CSA ANSI NGV 4.7 pdf free download
CSA ANSI NGV 4.7 pdf free download.Automatically pressure operated valves for natural gas dispensing systems.
3 Definitions
The following definitions shall apply in this Standard:
Dispensing system — a device intended to transfer compressed natural gas.
Fitting — an item in a piping or tubing system that is used as a connector, such as an elbow, return bend, tee, union, bushing, coupling, cross, or nipple, but not including such functioning items as a valve or pressure regulator.
Manufacturer — the person or organization responsible for the design, fabrication, and testing of the equipment and components.
Maximum allowable working pressure — the maximum pressure to which a component is designed to be subjected when handling the specified fluid at the maximum specified temperature.
Pressure — Service — the settled pressure at a uniform gas temperature of 21 °C (70 °F). This pressure is
typically 20.7 MPa (3000 psi) or 24.8 MPa (3600 psi).
Test — the pressure to which a component or equipment is taken during testing.
Note: Pressure is expressed as psi, kPa, MPa, or bar.
Tool, special — a tool that is not available on the open retail market.
Valve — a device by which the flow of a fluid can be started, stopped, or regulated by a movable part which opens or obstructs passage.
Automatic — a self-actuated or remotely actuated device consisting essentially of a valve and operator.
Check — a valve which allows gas to flow in only one direction.
a) Class A — a valve which is used as a normal part of the appliance or system operation.
b) Class B — a valve which is used to shut off gas flow to a component or components for the purpose of service or replacement.
Pressure relief — a device that prevents a pre-determined upstream pressure from being exceeded.
4 Construction
4.1 General
4.1.1 Items unique to Canada For items unique to Canada, see Annex A.
4.1.2 Class A and Class B valve clarification
A valve that complies with the requirements for a Class A valve may be used for a Class B valve application; however, a Class B valve shall not be substituted for a Class A valve (Clause 3).
4.1.3 Gauge pressure statement
All references to MPa or bar throughout this Standard shall be considered gauge pressures unless otherwise specified.
4.1.4 General construction
The construction of parts not covered by these requirements shall be in accordance with reasonable concepts of safety, substantiality, and durability.
All specifications as to construction set forth herein may be satisfied by the construction actually prescribed or such other construction as will provide at least equivalent performance.
4.1.5 Enclosure protection
The mechanisms of valves shall be protected by enclosures so as to prevent interference with the safe operation of the valves.
4.1.6 Pins, stems, or other linkages
Pins, stems, or other linkages passing through the valve body or casting shall be sealed to provide gas- tight construction.
4.1.7 Diaphragm valve enclosure
Diaphragm type valves in which a flexible non-metallic diaphragm constitutes the only gas seal and which utilize control gas on the atmospheric side of the diaphragm shall have the atmospheric side of the main diaphragm enclosed in a gas-tight casting with means provided for bleeding the control gas.
4.1.8 Diaphragm valve durability
Valves in which a flexible non-metallic diaphragm constitutes the only gas seal shall have the atmospheric side of the diaphragm enclosed to limit the leakage to atmosphere in the event of diaphragm rupture to not more than 0.028 m3/h (1.0 ft3/h) at the maximum pressure rating of the valve when tested with a gas having a specific gravity of 0.55, or shall be provided with means for venting the gas in the event of diaphragm rupture.
4.1.9 Automatic pressure valve clarification
An automatic valve, which uses pressure to actuate, may include a means to hold the valve in an open position during pressure failure, provided the means does not affect the intended safety function of the valve.CSA ANSI NGV 4.7 pdf download.
