Which statement describes the longest length sizing method?

Which statement describes the longest length sizing method?

• A. It uses the longest piping run to determine pressure drop
• B. It uses the smallest pipe diameter
• C. It uses the fastest flow rate
• D. It ignores fittings

Answer: (A)

The longest length sizing method designs for the worst-case pressure drop by using the longest run of piping from the gas source to the farthest appliance as the basis for sizing. By focusing on the longest path, you account for the maximum friction loss the system could experience, so the pipe size is chosen to maintain the required pressure at the most distant point. This ensures every appliance along the run receives adequate gas pressure, not just the ones closer to the supply. Fittings aren’t ignored in this approach; their impact is included by converting them into an equivalent length that adds to the total length and pressure drop. The method isn’t about using the smallest diameter or about choosing the fastest flow rate; those aren’t defining features of this sizing approach.

The longest length sizing method designs for the worst-case pressure drop by using the longest run of piping from the gas source to the farthest appliance as the basis for sizing. By focusing on the longest path, you account for the maximum friction loss the system could experience, so the pipe size is chosen to maintain the required pressure at the most distant point. This ensures every appliance along the run receives adequate gas pressure, not just the ones closer to the supply.

Fittings aren’t ignored in this approach; their impact is included by converting them into an equivalent length that adds to the total length and pressure drop. The method isn’t about using the smallest diameter or about choosing the fastest flow rate; those aren’t defining features of this sizing approach.