Plast-O-Matic - Pressure Regulators - Technical

Thermoplastic Pressure Regulators are normally open valves manufactured by Plast-O-Matic in a variety of styles, sizes and materials.

Pressure Regulators are one of the most indispensable "valves" used in process systems, but are also one of the most misunderstood and misapplied. Often referred to as "The Protectors", they protect expensive, sensitive, downstream instruments, filters and tools against damage from overpressure. They also regulate to the correct pressure range so that a flow system or piece of equipment operates safely and effectively.

This "Normally Open" valve senses and reacts to downstream pressure. Regulators are often confused with pressure relief valves, which are "normally closed", and react to upstream pressure. The primary purpose of a regulator is to convert varying or excessive upstream pressures to a pre-determined maximum downstream pressure (prevents the downstream pressure from ever exceeding the set pressure).

The downstream pressure will fall below the set pressure as flow rates takes place, the more the flow the greater the pressure drop. The ability to reduce/regulate a higher inlet pressure is accomplished internally within the regulator body by its design and sensing orifice.

Sizing the Pressure Regulator

The proper sizing of the regulator (commonly referred to as a pressure-reducing valve) is critical to system performance. Unlike typical on/off valves, pressure regulators do not have constant Cv flow factors to simplify the sizing process. Instead, a number of factors are involved and the customer must provide the following basic information before determination can be made regarding the regulator needed: 1) maximum system inlet pressure, 2) desired set pressure, 3) required flow rate, 4) desired outlet pressure at required flow rate, 5) material construction 6) pipe size.

Flow Reference Chart

Once this information has been obtained, it is then necessary to determine which valve has the appropriate capacity required for the application. To facilitate this, refer to the "Flow Reference Chart" found in the Plast-O-Matic "PR" Catalog or to our brochure titled "How To Select a Pressure Regulator". This chart is designed to provide maximum flow rate according to pipe size, inlet pressure and set pressure.

All Regulators Are Not Created Equal

It is important to understand all similar size pressure regulators do not perform equally well. The user/buyer is cautioned to look beyond basic pipe size and pressure specifications. The most critical performance criteria in the selection of liquid pressure regulators are… flow capacity… minimum system pressure and… repetitive sealing ability. Effective pressure regulation however should never be accompanied by excessive pressure loss; otherwise it will strangle the capacity of the system.

One of the most important and obvious differences between Plast-O-Matic’s regulators and competitive units is flow capacity, shown in the "performance Curve Chart" (below). This sharply identifies the superiority of our valves over competitive regulators A, B, and C in terms of: Their higher flow capacities; achieved with much lower pressure losses (drop-off), resulting in their greater sensitivity, superior accuracy and dependable repeatability. 

A Regulator for Every Application

Plast-O-Matic manufactures several different pressure regulator models, designed to meet the specialized requirements of our customers. The basic Series "PR" Regulators are for general applications requiring down-stream pressure settings in the range of 5 to 50 PSI and are available in sizes ¼" – 3". Series "PRH" units are an adapted version of the "PR" for applications requiring higher spring settings in the range of 30 to 125 PSI and are available in the same seven sizes.

The Compact Series "PRE" is a recent addition to our line and was specifically designed for those marginal applications where lower flow rates can be tolerated and where reduced pricing is required. The "PRE" model are available in ¾" and 1" sizes with downstream pressure settings of 10 to125 PSI.

PLAST-O-MATIC PRODUCT COMPARISON PRESSURE REGULATOR PERFORMANCE CURVES FLOW CAPACITY vs. PRESSURE DROP OFF

FLOW REFERENCE CHART FOR SERIES PR

INLET PRESSURES