Turbine Meters Vs PD meters

[psozot]

we used Smith Turbine meters for loading of Tank Truck. the product is Diesel. the piping network is such that one pump feeds multiple loading arms. we observe variation of about 60- 100 litres on filling of 24000 litres. will any one tell us solution for this. either meter are required to be replaced or the any thing else.

 

[TayJ]

Without any other information I would say to check the minimum flow rate for your turbine meter. This minimum flow rate can vary between 70-120 gpm depending on the size and type of turbine meter. Below this level the turbine meter will not measure accurately. If you have multiple loading arms being fed by the same pump you must be sure that either the pump is sized correctly to provide sufficient flow when all the loading arms it feeds are being used, or have your terminal automation system only allow the maximum number of arms to load at one time based upon what your pump is capable of providing. In short, check both your pump and meter specifications and be sure you are meeting the minimum flow requirements.

-Taylor

 

[jmw]

You might also comment on your batch control and shutdown sequences. As you near the end of batch you should part close the valve to restrict the flow for a more precise shut-off. Make sure this part flow condition is also within acceptable flow rates for the meters.
You may have a ramp down function for the end of batch rather than a simple stage closure of the shut off valve.
In either case if the flow conditions vary due to the load on the pump then many of the end of batch sequence settings may be affected. It all depends on how sophisticated or otherwise your batch controller is.
For example, the final close signal may be set to initiate as the batch reaches the end point or at a pre-set value before the end point to allow for a finite close time with a finite amount of fluid flowing during this final stage. Flow rate changes may affect this even if they are within the accurate range for the meter.

JMW

http://www.ViscoAnalyser.com

 

[zdas04]

100 liters in a 24,000 liter fill? That is 0.4% difference. For liquid turbine meters I generally see the total uncertainty around 0.75-1.00% so you are right in the middle of the dead band.

To do better you would have to go to a device with lower uncertainty. Maybe a truck scale?

David

 

[jmw]

Sorry, if you are saying you check weigh and find a difference between the metered readings and the load cells then zdas04 has a good point.
I interpreted you to mean that your meter readings varied by this amount i.e. batch set 24000 litres against batch delivered 23900-24100; in other words undershoot or overshoot errors in the batch control.
Many batch controllers have sophisticated shift down sequence control that compensates for closure time, was the point I was making, and variable f;low rates due to other demands on the pump will affect these settings.

JMW

http://www.ViscoAnalyser.com