Learn what common mechanical seal damage patterns can tell you about dry running, contamination, heat, misalignment, vibration, installation problems, and material compatibility.
Mechanical seals fail for many reasons. This guide describes common visible symptoms and what they may indicate. No single symptom is absolute proof of a cause. Use this information as a starting point for your own investigation.
Each section describes a visible symptom, possible causes, and what to inspect next. The wording "may indicate" and "common cause" is intentional. A symptom can have more than one cause, and the only way to confirm the root cause is to inspect the seal, the equipment, and the operating conditions together.
Possible causes may include dry running, rapid heating, thermal shock, insufficient liquid at the seal faces, or high temperature operation without proper flushing.
What to inspect: Was the pump fully flooded before startup? Was the pump run dry? Was adequate flush or process liquid reaching the seal?
Possible causes may include dirty process, abrasive contamination, or solids between the seal faces.
What to inspect: Check process cleanliness, suspended solids, flush quality, and seal face contamination.
Possible causes may include higher chemical concentration than expected, higher temperature than expected, or incorrect material selection.
What to inspect: Check the actual product concentration, operating temperature, elastomer compatibility, and face material suitability.
Possible causes may include improper installation, misalignment, or uneven loading.
What to inspect: Check the installation condition, face seating, shaft alignment, and seal position.
Possible causes may include excessive temperature, dry running, cavitation, or elastomer aging.
What to inspect: Check the operating temperature, evidence of dry running, cavitation symptoms, and elastomer material.
Possible causes may include heat, dry running, cavitation, abrasive service, or insufficient lubrication at the seal faces.
What to inspect: Check process conditions, flush, face materials, and pump operation.
Possible causes may include chemical incompatibility, incorrect elastomer material, or unexpected process concentration or temperature.
What to inspect: Check the actual fluid composition, concentration, temperature, and elastomer type.
Possible causes may include vibration, coupling misalignment, or periodic loss of lubrication at the seal faces.
What to inspect: Check pump and motor alignment, vibration, flush conditions, and dry running events.
Possible causes may include coupling misalignment, excessive shaft movement, or vibration.
What to inspect: Check alignment, bearings, shaft condition, and vibration.
Possible causes may include shaft end play, radial shaft movement, bent or damaged shaft, or bearing condition.
What to inspect: Check bearings, shaft runout, radial movement, and axial movement.
Mechanical seal faces normally depend on a thin fluid film for lubrication and cooling. Running the pump dry can cause rapid heat buildup and severe seal damage. The exact failure pattern depends on the seal materials, the speed, and how long the pump runs dry. If you suspect dry running, check whether the pump was fully flooded before startup and whether the seal received adequate flush or process liquid.
Many seal failures are actually installation problems. Common issues include dirty seal faces, fingerprints or contamination on lapped faces, scratched mating ring surfaces, improper seating, incorrect spring engagement, wrong installation lubricant, and starting the pump dry.
Do not use silicone or PTFE based installation lubricants for elastomer installation where the seal manufacturer's guidance warns against them. Follow the manufacturer's recommended lubricant. The seal faces should be clean before final assembly.
Use this checklist when investigating a seal failure. Answer each question as completely as possible.
What fluid is being pumped?
What is the actual operating temperature?
Has the pump run dry?
Is the pump fully flooded before startup?
Is there adequate flush or circulation at the seal?
Is the product abrasive or dirty?
Is the pump and motor alignment acceptable?
Is there excessive vibration?
Is there shaft end play or radial movement?
Are the seal materials compatible with the fluid?
Was the seal installed correctly?
If you are replacing a failed seal and do not know exactly what you have, use our identification guide to collect the dimensions and application information we need.
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