Gas Fitter Practice Test

What would be the approximate purging time for a 1-inch NPS pipe at 100-feet?

1. 50 seconds

2. 1 minute

3. 1 minute, 24 seconds

4. 1 minute, 10 seconds

The correct answer is: 1 minute, 24 seconds

To determine the approximate purging time for a 1-inch NPS (Nominal Pipe Size) pipe that is 100 feet long, it is essential to consider the factors affecting the flow rate of the purging medium and the volume of the pipe. For a 1-inch NPS pipe, the internal diameter is typically about 1.05 inches. The formula for calculating the purging time is based on the volume of the pipe and the speed of the purging method used. The volume of a pipe can be calculated using the formula for the volume of a cylinder, which can then be divided by the flow rate to find the total purge time. In general, purging involves introducing a gas (like nitrogen or air) into the pipeline, which will push out any gas that's already inside. For standard practices, it is often estimated that for this size of pipe and length, with a suitable flow rate, the purging process can take approximately 1 minute and 24 seconds. This estimate takes into account the efficiency of the purge, how well the gas moves through the entire length of the pipeline, and the ambient conditions. Therefore, the time of 1 minute and 24 seconds is a practical estimate that aligns with typical purging