Current position > Product detail
『Ammonia Gas Flow Meter: Thermal Mass Systems for Harsh Chemical Venting』Related information(flow rotameter|digital flow meter|balo meter|hydraulic flow meter|volumetric meter|positive displacement meter|pitot tube flow meter|displacement meter|cfm meter|variable area flow meter|inline flow meter|differential pressure flow meter|calibrated flow meter|velocity meter|paddle wheel flow meter|oval gear flow meter|anemometer hvac|multiphase flow meter|doppler flow meter|thorpe tube flowmeter|heat flow meter)
Ammonia Gas Flow Meter: Thermal Mass Systems for Harsh Chemical Venting
Quick Answer: A thermal mass flow meter is the most practical choice for ammonia gas in chemical vent headers and low pressure exhaust lines. The meter gives direct mass flow in kg/h without a separate pressure transmitter or temperature transmitter. For most DN15 to DN50 ammonia vent lines in fertilizer or refrigeration plants, specify Silver Instruments TMF series with C276 wetted parts and 4-20 mA HART output.
Silver Automation Instruments has supplied thermal mass systems for ammonia vent lines in Vietnam, Indonesia, Chile, Saudi Arabia, and Australia. The key is sensor material. Ammonia gas is aggressive when moisture is present. Standard 316L sensors fail early. Specify Hastelloy C276 sensor elements and PT100 temperature sensing. The electronics housing should be ATEX Zone 1 certified for most chemical vent areas.
Why Thermal Mass Works for Ammonia Venting
Ammonia vent lines often run at low pressure. Some lines operate at 0.1 bar to 0.5 bar. A thermal mass flow meter does not need high pressure to measure gas velocity. The insertion probe sits directly in the pipe and measures heat transfer from the heated sensor to the flowing gas. The meter calculates mass flow because the cooling effect depends on gas molecular mass and flow velocity.
Most engineers skip differential pressure devices here. The pressure loss is high and the ammonia concentration changes the density. Thermal mass gives a direct kg/h output for the gas mixture. We have seen drift failures on customer sites many times. A fertilizer plant in Vietnam replaced a pitot tube with a Silver Instruments TMF because the pitot reading drifted after three months.
Key Specifications for Ammonia Vent Lines
For harsh chemical venting, the meter body and sensor must resist corrosion. We normally recommend C276 wetted parts for ammonia gas and trace moisture. The process connection can be DN15, DN25, DN50, or DN80 with ANSI 150 lb flanges. For high ammonia concentrations above 20 percent, use PTFE packing and avoid aluminum housings.
Outputs from the Silver Instruments TMF include 4-20 mA HART. You can also get RS485 Modbus RTU and two alarm relays. Accuracy is plus or minus 1.0 percent of reading for gas flow from 0.5 to 100 Nm³/h. Temperature rating is up to 120 °C. Pressure rating is up to 1.6 MPa for DN25 and smaller. The display shows mass flow in kg/h. The display also shows standard volumetric flow in Nm³/h and gas temperature.
Because the sensor element includes a PT100 reference, the flow meter also reads gas temperature. Temperature data is useful for vent line diagnostics. So you can trend temperature and mass flow on the same 4-20 mA HART loop.
Sizing Notes for Ammonia Venting
Do not size a thermal mass flow meter from pipe diameter alone. You need gas composition, pressure, temperature, and the expected flow range. In practice, a DN25 vent line can carry 0.5 kg/h or 30 kg/h depending on the process. Tell us the pipe size and the normal and maximum vent flow. We will select the sensor wattage and insertion length.
For low velocities below 0.2 m/s, a standard insertion probe may not have enough cooling response. In that case, use an inline flow body or a flow conditioner. Most ammonia vent headers run from 0.5 to 1
ATEX Zone 1 and Installation
Ammonia is flammable at certain concentrations in air. Chemical vent stacks and exhaust ducts near storage tanks often fall in hazardous area Zone 1 or Zone 2. The TMF series is available with Ex d IIC T4 or Ex db IIC T4 flameproof enclosure. You need the right cable gland and cable type for the installation. We have supplied units for an ammonia storage facility in Saudi Arabia with Zone 1 vent lines.
Install the probe at least 10 pipe diameters downstream from any elbow or valve. For DN50 pipe, that means 500 mm of straight run. If you have only 3 to 5 diameters of space, use a flow conditioner. But the flow profile matters more than the exact straight run in small vent lines. The meter does not need temperature and pressure compensation, but you must set the gas composition in the menu. For ammonia, select ammonia or enter the heat capacity factor.
Recommended Models for Common Ammonia Vent Cases
For a DN25 ammonia vent line at 2 bar and 0 to 50 kg/h, use Silver Instruments TMF-025-C276 with insertion probe and 4-20 mA HART. For a DN50 vent header with flow up to 150 Nm³/h, use TMF-050-C276 with a ball valve retractor. For low flow below 0.5 kg/h, use a small inline thermal mass body with DN15 connection. Silver Instruments can supply calibration for ammonia gas mixtures before shipment.
Contact Silver Automation Instruments for a specific quote. Send us your pressure (bar), temperature (°C), pipe size (DN), and flow range. Tel: +86-135-1213-1526. Whatsapp: 86-135-12131526. WeChat: +86 13512131526. We reply within 24 hours on business days.
FAQ
Can a thermal mass flow meter measure ammonia gas at low pressure?
Yes. Thermal mass flow meters do not need high differential pressure. They work well at 0.1 bar and above. The insertion probe measures the cooling effect of gas moving across the heated sensor.
What materials do I need for ammonia gas service?
Use C276 sensor elements and 316L stainless steel process parts as a minimum. For wet ammonia or high concentration, specify PTFE seals and avoid aluminum. The standard TMF body comes in 316L.
What output signals are available on the Silver Instruments ammonia flow meter?
Standard output is 4-20 mA HART. Optional outputs are RS485 Modbus RTU, pulse, and two relay alarms. The 4-20 mA signal can carry mass flow, gas temperature, or total flow.
How do I size a thermal mass flow meter for an ammonia vent stack?
Provide gas composition, pressure, temperature, pipe size, and flow range. The vendor selects sensor wattage, insertion length, and process connection. Pipe diameter alone is not enough for low velocity ammonia vents.
What is the price for a DN25 ammonia thermal mass flow meter?
Price depends on certification, material, and calibration. A DN25 TMF with C276 sensor, ATEX Zone 1, 4-20 mA HART, and standard calibration starts around USD 1,800 to 2,600 FOB China. Send your full parameters for a quotation.
Silver Automation Instruments supplies ammonia gas flow meters for chemical plants, fertilizer storage, and refrigeration systems. We serve customers in Southeast Asia, Oceania, Latin America, the Middle East, and Africa. Use the contacts above for technical sizing and current lead times.