F56 Metal Tube Variable Area Flowmeter

How It Works

A variable-area flowmeter (rotameter) measures flow by letting a free-floating "float" ride up and down inside a tapered tube — the higher it rises, the more flow is passing through. Most compact rotameters use a clear glass or plastic tube so you can watch the float directly, but the F56's metal tube is built for higher pressure, higher temperature, and harsher conditions where glass isn't an option. To keep the reading just as clear, a magnet inside the float communicates its position straight through the metal tube wall to the indicator outside — no window needed, nothing touching the process fluid, just a needle (and, on remote models, a live digital signal) that tracks the float in real time.

Learn more: What is a Rotameter?

Metal Construction for Demanding Conditions

A glass or plastic tube can crack under high pressure or heat — the F56's all-metal body doesn't have that limit. Depending on size and material, it handles pressure up to 42 MPa and media temperature up to 400°C, so it keeps reading accurately on steam lines, high-pressure gas service, and other duty a lighter-built flowmeter simply can't survive.

A Material for Every Process

Every F56 shares the same measuring principle — what changes is what touches your fluid. Pick the wetted material based on what's actually flowing through the line:

Stainless Steel (304 / 316 / 317) — The Everyday Workhorse

For water, steam, oil, and general chemical duty, 304 and 316 stainless steel cover most installations — 316 adds extra resistance to chlorides and mild acids, and 317 steps up further where 316 isn't quite enough. Low-carbon "L" grades (304L, 316L, 317L) resist the corrosion that welding can cause at the seam, making them the standard choice in food, beverage, and pharmaceutical lines where the meter is welded directly into the pipe.

PTFE-Lined Tube — For Aggressive Chemicals

When a process fluid is too corrosive for bare stainless steel, a full PTFE lining puts a chemically inert barrier between the fluid and the metal body, standing up to most strong acids and alkalis that would otherwise attack the tube. (PTFE lining is rated 0–80°C — see Specs for the full range.)

Hastelloy & Nickel — Built for Extreme Corrosion

For duty beyond what stainless steel or PTFE can take — hot hydrochloric or sulfuric acid, chlorine-bearing streams, or concentrated caustic soda — Hastelloy (B1/B2/C276) and pure nickel (N6) wetted parts hold up where ordinary metals would corrode away.

Titanium — Seawater and Oxidizing Acids

Titanium resists the chlorides and oxidizing acids that quickly attack stainless steel, making it the natural choice for seawater, bleach lines, and other chloride-heavy or oxidizing processes.

Zirconium — The Toughest Acid Duty

Zirconium is reserved for the most aggressive acid service — concentrated, near-boiling sulfuric or hydrochloric acid — where even Hastelloy reaches its limit.

PP & PV — Economical Plastic Construction

For utility water, dilute chemical dosing, and other mild-duty lines that don't need a full metal body, PP and PV plastic construction offers a lighter, lower-cost option for general plant service at ambient temperature (vertical mounting only, up to DN100).

One Flowmeter, However You Need to Read It

The F56 mounts the same way and measures the same flow whichever indicator you choose — so you're picking how you read it, not a different meter:

Steady Readings, Even When Flow Isn't

A valve opening suddenly, or a pressure spike hitting the line, can send the float bouncing or spinning — and a jumpy float means a jumpy reading. On gas-service models, the F56 fits a self-centering damper machined from ultra-pure ceramic, so the float settles quickly and stays put. It won't corrode, won't wear down, and keeps your reading — and your 4-20mA signal — steady even when the process isn't.

F56 flowmeters are put to work across oil & gas, chemical, metallurgy, power, food & pharmaceutical, and pulp & paper processes — measuring and controlling liquid, gas, and steam flow wherever the line demands.