TL;DR
A drip at the agitator shaft seal means the mechanical seal faces or the seal flush system has failed. Stop the agitator, isolate the reactor, and replace the seal.
What you might see
- liquid dripping from agitator shaft seal housing
- seal flush return discolored with product
- bearing housing temperature rising
- reduced agitator shaft seal flush pressure
Likely causes
Seal face wear from abrasive slurry or dry running during flush loss
Seal flush supply pressure below the minimum required differential
O-ring material incompatibility or aging causing bypass leakage
Agitator shaft misalignment or vibration accelerating face wear
Required tools
- LOTO kit
- Seal replacement kit for the agitator shaft diameter
- Dial indicator with magnetic base
- Calibrated torque wrench
- Chemical-resistant PPE appropriate to reactor contents
Safety first
- Glass-lined reactors in pharma service typically contain toxic, corrosive, or flammable chemicals. Full chemical PPE is required before approaching the reactor for any maintenance.
- Pressurized reactors must be fully depressurized and vented to a safe point before opening any nozzle or seal housing. Verify pressure at zero with a local gauge.
- Reactor jacket circuits may contain hot or cold heat-transfer fluid. Isolate the jacket supply before removing any agitator drive components.
Procedure
- 1
Stop the agitator and depressurize the reactor. Block in the process feed and discharge valves.
Warning: Verify the reactor contents are depressurized and cooled before approaching the seal housing. Reactors may contain hazardous or reactive chemicals under pressure. - 2
Isolate and depressurize the seal flush supply line.[1]
- 3
Check the seal flush supply flow rate and pressure. Compare to the specified minimum differential over reactor pressure.[1]
- 4
Drain and decontaminate the reactor contents before starting seal disassembly. Follow the site chemical decontamination procedure.
- 5
Remove the seal housing, agitator shaft coupling, and seal assembly per the general maintenance procedure.
- 6
Inspect the seal faces for scoring, chipping, or thermal damage. Replace both faces as a matched set.
- 7
Check the shaft runout with a dial indicator. Runout above 0.05 mm contributes to accelerated seal wear.
- 8
Reinstall the seal, restore flush flow, and confirm zero leakage during a brief nitrogen pressure test before returning to service.
Sources
Pfaudler Pfaudler RA / RT glass-lined Reactor / Pressure Vessel general technical documentation, Pfaudler
Pfaudler RA / RT glass-lined reactor general agitator seal maintenance procedures (general)
More guides for Pfaudler Pfaudler RA / RT glass-lined
How to inspect for glass lining damage on a Pfaudler RA / RT glass-lined reactor
Iron contamination in the product or a failed spark test confirms glass lining damage. Schedule a spark test inspection during the next cleaning cycle and assess for repair or re-lining.
How to diagnose jacket fouling on a Pfaudler RA / RT glass-lined reactor
Declining heat transfer in a jacketed reactor means fouling on the jacket side. Track the overall heat transfer coefficient trend and plan a jacket clean at the next opportunity.
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