CPD Gas Piping Systems Design 2

Question 1

Polyethylene (PE) gas piping installed underground must be installed at a minimum depth below finished grade to provide adequate protection. What is the typical minimum cover depth required?

Accepted Answer

18 inches

Answer

NFPA 54 and most codes require a minimum burial depth of 18 inches for plastic gas piping installed in private property to protect against accidental damage from digging and frost.

Question 2

Which code is the primary model code governing the installation of natural gas and LP-gas piping systems in the United States?

Accepted Answer

NFPA 54 / ANSI Z223.1

Answer

NFPA 54, also known as ANSI Z223.1 National Fuel Gas Code, is the primary model standard governing fuel gas piping, equipment, and appliance installations in the US.

Question 3

Bonding of CSST (corrugated stainless steel tubing) gas piping is required primarily to protect against:

Accepted Answer

Lightning-induced electrical surges that can perforate the tubing

Answer

CSST must be bonded to the electrical grounding system because lightning-induced transient electrical surges can arc through the thin stainless steel wall, causing pinhole perforations and potential gas leaks.

Question 4

An appliance requiring a gas supply pressure of 7 in. w.c. is connected to a medium-pressure branch line operating at 5 psi. Which component must be installed to reduce pressure to the appliance?

Accepted Answer

A line pressure regulator

Answer

A line pressure regulator must be installed upstream of the appliance to reduce the medium distribution pressure (5 psi) to the low appliance inlet pressure (7 in. w.c.).

Question 5

When calculating the gas pipe size for a branch serving multiple appliances, the designer should use the:

Accepted Answer

Diversity-adjusted total load or the values from NFPA 54 sizing tables

Answer

Gas pipe branches are sized using either the diversity-adjusted connected load or the applicable sizing tables in NFPA 54, which account for pipe length, pressure drop, and specific gravity of the gas.

(CPD) Certified Plumbing Designer Practice Test

(CPD) Certified Plumbing Designer Practice Test

CPD Gas Piping Systems Design 2