4.25" Flowserve UO cartridge seal Silicon vs Silicon / Viton / 316 SS sent in for failure analysis from chemical plant in Louisiana: customer stated the seal ran for 1 week prior to failure.
The rotary Silicon Carbide seal face was cracked from I.D. to O.D. edge. The crack extended from one of the drive slots on the under side of the lapped face that engages an indent in the surrounding rotary face holder. The wear pattern on the rotary Silicon face from the stationary Silicon seat was narrow showing the stationary Silicon seat was only making contact with the rotary seal face on the outer edge of its lapped surface.
The stationary Silicon seat was chipped out around the outer edge of the lapped surface due to not sitting properly against the rotary Silicon seal face. Also, the anti-rotation pin in the O.D. surface of the stationary seat was sheared off (should extend by 0.06" to engage a slot in the stationary seal gland).
Seal failure was due to distortion / misalignment causing the Silicon seal parts to exceed their upper physical limits.
Robco asked the end user to check the perpendicularity of the stuffing box face to the shaft. After Inspection they stated it was off by 0.025".
Robco made recommendation to customer to upgrade the rotary Silicon face to Tungsten Carbide (it is less prone to chipping & cracking around drive pins and slots).
Seal was repaired in 7 working days and is operating normally.
4.250" Flowserve UO cartridge seal sent in for failure analysis
Seal taken apart to inspect
This is the anti rotation slot in stationary seal gland that engages the pin protruding from O.D. edge of stationary Silicon seat (pin had sheared off).
Underside of rotary Silicon face. The Silicon chipped & cracked close to the drive lug in the outer stainless face holder (Silicon is prone to chipping & cracking when physical stress is applied from such assemblies).
This is the narrow wear pattern on the rotary Silicon seal face from the contact it made against the stationary Silicon seat. This abnormal contact is what caused the chipping damage to the O.D. edge of lapped surface of stationary Silicon seat.
Rotary Silicon face assembly on rotary seal sleeve.
Stationary Silicon seat with the sheared off anti rotation pin on O.D. edge. Pin should protrude 0.060” to engage pin slot in stationary seal gland.
Damage to the stationary Silicon seat.