Quaternary Annulus Cleaned for Gas Fired Power Station

Iron Oxide removal avoids outage

Summary

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.

Challenge

• 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. 

Solution

• 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 plate 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 Platejett™ will prevent future unscheduled station outages is big news and Gas power stations can breath a sigh of relief”