Hedland Corrosive Air & Gas — Variable Area Flow Meters

Specifications

Common Applications

• Chlorine, hydrogen chloride and acid-gas dosing / scrubber feed flow
• Sulfur dioxide and other corrosive process-gas metering
• Chemical-plant and water-treatment gas-injection flow indication
• Corrosive purge and blanketing gas flow checks

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 — this family is solid T316 stainless rated 1,500 psi for compressed corrosive-gas service, all to a 10:1 safety factor, and stainless does not derate with temperature. The Hostile-Environment build (Pyrex glass guard, T416 indicator, all-stainless externals) 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 whether you need the Hostile-Environment 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.