『Isco 4230 Flow Meter Maintenance: Clearing internal Air Lines and Calibrating Transducers for High-Solid Slurries』Related information(clamp on meter|electromagnetic meter|venturi meterrotameter|orifice meter|ultrasonic flow meter|mass flow meter|coriolis mass flow meter|coriolis flow meter|magnetic flow meter|magmeter flow meter|magflow flow meter|mag meter flow meter|electromagnetic flow meter|vortex flow meter|turbine flow meter|thermal mass flow meter|thermal flow meter|rotameter flow meter)
Isco 4230 Flow Meter Maintenance: Clearing Internal Air Lines and Calibrating Transducers for High-Solid Slurries
Quick Answer: For high-solid slurries, clean the Isco 4230 internal air lines every 30 days and dry the desiccant cartridge. Calibrate the pressure transducer against a known water head after cleaning. If the sensor drifts more than 2 percent between cleanings, switch to a full-bore electromagnetic flow meter from Silver Automation Instruments.
High-solid slurries create a specific maintenance problem for bubbler type flow meters like the Isco 4230. A starch plant in Vietnam called us after the 4230 read 40 percent low on a flume handling 8 percent solid potato waste. The internal air line had packed with fines. The pressure transducer was still working but the air path was not clear.
The Isco 4230 uses a small air pump and a bubble line to measure liquid level. The controller sends air into the line. The pressure needed to push a bubble out equals the liquid head. That pressure goes to a differential transducer. For clean water this works well. For slurry with sand, clay, starch or sludge, the bubble line and the internal air passages collect solids. The result is a slow drift or a sudden drop in flow reading.
Clearing Internal Air Lines on the Isco 4230
Power down the unit first. Disconnect the bubble line at the bulkhead fitting. Remove the desiccant cartridge and inspect the color. If the desiccant is pink or dark, replace it or dry it at 120 degrees Celsius for two hours. Most engineers skip this part. Moisture in the air system combines with slurry fines and forms a hard paste inside the small internal tubing.
Next, remove the internal air line from the pump outlet and from the transducer inlet. Use compressed air at no more than 1 bar to blow backwards through the transducer port. Never blow high pressure air into the transducer. That damages the diaphragm. If the line is blocked, soak the small tubing in warm water with a mild detergent for 30 minutes. Then flush with clean water and blow dry.
On a job site in Thailand, we found the internal 4 mm air line completely plugged with dried cassava starch. The plant was using the 4230 on a parshall flume with 9 percent solids by weight. Cleaning with compressed air alone did not work. We replaced the line with new 4 mm polyurethane tube and added a weekly air purge routine.
After cleaning, check the pump output. A healthy Isco 4230 air pump produces a steady pulse. If the pump runs but no air reaches the bubble line, the internal check valve may be stuck. Remove the check valve and clean it with isopropyl alcohol. If the ball inside does not move freely, replace the check valve.
Calibrating Transducers for High-Solid Slurries
Calibration of the pressure transducer should follow every cleaning. Fill a clear plastic tube with clean water to a known height. 30 cm of water equals 29.4 mbar. Connect the tube to the transducer port. Set the 4230 to display level in meters. If the display does not match, adjust the zero and span from the setup menu.
In practice, a two point calibration works better for slurry service. Use zero pressure for the low point. Use a water column of 50 cm for the high point. Record the 4-20 mA output if your 4230 has the analog output option. The output should be 4.0 mA at zero and 20.0 mA at full span. A drift of 0.5 mA after 24 hours usually means a damaged diaphragm or a loose internal connection.
We have seen many Isco 4230 units with transducer drift after a solids plug. The pump sends a pressure spike into the transducer. The diaphra
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Signs That High-Solid Slurry Has Damaged the 4230
Watch for these signs in the field. The flow reading drops while the pump duty cycle increases. The desiccant cartridge turns dark within one week. The bubble line blows off at the bulkhead fitting. The level reading stays flat even when the flume level changes. These failures become more frequent once the solids content passes 5 percent by weight.
A Better Flow Meter for High-Solid Slurries
If you spend more than two hours per month cleaning an Isco 4230, the total cost of ownership is too high. A full-bore electromagnetic flow meter solves the air line problem because it has no air pump, no bubble line, and no pressure transducer exposed to solids. Silver Automation Instruments supplies electromagnetic flow meters with PTFE or polyurethane liners, 316L electrodes, and 4-20 mA HART output. The meters work in sludge, starch slurry, mining tailings, and dredge slurry. Pipe sizes range from DN10 to DN1200. Accuracy is 0.5 percent of reading. For a high-solid slurry line in a ceramic tile plant in Mexico, we supplied a DN80 electromagnetic flow meter with a polyurethane liner and tungsten carbide electrodes. The meter has run for 18 months with no cleaning and no drift.
The initial price of an electromagnetic flow meter is higher than a bubbler flow meter. But the maintenance saving often returns the cost in less than one year. Most customers in the wastewater and food industries choose the electromagnetic meter after their second Isco 4230 failure. If you want a quote, send us your pressure in bar, temperature in degrees Celsius, pipe size in DN, and flow range in cubic meters per hour. We respond within one business day.
Contact Silver Automation Instruments. Tel: +86-25-68650347. Whatsapp: +86-25-52155837. WeChat: +86 15365082610. Our website is flow-meter.com.au.
Frequently Asked Questions
How often should I clean the internal air lines on an Isco 4230 in high-solid slurry service?
Clean every 30 days when solids are between 2 and 5 percent by weight. Clean every two weeks when solids exceed 5 percent. Install a clean dry desiccant cartridge after every cleaning.
What air pressure should the Isco 4230 produce after cleaning?
The pump should produce a steady bubble stream at 0.3 to 0.7 bar depending on the liquid head. If the pressure is higher than 1 bar, a blockage still exists downstream. Do not increase the pump pressure to force the line open.
Can the transducer be calibrated in the field without a dead weight tester?
Yes. Use a known water column. 30 cm of water equals 29.4 mbar. Use two points, zero and 50 cm. The 4-20 mA output should track the water level within 0.1 mA.
When should a high-solid slurry application switch to an electromagnetic flow meter?
Switch when cleaning frequency exceeds once per month or when transducer drift exceeds 2 percent between calibrations. An electromagnetic flow meter from Silver Automation Instruments has no air line to block. It measures flow directly in the pipe.
Does Silver Automation Instruments supply spare parts for Isco 4230 flow meters?
We do not sell Isco spare parts. We supply replacement flow meters and full-bore electromagnetic flow meters for high-solid slurries. Send your pipe size and flow range for a specific model and price.
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