Economical Positive Displacement Oval Gear Flow Meters for Industrial Applications
The DON series from KOBOLD delivers reliable positive displacement oval gear flow meters designed for accurate volumetric measurement of clean, viscous, and non-abrasive liquids in industrial processes. These meters come in various sizes to handle flow rates as low as 0.13 GPH up to a maximum of 660 GPM (0.5 L/h to 2500 L/min). They are the preferred choice for highly viscous fluids handling viscosities of up to 1000 cP with standard rotors, with special cut rotors available for significantly higher viscosities.
Available in aluminum or 316L stainless steel construction, the DON supports line sizes from 1/8 inch to 4 inches with threaded NPT/BSP or flanged connections (ANSI/DIN). Maximum pressure ratings reach 1450 PSIG (100 bar) on smaller models, while temperature capability spans -4°F to 302°F (-20°C to 150°C) depending on seals and electronics chosen.
Compact design eliminates the need for straight pipe runs, making installation simple in space-constrained systems. Options include a variety of pulse outputs, local LCD totalizers and batch controllers, or the advanced U-PACE electronics with integrated temperature measurement, IO-Link communication, and fully configurable outputs. The large selection of options to choose from provides flexible integration options for batching, filling, and process monitoring applications. Specialized models include bipolar sensors alternating polarized magnets for pulsating flows and a quadrature pulse output that is well suited for measuring bidirectional flows.
New DON with U-Pace Electronics
The DON is now available with our new U-Pace electronics which offer a wide variety of features and easy programming through the touch display. It offers an IO-Link function and totalizing, batching, and switching capabilities. There are two configurable outputs and a grand and resettable totalizer. Temperature measurement is also integral and bi-directional flow measurement is also possible. To learn more about our U-Pace electronics package, view our U-Pace Video.
How the DON Works: Positive Displacement Oval Gear Measurement Principle
The DON operates using proven positive displacement technology. As liquid flows through the precision-machined measuring chamber, it forces two intermeshing oval rotors to rotate. Each complete rotation displaces a fixed volume of liquid, ensuring direct volumetric measurement regardless of viscosity, density, or conductivity.
Magnets embedded in the rotors generate high-resolution pulses detected by Hall-effect or reed sensors. These pulses are transmitted to remote displays, PLCs, integrated LCD display electronics, or the U-PACE electronics for flow rate, totalization, and temperature monitoring.
This mechanical principle delivers typical repeatability of ±0.03% and accuracy from ±0.2% to ±1% of reading (model and electronic dependent).
Visit our article about Positive Displacement Flow Meters to learn all about the technology type and its advantages and limitations.
Ideal for Intermittent and Fluctuating Flow Rates
Because the measurement principle provides a true volumetric flow measurement, the DON is also ideal for flow rates that fluctuate widely and for flow that is intermittent. High accuracy measurement is assured even though these are process variables that would render other flow meter technology types non-compatible.
Key Features and Performance Advantages
The DON series combines rugged construction with versatile electronics to meet diverse industrial requirements. Multiple output options and hazardous-area approvals (ATEX/IECEx) support safe operation across industries.
