Problem & Solution

Dip Tube Erosion & Blockage - Causes, Solutions & Compliance

Dip tube erosion and blockage is a persistent problem in cement, power, and steel plants, set in a kiln or furnace gas stream reaching 1400°C with 2000 g/m³ of dust. Dust wears the tube while deposits and condensed salts plug its bore, so gas sampling and reagent injection fail and emission control loses accuracy. UGES wear-resistant, purged dip tubes keep the bore clear.

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Understanding Dip Tube Erosion and Blockage

Problem Description

Dip tubes carry gas samples out of, and inject reagents into, kiln, preheater, and furnace gas streams in cement, power, and steel plants for process control and emission management, which places them in one of the most hostile environments in the plant. At the kiln inlet, process temperatures can reach up to 1400 degrees Celsius and dust concentrations up to 2000 grams per cubic metre, with high mechanical stress on anything inserted into the flow. Two failure modes dominate. Abrasive dust erodes the tube wall and tip until it thins and fails, and sticky dust together with condensed chloride and sulphate salts builds up on the walls and plugs the bore, the same buildup mechanism that blocks preheater cyclones and dip tubes elsewhere in the kiln circuit. Condensation in cooler sections adds blockage, corrosion, and unstable readings. When the tube erodes or plugs, gas analysis drifts or fails and reagent injection becomes uneven, so both process optimization and the continuous emission monitoring required under CPCB, US EPA, and EU rules are compromised, and manual cleaning of a plugged probe is difficult and hazardous work.

Cost of Inaction

A degrading dip tube rarely stops the plant, it quietly corrupts the data and injection the process relies on, so operators may run on misleading gas readings or uneven reagent dosing without realizing it. Left unattended, erosion thins the tube until it fails inside the duct, and salt and dust buildup plugs it completely, forcing dangerous manual cleaning or an unplanned stop to replace it. Lost process control, out-of-compliance emission monitoring, wasted reagent, and emergency probe replacement cost far more than fitting a wear-resistant, self-purging dip tube engineered for the duty.

Root Causes

Abrasive Dust Erosion in the Gas Stream
The very high dust load and velocity at the kiln inlet abrade the dip tube wall and tip, thinning the material until it perforates or breaks. Tubes made of standard materials and left unprotected wear quickly in this environment and fail inside the duct.
Dust and Salt Buildup Plugging the Bore
Sticky dust and the condensation of chloride and sulphate salts coat the inside and outside of the tube, the same mechanism that blocks preheater cyclones and ducts, gradually plugging the bore. Once restricted, the tube can no longer pass a representative gas sample or deliver an even injection.
Condensation and Thermal Degradation
In cooler sections and during stops, moisture condenses inside the tube and sample path, causing further blockage, corrosion, and unstable measurements, while thermal cycling stresses the tube. Without heated paths and correct material selection, these effects degrade both the tube and the reliability of the reading.

Engineering Solutions

Wear-Resistant, High-Temperature Dip Tubes
UGES makes dip tubes from high-temperature, abrasion-resistant materials and coatings matched to the kiln environment, so the tube resists the erosion that thins standard probes. Correct material and wall selection extends service life in the high dust load and temperature of the kiln inlet.
Back-Purge and Pulse Cleaning
UGES dip tubes can be fitted with air back-purge and pulse cleaning that periodically clears dust and incipient buildup from the bore and tip, keeping the path open without manual intervention. Retractable designs allow the tube to be withdrawn for inspection and cleaning safely.
Heated Paths and Correct Placement
UGES specifies heated or insulated sample paths and the correct insertion point and orientation so condensation and salt deposition are minimized and the sample stays representative. Proper placement and heat management keep readings stable and the bore clear between services.

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