Engineering Specifications
Ultra High Purity Pressure Differential Changeover Stations
PDC Series (Brass Construction)
Regulator Module
The panel-style changeover station shall be specifically made and cleaned for ultra high purity laboratory
gases. All fittings shall be made out of brass. All pressure reducing regulators shall be brass barstock with
stainless steel diaphragms (neoprene diaphragm regulators are not acceptable). The changeover station
shall be designed so that when the automatic changeover from the primary bank to the reserve bank occurs
there will be no drop in the line pressure (a line pressure regulator).
A simple rotation of the primary bank selector shall reset the changeover station (units equipped with a
crossover valve are not acceptable). The changeover station shall have a minimum flow coefficient of Cv =
0.1. The changeover station shall be equipped with an optional pipeline pressure relief valve with a
setpoint no greater than 200 psig.
Alarm Box
A low pressure alarm signal shall be actuated by a pressure switch installed behind the changeover station
mounting panel (one pressure switch per cylinder bank). The alarm box shall be equipped with green and
red lights indicating the status of each cylinder bank (adequate pressure or depleted). A buzzer shall sound
when a bank is depleted. The buzzer shall be cancelled by a silence push button without canceling the red
light. The alarm box shall actuate a dry contact for remote alarm connection.
Header Bars and Hoses
The header bars shall be made out of brass. All parts shall be silver brazed, acid cleaned, bright dipped and
nickel plated to the outside (painted header bars are not acceptable). The 36”-long flexible hoses (or rigid
pigtails) shall be suitable for ultra high purity applications and compatible for the intended gas service. For
carbon dioxide and nitrous oxide service equipment, each header bar shall be equipped with an optional
electric gas heater (110 VAC).
Acceptable Manufacturer
PDC Series as manufactured by Square One Gas & Cryo Equipment.