Purge flow meters & regulators

[MarkTX]

I have a number of questions, any comments are appreciated.
I am working with a heavy oil pitch wedge meter with extended diaphragm d/p meter. The system is setup with a purge oil. First I would think if I am using a purge then I don't need the diaphram type pads. But I think this happened because all the wedge meters come with this type of setup. The heavy pitch runs around 300 deg F. On second thought the pitch gets hard at lower temperatures so maybe the purge is still neeeded.
I am haveing trouble regulating the purge. It has the standard inlet flow regulator (W&T) with a armored flow indicator. I am wondering if the constant flow regulator is installed on the wrong side of the purge flow indicator. It is installed on the upstream side. The salesman I spoke with tells me if the upstream pressure varies it should be installed upstream, if the down stream pressure varies it should be on the outlet of the purge meter. Any comments on this, and second, the purge regulator is setup for 1 gpm. Is this considered a lot of flow or not. The wedge meter is a 6", the discharge of the pitch pump is around 225 psig.
Thank you,
Mark

 

[Assumptions]

Purging.
To obtain a constant flow one requires a flow measurement or at least an index of flow. Next a means of regulating the flow to bring the flow or index back to that required.
Normally how this is achieved is a manual valve or restrictor, a differential pressure measurement across the restriction and a regulator using the D/P across the restriction as the manipulated variable.
The rotameter is an additional device so that one may know what the purge rate is.
From your description it seems that you may have a pressure regulator and not a D/P regulator?
As to the quantity of purge fluid required I would suggest a trial and error method to find a suitable operating point starting at the specified value and slightly decreasing the purge rate, if that is acceptable to operations.

 

[ICman]

I haven't had good luck with wedgemeters (gas), but you are introducing another unknown (purge flow) into your measurement.

I used ultrasonic flowmeters to measure asphalt once - they worked great! No line restrictions, no purging, accurate.

Just a suggestion.