Model 109

Bourdon Type

Mid-West® Instrument Model 109 Bourdon Tube ΔP Gauge – ± 1/2% or ± 1% Full Scale Accuracy. System pressure is applied to the inside of a slightly flattened arc- shaped tube. As pressure increases, the tube tends to restore to its original round cross-section. This change in cross-section causes the tube to straighten. Since the tube is permanently fastened at one end, the tip of the tube traces a curve that is the result of the change in angular position with respect to the center. Model 109 is powered by a test quality Bourdon Tube Assembly. The assembly is encapsulated in a high pressure chamber that is fitted with a pressure connection to the inside of the Bourdon Tube and a second connection to the pressure chamber. The Model 109 indicates the difference between the pressure applied inside the Bourdon Tube and the pressure inside the chamber.

The Model 109 Bourdon Tube Assembly is protected against over-range in either direction to the rated working pressure by a bi-directional relief valve. The output shaft of the gauge assembly is magnetically coupled through the solid wall of the pressure chamber to a sensitive jeweled pointer shaft in the dial housing outside the chamber. The magnetic coupling transmits the exact motion of the assembly to the pointer to give an accurate dial reading of the differential pressure.

NOTE: The use of diaphragm seals is not recommended for Model 109 series gauge. Attempts to install such seals on these gauges will void the warranty

Contact Us Today For Availability

Product Features/Benefits

  • Rugged Bourdon Tube Sensing Element
  • Glass Reinforced Thermoplastic Dial case (Panel Mountable)
  • Weather Resistant & Corrosion Resistant Gauge Front
  • 270° Dial Arc
  • Shatter Resistant Lens
  • Over-Range Protection, High over Low and Low over High
  • Locked-Logic Switch options
  • 5 Year Warranty
  • For complete model details See Bulletin_109.pdf
  • Installation and Operation Manual See Bulletin: IOM_109.pdf

Specifications / Configuration

  • Dial Sizes available: 4-1/2” and 6” Diameters
  • Dial Scale Ranges: 0-15 PSID to 0-6,000 PSID
  • Differential Full Scale Ascending Accuracy available: ±1/2% (ASME B40.1 Grade 2A)/±1% (ASME B40.1 Grade 1A)
  • Available in a Variety of Dial Scales: Bar, Mbar, kPa, Kg/Cm2, Dual Scale and Square Root for Flow Indication etc.
  • Working Pressures up to 6000 PSIG (400 Bar)
  • Operating Temp -40°F to +200°F (-40°C to +93°C)
  • Weather Protection & Corrosion Resistant
  • Material of Construction of Body - Aluminum, Carbon Steel, 316/316L Stainless Steel and Brass (Wetted Part)
  • Internal wetted parts-316 Stainless Steel
  • Back Process connections
  • Optional O-rings Materials Buna-N, Viton, Neoprene, and Ethylene Propylene
  • For complete specifications see: Specificationsheet_109.pdf

Common Applications

  • Square Root Graduations for Direct Reading Flow Rates
  • Pump Performance Testing
  • Hydraulic Filter Monitoring
  • Heat Exchanger Pressure Drop Monitoring

Locked Logic Switch Electrical Specifications: 6” DIAL ONLY

See Electrical Installation and Operation Manual: imllc

“Locked Logic” alarm control is a solid-state optical-electronic control available as an option on Mid-West Models 105 differential pressure gauge. The control is an optical “no-contact” design that does not affect the indicated accuracy of the instrument. The standard unit is designed for an 8 to 28 VDC uninterruptable power input. Optional power inputs include  115 VAC 50-60 hertz, or 220/240  VAC 50-60 hertz. Output interface is via a set of (1) or (2) isolated SPDT or DPDT relay contacts, dependent on the number of set points specified. Visible set pointers are provided, adjustable to within 5% of full scale of each other.  Interface to the relay contacts is customer configurable provided the relay contact ratings are not exceeded. An alternate option allows the incorporation of an adjustable dead band. For this configuration the right set pointer determines the upper trigger point, while the left set pointer determines the lower trigger point.

  • 1 or 2 Independently adjustable switches with Set Point Feedback
  • SPDT or DPDT Output Options
  • Adjustable Deadband option for SPDT or DPDT output (2 set pointers)
  • Accuracy of Gauge unaffected by the switch
  • Adjustable from 5 to 95% F.S.
  • Electrical Enclosures Weather-Proof NEMA 4X or NEMA 7

Hazardous Locations:

  • Designed for Class I Division I, Groups B, C & D, Class II Division I, Groups E, F and G

Additional Options:

  • Pipe Mounting Kit - 2" U-Bolt
  • Wall Mounting Kit
  • Maximum Follower Pointer
  • Oxygen Cleaning
  • Liquid Fill
  • NACE Certificate (Available for Aluminum and Stainless Steel Bodies only)
  • CRN – Canadian Registration Number (1500 PSI Safe Working Pressure Stainless Steel Bodies only)

The Mid-West Advantage

Model No. Differential Pressure Range Accuracy Working Pressure Electrical Available Specifications Installation/ Operation Manual Electrical IOM Drawing
Model 109 0-15 PSID to 0-6000 PSID (Dependent on Body Material and Safe working Pressure) 1/2% or 1% Full Scale
(1/2% Not available above 1,000 PSID or Bi-Directional Ranges)
Bi-Directional Accuracy is 1% Total Span
±3% Total Span
(For Ranges above 1,500-0-1,500 PSID)
Weather-proof Housing, NEMA 4X, Class I Division I, GROUP. B, C & D, Class II Division I, GROUP. E, F & G