CPD Gas Piping Systems Design

Question 1

According to NFPA 54, what is the minimum required distance between an above-grade outdoor gas meter and a source of ignition such as an electrical panel?

Accepted Answer

3 feet

Answer

5 feet

Answer

10 feet

Answer

15 feet

Question 2

A sediment trap (drip leg) installed in a gas supply line should be located:

Accepted Answer

Downstream of the appliance shut-off valve, immediately upstream of the appliance inlet

Answer

Upstream of the gas meter at the service entrance

Answer

At every change in pipe direction throughout the distribution system

Answer

Only on high-pressure gas lines above 2 psi

Question 3

When sizing a natural gas piping system, the designer must account for the total connected load in BTU/hr. Which method is commonly used when diversity of gas usage is expected in a large system?

Accepted Answer

Diversity factor method applying a usage factor less than 1.0

Answer

Maximum demand method using 100% of all connected appliances

Answer

Pressure drop method based only on peak single-appliance load

Answer

Static pressure method ignoring flow velocity

Question 4

What is the maximum allowable pressure drop permitted in a low-pressure natural gas distribution system (under 2 psi) supplying residential and light commercial appliances, per NFPA 54?

Accepted Answer

1.0 in. w.c.

Answer

0.5 in. w.c.

Answer

3.0 in. w.c.

Answer

6.0 in. w.c.

Question 5

Which gas pipe material is prohibited for use inside a building above ground, per most model codes?

Accepted Answer

Cast iron pipe

Answer

CSST (corrugated stainless steel tubing)

Answer

Black steel pipe

Answer

Copper tubing (Type K or L)

Question 6

Per NFPA 54, a gas appliance flexible connector used to connect a range to the gas supply line must not exceed:

Accepted Answer

6 feet in length

Answer

18 inches in length

Answer

3 feet in length

Answer

10 feet in length

Question 7

When pressure-testing a new gas piping system before placing it in service, what is the minimum test pressure and duration required by NFPA 54 for systems operating at 14 in. w.c. or less?

Accepted Answer

3 psi for 10 minutes

Answer

1.5 times operating pressure for 15 minutes

Answer

6 in. w.c. for 5 minutes

Answer

10 psi for 30 minutes