Section 56.20-9 - Valve construction(a) Each valve must close with a right-hand (clockwise) motion of the handwheel or operating lever as seen by one facing the end of the valve stem. Each nonrising-stem valve, lever-operated valve, or other valve where, because of design, the position of the disc or closure mechanism is not obvious must be fitted with an indicator to show whether the valve is opened or closed. No such indicator is required for any valve located in a tank or similar inaccessible space when indicators are available at accessible sites. The operating levers of quarter-turn valves must be parallel to the fluid flow when open and perpendicular to the fluid flow when closed.(b) Valves of Class I piping systems having diameters exceeding 2 inches must have bolted, pressure seal, or breech lock bonnets and flanged or welding ends. Socket type welding ends must meet § 56.30-5(c) and § 56.30-10(b)(4) . For diameters not exceeding 2 inches, screwed union bonnet or bolted bonnet, or bonnetless valves, which prevent the stem from screwing out of the body, may be employed. Outside screw and yoke design must be used for valves 3 inches and larger for pressures above 600 psig. Cast iron valves with screwed-in or screwed-over bonnets are prohibited. Union bonnet type cast iron valves must have the bonnet ring made of steel, bronze, or malleable iron.(c) Valves must be designed for the maximum pressure to which they may be subjected, but in no case must the design pressure be less than 50 psig. The use of wafer type resilient seated valves is subject to the requirements of § 56.20-15 .(d) Disks or disk faces, seats, stems, and other wearing parts of valves must be made of material possessing corrosion and heat-resisting qualities suitable for the service conditions to which they may be subjected.(e) Plug cocks must be constructed with satisfactory and positive means of preventing the plug from becoming loosened or removed from the body when the plug is operated.(f) Cocks must be marked in a straight line with the body to indicate whether they are open or closed.CGFR 68-82, 33 FR 18843, Dec. 18, 1968, as amended by CGD 77-140, 54 FR 40604, Oct. 2, 1989; CGD 95-012, 60 FR 48050, Sept. 18, 1995; USCG-2004-18884, 69 FR 58346, Sept. 30, 2004; USCG-2003-16630, 73 FR 65176, Oct. 31, 2008