ADV06-15_1-412

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2007 vol. 2

GC Accessories

Peak Performers

Introduction to Pressure Regulators

by Donna Lidgett, GC Accessories Product Manager

General Purpose or Analytical?

General-purpose regulators usually are best suited for applications involving gases that are less than 99.995% pure: pneumatically-

actuated valves and autosamplers, blanketing, inert atmospheres, and any other application not directly integrated with analytical

data production. General purpose regulators have nylon-reinforced neoprene diaphragms that provide very good pressure control

but are prone to air and moisture diffusion and hydrocarbon off-gassing.

Analytical regulators are recommended for applications in which maintaining the purity of a gas or mixture is the overriding con-

cern, i.e., for applications requiring gases that are greater than 99.995% pure. They are commonly used in analytical labs. Analytical

regulators have stainless steel diaphragms for pressure control. Stainless steel is not subject to the diffusion and off-gassing associated

with neoprene diaphragms, and is easily purged of atmospheric contaminants when put into service.

Dual- or Single-Stage?

Dual-stage regulators reduce the source pressure to outlet pressure in two steps. The first stage reduces the inlet pressure to about

three times the maximum working pressure. Outlet pressure regulation is controlled by the second stage and is set through an adjusting

knob. This two-step regulation is highly recommended for services requiring a near constant delivery pressure as the source pressure

decays, including chromatographic analyses.

Single-stage regulators perform the same function as dual-stage regulators, but in a single step down from source pressure to outlet

pressure. For this reason, the outlet pressure cannot be as accurately maintained as the source pressure decays. We highly recommend

that single-stage regulators be used only in circumstances in which the operator can monitor and adjust the regulator as needed,

when the regulator is supplied with a nearly constant source pressure, or when additional pressure regulation is supplied

downstream.

Brass or Stainless Steel?

Analytical regulators made from brass bar stock provide optimum performance for most analytical applications. Brass provides excel-

lent strength and cleanliness and the machined bar stock design has less dead volume than forged-body regulators, making purging

of atmospheric contaminants faster and more assured.

Regulators with stainless steel bodies were designed for delivering corrosive gases that would be incompatible with brass. With the

advent of semiconductor manufacturing and high sensitivity analytical techniques, stainless steel also has proven to be a better sur-

face for removing “sticky” atmospheric contaminants that interfere with detectors downstream. Unless these regulators are used in

an all-stainless-steel system that incorporates welded tubing and special fittings, and in which rigorous cleaning and proper gas man-

agement are practiced, the extra expense relative to brass is not justified.

Ultra-High-Purity Stainless Steel Body Regulators

These regulators are the standard for ultra-high-purity and corrosion-resistant pressure regulation. They are more easily purged of

atmospheric components, compared to brass regulators, making them ideal for the most demanding applications. Regulation per-

formance is equal to our brass body regulators. For use in all-stainless steel systems where welded tubing and special fittings are used,

and rigorous cleaning and proper gas management are practiced.

Overview of Restek’s Brass and Stainless Steel Body Ultra-High-Purity Regulators

These regulators feature metal-to-metal seals throughout for long-term leak-tightness, and a metal diaphragm outlet valve ensures

gas purity. Each regulator is helium leak-test-certifiable to 1x10

-8

scc/sec. and is fully assembled and tested for your convenience.

100psig maximum delivery pressure supports pressure controlled operation. Maximum inlet pressure is 3000psig. Brass bar stock

construction minimizes dead volume. Stainless steel construction is more easily purged of atmospheric contaminants, and is more

resistant to attack from dry corrosive gases.

Dual-Stage Ultra-High-Purity Stainless Steel Regulators

• Most stable outlet pressure control throughout the life of a high-pressure gas cylinder.

• Secondary pressure regulation not needed.

Outlet pressure:

0 to 100psig

Outlet gauge:

30" – 0 to 200psig

Inlet gauge:

0 to 4000psig

Outlet assembly: diaphragm valve,

" tube fitting

Fitting

qty.

cat.#

price

CGA 580 (N

, He, Ar)

ea.

20662

$797

CGA 350 (H

, P

)

ea.

20663

$797

CGA 590 (Air)

ea.

20664

$797