Sierra FastFlo 620S Fast Response Thermal Gas Mass Flow Meter

Overview

The Sierra FastFlo 620S is an immersible thermal mass flow meter that offers an economical solution for gas flow measurement. Its sensor provides long-term reliability and a 200 millisecond response to changes in flow rate, which is much faster than most thermal instruments. A microprocessor-based transmitter in a probe-mounted NEMA 4X (IP65) housing handles flow-range adjustment, meter validation and diagnostics, and it displays mass flow rate and totalized flow on an optional 2 x 12 character backlit LCD.

The meter is suitable for pipes and ducts from 1 inch to 48 inches (DN25 to DN1200). Facilities in Oman use air and gas flow measurement to manage compressed air systems, ventilation, combustion air, aeration and process gas dosing, and many of those points are large ducts where a compact insertion meter is the practical choice. Seven Star LLC supplies the Sierra FastFlo 620S with regional stock and engineering support in Muscat, with probe lengths, outputs and gas calibrations matched to each application.

Fast-Response Sensing Principle

Like other thermal mass meters, the Sierra FastFlo 620S measures how much heat a flowing gas removes from a heated sensor. One element tracks the gas temperature while a second is heated above it, and the heater power required to hold the difference is proportional to the mass flow of the gas. The measurement is therefore a mass measurement without separate density, pressure or temperature correction, which is valuable when air or gas conditions change through the day.

The FastFlo sensor is built with a 304 stainless steel sensor body and a glass-coated epoxy finish, mounted on a 316 stainless steel probe, and it reaches 63 percent of a final velocity value in 200 milliseconds. That response makes the Sierra FastFlo 620S well suited to processes in which flow changes quickly, such as burner control, blower modulation, process purging and test stands. Pressure drop through the probe is negligible.

Engineering Design of the Sierra FastFlo 620S

The transmitter is housed in a powder-coated cast aluminum NEMA 4X (IP65) enclosure mounted directly on the probe or remote with a junction box. Probe lengths are 4, 6, 9, 13 and 24 inch, and mounting options include a 3/8 inch tube compression fitting with a 1/2 inch male NPT, a weldolet, and flat or curved duct brackets. Electrical connection is by one 1/2 inch female NPT port. Power is 18 to 30 VDC regulated at up to 625 mA, with a maximum inrush current of 2 amps.

Outputs are linear 4 to 20 mA, 0 to 5 VDC or 0 to 10 VDC, with the 4 to 20 mA signal optically and galvanically isolated, and two hard-contact alarms with adjustable dead band. The meter can be configured through RS-232 with Sierra Smart Interface software or through three push buttons on the device, and Modbus RTU is supported. Adjustable settings include full scale, response time, correction factor, zero and span, and alarm levels, with an eight-digit totalizer that can be reset by software or by an external magnet.

Key Features

The Sierra FastFlo 620S offers these capabilities:

• 200 millisecond response to changes in flow rate for fast process control and monitoring.
• Smart electronics that allow field adjustment of critical flow meter settings.
• Field validation of flow meter calibration through Smart Interface software.
• Outstanding rangeability with minimal flow blockage and low pressure drop.
• Suitable for pipes and ducts from 1 inch to 48 inches (DN25 to DN1200).
• Optional 2 x 12 character backlit LCD display and optional Modbus RTU communication.
• Calibrations for air, argon, carbon dioxide, helium and nitrogen, with other gases on request.
• Optional totalizer pulse output, non-resettable totalizer, remote cable and oxygen cleaning.

Industrial Applications

The Sierra FastFlo 620S targets air and non-corrosive gas measurement where speed and economy matter. Typical uses include compressed air distribution, combustion air to burners and boilers, aeration blowers in water and wastewater plants, HVAC ducts and process gases such as nitrogen and carbon dioxide. In the Sultanate of Oman those applications appear at desalination and water treatment works, industrial estates at Sohar and Salalah, hospitals, data facilities and manufacturing plants that monitor utilities for efficiency.

Specifiers should note that the sensor is limited to gas temperatures from −40 to 176 °F (−40 to 80 °C), and design pressure is 150 psig (10.34 barg), so heavier-duty services call for the SteelMass or QuadraTherm meters. Seven Star LLC supplies the Sierra FastFlo 620S together with related instruments such as the Sierra Instruments QuadraTherm 640i thermal mass flow meter, the Fluidwell F126-EG field mount flow computer and the Fluidwell F114 ratio monitor and totalizer.

Technical Specifications

The table lists data from the manufacturer datasheet for the Sierra FastFlo 620S. Confirm probe length, output and gas calibration against the ordering chart.

Request a Quote for Sierra FastFlo 620S

Request a quotation for the Sierra FastFlo 620S by sending an RFQ to the Seven Star LLC instrumentation team in Muscat with the gas, duct or pipe diameter, flow range, temperature and preferred output. We will confirm the probe length, mounting and calibration, arrange supply to Oman and the GCC, and include the manufacturer’s Sierra FastFlo 620S datasheet with our quotation for your engineers to review.