A method for increasing process run-length
INDUSTRY TERMS | 3 min read
Online spalling, also known as steam spalling or ‘zinging’, is an operational method used in oil, gas, and chemical facilities to improve the run-length and throughput of a refinery process. It is an example of fouling mitigation.
How online spalling works
Online spalling uses a combination of thermal expansion, contraction, and shear from high-velocity steam to remove organic and inorganic deposits from inside of tubes and pipes.
The process starts by carefully closing off the process control valve and replacing the process fluid with high-velocity steam. The substantial shear and change in temperature will act to loosen and remove some fouling.
After a few minutes, the operator returns the steam to normal velocity, and then opens their process flow valve to 100%. The more powerful shear of the liquid, combined with the thermal contraction or expansion of the tube walls, will knock off many remaining deposits.
When you get to a point where the fouling is causing reduced flow, you can use online spalling to get several hundred bbls of flow back, and increase the run-length of your process. Online spalling is not the same as Clean-in-Process.
Where can online spalling be used
Online spalling is mostly used in Delayed Coker Units, however it has been effectively used to increase run-length in FCC slurry heat exchangers. It is used to remove organic scale, while pigging may be necessary at some refineries after several spalls to remove the remaining inorganic deposits.
It is imperative that the Lead Operator or Operating Engineer who is responsible for oversight of the online spalling process be knowledgeable of the procedure, mechanical limitations and process limitations of the equipment (Note: this is not a definitive guide to implementing online spalling your process).
Limitations of online spalling
Online spalling is just a bandage until you pull your exchanger, which will require reduced charge and an economic expense regardless of how effectively it is executed. The use of ultrasonic online cleaning technology as a standalone solution or in combination with online spalling can extend the run-length of your process’ heat exchangers.
Depending on the type of contamination you want to remove, online spalling may be more, or less, effective. Some inorganic compounds present in refinery feeds cannot be removed by online spalling alone and may require the added cleaning disruption of a Clean-in-Process system.
Additionally, online spalling can be very detrimental to the unit if done improperly. Too rapid spalling can plug the tube outlet, and too high steam velocity can erode the metal in the elbows.
During higher temperature months, air blowers may be limited by lower air density. As such, there may not be an opportunity to use a large amount of velocity steam for online spalling purposes.