UL-644:2014 pdf free download – STANDARD FOR SAFETY Container Assemblies for LP-Gas.
9 Excess-Flow Valves
9.1 An excess-flow check valve in combination with a vapor-return valve shall operate at a pressure differential of not more than 20 pounds per square inch gauge (psig) (138 kPa). All other excess-flow valves shall operate at a pressure differential of not more than 15 psig (103 kPa).
10 Liquid-Level Gauging Devices
10.1 A container assembly shall be provided with a fixed liquid-level gauging device to indicate the maximum permissible filling level of the container during a filling operation. A variable type liquid-level gauge may be provided in addition to the fixed-tube type.
10.2 The dip tube of a fixed-tube type gauge shall be of such length that it indicates the maximum level to which a container can be filled at a temperature of 40°F (4°C) for an aboveground or for an interchangeable container, and 50°F (10°C) for an underground container, based on the maximum permitted filling density.
10.3 For gauges where the tube is not welded in place, a permanent marking shall be provided adjacent to the fixed-tube type gauge or on the container nameplate, consisting of the following: Letters “DT followed by the vertical distance expressed in inches and carried to one decimal place (or in whole mm) measured from the top center of the container boss or coupling into which the gauge is installed, to the maximum permitted filling level.
10.4 The “percentage full” that will be indicated by the fixed-tube type gauge shall be included as a permanent marking attached to the container adjacent to the gauge, or on the container nameplate.
10.5 Variable liquid level gauges shall be so marked that the maximum liquid level, in inches or percent of capacity of the container in which they are to be installed, is readily determinable. These markings shall indicate the maximum liquid level for propane, for 50 — 50 butane-propane mixture, and for butane at liquid temperatures from 20 — 130°F (minus 7 — 54°C) in increments not greater than 20°F (11°C).
10.6 A float or a rotary-type gauge shall be marked to indicate whether it is designed for a cylindrical or a spherical container, and whether for aboveground or underground service.
10.7 A float or a rotary-type liquid level gauge for use with an interchangeable container shall be of the type suitable for use on an aboveground container.
10.8 A dial of a magnetic float or of a rotary tube-type gauge for use only on aboveground containers of over 1200 gallons (4.54 m3) water capacity shall be so marked.
10.9 A gauging device that requires bleeding of the product to the atmosphere, such as a rotary-tube, fixed-tube, or slip-tube type, shall be so designed that the bleed opening of the bleed valve is not larger than a No. 54 drill size (0.055 inch) (1 .40 mm).
11 Filler Valves and Vapor-Return Valves
11 .1 A container assembly shall be provided with a double backflow check filler valve. This valve is required, but is not prohibited from being a part of a multipurpose valve.
11 .2 A filler valve shall be arranged to permit filling into the vapor space.
11 .3 A vapor-return connection shall be constructed with an internal back-pressure check valve and an excess-flow valve, or with a positive manual shutoff valve and an internal excess-flow valve.
11 .4 A filler connection and a vapor-return connection shall be provided with a threaded cap or plug designed to provide a gas-tight closure when the valve is not in use.