Gas Meters: 2017 #40

A gas meter orifice:
(A) Typically has less than 10% of an effect...
(B) Should be installed with the beveled edge upstream. 
(C) Should be installed with the sharp edge downstream. 
(D) Typically has less than 20% of an effect...

The Guidebook (8 FAC 3 & 4) states gas orifice plates are installed with beveled edge downstream. So we know B & C are false.

The same page also says an orifice installed backwards reads about 15% low. So we know A is false.

Finally, since we know backwards is the greatest error it can have due to orientation (15%), D must be true.

Metering: 2017 #5

Gas metering problem; four scenarios are given: 1) orifice plate installed backwards, 2) plate leading edge worn, or 3 & 4) flow computer orifice entry too large/small.

The first situation is described on 8 FAC 3 & 4 (negative bias). This infers the answer to the second situation (worn leading edge is then a negative bias). So the only remaining question: does a larger or smaller computer entry for the orifice provide a positive bias on flow?

The answer: a larger value entered for the orifice ID gives a positive bias to flow. You can see this from the Guidebook's Fb table; a larger orifice ID has a larger Fb constant thus giving a larger q.

Yet be ready for pipe diameter computer entry errors as well. Unlike orifice diameter this has an inverse effect on Fb and thus q (again, this can be seen from the Guidebook table). So be careful when reading the wording of the question.

Metering: 2005 #60 (similar)

Gas metering? Lots of word problem potential.
Guidebook notes on metering are on 8 FAC 3-4:

1) Flange taps are 1" on either side of the plate.
2) Pipe taps location to plate: 2.5 and 8 pipe diameters upstream & downstream
3) 27.67 inches of H20 is 1 psi
4) Gas orifice plates are installed with beveled edge upstream downstream.