Energy Systems GT Exhaust Systems Seminar

Energy Systems
GT Exhaust Systems Seminar - Stavanger
Mark Wickham/Andy Dyson/Paul Kingston
2007
Energy Systems
Company History
Energy Systems
Operational Units Worldwide –
140 Fired Heaters – Designed to API560
126 GT WHRU’s – Cold Casing, Pressure parts
designed to API 560
49 GT WHRU’s – Hot Casing, Designed to mostly
NORSOK
Total WHRU’s in design, build or operation - 213
Relevant Experience
Energy Systems
The cost, weight and size of a WHRU system has a
direct relationship to exhaust gas velocity. The higher the
velocity the smaller the WHRU.
Traditionally flow has been assumed as average across
the duct – 45m/s max on hot casings and 35m/s max on
cold casings (internally insulated)
Design Basis
Energy Systems
Silencers – Baffle disintegration/insulation erosion
Diverters - Cracked hot casings
Casings - Cracked hot casings
Pressure Parts – external tube wall damage/header
tube welds failure/tube leaks
Component Failures
Energy Systems
Heat Exchanger
Heat Exchanger
Valve
Bypass Valve
Silencer
Hammerfest Design
Energy Systems
Development work with Statoil and Dresser over the
past year on Sleipner, and with Statoil on Hammerfest
has revealed two probable causes:-
•Vibration
•Overstressing of hot casings
Causes of Failure
Energy Systems
Typical Velocity Profile – LM6000 Outlet from Silencer
Energy Systems
Velocity Profile – LM2500+ Oseberg
Energy Systems
Velocity Profile – LM2500+ Sleipner
Vibration calculations
Energy Systems
Development of the replacement Sleipner WHRU with
Dresser and Statoil has highlighted the need for a velocity
profile to be provided to WHRU suppliers with the enquiry
Transient FEA analysis has established that hot casings
are more difficult to design than cold casings due to high
stresses caused by thermal gradients, particularly during
start up
Sleipner Findings
Energy Systems
Sleipner Findings
Energy Systems
Failures can be prevented if the interface point between GT
and WHRU is fully defined
It is more simple and effective to correct the velocity profile
in the WHRU system where velocities are lowest
Hot casing designs need detailed transient stress analysis
of all significant casing attachments
Conclusions
Energy Systems
Ensure vibration does not occur
• Reduce velocity to acceptable levels as soon as possible
after the GT flange
•Ensure heat exchanger support system is designed for the
maximum velocity plus good margin and support on fins
rather than pressure parts
•Ensure silencer design considers maximum velocity plus a
good margin
Recommendations
Energy Systems
Include the following in the enquiry specification
•Velocity profile at GT/WHRU interface point (max flow)
•Requirement for CFD modelling
•Requirement for vibration analysis
•Requirement for Transient FEA analysis on hot casings
•Make the design and supply of all components
downstream of the GT outlet flange the responsibility of
one company (including silencer)
Recommendations
Energy Systems
Consider the use of cold casings (internally insulated) in
areas requiring extensive external stiffening – coil casings,
support points, flanges, rectangular sections
Minimise the number of corners – circular ducts are ideal
Radius corners
Avoid corner welds
Recommendations