Chemical Pressure Regulators for Corrosive and Ultra-Pure Liquids
Operation - A pressure regulator prevents downstream pressure from exceeding the desired set pressure.  The regulator will remain closed as long as the set pressure is maintained.  As equipment or valves downstream of the regulator begin to open and demand flow, the downstream pressure begins to fall and the regulator opens. It continues to open further as more flow is needed until its maximum opening is reached.  As the process is reversed, the downstream pressure begins to increase and the regulator starts closing.  When the downstream pressure again reaches the set pressure, the regulator closes.

Regulators will create a certain level of pressure drop of the liquid as it passes through the valve.   This is how the pressure is decreased.  If recommend flow rates are exceeded, the down stream pressure may be less than expected.  Each of the following valves has slight differences as to flow vs. pressure drop.  This information must be considered when designing a system and selecting a valve.  We recommend that a valve be selected with inlet pressure, flow rate and set pressure data being supplied.

Applications / Advantages

  • Automatically regulates downstream pressure
  • Converts varying upstream pressure to a pre-determined maximum downstream pressure
  • Regulates maximum pressure for flow systems or equipment operation
  • Maximum inlet pressures up to 150 PSI
  • Adjustable setting available from 5 to 50 PSI with standard supplied springs
  • Adjustable setting available from 5 to 75 PSI (PRM  only)
  • Adjustable setting available from 5 to 125 PSI (PRH only)
  • Adjustable setting available from 10 to 65 PSI (PRE only)
  •  PRHM valves are molded PVC and CPVC valves in 1/2", 3/4" and 1" sizes - replaces these sizes of PR or PRH valves

Design -  The design incorporates a poppet seat at the valve orifice to prevent sticking and double U-cup seals on the internal shaft to prevent inlet pressure from affecting the sensing of the downstream line pressure.  Also, the one piece body construction eliminates internal leakage that could cause the set pressure to creep beyond a safe limit.  A unique rolling diaphragm seal isolates the spring chamber from the downstream pressure sensing liquid.   A pressure balanced shaft assures smooth and stable control.

For further information regarding pressure regulators - CLICK HERE.

POM PRM.jpg (12903 bytes)

smallnew.gif (926 bytes)PRHM Series - Molded body for downstream pressure control 5 to 125PSI set pressures  - PVC and CPVC materials

A molded body version of the PR and PRH valve offering flows and performance near the PR Series

See PR or PRH valves for larger sizes and polypropylene, PVDF or PTFE materials - all PRM valves are now PRHM valves


PR and PRH Series for downstream pressure controlPOM PR.jpg (9781 bytes)

PR Series is designed for a maximum inlet pressure of 150 PSI with a set pressure of 5 to 50 PSI  - bulletin for PR Series

PRH Series is designed for a miximum inlet pressure of 150 PSI with a set pressure of 30 to 125 PSI - bulletin for PRH Series

Designed for high flow rates with a minimum for pressure setting tolerance.  

PVC, polypropylene, PTFE and PVDF

  • Viton®, EPDM or Buna-N® seals
  • 1/4" to 3" FNPT
  • 5 to 50 PSI (standard)
  • 30 to 125 PSI (PRH version)
  • flow rates to 200 GPM

(See above PRHM for PVC and CPVC construction valves of 1/2" to 1" sizes)

PRD Series - Differential Pressure Regulators

For controlling the differential pressure across equipment such as membrane filters

  • PVC, polypropylene, Teflon® and PVDF
  • 1/4" to 3" FNPT

pom-pre.jpg (7075 bytes)PRE Series - Compact Pressure Regulators

Designed for application requiring lower flow rates than the PR Series at a reduced cost for the valve.  For less demanding applications that still require downstream pressure regulation.

  • PVC, polypropylene and PVDF
  • Viton®, EPDM or Buna-N® seals
  • 3/4" and 1" FNPT
  • 10 to 125 PSI Set Pressures
  • flow rates to 22 GPM for 3/4" size
  • flow rates to 35 GPM for 1" size

PRA Series - Air loaded pressure regulator

Series PRA uses the standard air from a compressor instead of a spring to generate the force needed to regulate pressure. It is based on the same heavy duty architecture as Series PR (above) with a significantly broader set pressure range and improved performance. Design incorporates a poppet seat, double u-cups, large area rolling diaphragm and one piece body construction. A pressure balanced shaft assures smooth and stable control, while the valve design provides excellent flow performance.

