Preso — DP Flow Elements

A differential-pressure (DP) flow sensing element is the primary device in a DP flow meter: it creates the DP signal — a pressure drop proportional to flow — that a DP transmitter then senses and converts to a flow reading (flow tracks the square root of ΔP). Because the element is just a shaped obstruction with no moving parts in the line, DP covers service that displacement, turbine, and even magnetic or ultrasonic meters struggle with — very large lines, high temperature, high pressure, and steam — and works on liquid, gas, or steam with one technology. Preso supplies the primary element; you pair it with the DP transmitter and readout of your choice.

Choose by line size, fluid, the permanent pressure loss you can accept, and the straight run you have. The Ellipse averaging-pitot tube is the low-loss insertion choice — clean liquid, gas, or steam in large lines (2–72 in), ±0.75%, hot-tappable. A Venturi (full-bore LPL/SSM/SSL or short-form VI inserts / CV series) gives high accuracy with strong pressure recovery for clean fluids where you want a permanent element. The Coin segmented wedge is for dirty, abrasive, slurry, and fouling service (Reynolds as low as 300, to 800 °F). The Gemini cone conditions the flow itself, holding ±0.5% in just 0–3 pipe diameters of upstream straight run — the answer for tight piping.

Every DP element leaves some unrecovered (permanent) pressure loss, which costs pumping energy over the life of the line, so it is a real selection factor. The Ellipse averaging pitot has the lowest loss (it only samples the flow); a Venturi recovers most of its pressure (low permanent loss for a full-bore element); segmented-wedge and orifice-type elements run higher. Tell us how much loss you can give up and it steers the element choice.

Like any inferential element, averaging-pitot and Venturi elements need straight upstream run to settle the flow profile — how much depends on the upstream fittings. Where you cannot give that, the Gemini cone is the fix: its shape conditions the flow as it passes, so it holds accuracy in as little as 0–3 pipe diameters of upstream straight run. If your piping is cramped, say so up front and the selection moves toward the cone.

Yes — this is where DP elements earn their place. The Ellipse handles up to about 800 °F and 800 psi, with dedicated steam variants (AS/AHS); Venturi tubes and nozzles suit large high-pressure liquid, gas, and steam lines. For saturated or superheated steam, compressed air, and process gas in large or hot lines, a DP element is often the most practical and economical primary device.

Use the Coin segmented wedge. Its V-shaped restriction sweeps solids through instead of trapping them, so it reads dirty, abrasive, and slurry flows and stays accurate at low Reynolds numbers (down to about 300) and up to 800 °F — conditions that foul or erode a pitot or orifice. Averaging-pitot and Venturi elements are for cleaner fluids.

Preso elements are engineered to your line and can ship with a factory 6-point flow calibration, 3- or 5-valve instrument manifolds, hardcoating for abrasive duty, and traceable material certifications — including NACE MR-0175 / MR-0103, PMI, and radiographic or dye-penetrant (NDE) examination. Specify the certs your project requires and they are built into the order.

Preso DP elements are engineered to your specific line size, fluid, and operating conditions, so they are quote-only — there is no published pricing. Tell Prater Technical the line size, fluid, temperature and pressure, available straight run, and any material or NDE certifications, and we spec the element, calibration, manifolds, and certs and ship from Badger’s WI facility.