Harris Products Group
A station regulator is essentially a pipeline regulator with a "C" hose connection installed on the inlet to prevent the regulator from being used on a pressure source higher than its intended use.
Visually, a "C" nut and stem is a little larger (7/8"-18") than the more popular "B" size (9/16"-18") found a the majority of regulators and torches in the welding industry. Both "B" and "C" hoses are limited to a maximum gas pressure of 200 psig according to the standard set in 1985 by the Compressed Gas Association.
The station regulator with the "C" inlet connection is, therefore, limited to a maximum gas pressure of 200 psig. A pipeline regulator, on the other hand, has no inlet pressure limit other than that specified by its manufacturer. For example, Harris Models 247, 447 and 547 pipeline regulators are limited by Harris to a stated maximum of 500 psig, unless equipped with a "C" inlet, thus limiting them to 200 psig.
The intent of the "C" connection station regulator standard is to prevent the use of a low pressure design regulator on a high pressure source, causing an accident and/or possible injury.