Model 106

Bellows Type

High-Accuracy Measurement with Switch Capability and Over-Pressure Protection

The Mid-West® Instrument Model 106 Bellows Differential Pressure Gauge is designed for accurate measurement of low differential pressures, offering ±0.5% or ±1.0% full-scale accuracy. This model includes optional integrated electrical switches, allowing for both visual indication and remote signaling.

Key Features:

Bellows & Linkage Assembly: Converts system pressure into a mechanical or electrical output.
Integrated Switch Option: Enables remote monitoring and control based on user-set pressure points.
Two-Piece Body Design: Houses and isolates high- and low-side pressures while clamping internal components securely.
Torque Tube & Range Spring Assembly: Ensures reliable, repeatable gauge pointer movement.
Bi-Directional Over-Pressure Relief Valve:
- High-Side Over-Pressure: Relief valve opens via mechanical stop at full bellows travel.
- Low-Side Over-Pressure: Spring-loaded valve opens automatically to equalize pressure when safe limits are exceeded.

Note: Because of its high sensitivity—especially in low-pressure ranges—Model 106 must be protected from pressure surges and improper handling to maintain accuracy and prevent internal damage.

Product Features/Benefits

Rugged Bellows 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
Micro Switch options
5 Year Warranty
For complete model details See bulletin_105_106.pdf
Installation and Operation Manual See Bulletin: im105_106.pdf

Specifications / Configuration

Dial Sizes available: 4-1/2” and 6” Diameters
Dial Scale Ranges: 0-80” H2O to 0-800” H2O (0-3 PSID to 0-30 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
Dual Top and Bottom Process connections
O-rings Materials Buna-N, Viton, and Ethylene Propylene.
For complete specifications see: Specificationsheet_105-106.pdf

Common Applications

Pressurized Tank Level Monitoring
Stationary Tanks – Horizontal or Vertical
Tanker Transport (For materials such as LOX, CO2, Ammonia, Nitrogen, Helium, Nitrogen, Hydrogen and Argon)
Water Treatment and Air Conditioning Systems
Square Root Dials for Direct Reading of Flow Rates
Pump Performance Monitoring
Hydraulic Filter Monitoring
Filter monitoring for Gases

Micro-Switch Specifications (6″ Dial Only)

Model 106 can be equipped with one or two independently adjustable SPDT (Single-Pole, Double-Throw) micro-switches. These switches can be set to activate on either increasing or decreasing pressure.

⚠️ Minimum Range for Switch Option: 80″ H₂O

Switch Features:

1 or 2 independently adjustable SPDT switches
No input power required – mechanical snap-action
Accessible adjustment screws after removing lens and bezel (4 screws)
Color-coded 18 AWG flying leads
½” FNPT conduit connection

Switch Ratings:

5 A @ 120 VAC
3 A @ 240 VAC
4 A @ 30 VDC

Set Point Adjustability:

On decreasing pressure: 3% to 90% of full scale
On increasing pressure: 15% to 95% of full scale

Certifications:

CSA Listed – Industrial Control Equipment

📄 View Installation and Operation Manual for Micro-switch

Additional Options:

Pipe Mounting Kit - 2" U-Bolt
Wall Mounting Kit
Oxygen Cleaning
Stainless Steel Tagging
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

5 year warranty
30 + Years Hazardous Location product manufacturer.
OEM and Private Label Capabilities
Fast on-time Deliveries
Friendly Customer Support
Certified Quality System CSA B51-09 SAI GLOBAL

Model 106Documents

Model No.	Differential Pressure Range	Accuracy	Working Pressure	Electrical Available	Electrical IOM
Model 105	0-10" H2O (0-0.4 PSID) to 0-79.9" H2O (0-2.9 PSID)	±1/2% or 1% Note: 1/2% Full Scale available 30" H2O & above	Up to 3,000 PSI	None available
Model 106	0-80" H2O (0-3 PSID) to 0-800" H2O (0-30 PSID)	±1/2 or ±1% FS	Up to 3,000 PSI	MICRO SWITCHES 0-80" H2O to 0-800" H2O, CSA LISTED IND. CONT. EQUIP.
Model 115	0-10" H2O to 0-69.9" H2O Tank Level Applications	±1%	500 PSI (Optional 1,000 PSI)	None available	N/A
Model 116	0-70" H2O to 0-800" H2O Tank Level Applications	±1%	500 PSI (Optional 1,000 PSI)	MICRO SWITCHES 0-80" H2O to 0-800" H2O NEMA 4X, CSA LISTED IND. CONT. EQUIP.