ANSI B109.4-1998 pdf download SELF-OPERATED DIAPHRAGM-TYPE NATURAL GAS SERVICE REGULATORS
1.0 Scope
This standard shall apply to the minimum design, material, performance and testing requirements of 1 !AI inches (32 mm) and smaller self-operated diaphragm-type natural gas service regulators operating at inlet pressures up to 125 psig (861.8 Ha). These regulators are used to control the gas delivery pressure to pressures at a maximum 14 inches water column (3.48 Ea). This standard shall apply only to regulators manufactured after the approval date of this standard.
2.0 Definitions
Diaphragm: A flexible element used to sense the outlet pressure and, in combination with the loading spring and linkage, to position the valve to control the downstream pressure.
Diaphragm case or casing: The housing for the diaphragm usually consists of an atmospheric or ambient casing and a gas or fuel casing. The gas or fuel casing and the diaphragm form the gas or fuel chamber. The atmospheric or ambient casing and the diaphragm form the atmospheric or ambient chamber. The diaphragm seals and separates the gas or fuel chamber from the atmospheric or ambient chamber. The atmospheric or ambient chamber houses the loading spring and vents into the atmosphere.
Droop: The drop in outlet pressure from set point with respect to increasing gas flow rate.
Hysteresis: Characteristic used to describe a deviation in the regulator performance based on internal fnction, the diaphragm material and flow.
Internal relief valve WV): A relief valve that relieves excessive outlet pressure through the diaphragm and vent assembly. The internal relief set point is a function of the regulator’s set point and the maximum allowable build-up of downstream pressure.
Loading spring: A spring placed on the diaphragm or diaphragm plate and contained in the atmospheric casing, which opposes the gas pressure exerted against the opposite side of the diaphragm. The outlet pressure of the regulator is set by the compression of this spring.