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Quick Answer: Silver Automation Instruments supplies insertion Pitot tube flow meters for large smoke stacks and chimneys. The high-temperature rod version handles flue gas up to 800 °C and stack diameters from DN300 to DN6000. Send stack diameter, gas temperature, pressure, and flow range to WhatsApp +86-25-52155837 for a price quote. You can also review the product range at flow-meter.com.au.
Large smoke chimneys in power plants, cement kilns, and incinerators carry hot dirty gas at velocities from 5 to 40 m/s. A full bore flow meter is often too expensive or impossible to install in a DN2000 or DN4000 stack. An insertion Pitot tube solves that problem with a small probe and a differential pressure transmitter. The rod measures velocity pressure at a single point or across multiple points. Flow rate derives from the square root of differential pressure.
High-temperature rods use 316L stainless steel up to 400 °C. For hotter flue gas we use Inconel 625 rods with ceramic coated tips. The rods withstand 800 °C continuous service. The rod connects to a strong flange or compression fitting on the stack wall. That layout keeps the transmitter and impulse lines away from the hottest face.
We have supplied these meters for coal fired boilers in Vietnam, waste heat recovery systems in Indonesia, and cement kiln stacks in Mexico. One customer in Vietnam measured flue gas from a coal boiler. Stack diameter was DN2400. Gas temperature was 340 °C. Dust loading was moderate. We supplied a 316L insertion rod with a 0 to 1.5 kPa differential pressure transmitter and a PT100 temperature sensor. The system output 4-20 mA HART directly to the plant DCS.
For a steel mill in Turkey the stack diameter was DN3500 and gas temperature reached 620 °C. We used Inconel 625 for the rod and a 0 to 4 kPa DP range. The rod length was 2200 mm. The customer installed it at 0.5 of stack diameter depth. The signal was stable after purge air was added.
Silver Instruments recommends the SIT-800H insertion Pitot tube for large smoke chimney service. The standard rod length covers DN300 to DN6000. Materials are 316L stainless steel, Inconel 625, or ceramic coated Inconel. Differential pressure ranges cover 0 to 1 kPa up to 0 to 100 kPa. Process temperature limits are 400 °C for 316L and 800 °C for Inconel 625. Process pressure rating is PN16 or ANSI 150. The DP transmitter provides 4-20 mA HART as standard. Optional outputs include RS485 Modbus and pulse.
The meter ships with a flanged or compression fitting, a three valve manifold, and a purge air port for dusty stacks. We pair it with a temperature transmitter model STT-100 if density compensation is needed. A pressure transmitter model SPT-208 can compensate for stack pressure changes. Total flow output in kg/h or m3/h is available from a flow computer or from the plant control system.
Here is the thing. Stack gas rarely flows in a neat uniform profile. Insert the rod at a depth of 0.5 to 0.75 of the stack diameter. Use a straight run of 10 pipe diameters upstream and 5 downstream where possible. For short stacks use a multipoint averaging Pitot tube to handle skewed flow profiles.
Slope the impulse lines downward to the transmitter so condensate drains away. In dusty gas connect a low flow purge air line to the probe port. Insulate the rod and impulse lines if stack gas temperature drops below dew point. Use a differential pressure transmitter with a five valve manifold for easier zero checks. Most engineers skip these details until the meter reads wrong.
A single point Pitot tube gives 1 to 3 percent of actual flow when the flow profile is stable. A multipoint averaging Pitot tube can reach 1 percent of full scale. Actual accuracy depends on straight run, dust buildup, and correct density compensation.
Because hot flue gas expands as temperature rises, density compensation changes the flow reading by more than 10 percent on some stacks. Calibrate the DP transmitter with the exact range from the flow calculation. For large stacks we recommend a velocity traverse test during commissioning. The traverse data corrects the flow coefficient of the Pitot tube. That step reduces the error from swirl and uneven velocity.
What is the maximum flue gas temperature for these Pitot tube flow meters?
The high-temperature rod version handles up to 800 °C with Inconel 625 and ceramic coated tips. For continuous temperatures above 800 °C contact our engineers with your gas composition and stack design.
What stack diameters can the insertion rod cover?
Standard rod lengths cover DN300 to DN6000. Longer rods are available for rectangular ducts with widths above 6000 mm. Send the internal stack diameter and wall thickness for a confirmed fit.
Does the meter work with dust or soot in the flue gas?
Yes. Choose a purge air connection and a larger probe port. The Pitot tube resists clogging better than an orifice plate. Clean the probe tip during scheduled shutdowns.
What output signals can the differential pressure transmitter provide?
4-20 mA HART is standard. Optional outputs include RS485 Modbus and pulse. The transmitter can also send temperature and pressure compensated flow when paired with STT-100 and SPT-208 transmitters.
How do I request a quote?
Send stack diameter (DN), gas temperature (°C), pressure (bar), flow range (kg/h or m3/h), and gas composition. Contact Silver Automation Instruments via Tel +86-25-68650347, WhatsApp +86-25-52155837, or WeChat +86 15365082610.
