DAF - Paddle-wheel Flow Indicator for Liquids - Low Min. Flow Indication

DAF Paddle Wheel Flow Indicator for Liquids

The KOBOLD DAF is a paddle-wheel (rotating-vane) flow indicator that provides visual confirmation of liquid flow without measuring flow rate. A rectangular housing with two transparent windows contains a paddle wheel that is set into motion by the flowing media, so a clearly visible rotating wheel signals that flow is present.

Because the DAF indicates rather than measures, it is intended for applications where an operator needs to see at a glance whether liquid is moving through a line. The DAF is designed with 7 flow ranges starting from 0.5-1.6 GPH up to 80-2380 GPH. This indicator is well suited to applications such as lubrication, cooling, and dosing circuits.

How the DAF Works

A rectangular housing fitted with transparent windows on the front and back holds a paddle wheel. As liquid flows through the chamber, the wheel spins, and that rotary motion is the flow indication. With one housing size, different minimum and maximum flow ranges are achieved by changing the inlet port orifice, so a single body covers the full range lineup. The all-mechanical design uses no electrical power or external connections.

Installation and Orientation

The DAF can be installed in any position, provided flow follows the direction of the arrow on the housing and the front of the unit stays in the vertical plane. The manual advises arranging the process flow path, so the chamber stays completely filled with liquid; no additional inlet or outlet straight-run lengths are required. Threaded connections are available from 1/8” up to 1-1/2” in NPT or G. Flange connections are available from 1/2” to 2” in ANSI class 150 or PN16 DIN flanges. Threaded connections should be sealed with PTFE tape or similar material, and flange connections use a customer-supplied flat seal.

• Counter the union fittings with an open-end wrench when tightening to avoid transferring stress to the housing, which can damage the device.
• Introduce media slowly to avoid pressure peaks; sudden valve action (water hammer) can damage the unit.
• Keep the indicator housing constantly filled — large bubbles or a partially filled chamber can cause rotation errors or damage to the bearings.

Rotatable Windows During Operation

The DAF may be rotated along its long axis even while in operation, thanks to its rotatable fittings, so the viewing windows can be aligned to the best orientation once installed. This applies to all material combinations except Material Combination IV, whose connections are non-rotatable. This lets operators orient the indicator for clear sightlines in tight or awkward installations.

Materials and Media Compatibility

The DAF is offered in four material combinations (I-IV) so the wetted materials can be matched to the process liquid. Housings range from polyamide (I) and polysulfone (II) to nickel-plated brass (III) and 316Ti stainless steel (IV); paddle wheels are POM or PTFE, and O-rings are NBR or FKM depending on the specific material combination. The axle is 316L stainless with a PTFE bearing in every combination. The maximum operating pressure is 145 PSI for Combinations I and II, and 235 PSI for Combinations III and IV. The maximum operating temperature is 140°F (60°C) for Combination I and 230°F (110°C) for Combinations II, III, and IV.

For higher-temperature applications, the nickel-plated brass, stainless-steel, and polysulfone combinations (II–IV) extend the usable envelope over the polyamide housing (I). The nickel-plated brass and stainless steel housings (III-IV) are suitable for higher pressures, up to 235 PSI, compared to the plastic housing options. For more aggressive or corrosive media, material combinations with polysulfone housing (II) or with a stainless steel housing (IV) offer more resistant materials including FKM O-rings and PTFE paddlewheels.

Common Questions about DAF