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Digital Flow Meter for Gas: Inline Saturated Vapor Mass Sourcing Frameworks
Quick Answer: For inline saturated vapor mass measurement, a digital vortex flow meter with pressure and temperature compensation is the most practical choice for DN15 to DN300 steam lines. If your line size is small and accuracy must be better than ±1.0 percent, choose a Coriolis mass flow meter. Send your pressure in bar, temperature in °C, pipe size DN, and flow range in kg/h to Silver Automation Instruments for a direct model selection.
Saturated Vapor Is Not Dry Gas
In practice, a boiler in a textile mill in Bangladesh may run at 7 bar g after lunch and 9 bar g at full load. A vortex meter that reads volume only will not see the density change. The plant operator sees a stable m3/h value and assumes the mass total is correct. The mass balance at the end of the week is off by 9 percent or more. This is why inline saturated vapor mass measurement is a sourcing problem, not only a product problem.
Most engineers skip this part during the first RFQ. They ask for a digital flow meter for gas and stop there. But saturated steam is not a stable gas. It moves close to the saturation line. A small pressure drop across the pipe can change the density faster than the control system responds. Because of this, mass flow measurement needs a live pressure input and a live temperature input.
Two Meter Types That Work Inline
Silver Automation Instruments usually recommends a digital vortex flow meter with integrated steam density compensation for pipe sizes from DN15 to DN300. The meter accepts a PT100 temperature signal and a 4-20 mA HART pressure signal from two external transmitters. The electronics calculate mass flow in kg/h from the vortex frequency, temperature, and pressure. Typical accuracy is ±2.0 percent of reading for saturated steam. Another option is a Coriolis mass flow meter. It measures mass directly. Accuracy reaches ±0.5 percent of reading. The cost is higher above DN80. We have supplied this configuration to chemical plants in Vietnam and a beverage factory in Mexico.
Thermal mass flow meters are not a good fit for saturated vapor. They work well on dry gas lines. Condensate droplets create unstable heat transfer readings and false mass totals. Use vortex or Coriolis inline instead.
Inline Saturated Vapor Mass Sourcing Framework
Here is the thing. Most sourcing projects go wrong at the data stage, not the product stage. Send pressure in bar g, temperature in °C, pipe schedule, inner diameter in mm, and minimum and maximum flow in kg/h. Then define the output. Most sites use 4-20 mA HART to the DCS or PLC. Some also need RS485 Modbus for the energy management system. After that, check the hazardous area. In the Middle East and North Africa, many gas lines require ATEX Zone 1 or IECEx Ex d ia IIC T6. Silver Instruments supplies both Ex d and Ex ia types.
Do not forget the installation conditions. A vortex meter needs straight run. We recommend 15D upstream and 5D downstream. For a DN80 line, that means 1.2 m of clean pipe before the meter and 0.4 m after. If the meter sits after a pressure reducing valve, add a straightening plate or increase the upstream run.
Where We See Field Failures
Most engineers skip the temperature element check. A PT100 that is too short in a DN100 line will read the pipe wall temperature, not the steam core. The mass flow reading then shifts. We have seen this on customer sites in Indonesia and Saudi Arabia. Another common failure is installing the vortex meter after a pressure reducing valve without enough straight run. The swirl from the valve corrupts the vortex signal. The meter may show a flow value, but the repeatability is poor and the totalizer drifts.
So specify the thermowell length and the insertion depth. For a DN100 pipe, the sensor tip should sit near the center
Regional Sourcing Notes
Australia and New Zealand buyers often ask for inline saturated vapor mass flow meters with local display and simple wiring. The AS/NZS standards matter, especially for gas skids and packaged boilers. Southeast Asia and Africa tend to prioritize price and ease of maintenance. For these regions, Silver Automation Instruments offers a wafer style vortex meter in 316L stainless steel with no moving parts. Latin America food and beverage plants often need stainless steel enclosures and sanitary connections. The meter body stays the same. The difference is in flanges, gaskets, and signal options.
We have also shipped to desalination plants and offshore support vessels where the gas flow meter must survive humid salt air. In those cases, the enclosure rating should be IP67 or better and the cable glands should be metal, not plastic.
Recommended Models and Signal Details
Silver Instruments digital gas flow meter types include the SAI-VF100 vortex flow meter with inline display and 4-20 mA HART. This unit covers DN15 to DN300 and works from -40 °C to 350 °C fluid temperature. The transmitter can accept external pressure and temperature input. The local display shows kg/h, total mass, pressure, and temperature at the same time. For lines above DN80 where mass accuracy is critical, we quote the SAI-CMF series Coriolis mass flow meter. It measures steam, liquid, and gas in one device. We also offer a complete panel with a paperless recorder for energy audits.
The pressure transmitter input is usually a 0 to 16 bar or 0 to 25 bar range with 0.075 percent accuracy. The temperature input is a PT100 three wire. These two signals turn a standard vortex meter into an inline saturated vapor mass flow meter. This is the part that saves the plant from totalizer errors during load swings.
How to Send an RFQ
Send us a short list with these values: pressure in bar, temperature in °C, pipe size DN, minimum and maximum flow in kg/h, and the required output signal. That is enough for a budget price. If the application is in a hazardous area, add the zone classification and gas group. For urgent quotations, contact Silver Automation Instruments via Tel +86-135-1213-1526, WhatsApp 86-135-12131526, or WeChat +86 13512131526.
Frequently Asked Questions About Inline Saturated Vapor Mass Meters
Which digital flow meter is best for saturated steam mass measurement? A vortex flow meter with pressure and temperature compensation is the most practical for DN15 to DN300 lines. For smaller lines or stricter accuracy needs, a Coriolis mass flow meter is a good alternative.
Can a thermal mass flow meter measure saturated vapor? No. Thermal mass flow meters work well for dry gas. Saturated steam causes condensation and unstable heat transfer readings. Use a vortex or Coriolis meter for this service.
What accuracy can I expect for inline saturated vapor mass flow? A compensated vortex meter normally gives ±2.0 percent of reading for steam mass flow. Coriolis meters give ±0.5 percent of reading or better. The price difference grows with line size.
What data should I submit for a quote? Send pipe size, pipe material, pressure in bar, temperature in °C, flow range in kg/h, hazardous area requirements, and the required output signal. This helps us give a fixed offer instead of a broad estimate.
Do you supply meters for ATEX Zone 1 or Zone 2? Yes. Silver Automation Instruments offers Ex d and Ex ia versions for vortex and Coriolis gas flow meters. Mention the gas group and temperature class when you send the RFQ.