Series-ST50

Supported Applications

The FCI ST50 Series is a thermal dispersion mass flow meter designed for measuring air, compressed air, and nitrogen. These instruments provide direct mass, volumetric, or velocity flow measurement in process and plant applications. The series supports line sizes ranging from 2 to 24 inches (51 mm to 610 mm) and utilizes non-clogging sensors with no moving parts.

Operating Conditions & Performance

The ST50 Series operates within an ambient temperature range of 0°F to 140°F (-18°C to 60°C). Process temperatures are rated up to 250°F (121°C) with stainless steel ferrules and up to 200°F (93°C) with Teflon ferrules. Measurement ranges vary by configuration, including options such as 0.75 SFPS to 400 SFPS [0.23 MPS to 122 MPS] for air/nitrogen/compressed air applications.

Accuracy is available in two classes: Standard calibration at ±2% of reading and ±0.5% of full scale, or Optional high-accuracy calibration at ±1% of reading (with specific conditions). Repeatability is specified as ±0.5% of full scale. The series supports pressure ratings up to 500 psig [34 bar(g)] with stainless steel ferrules and retractable packing glands, while Teflon ferrule configurations are rated to 150 psig [10 bar(g)].

Configuration Options

The series offers extensive configurability across transmitter housing styles, process connections, insertion lengths, and output signals.

• Housing & Mounting: Available with blind integral transmitters or integral/remote transmitters featuring a local digital display. Enclosures are standard aluminum (epoxy coated) or optional 316 stainless steel, rated NEMA 4X [IP67]. Electrical connections include dual conduit ports with either 1/2" Female NPT or M20x1.5 entries.
• Process Connections: Options include 1/2" MNPT or 3/4" MNPT compression fittings (stainless steel or Teflon ferrule) and retractable packing glands with graphite or Teflon packing.
• Insertion Lengths: Field-adjustable insertion lengths are available in maximum "U" lengths of 6 inches [152 mm], 12 inches [305 mm], or 18 inches [457 mm].
• Sensor Materials: Wetted materials include a 316 stainless steel body and Hastelloy C-22 thermowell sensors.
• Outputs & Communication: Standard features include dual 4-20 mA analog outputs (NAMUR NE43 compliant, assignable to flow rate or temperature) with a maximum load resistance of 500 ohms. Optional pulse output for total flow and standard RS-232C serial communication are available.
• Power Supply: Supports DC: 18 VDC to 36 VDC (6 watts max.) or AC: 85 VAC to 265 VAC (12 watts max.).
• Approvals: Configurations include FM/CSA Nonincendive for Class I, Division 2 locations; ATEX/IECEx II 3 G EEx nA II T6 and II 3 D T65°C (DC input power only); plus CPA, EAC/TR CU, CE Marking, CRN, and PED.

Key Product Differences

The ST50 Series distinguishes itself through specific model configurations defined by base unit style, mounting orientation, and calibration parameters. Base units range from blind integral transmitters to remote transmitter setups with digital displays. Mounting orientations are configurable for horizontal or vertical pipe installations, specifying flow direction (left-to-right, right-to-left) and display face position.

Calibration variations include standard air/nitrogen ranges versus customized compressed air profiles, often paired with optional Vortab flow conditioners to achieve high-accuracy 1% calibration. Transmitter housing material options allow selection between aluminum or stainless steel enclosures depending on environmental requirements. For applications requiring Div. 1 / Zone 1 environments or dual-line digital displays with built-in totalizers, the FCI Model ST51 is referenced as an alternative.