- Wide viscosity range up to 1000 cP for standard rotors; special cut rotors for up to 30,000 cP
- No inlet/outlet straight runs required for accurate measurement
- A large variety of different outputs such as pulse, analog, frequency, or IO-Link
- Mechanical 4-digit resettable totalizer available (no power required)
- IP66/67 protection and ATEX approvals for harsh or explosive environments
| Model | Connection Size | Flow Range (GPM) | Max Pressure (psig) | Typical Accuracy |
|---|
| DON-x04 | 1/8" | 0.13 – 9.5 (GPH) | 1450 | ±1%-3% |
| DON-x05 | 1/8" | 0.13 – 9.5 (GPH) | 1450 | ±1% |
| DON-x10 | 1/4" | 0.5 – 27 (GPH) | 1450 | ±1% |
| DON-x15 | 3/8" | 4 – 145 (GPH) | 1450 | ±1% |
| DON-x20 | 1/2" | 0.26 – 10.6 | 1000 | ±0.2% – ±1% |
| DON-x25 | 1" | 2.6 – 40 | 870 | ±0.2% – ±1% |
| DON-x30 | 1-1/2" | 4 – 66 | 725 | ±0.2% – ±1% |
| DON-x35 | 2" | 8– 120 | 725 | ±0.2% – ±1% |
| DON-x40 | 2" | 13 – 150 | 230 | ±0.2% – ±1% |
| DON-x45 | 3" | 10 – 200 | 230 | ±0.2% – ±1% |
| DON-x50 | 3" | 13 – 260 | 230 | ±0.2% – ±1% |
| DON-x55 | 4" | 20 – 400 | 230 | ±0.2% – ±1% |
| DON-x60 | 4" | 40 – 580 | 230 | ±0.2% – ±1% |
Industry Applications and Use Cases
In petroleum and fuel transfer systems, the DON accurately meters diesel, lubricants, and heating oils even with temperature-induced viscosity changes. Stainless steel models handle aggressive solvents and resins in chemical batching, providing pulse outputs for precise dosing control.
Paint and ink manufacturers rely on the DON for consistent pigment and solvent blending, benefiting from its ability to manage high-viscosity media.
Hydraulic test stands and grease dispensing systems choose the DON for its compact footprint and reliable performance with intermittent flows, helping maintain accuracy during pressure testing and lubrication cycles.
Technical Specifications Overview
- Measuring ranges: 0.13 GPH to 660 GPM (0.5 L/h to 2500 L/min)
- Viscosity: up to 1,000 cP standard rotors; special cut rotors for up to 30,000 cP
- Accuracy: ±0.5% to ±1% of reading (rotor/electronics dependent); repeatability ±0.03%
- Max pressure: up to 1450 PSIG (100 bar) threaded; flange rating applies when used
- Medium temperature: -4°F to 302°F (-20°C to 150°C) with appropriate seals and electronics
- Body materials: aluminum or 316L stainless steel
- Rotor materials: PPS/PTFE, PEEK, or stainless steel
- Outputs: reed/Hall pulse, 4-20 mA, frequency, IO-Link, quadrature, mechanical totalizer
- Electronics: U-PACE with TFT display, temperature measurement, two configurable outputs, and IO-Link capability
- Protection: IP66/67 (IP65 for mechanical totalizer option)
- Approvals: ATEX and IECEx
Higher Pressure Oval Gear Positive Displacement Flow Meters
To accomodate even higher process pressure than our standard DON Oval Gear Flow Meter, KOBOLD also makes the DON-H High Pressure Oval Gear Flow Meter. It offers the exact same rugged and reliable service for high viscosity liquid measurement.
Other Positive Displacement Flow Meters and Gear Meters from KOBOLD
KOBOLD offers a comprehensive line of Positive Displacement Flow Meters including other Oval Gear Flow Meters, Rotary Piston Flow Meters, and Helical Screw Gear Flow Meters.
Application Guide Required for Product Specification
**This product requires completion of our Application Guide before specification and ordering.**
This product line offers multiple configuration options and technical specifications that must be precisely matched to/calibrated for your specific application requirements. Unlike standard configurable items, these products are engineered solutions that require detailed application information to ensure optimal performance.
The Process
- Complete the Application Guide - Provide detailed information about your specific application
- Technical Review - Our engineering team reviews your requirements
- Product Specification - We specify the exact configuration for your needs
- Quotation & Ordering - Receive your custom quote with precise part numbers
Important Notice
Unless this is a repeat order of a previously specified product with Kobold, we cannot accept orders or provide quotations without a completed Application Guide. Product numbers selected without proper application review may not meet your system requirements and could result in performance issues or compatibility problems.
Even if you believe you've identified the correct part number, the Application Guide process is required to verify compatibility and ensure a streamlined quote/order process.
Ready to get started?
The PDF Application Guide can be downloaded directly from this product page in the “Resource Tab” below and is also attached to the end of the product datasheet. Completed forms can be submitted to customerservice@koboldusa.com.
Need help filling it out? Contact our engineering team: call 412-788-2830 or schedule a free online engineering consultation at your convenience.