Safety first. Isolate and lock out the drive, and drain and depressurise the vessel, before you open the seal area. Hot product and cleaning chemicals can be trapped behind the seal.
Symptoms
- Product or flushing liquid dripping from the seal area or the lantern.
- Wet or crusted residue around the seal housing after a run.
- Seal faces squealing, or the seal area running hotter than usual.
- A leak that appears only during CIP, only at start-up or only at high speed.
Likely causes
- Dry running. The seal faces need a liquid film. Starting the mixer with an empty vessel, or running it while the vessel drains, can crack or burn the faces in seconds.
- Flush or quench problems. On double or flushed seals, a closed valve, low flow, low pressure or a blocked line removes cooling and lubrication from the faces.
- Worn or damaged faces. Abrasive powders, crystallising product and normal wear leave grooves or chips on the faces, so they no longer seal.
- O-rings and elastomers. Elastomers can swell, harden or crack when they meet a product, temperature or cleaning chemical they are not suited to.
- Installation. Wrong working length, a seal fitted without lubricant on the O-rings, or dirt on the faces during assembly gives an early leak.
- Shaft and bearings. Worn bearings, shaft run-out or vibration make the faces open and close as the shaft turns.
What to check, in order
- Note when the leak happens: at start-up, during production, during CIP or at standstill. This narrows the cause quickly.
- If the seal has a flush or quench, check that the supply valve is open and that flow and pressure are within the values in your service documentation.
- Ask operators whether the mixer was started or left running with a low level in the vessel.
- Check the cleaning chemicals and temperatures against the elastomer material listed for the seal.
- Listen and feel for vibration or bearing noise. A damaged bearing will destroy a new seal.
- When the seal is removed, inspect the faces, springs and O-rings. Keep the old parts: their wear pattern shows the cause.
- Fit the replacement with the working length and procedure from your service documentation, with clean faces.
When to call a TPS engineer
Call a TPS engineer if a new seal leaks again within a short time, if you find damage on the shaft or bearings, or if you are unsure which seal type or material is fitted.
Ask LiveAccess
Photograph the mixer nameplate and the seal area, and ask which seal is fitted and what flush values it needs. In the app you can also find a high shear mixing expert in the Expert Network and chat or call them.
This guide gives general checks. Settings, limits and procedures differ between machines: always use the values in your service documentation and your site procedures.
