UL 536

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Flexible Metallic Hose
UL 536
1 Scope
1.1 These requirements cover flexible metallic hose having a nominal inside diameter of not more than 4 inches intended for use in piping systems carrying compressed gases, such as anhydrous ammonia, and combustible fuel gases such as natural gas, liquefied petroleum gas, propane, and butane, at pressures not exceeding 500 psig (3.45 MPa) and temperatures not greater than 450°F (232°C) or lower than minus 40°F (minus 40°C). Flexible metallic hose is supplied with end fittings.

1.2 Flexible metallic hose is intended for aboveground applications and for underground applications not involving contact with soil.

1.3 Flexible metallic hose is not considered a substitute for standard pipe or tubing and its use should be confined to applications where flexible connections cannot be avoided.

1.4 Flexible metallic hose should not be subjected to excessive torsion, tension, compression, or bending stresses and should be protected against physical damage and ignition sources.

1.5 This standard does not apply to hose connectors used in natural gas processing plants, refineries, petrochemical plants, marine terminals, or gas-transmission and distribution-piping systems.

1.6 These products have not been evaluated for use after fires, natural disasters such as earthquakes, or excessive physical damage beyond the expected assembly, installation and uses as identified in these requirements.

1.7 These products are intended to be periodically inspected and maintained for continued service, or taken out of service if necessary by qualified persons in accordance with industry recommended practices and/or the manufacturers instructions.

1.8 Products covered by this standard are intended to be installed and used in accordance with the National Fuel Gas Code, NFPA 54/ANSI Z223.1, the Liquefied Petroleum Gas Code, NFPA 58, and applicable Federal and State regulations for gas piping.

1.9 This standard does not cover the following:

• a) Gas appliance hose connectors for handling fuel gases at 5 psig (34.5 kPa) or less, which is covered by Metal Connectors for Gas Appliances, ANSI Z21.24;
• b) Portable outdoor cooking appliance fuel hose, which is covered by Gas Hose Connectors for Portable Outdoor Gas-Fired Appliances, ANSI Z21.54;
• c) LP-Gas and natural gas delivery hose or fuel supply systems, which is covered by the Standard for Pigtails and Flexible Hose Connectors for LP-Gas, UL 569 and the Standard for LP-Gas Hose, UL 21;
• d) Underground piping products for liquid fuels, which is covered by the Outline of Investigation for Metallic Underground Fuel Pipe, UL 971A;
• e) Flexible connector piping for liquid fuels, which is covered by the Outline of Investigation for Flexible Connector Piping for Fuels, UL 2039;
• f) Motor fuel dispensing hose, which is covered by the Standard for Hose and Hose Assemblies for Dispensing Flammable Liquids, UL 330.