article, we will explore these in greater detail.
Accuracy, and Precision
The accuracy of a measurement is gauged by the difference between the actual value and what is read. For example, if a pump has an accuracy of 0.5 per cent, that means the actual value is 0.5 higher than the reading itself. On the other hand, precision measures how close two readings taken under identical conditions are to each other. Returning to our example, if a pump has a precision rate of 0.5 per cent, this would mean there’s only a 0.005 margin for error between both measurements.
Resolution refers to the slightest change in a measurement that can be detected. You calculate resolution by multiplying the measurement’s standard deviation times 3. So, for instance, if a measure has a resolute of 0.01 per cent, then this means that you could detect any changes within 0.03%
A pump with a resolution of 0.05 can detect changes in the flow as small as 0.005. In other words, if 1.00 is the reading before the adjustment, 0.98 would be the limit of accuracy, and 0.97 would represent the limit of precision.
Placement of Instruments for Measurement
The pump curve provides specific information about a pump’s discharge properties, including its pressure-flow relationship.
You will use a tangent to the pump curve to more accurately reflect pressure losses throughout the system. This is because pressure losses are not based on speed like most people think; however, they are actually independent of it. The line representing pressure loss will show the true head values for every part of the suction and discharge pipes as well as the valves located in both sections. By getting rid of these myths about pumps, you can improve your knowledge so that you’re able to make smart decisions regarding future projects.
Operational head is usually given in feet of water and this represents the difference between the total head and the losses in pipelines and valves. These losses are often stated as being X amount of feet in a certain measurement such as metres or centimetres. To calculate the lost fluid volume, you need to multiply specific gravity by the loss rate per foot.
The labels on most curves are arranged in a line of text that goes from left to right. Each label is associated with a particular pump setting and another specific metre setting.
A pump curve shows the pressure-discharge relationship for a pump. You can determine the flow rate of discharge at every point along the curve.
The head loss of a pipe system is affected by many things, like the flow rate and specific gravity of the fluid running through it. You can calculate the head loss in feet by multiplying the number of feet that fluid will travel with its specific gravity.
If you understand how a pump works and what its performance capabilities are, you can optimise its use to get the results you want.