The DON-H is a high-pressure oval gear flow meter, a positive displacement instrument, that meters clean, low- to high-viscosity liquids at line pressures up to 5800 PSIG (400 bar). Constructed entirely from 316L stainless steel in compact 1/8- to 1/2-inch sizes, it is built for demanding high-pressure environments that exceed the working range of a standard oval gear meter.
When to Choose the DON-H vs the Standard DON
Choose the DON-H when line pressure exceeds what the standard DON handles: it is rated to 5800 PSIG (400 bar), versus up to 1450 PSIG on the standard DON. The standard DON covers larger sizes and higher flows — to 4 inches and 660 GPM, with an aluminum option, while the DON-H is stainless-only, in 1/8- to 1/2-inch sizes to 10.6 GPM. Both share the same oval gear principle, output range, and U-PACE electronics, so the decision comes down to pressure, size, and flow.
High-Pressure Design and Materials
The DON-H body, oval gears, and axles are all 316L stainless steel, running on a carbon graphite bearing, with GEOMET-coated steel pressure screws that carry the full 5800 PSIG (400 bar) rating. Units certified under CSA and IECEE are rated to 2900 PSIG. The single all-stainless build keeps the meter compatible with most industrial products and chemicals.
Measuring Range, Sizes, and Connections
Four sizes, DON-H05 through DON-H20,span 0.13 GPH up to 10.6 GPM. Process connections are 1/8-, 1/4-, and 1/2-inch NPT thread, or the matching G (BSPP) thread. The compact bodies fit tight high-pressure manifolds and install without straight pipe runs before or after the meter.
How the Meter Measures Flow
Within the chamber, a pair of oval rotors splits the stream into precise, repeatable crescent-shaped pockets; each turn advances a fixed quantity of liquid past the gears. That rotation is picked up magnetically and issued as a scalable pulse, which local or remote electronics accumulate and convert into rate and total. Because the reading is volumetric, media conductivity is irrelevant.
Viscosity and Suitable Media
Standard rotors read to 1000 cP; for thicker fluids, special-cut DON-S rotors extend coverage to very high viscosities, with the maximum flow derated by a published factor. A DON-S20G on 8000 cP oil, for example, runs to about 5.3 GPM. The meter is intended for clean, non-abrasive media such as oils, fuels, chemicals, greases, inks, and pastes.
Temperature, Accuracy, and Repeatability
Media temperature runs from -4°F to 248°F (-20°C to 120°C), with the exact ceiling set by the O-ring and electronics selected. Rated accuracy spans ±0.2% to ±1% of reading, the DON-H20 reaches ±0.5%, or ±0.2% with optional linearization, and typical repeatability is ±0.03%. Each meter ships with a calibration certificate recording its values.
Outputs and Electronics
Signal options include Hall-effect and reed-switch pulse outputs plus a 4-20 mA analog output. Local LCD units handle totalizing, rate display, and batch/dosing control, while the U-PACE package adds a rotatable configurable TFT display, on-board temperature measurement, two freely configurable outputs, and IO-Link communication for combined flow-and-temperature monitoring.
Approvals and Installation
The DON-H is approved to ATEX and IECEx for hazardous locations, and its U-PACE electronics add CSA and IECEE CB-scheme certification. Enclosure protection is IP66/67, with M20×1.5 or 1/2-inch NPT cable entry. Intrinsically safe and flameproof(Ex d) options are available; the voltage-free reed contact suits I.S. loops installed without external power.
See It in Action: Dosing Viscous Fluids
Wondering how this meter performs on a real dosing application? Our use case walks through a lubricant blending skid dosing an 800 cP additive to a 50-gallon target, and explains why oval gear measurement holds its accuracy where velocity-based meters struggle. Read Precise Viscous Fluid Dosing with the KOBOLD DON.
Common Questions about DON-H - Oval Gear Flow Meter for High Pressures
The working pressure limit is 5800 PSIG (400 bar); versions built to CSA and IECEE certification are held to 2900 PSIG. This headroom, paired with an all-316L-stainless body, is what sets the DON-H apart from standard-pressure oval gear meters.
The line has four models (DON-H05, H10, H15, and H20) from 0.13 GPH at the low end up to 10.6 GPM on the H20. Threaded ports are 1/8-inch NPT on the H05, 1/4-inch on the H10 and H15, and 1/2-inch on the H20, with equivalent G threads available.
Every wetted part (body, oval gears, and axle) is 316L stainless steel, turning on a carbon graphite bearing, and the pressure screws are GEOMET-coated steel. This single stainless construction makes the meter suitable for most industrial products and chemicals.
This model handles media from -4°F to 248°F (-20°C to 120°C); the achievable maximum depends on seal and electronics choice. FKM Vi 840 seals cover the full span, while cooling-fin options raise the limit for certain pulse builds. Match the seal to your process temperature when ordering.
Yes. Hazardous-area versions are available. Order an intrinsically safe (Ex ia) build for Zone-rated I.S. loops, or a flameproof (Ex d) enclosure where that protection method is preferred. The two-wire reed contact is popular for I.S. installations because it needs no local power. Approvals include ATEX, IECEx, CSA, and IECEE.
Accuracy is ±1% of reading on the H05 through H15 and ±0.5% on the H20, tightening to ±0.2% when the H20 is ordered with optional linearization electronics. Typical repeatability is ±0.03%. The exact calibration figures for each unit appear on its supplied certificate.
An upstream filter is advised so particles cannot reach the close-tolerance gears. For the H05 through H15, a screen finer than 75 µm (200 mesh) is recommended; for the H20, finer than 150 µm (100 mesh). Sizing the filter to the meter safeguards accuracy and service life.
Pick reed-switch or Hall-effect pulse signals, a 4-20 mA current output, or local LCD readouts for totalizing, rate, and batching. The U-PACE option adds IO-Link, built-in temperature measurement, and two configurable outputs on a rotatable display, enabling combined flow-and-temperature monitoring from one device.