Hedland Phosphate Ester — Variable Area Flow Meters

Specifications

Common Applications

• Turbine electro-hydraulic control (EHC) fluid flow on power-generation units
• Fire-resistant hydraulic circuits in steel, die-cast and foundry equipment
• Aviation and aerospace ground-support hydraulic systems running phosphate-ester fluid
• Lubrication and control-fluid flow checks where a non-flammable fluid is mandated

Design & Selection Considerations

• Match the body and seals to the fluid — the meter is offered in anodized aluminum, brass and 303 / 316 stainless steel with Viton or EPR seals, and the right pairing is fluid-driven: aluminum for petroleum and air, brass for water, and 316 stainless for caustics and corrosive liquids or corrosive gases. Phosphate ester is the seal exception — it attacks Viton, so that family alone runs EPR in place of the standard Viton seals. Use the input form to tell us the fluid and we’ll pair the body alloy and elastomer to it — the wrong seal is the usual failure mode.
• Order the scale for your fluid — the meter is calibrated to a specific gravity — a Hedland scale is printed for one fluid: 0.876 s.g. for petroleum, 1.18 s.g. for phosphate ester and 1.0 s.g. for water and water-based fluids. Read a different fluid and the indication shifts with density. Hedland computer-corrects the phosphate-ester and water-based scales at the factory, and special scales are available in any unit for off-standard gravities or viscosities. Use the input form to give us the actual fluid, specific gravity and units — we order the scale that reads true in service.
• Size to the flow, not the pipe — and watch the pressure drop — a variable-area meter reads full scale at the top of its band, so size to the real flow and keep the permanent pressure drop in check (most hydraulic sizing targets 10 psid maximum). Each port size offers several full-scale ranges. Use the input form to send the normal and maximum flow and we’ll pick the range that reads mid-scale and stays inside your allowable ΔP.
• Install it anywhere — no straight run or flow straighteners — the spring-loaded piston design reads accurately in any orientation, including inverted, and tolerates mounting immediately next to elbows, valves and pumps with no upstream straight run or flow straighteners. The guard / scale rotates 360° after install for readability. This is the meter for tight, awkward plumbing where a turbine or rotameter would need straight pipe it doesn’t have.
• Filter the line to 200 mesh — the meter is more contamination-tolerant than most system components, but 200 mesh (74 micron) or better filtration is required for reliable indication and to protect the metering orifice and piston. Confirm upstream filtration before commissioning — grit in the annulus is what pulls a variable-area reading off.
• Mind material and temperature when you set the pressure rating — pressure capability follows the body alloy: in ¼–1½ in. liquid service aluminum and brass are rated 3,500 psi and stainless 5,000–6,000 psi, all to a 3:1 safety factor. Aluminum and brass derate above 240°F; stainless does not. A high-temperature build extends the range to +400°F continuous (+500°F intermittent). Use the input form to give us the working pressure and the peak temperature together — they set the alloy and whether you need the HT build.
• Add the electronics only where the job needs a signal — the standard meter is direct-reading. Where the application needs an alarm or a feed to a control system, specify a Flow-Alert switch for a trip contact at a set flow, or an MR transmitter for rate / total plus a 4–20 mA or DC-voltage output. Local indication is free; choose the switch or transmitter when you need a contact or an analog signal.