Sierra SteelMass 640S Insertion Thermal Gas Mass Flow Meter

Overview

The Sierra SteelMass 640S is an immersible thermal mass flow meter designed for the toughest industrial gas flow measurement applications. A microprocessor-based transmitter combines flow measurement, flow-range adjustment, meter validation and diagnostics in either a probe-mounted or a remote housing, and it reports mass flow rate and totalized flow on an optional 2 x 12 character backlit display. Because the sensor responds directly to mass flow, the meter does not need separate temperature and pressure inputs.

Natural gas, flare gas, compressed air, nitrogen, biogas and process gases are measured throughout Oman’s oil, gas, power and water sectors, often in large ducts and headers where inline meters are impractical. Seven Star LLC supplies the Sierra SteelMass 640S with engineering support in Muscat, along with hot-tap hardware, remote cables and gas calibrations, so insertion flow points can be specified completely.

Thermal Mass Measurement Principle

A thermal mass flow sensor places two temperature-sensing elements in the gas stream. One element senses the gas temperature and the other is heated to a fixed temperature above it. Gas flowing past the heated element carries heat away in proportion to its mass flow, so the power needed to hold the temperature difference is a direct measure of mass flow. The Sierra SteelMass 640S uses Sierra’s patented Dry-Sense thermal sensor technology, which is designed to eliminate sensor drift and hold calibration over time.

Calibration of the Sierra SteelMass 640S is performed in Sierra’s calibration facility so that it matches the application gas. Sierra’s Smart Interface software also guides users through a procedure that validates meter electronics and sensor resistance in the field, which allows the instrument to be verified without removing it from the line. Response time is one second to 63 percent of the final velocity value.

Engineering Design of the Sierra SteelMass 640S

The wetted parts are 316 stainless steel on a 3/4 inch diameter probe, with probe lengths from 6 inch to 42 inch in the standard ordering codes and a high-temperature option to 750 °F (400 °C) for air. The enclosure is either a hazardous-area location enclosure rated IP66 or a NEMA 4X (IP65) enclosure, both powder-coated cast aluminum, mounted on the probe, or remote with a junction box. Mounting options include a 3/4 inch tube compression fitting with a 1 inch male NPT, a 1 inch ANSI 150 lb flange and hot-tap systems.

Two hot-tap versions are offered. The low-pressure hot tap is rated to 150 psig (10 barg) and the high-pressure hot tap depends on the flange, up to 400 psig (27.6 barg), allowing installation and removal without shutting down the process. Power is 18 to 30 VDC or 100 to 240 VAC, outputs are linear 0 to 5 VDC, 0 to 10 VDC or 4 to 20 mA, and Modbus RTU and a totalizer pulse output are available as options.

Key Features

The Sierra SteelMass 640S offers these capabilities:

• Direct mass flow monitoring that eliminates separate temperature and pressure measurements.
• Accuracy of plus or minus 1 percent of reading plus 0.5 percent of full scale, with repeatability of plus or minus 0.2 percent of full scale.
• Patented Dry-Sense technology that eliminates sensor drift and a one-second response to changes in flow rate.
• Field validation of meter electronics and sensor resistance to verify performance.
• FM, CSA, ATEX and GOST R/RTN certification for hazardous areas, plus CE approval.
• Low-pressure and high-pressure hot-tap options for installation without process shutdown.
• Optional high-temperature version up to 750 °F (400 °C) for air service.
• Smart Interface software for configuration over RS-232, with high and low relay alarms and an eight-digit totalizer.

Industrial Applications

Immersible thermal meters are the usual choice for large pipes and ducts, and the Sierra SteelMass 640S is applied to compressed air, natural gas, nitrogen, oxygen, hydrogen, digester gas, flare and vent lines and combustion air. In the Sultanate of Oman that includes compressor stations, gas gathering and processing plants, power stations and fertilizer and petrochemical complexes at Sohar and Salalah, where mass flow supports fuel accounting, emissions reporting and efficiency monitoring.

Insertion meters need adequate straight pipe, with 15 to 40 upstream and 5 to 10 downstream diameters depending on the disturbance, and Sierra’s FlatTrak 780S with built-in flow conditioning is available when space is short. Seven Star LLC supplies the Sierra SteelMass 640S alongside related instruments including the Sierra Instruments QuadraTherm 640i thermal mass flow meter, the Endress+Hauser t-mass 65F thermal mass flowmeter and the OMNI 7000 flow computer.

Technical Specifications

The table lists data from the manufacturer datasheet for the Sierra SteelMass 640S. Confirm gas, probe length, enclosure and approvals against the ordering chart.

Request a Quote for Sierra SteelMass 640S

Submit an RFQ for the Sierra SteelMass 640S to the Seven Star LLC instrumentation team in Muscat with the gas composition, pipe or duct size, temperature and pressure, flow range and approval requirement. We will confirm probe length, hot-tap hardware and calibration, arrange supply to Oman and the GCC, and include the manufacturer’s Sierra SteelMass 640S datasheet with our quotation for your engineers to review.