TL;DR

Rotor end seal leakage contaminates the batch and allows compound to escape the mixing chamber. Replace the rotor seals before leakage reaches the drive side bearing, which is much more expensive to repair.

What you might see

compound leaking around the rotor shaft at the chamber end
compound contamination on the mixer body near the rotor end caps
increased frequency of seal inspection required
compound color or filler appearing outside the mixing chamber

Likely causes

Tap to mark as ruled out

Rotor end seals worn past their service limit from abrasive compound
Seal lubrication (seal oil or grease) depleted or contaminated
Rotor shaft surface worn at the seal running face
Mixing chamber operating pressure elevated from ram force settings

Required tools

Rotor seal replacement kit (Farrel-Pomini specified)
Seal lip lubrication per mixer specification
Torque wrench
Heat-resistant gloves
LOTO kit for drive and hydraulic systems

Safety first

Lock out the Banbury main drive and the ram hydraulic supply before any work in the mixing chamber end area.
Hot compound residue inside the chamber can reach 150 C or higher. Allow cooling and wear heat-resistant gloves.
High-pressure hydraulics on the ram system can cause injection injuries. Verify zero hydraulic pressure before opening any hydraulic connection.

Procedure

7 steps · ~90 min

1
Stop the mixer and lock out both the main drive and the ram hydraulic system before accessing the rotor end seals.
Warning: The Banbury mixer ram operates at high hydraulic pressure. Lock out the hydraulic supply before any work near the ram or mixing chamber opening.
2
Allow the mixing chamber and compound to cool before opening the end cap area.
Warning: Rubber compound in the Banbury operates at temperatures above 150 C. Allow sufficient cooling time and wear heat-resistant gloves.
3
Remove the rotor end cap and extract the seal assembly per the Farrel-Pomini service procedure.[1]
4
Inspect the seal faces and elastomer lips for wear, hardening, or extrusion damage. Measure the seal lip thickness and compare to the minimum specification.[1]
5
Inspect the rotor shaft surface at the seal running face for scoring or wear grooves. A grooved shaft requires sleeve repair before installing new seals.
6
Install new seals with the correct orientation and lubricate the seal lips per the Farrel-Pomini lubrication specification.
7
Reassemble the end cap and torque all bolts to specification. Run the mixer unloaded for 15 minutes and inspect the seal area for leakage.

Sources

Farrel-Pomini Farrel BR / F-Series Rubber Banbury Mixer general technical documentation, Farrel-Pomini
Farrel-Pomini Banbury mixer maintenance documentation, rotor seal inspection and replacement (general)

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