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Series PRU Ultra-Pure Pressure Regulators

Superseded by Series UPR

PTFE and Kynar ultra-pure pressure regulator



Designed for ultra-pure water and chemicals, this pressure regulator uses isolated spring force to control downstream pressure.

This regulator should be set while in a 1 GPM (3.8 LPM) flowing condition. The PRU will handle inlet pressure up to 120 psi and the downstream pressure can be set from 5 to 100 psi.

The design of the PRU features a convoluted PTFE diaphragm that acts upon a PTFE shaft. The tapered end of the shaft is extended through an orifice. Process pressure from the outlet is applied to one side of the diaphragm; spring pressure is applied to the other. The spring force is adjusted while in the flowing condition to "set" the regulator. The flow path is open, eliminating dead-legs and crevices.

PTFE and Kynar ultra-pure pressure regulator

Materials of Construction:

Standard body materials are PTFE, Natural Polypropylene, and Kynar® PVDF. Shaft and seat materials are PTFE. Diaphragm is PTFE. The spring housing and adjusting screw (non-wetted) are natural polypropylene. These could be constructed of other materials; consult factory. The springs are stainless steel. Standard connections for polypropylene and PVDF bodies are socket and flare. Standard connections for PTFE are threaded and flare. Flanges and other custom connections are available.


Series PRU pressure regulators prevent downstream pressure from exceeding the desired set pressure. An isolated spring holds the valve in the open position. When outlet pressure rises near the set point (determined by the spring force), the regulator will begin to close, keeping the downstream pressure from exceeding the set pressure. As equipment or valves downstream of the regulator begin to open and demand flow, the downstream pressure drops below the set point, so the regulator will open.

Because of the high purity, high flow design of Series PRU, it is not designed to close completely. In a "no-flow" condition, outlet pressure will equalize to inlet pressure.


Chart shows typical lab tested performance of 1" Regulators Flow Capacity (GPM) versus Pressure Droop (PSI).

pressure drop-off chart of ultra-pure PTFE regulator

Droop is the difference between the pressure regulator set pressure and the downstream pressure. Performance chart, above, identifies the high flow capacities and the low pressure droop of Plast-O-Matic regulators which result in their greater sensitivity, finer adjustability and superior accuracy. The dashed line in the chart above represents the "theoretically perfect" pressure regulator; i.e., no droop regardless of flow rate.


Pipe SizeABCD
1"4.25 typ.104.1 typ.7.75 max.189.8 max.1.9046.54.50110.2

dimensional drawing of series pru

Model Numbers

Valve Pipe SizeModel# w/Kynar BodyModel# w/PTFE BodyModel # w/Natural Polypro Body
The final suffix indicates the body material. The connection type must also be specified (connections shown in above part number are flare type, indicated by the -FR-). For questions about other sizes/connections, or any other questions, please consult factory at 973-256-3000.


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Plast-O-Matic Valves, Inc.
1384 Pompton Avenue
Cedar Grove, NJ 07009 USA
Voice: (973) 256-3000
Fax: (973) 256-4745


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