Operation Explained
The Differential Pressure Principle
How RCM Industries Flo-Gage™ flowmeters deliver simple, rugged, direct-reading flow measurement — no external power, no separate orifice plates, no calculations required.
RCM Industries Flo-Gage™ Flowmeters
RCM Industries, Inc. has specialized in reliable industrial flow measurement since 1972. The company was founded by Roy C. Marker after he observed unreliable flow gauges during a NASA facility tour. Inspired to create something better, he developed the Flo-Gage™ — a straightforward, durable, direct-reading flowmeter that is easy to install and maintain.
Today, RCM continues that legacy with a focus on rugged, reliable products backed by outstanding service and a strong guarantee: try it for 30 days; if you're not satisfied, return it for a full refund or credit. Products are also warranted against defects in materials and workmanship for one year.
How Flo-Gage™ Flowmeters Work
The Flo-Gage™ operates on a classic differential pressure (ΔP) principle, similar to an orifice-plate meter but fully integrated for simplicity and reliability:
- 01
Built-In Calibrated Nozzle
Fluid (liquid or gas) flows through a built-in calibrated nozzle inside the meter body.
- 02
Pressure Drop Created
The nozzle creates a restriction, causing a pressure drop (ΔP) across it. This pressure difference is proportional to the square of the flow rate — from Bernoulli's principle: higher velocity through the restriction lowers pressure.
- 03
Bellows Mechanism
The ΔP is sensed internally by a bellows mechanism connected to the pointer on the large, easy-to-read 3.5-inch (90 mm) dial.
- 04
Direct-Reading Dial
The dial is factory-calibrated directly in engineering units (GPM, LPM, SCFM, Nm³/h, etc.), so you see the actual flow rate at a glance — no calculations or external displays needed for the basic model.
- 05
Fully Self-Contained
The meter is mechanical and self-contained: no external power, no purging valves, and no separate orifice plates required.
Why This Matters in Practice
- The ΔP relationship is inherently accurate (±3% of full scale) over a 6:1 flow range.
- The design is rugged (all-metal construction) and resists piping stresses, vibration, and accidental damage.
- It works with both clear and opaque fluids — you don't need transparent liquids.
- For flow switches, reed-switch contacts (Options 1S2 or 2S2) detect the exact position of a magnet on the pointer mechanism, providing reliable high/low flow alarms. These switches are adjustable (30–90% of full scale), tamper-resistant, and immune to small particles in the flow.
- Electronic transmitters (Options W, W2, W3, etc.) convert the same ΔP into 4–20 mA, frequency, or digital outputs for remote monitoring, totalization, or control.
- Pressure-drop characteristics vary slightly by body material (bronze, Monel, or stainless steel), but the catalog provides easy-to-use curves so you can confirm the meter fits your system's available head pressure.
Key Features & Benefits
Large, Readable Display
270° expanded analog dial — easy to read from a distance without external power or displays.
Rugged In-Line Design
Withstands piping stresses; no external components to break or leak.
Low Maintenance
No moving parts in the flow stream except the nozzle; dial won't crack or glaze.
Versatile
Handles water, oils, low-viscosity liquids, compressed air/gases, and saturated steam (with appropriate options).
Compact and Economical
Ideal where space, cost, and durability matter most.
Field Configurable
Housing and indicator can be rotated 90° in four positions for easy viewing.
Product Configurations
Series 7000 — Threaded
Female NPT (standard) or FBSP threads
Series 8000 — Wafer
Mounts between standard 150 or 300 lb flanges
Body Materials
- Bronze (most common)
- Monel
- 316 Stainless Steel
Liquid Ranges
From very low (e.g., 1 GPH) up to thousands of GPM depending on size.
Gas & Steam
SCFM or Nm³/h (Option I required). Steam lb/h up to 120 psig (Option K).
Popular Options & Accessories
| Category | Options Include | Benefit |
|---|---|---|
| Seals | Viton (A), EPR (B), PTFE (B2) | Chemical compatibility |
| Case | Gasketed (D/D2) — NEMA-4X / IP-66 | Weather, marine, dusty environments |
| Service | Compressed gas (I), Saturated steam (K), Ammonia (N), High viscosity (V) | Specific media |
| Indication | Peak flow pointer (J), Custom dials (G) | Extra insight |
| Electronics | 4–20 mA transmitters (W/W2/W3), Frequency (Y), Reed switches (1S2/2S2) | Remote monitoring & alarms |
| Readout | Remote mechanical (R2/R3), Digital rate + total (RW3) | Convenient viewing |
| Special | High pressure 400 psig (H), Panel mount (P), Intrinsic safety (IS) | Harsh or hazardous conditions |
The Compressed Air Survey Kit (SK-1) is a portable aluminum-body meter with multiple orifices, pressure gauge, and carrying case — perfect for energy audits.
Typical Applications
Services to Avoid
- High-viscosity fluids (>500 cps)
- Resins or paints that deposit solids
- Sulfuric acid
- Foods/pharmaceuticals requiring clean-in-place
- Toxic gases needing hermetic seals
- Piston-pump systems with pulsating flow
Why Choose RCM Flo-Gage™?
Whether you need a simple local gauge, a low-flow alarm switch, or a 4–20 mA transmitter for PLC integration, the Flo-Gage™ delivers dependable performance with minimal installation hassle. Its mechanical simplicity, large readable dial, and robust construction make it a favorite in plants where reliability and quick visual checks matter most.
Flo-Gage™