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Spring Support Alert in Delayed Coker Plant

Written by a Refinery Maintenance Engineer

Synopsis of technical content

Refineries have experienced many spring support failure/malfunctions in critical piping and valves. Improper spring supports can cause loss of positive containment (LOPC) piping failures, vessel damage, and serious safety events. 

Generally, this is due to a lack of understanding of the severity and consequence of constant and variable spring support failures. Major failures have occurred due to a 

To facilitate proper movement of the supports, springs should be designed with double corrosion protection with detailed PM & inspection schedules. To facilitate proper inspection by operations, they should be designed to provide a travel indicator that visually verifies movement towards COLD/HOT position as per load/spring datasheets. Sometimes, the movement can be counter intuitive with large piping systems. Time to time, sites should invite spring vendor to provide support, advice and training to the maintenance and operations teams. The vendors recommendations are key to understanding critical support functions, troubleshooting and ensuring reliability for plant operations. It is highly recommended to involve the spring vendor prior to every turnaround for joint inspection with Coker units so that any deficiencies can be properly addressed during the turnaround. Thermal cycling of the delayed Coker unit requires more dynamic spring support scenarios than any other unit in the refinery. Following any major turnaround, it is important to have a comprehensive inspection and verification plan for all types of supports, especially those who have been worked on during the shutdown.

Detailed technical content


Standard features of critical piping spring supports are position (cold/hot), travel scale, load adjuster, level rotation indicators, and locking (lock pin) or balancing devices. Pipework stress and load analysis is calculated based on deadweight, thermal and dynamic effects, system stress levels, and equipment loadings along with loads and movements acting at the support positions. Various codes and calculation methods should be considered, such as but not limited to ASME B31.1, B31.3, Finite element analysis (FEA) and relevant design codes. There are two major types of spring supports (Constants & Variable) used in Coker plants based on the nature of the process and piping/equipment. The piping around the coke drum is especially complicated and each licensors has different strategies to manage piping and the coke drums which utilizes additional types of struts and snubber supports due to the nature of drum piping, support and special spring support for BUD (Bottom Un-heading Device) to control BUD movement with Coke Drum.

Constant Spring Support (photo):

Constant Spring support

Variable Spring Support (photo):

variable spring support

Common Problem/Issues Observed in Refineries:

Spring Coil Coating Process (photo):

spring coil coating process


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