Quaternary Annulus Cleaned for Gas Fired Power Station

Iron Oxide removal avoids outage


Imagine a 20” diameter steel vessel x 20” high containing a built in 25mm deep hollow steel jacket of similar proportion, full of loose, flaky, rust like deposits on the inside of the annulus’ (fuel distribution belt). A UK gas fired power station required the deposit removing speedily but to a high standard to avoid an unscheduled outage once back on-line. Tube Tech succeeded where other contractors had failed – cleaning 18 quaternary annulus’ in less than 48 hours to a much higher standard.


  • The quarternary annulus manifold provides a vital function within the power generation cycle and any fouling within the annulus negatively effects the fuel delivery to the power station turbine.
  • An endoscope inspection located serious corrosion build up.
  • Unscheduled outages occur due to fouling blocking the small diameter nozzles. Corrosion build up elevated the annulus dynamics and trips led to forced and costly outages.
  • An ultrasonic cleaning contractor had previously tried to clean the annulus’ but the power station found sludge like deposit remaining inside them.
  • The steel annulus’ needed cleaning every major outage so a viable alternative was needed.
Borescope image of annulus at gas fired power station before clean Annulus interior with flaky rust being removed Gas fired power station annulus Morning cleaning information


Tube Tech studied the inspection images, measured fouling characteristics, took videos and studied drawings as access was severely limited via a solitary 1.5” x 3” deep, right angle nozzle welded to the outer steel wall.

Having cleaned very tight bends on other heat transfer equipment the research & development department developed and tested a flexible Shell Jett, a mechanical, non chemical system which could be inserted through the nozzle and then turn a tight 90-degree delivering the cleaning medium across the entire surface of the annulus.
All 18 annulus’ were cleaned to a standard and speed exceeding all the clients expectations.

Tube Tech comment

Mike Watson, Managing and Technical Director. “This was the first time Tube Tech had done this and our ever expanding research team with their latest Solid Edge CFD flow and force modelling software enabled us to create a fast and effective, mechanical cleaning solution. To say this modified Shell Jett will prevent future unscheduled station outages is big news and Gas power stations can breath a sigh of relief”

For more information or to discuss your cleaning challenge call us on +44 1268 786999 or e-mail info@tubetech.com, alternatively click here to fill out our contact form.