Company Profile

Exhaust Gas Flow Meter: Thermal Mass Emissions Testing Tools

Quick Answer

For emissions monitoring, a thermal mass flow meter provides direct exhaust gas mass flow measurement without external temperature or pressure compensation. Silver Instruments offers both inline and insertion models that handle dirty, hot stack gases, and output standard 4-20 mA signals for your CEMS or DAHS.

These meters rely on a constant temperature differential method with two PT100 sensors. One sensor measures gas temperature, the other is heated. The cooling effect of the gas flow gives a direct mass flow reading in kg/h. No moving parts, wide turndown ratio, and low maintenance make them practical for continuous stack monitoring.

Where Thermal Mass Flow Meters Excel in Exhaust Gas

Power plants measure flue gas after desulfurization. Refineries monitor flare gas and FCC unit emissions. Cement plants need reliable flow data out of hot kiln exhaust ducts. In marine, diesel engine scrubber discharge monitoring demands corrosion resistance. A sugar mill in Thailand used our insertion thermal meter to measure boiler exhaust at 280 °C. The duct diameter was DN1000. We supplied a 700 mm probe with Hastelloy C-276 wetted parts.

These meters also work in chemical plants for vent gas and thermal oxidizer outlets. Because the thermal sensor has no moving parts, dust and sticky particulates cause fewer problems than differential pressure devices.

Installation Considerations for Your Stack

Insertion probes need a straight pipe run. Most engineers aim for 10 pipe diameters upstream and 5 downstream. In practice, many stacks have limited space. A flow conditioner can reduce the required straight length if needed.

For ducts above DN400, insertion thermal mass flow meters are the first choice. We provide probes with lengths from 300 mm to 1500 mm as standard. Tell us your duct inner diameter and wall thickness, and we will size the compression fitting and probe length.

If the gas is explosive, specify ATEX or IECEx Zone 1 or Zone 2 certification. Silver Instruments offers Ex db and Ex tb protection. Remote mounted electronics keep the display and transmitter away from heat. Max gas temperature with our standard probe is 200 °C, but high-temperature models reach 400 °C.

Outputs and Integration

Most emission monitoring systems expect a 4-20 mA analog signal with HART overlap. Our thermal mass meters deliver mass flow, temperature, and totalized flow via dual 4-20 mA and RS485 Modbus. You can connect directly to a PLC, recorder, or CEMS data acquisition unit.

We have seen many cases where a customer needed to replace an old differential pressure device. The swap to a thermal meter removed the need for external flow computer and pressure transmitter. Here is the thing: you get a direct mass flow reading, which simplifies the control architecture and reduces leak points.

Get a Quote for Your Exhaust Gas Application

Send us these details and we will propose a meter within 12 hours:

Gas composition (e.g., flue gas, biogas, natural gas, air), temperature in °C, pressure in bar, pipe or duct diameter (DN), required flow range in kg/h or Nm3/h, and mounting type (inline or insertion). Also let us know if you need Ex certification.

Contact Silver Automation Instruments today.
Email: [email protected]
Tel: +86-25-68650347
WhatsApp: +86-25-52155837
WeChat: +86 15365082610

Frequently Asked Questions

Can a thermal mass flow meter handle wet and corrosive exhaust?
Yes, if you select the right materials and optional heated sensor to prevent condensation. We have supplied units with Hastelloy and PTFE coating for acid gas applications.

What is the minimum flow velocity it can detect?
Our