Badger's positive displacement meter, Model OP is one of the most cost effective methods for metering process fluids in the chemical, pharmaceutical and food industries. The simple but efficient design of the OP meter generates high accuracy and repeatability over the entire meter flow range. Magnetic, "through the wall" transmission, prevents operator exposure to corrosive fluids and protects the fluid from external contamination.

Offered in three sizes, 1/2",1" and 2", for flows up to 100 GPM, these meters are extremely rugged, reliable and need little maintenance and calibration. With only three internal moving parts, maintenance is seldom required. If necessary, it takes but a few minutes.

All parts are designed and built of materials recommended for your application, providing you with a long life, trouble-free, precision flow meter. All sizes of the meter are offered in chemical and sanitary, (3A approved), configurations with a wide variety of end fittings to match your piping. The meter's compact design and mode of operation allows for installation in tight spaces and in any position.

To complement the OP meter line, Badger offers a complete line of accessories that includes mechanical, pneumatic, electromechanical and electronic transmitters, totalizers, indicators and batch/process controllers.

The meter function is based on the continuous filling and discharging of the measuring chamber (positive displacement). Controlled clearances between the piston and the chamber insure minimum gap leakage for precise measurement of each volume cycle. As the piston oscillates, its' center hub rotates a magnet, whose movement is sensed through the meter wall by electromagnetic sensors or by a follower magnet. Each revolution of the magnet is equivalent to a fixed volume of fluid, which is converted to any engineering unit of measure for totalization, indication or process control.
Unit of Measure


Minimum Flow Rate, Q Minimum

N/A 1 gpm

Continuous Operating Maximum Rate

N/A 4 gpm
Short Duration Maximum Flow, Q Maximum1 N/A 6 gpm

Standard Flange Connections, Chemical

N/A 150 psi ANSI 16.5
Standard Connections, Sanitary2 N/A Tri-Clamp
Pressure Drop at Maximum Continuous Operating Flow (@ viscosity & specific gravity of water)3 N/A 1.8 psi
Maximum Viscosity Limit4 N/A 10,000 cps

Maximum Operating Pressure

N/A 150 psi300 psi (optional)
Maximum Operating Temperature5 N/A 250 ºF

Minimum Operating Temperature

N/A 40 ºF


N/A ± 0.5% over entire meter flow range


N/A ± 0.2% or better under similar repeatable batch operations

Dimension A

N/A 4.31 in

Dimension B

N/A 2.32 in

Dimension D

N/A 1.75 in

Dimension E

N/A 6.75 in

E (Tri-Clamp)

N/A 6.75 in


N/A 6.75 in


N/A Metric Conversion:
psi x 0.0703 = BARS
gpm x 3.785 - liters per minute
ºF - 32 x .555 = ºC
1/2" Chemical meter can be ordered with 1" flanges for low flow applications on 1" lines.
All sizes available with optional 300 psi flanges.
  • 1 Continuous operation is acceptable at these rates but accelerated wear of the piston and/or bushings may occur.
  • 2 Sanitary OP meters have 3A approval, Ultem piston is required.
  • 3 Pressure loss increases with fluid viscosity
  • 4 flow range is decreased as viscosity increases
    please contact factory for higher viscosities
  • 5 Minimum temperature for stated accuracy