This part of ISO 28921 specifies requirements for design, dimensions, material, fabrication and production testing of isolation valves for low-temperature applications.It applies to gate, globe, check, butterfly and ball valves and can be used for other valve types used in low-temperature services.This part of ISO 28921 covers isolation valves for use in cryogenic temperature service where the design low-temperature service is –50 °C down to –196 °C.This part of ISO 28921 does not apply to valves for cryogenic services, designed in accordance with ISO 21011, used with cryogenic vessels.Where the requirements of this part of ISO 28921 vary from those given in the valve product standards, the requirements of this part of ISO 28921 apply.This part of ISO 28921 covers valves with body, bonnet, bonnet extension or cover made of metallic materials.It covers valves of nominal sizes DN: 10; 15; 20; 25; 32; 40; 50; 65; 80; 100; 125; 150; 200; 250; 300; 350; 400; 450; 500; 600; 650; 700; 750; 800; 850; 900,corresponding to nominal pipe sizes NPS: 3/8; 1/2; 3/4; 1; 11/4; 11/2; 2; 21/2; 3; 4; 5; 6; 8; 10; 12; 14; 16; 18; 20; 24; 26; 28; 30; 32; 34; 36,and applies to pressure designations:— PN 16; 25; 40; 100; 160; 250.— Class 150; 300; 600; 800; 900; 1 500.NOTE PN 250 and Class 1 500 in sizes DN > 100 and NPS > 4 are not covered in this part of ISO 28921.