121-4208 - Miller Smith Silverline 120 Series Two-Stage Regulator CGA 540

Technical Overview of the Miller Smith 121-42-08 Silverline Regulator

The Miller Smith 121-42-08 is a premium component within the Silverline 120 Series, engineered specifically for general purpose applications requiring precise control of inert and non-corrosive gases. This two-stage regulator is designed to maintain a constant delivery pressure, mitigating the fluctuations often seen with single-stage counterparts as the supply cylinder pressure decays. The unit features a CGA 540 inlet connection, typically associated with oxygen service, but is specified by the manufacturer for use with Inert gases, Air, Nitrogen, CO2, and Argon in this configuration. It offers a delivery pressure range of 0-60 PSIG, making it suitable for low-to-medium pressure applications in laboratory and industrial settings.

Construction-wise, the regulator boasts a rugged brass bar stock body, bonnet, and gauges, all of which are plated to provide superior protection against environmental corrosion and wear. The internal mechanism includes a large 1-7/8 inch diaphragm which is pivotal for achieving high sensitivity and precise pressure modulation. A key technical feature is the Sure-Seat technology, which incorporates a filtered seat to prevent debris from entering the seating area, thereby ensuring gas stream purity and significantly extending the service life of the regulator. The outlet is equipped with a 1/8 inch tube stainless steel needle valve, allowing for fine flow adjustments directly at the regulator.

Safety and integration are also addressed in the design. The body is tapped for rear panel mounting, facilitating organized installation in gas manifolds or instrument benches. A preset safety relief valve vents to the atmosphere, reinforcing its suitability for non-hazardous gases. The unit is rated for a maximum inlet pressure of 3500 PSIG and includes large 2-1/2 inch single scale gauges that provide clear, immediate readouts of both cylinder and delivery pressures. This regulator is not recommended for applications where inboard diffusion of air or outgassing of elastomeric components is critical, but it excels in general plant and maintenance shop environments.