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

Air-Operated, Normally Open Valves

Series Series BST-NO • heavy-duty 2-way spring-return globe style valves for corrosive & ultra-pure liquids

Formerly Series EST-NO

Series BST normally-open air shutoff globe valve

Photo at right is Series BST-NO, 3/4" through 2" pipe sizes. Below left is Series BST-NO, which is the 1/2" version.

Plast-O-Matic Series BST-NO globe-pattern air operated normally open valves are ideal for handling pureliquids, chemicals, acids, and caustics where high flow and visual verification are important.


  • PTFE shaft for non-sticking operation.
  • Clear acrylic cylinder for visual verification of valve position.
  • Fail-Dry® safety feature.
  • 1,000,000 cycle design,
  • Low pressure drop with high flow rates; pressure or vacuum service.
  • Bubble-tight sealing.
  • Spring & fasteners not in contact with liquid.
  • Manual set throttling limit stop available.

  • Film Click here for video presentation of these advantages.
         Left Click to Play, Right Click to Download


The valve disk or main seal is held open via spring force. This spring will automatically keep the valve open regardless of line pressure. Standard shop air or hydraulic power is used to compress the spring and close the valve. Valves require a 3-way air solenoid valve to control the air or hydraulic pressure used. It is recommended to regulate the air pressure to 60 - 80 psi. The air should be filtered and lubricated for longer valve life.

A minimum of 40 PSI air pressure (30 PSI for 1/2", 45-50 PSI for the 3/4") is required to close the valve at liquid pipeline pressures up to 50 PSI. As liquid process pressure in the pipeline increases, the minimum air pressure required to close the valve increases as well. The maximum pipeline pressure the valve will close against is 125 PSI.

Series BST normally-open air shutoff valve in 1/2 inch pipe size

In situations where air pressure is not available, water pressure can be used so long as the pressure available is sufficient to actuate the valve. If hydraulic media is not clean, a filter should be used.

Valves should be mounted upright for best results and less strain on piping. Flow direction is indicated and should be adhered to for best results.

The Fail-Dry safety feature is a patented Plast-O-Matic design whereby the liquid seals and air pressure seals are separated by a vent, which will give indication of a valve problem before a system shutdown is necessary. For a complete explanation of the Fail-Dry system, please click here.

Sizes & Materials

Series BST-NO is available in 1/2", 3/4", 1", 1¼", 1½" and 2" pipe sizes. Standard valve body is Geon® PVC. Cylinder walls are high-strength acrylic. Shaft is PTFE. External fasteners are stainless steel. Spring is steel. Elastomeric seals are choice of Viton®, EPDM, or Buna-nitrile. For other materials, please contact the Plast-O-Matic Technical Department at 973-256-3000 or e-mail

Connections, Pressure Ratings

Standard connections are NPT. Optional connections are socket or flanged. Air inlet connection is 1/8" NPT. Maximum air pressure is 100 psi. Minimum air pressure required to close the valve is 40 psi (45 psi for 3/4", 30 psi for 1/2"). Use of an air flow rate valve may be required to prevent water hammer, depending on your application. Maximum liquid line pressure is 125 psi.

Series BST shutoff valves in nasty environment

Photo shows the normally-closed version of Series BST in an extremely harsh environment. Notice that despite the splattering acid, the valves are completely unaffected.


Series BST-NO automatic valves require air or hydraulic pressure to close and are normally open with a spring. The spring is not in the liquid. In 3/4" and larger sizes, three o-rings seal against a pressure balanced PTFE shaft; in the 1/2" size, five u-cups seal against a pressure balanced PTFE shaft. This in conjunction with a poppet seat at the valve orifice results in a non-sticking design.

Throttling Option:

A very simple and inexpensive throttling limit stop to control flow is available for BST-NO. This is adjusted in the field to a set opening and the valve will always re-open to that point. If the line pressure remains constant, the flow will then remain constant.

Series BST-NO Dimensions:

Please note that dimensions for Series BST-NO 1/2" size shown here do not use the same letter references as the printed catalog or .pdf file. All other pipe sizes listed refer to same dimensional parameters as the catalog.

dimensional drawing of Series BST air shutoff valve
Size1/2" 3/4" 1" 1¼"1½"2"
A2 3/860.33 1/288.93 3/495.34 9/16115.95127.06152.4
B1 3/444.51 3/444.51 3/444.51 5/841.31 3/444.52 3/860.3
C6 1/2165.19 1/16230.19 15/16236.511 5/16287.314 1/8358.614 3/4374.7
D1 3/834.91 5/3229.21 3/834.81 25/3245.21 25/3245.21 15/3237.1
E..1 15/1649.22 1/854.02 5/1650.82 1/263.5376.2
F2 3/860.33 76.24101.64 1/2114.36152.47 177.8
G..4 101.65127.05 3/4146.17 3/8187.28 1/2215.9

Point of clarification: The "D" dimension indicates distance from center of piping connection to bottom of valve. The "E" height indicates distance from center of piping connection to bottom of optional flange. The "G" dimension indicates length with optional flanges. The "B" dimension is a "maximum" dimension.