C = discharge coefficient, dimensionless
A = discharge hole cross-sectional area, m²
k = cp/cv of the gas
ρ = real gas density at P and T, kg/m³
P = absolute upstream pressure of the gas, Pa.
A: ISO 5167, Part 3, is the international standard for orifice plates. It can be found at http://tinyurl.com/4w3s23o.
Q: I would like to know if a new version of ANSI/ISA - 5.01.01, containing the primary element symbols that are shown in 4th edition of Volume 1 of the Instrument Engineers’ Handbook, on page 24, is already available.
A: ISA 5.1 was released in the fall of 2009.
A: No, the 5th edition of the Instrument Engineers’ Handbook has not been published yet. The 2009 edition of ISA’s "Instrument Symbols and Identification" (ANSI/ISA-5.1-2009) is available and costs $120 to ISA members and $145 to non-members. It can be ordered at http://tinyurl.com/4aytp8j. The minor changes that have been made to flow symbols in the 2009 edition are described in Mr. Jamieson’s answer.
A: I was the co-author of Chapter 1.1 of the IEH with Alberto Rohr, and also have been active on the ISA-5.1 subcommittee for Instrumentation Symbols and Identification for more than 10 years. It took many years to get the latest version approved (ANSI/ISA-5.1-2009).
As to changes made in the 2009 edition concerning the primary flow element symbols, we now have 31 instead of 22 in the previous edition. One difference is that the connecting pipeline symbols in and out of the flow element are not shown. As to changes to the previous 22 symbols, only two minor changes were made. One change involves the sonic flowmeters, which in the 2009 issue are shown as a rectangle with a single vertical backwards "S" inside it. The other change is in the symbol for variable area flowmeters, which now is a vertical rectangle with a "float" symbol inside it.
The rest of the flow symbols in the 4th edition of the IEH are correct, except that some have a second or alternate symbol in the ANSI/ISA-5.1-2009 version.
J.E. (Jim) Jamison, P.Eng., PE