46 CFR §63.15-5

1. (a)Strainers must be installed in the fuel supply line. Each strainer must be self-cleaning, fitted with a bypass, or be capable of being cleaned without interrupting the fuel oil supply.
2. (b)The strainer must not allow a quantity of air to be trapped inside which would affect the rate of fuel flow to the burner or reduce the effective area of the straining element.
3. (c)The strainer must meet the requirements for strainers found in UL 296 (incorporated by reference, see § 63.05-1) and the requirements for fluid conditioner fittings found in § 56.15-5 of this subchapter.