If listed strainers of the proper size are not available, strainers that have a ratio of open-basket area to inlet pipe size of at least 10:1 shall be used. What ratio is required?

If listed strainers of the proper size are not available, strainers that have a ratio of open-basket area to inlet pipe size of at least 10:1 shall be used. What ratio is required?

• A. 5:1
• B. 10:1
• C. 20:1
• D. 2:1

Answer: (B)

The concept tested is how large the strainer’s open area must be relative to the inlet pipe to avoid restricting flow in a foam-water system. When listed strainers of the proper size aren’t available, you must use a strainer whose open-basket area is at least ten times the inlet pipe size. This 10:1 minimum helps prevent substantial pressure drop and ensures adequate flow for the foam concentrate and system operation, reducing the risk of clogging or starving the proportioning device. So the required ratio is 10:1. (A larger ratio, like 20:1, would also meet the requirement, but the baseline specified is 10:1.)

The concept tested is how large the strainer’s open area must be relative to the inlet pipe to avoid restricting flow in a foam-water system. When listed strainers of the proper size aren’t available, you must use a strainer whose open-basket area is at least ten times the inlet pipe size. This 10:1 minimum helps prevent substantial pressure drop and ensures adequate flow for the foam concentrate and system operation, reducing the risk of clogging or starving the proportioning device. So the required ratio is 10:1. (A larger ratio, like 20:1, would also meet the requirement, but the baseline specified is 10:1.)