A common self-relieving type compressed air valve is needed to connect your compressed air line to the regulator. The PRA will mimic whatever pressure you apply to the top via the self-relieving valve. If you apply 40 psi to the top of the PRA, you can expect downstream liquid pressure to be 40 psi as well.

• Pressure setting is infinitely adjustable from 5 psi to 125 psi.
• Maximum inlet pressure is 150 psi.
• Available in PVC, Natural polypro, and Kynar PVDF;
• Sizes 1/4", 1/2", 3/4", 1", 1-1/2", 2" & 3".
• Seals in EPDM or Viton.
• High performance, heavy-duty design.
• Outperforms spring loaded regulators through improved response to pressure changes; pressure is maintained without sacrificing flow.
• Performance rivals exotic control valves but at much lower cost.
• Used with the optional Stabilizer -- U.S. Patent No. 6,418,956 -- Series PRS, this air-loaded regulator will perform with virtually zero drop off from set pressure.
• Incorporates the patented Fail Dry safety vent.

PRS - The Stabilizer Precise control of Downstream Pressure with Minimal Drop-Off from Set Pressure • Remote Setting • Easy Adjustment

pressure_stabilizer.jpgThe Stabilizer®
The Stabilizer is a closed-loop, proportional controller. It maintains process fluid pressure at a constant, preset value by modulating air pressure to the regulator. The combination of The Stabilizer and an Air-Loaded Pressure Regulator eliminates the need for an exotic, expensive control valve in most applications.

Series PRS in foreground, and shown in a typical configuration piped downstream of Series PRA, Air-Loaded Pressure Regulator.


  • Used with an Air-Loaded Regulator, Series PRS reacts instantly to fluctuations in pressure, significantly enhancing the accuracy of the air-loaded regulator - downstream pressure has virtually no deviation from set pressure.
  • Desired pressure is maintained without sacrificing flow. Performance rivals control valves, at much lower cost.
  • Ideal for applications with changing pressure requirements.
  • Can be conveniently teed into piping at desired control point, or may be mounted at a more convenient location and connected with tubing for static pressure sensing.
  • Easy to set; adjustable from 5 PSI to 125 PSI.
  • PTFE diaphragm for critical ultra-pure and corrosive liquid applications.
  • No wetted metal or elastomer parts.

Materials of Construction & Piping Connections:

Standard liquid connection is ½" male NPT threaded. Standard air or hydraulic connections are 1/8" female NPT. Connection to valve air chamber should be ¼" or larger tubing. Standard body materials are Geon® Grade 1 Type 1 PVC, Natural Polypropylene, Kynar® PVDF and Teflon® PTFE. Standard seal material is a PTFE diaphragm backed with Viton®. Some Kynar PVDF components are used in the Natural Polypropylene models for strength. Adjusting bolt and external fasteners are stainless steel. A Buna-N rubber seal is used in the air chamber. For connection types and materials other than listed, please consult factory.


Comparison of Air-Loaded Regulator performance with and without the patented Stabilizer. Note that the pressure axis in this graph shows only 16 PSI of the total range; this was done to better illustrate the effectiveness of the Stabilizer.  Within this limited range, competitive regulators are below the scale and therefore are not plotted.

Performance Comparison of 1" Air-Loaded Regulator with and without The Patented Stabilizer

flow curve comparison of air loaded regulator with and without the optional stabilizer


Pressure regulators - did you know?  - a power point slide show  

  Bulletins are available for these products in Adobe PDF format -
PR   PDF  Format                     
PRA PDF Format

PRE PDF Format
PRH PDF Format 
PRS PDF Format
PRM PDF Format
PRU PDF Format - Note:  PRU has been discontinued.

Please contact KTH Sales with your application to allow us to select the correct pressure regulating valve for your application. KTH Sales Home Page