TL;DR
Poor condensate drainage reduces drying efficiency and can cause differential thermal expansion damage. Check the stationary siphon clearance, steam pressure differential, and condensate flow rate.
What you might see
- reduced Yankee drying rate at same steam pressure
- increasing steam consumption for same production rate
- condensate flow at the siphon below expected rate
- uneven MD temperature profile on Yankee surface
Likely causes
Stationary siphon tip worn or broken, reducing pickup efficiency
Insufficient differential pressure between steam inlet and condensate outlet
Condensate return line partially blocked reducing back-pressure relief
Siphon orifice partially plugged by scale or iron oxide deposits
Required tools
- DCS historian for condensate flow and DP trending
- Differential pressure gauge
- Feeler gauge (for siphon clearance at outage)
- LOTO kit
Safety first
- The Yankee dryer operates under steam pressure. All siphon and condensate work must be done with the dryer fully depressurized and locked out.
- Steam condensate lines are at high temperature. Use heat-resistant gloves and face shield when working near condensate drain points.
Procedure
- 1
Log the condensate flow rate and compare to the baseline at the same steam pressure and machine speed.[1]
- 2
Check the differential pressure between the Yankee steam header and the condensate outlet. DP below the design minimum indicates a drainage issue.
- 3
Verify that the condensate return line control valve is fully open and not throttled below setpoint.
- 4
Inspect the condensate return line for blockages or partial closure of isolation valves.[1]
- 5
At the next planned outage, inspect the stationary siphon assembly. Measure the siphon tip clearance from the Yankee inner shell. Clearance outside specification reduces pickup.
- 6
Check the siphon orifice for scale buildup and clean with appropriate descaling solution if deposits are present.
- 7
Replace a worn or broken siphon tip. Even minor tip wear significantly reduces condensate removal at speed.
Sources
Valmet Valmet TurboDry Yankee Dryer general technical documentation, Valmet
Yankee dryer condensate drainage system maintenance, general tissue machine practice (general)
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