Many Bucket Elevator Wrecks rob crew morale

Root Cause Analysis (RCA): Many Bucket Elevator Wrecks rob crew morale.

Article Type:	Root Cause Analysis (RCA)
Category:	Mechanical
Equipment Type:	Pipelines and Miscellaneous Problems
Author:	S. Raghava Chari

Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of two or three decades ago. These articles will help you to improve your troubleshooting skills and knowledge.

Bucket Elevator Wrecks

The obvious root cause was Drive Sprocket Shaft extension mounted improvised and inadequate RRPs did not stop chain reverse rotation on intentional or failed power elevator stops.

The Author Root Cause Analysis identified the improvised RRP inadequacy’s below listed causes:

1. The sprocket shaft dia is 250 mm; but the shop’s machine could make a RRP for a 100 mm shaft only
2. Hence, both the shop made RRP and its shaft inserted in a square hole cut in the 250 dia sprocket shaft were inadequate; hence the shaft extension often bent attempting RR preventions
3. Harsh plant environs contaminating the exposed lubricating grease accelerated the failures

Author Solution

He studied Gearbox (GB) makers’ catalogs and learnt of professionally designed and built GB inside fitted RRPs. They furnish retrofit RRPs too at slight extra cost. Formerly GB high-speed shafts fitted RRPs failed.

Without a Root Cause Analysis they discarded GB fitted RRPs. To satisfy their wishes, the author tried an GB intermediate speed shaft driven RRP.

Its success made the plant fit GB IS driven RRPs for all elevators.

Eliminate Elevator Chain Wrecks

Substituted RRPs excellent features

The below listed excellent features eliminate the elevator chain wrecks long shutdowns forever:  

1. By design and manufacture their torque ratings meet plant needs
2. Dust and water tight enclosure protects the RRP from the plant’s corrosive and dusty environs
3. Copious uncontaminated oil supply besides lubrication cools the RRP also
4. The improvised grease lubricated RRP lacked this feature

Vanished elevator wrecks delighted all.

Author: S. Raghava Chari

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