HRSG boiler seismic loads.

[Bartolomew]

I am involved in structural calculations of a HRSG boiler 32 m. height, 6 m. length and 3,6 m. width, horizontal tubes bundles, vertical gas flow (european type), inlet gas temperature 650ºC (1200 ºF). The tube bundles rest on two vertical perforated plates which are suspended by lugs with pins from the next upper bundle and finally all the weight goes to the top steel by rods. Casing is internal insulated and also suspended by rods from the top steel. Seismic coefficient is 0.3g. My question is:
All analogies that I have seen show no connection between bundles and casing then, how seismic horizontal forces are transferred from the hanging tube bundles to the seismic bumper ties of the casing? Anybody knows?
Thanks in advance.

Bartolomew

 

[JStephen]

There is a "Boiler and Pressure Vessel Engineering" subforum, you might check there.
There is a possibility that the construction described hasn't been designed for seismic loading at all.

 

[SlideRuleEra]

Large vertical boilers, including Heat Recovery Steam Generators (HRSG), are suspended from the top. This is to allows for unhindered thermal expansion downward when the operating. Boilers of this type are suitable for seismic design. Seismic loads on anchor bolts and foundations are high since the boiler can impact horizontal restraints

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[vhengr]

As boiler is like pendulum, due to seismic forces it will swing & may cause sever damage to internals, ducting of boiler, so arrest it and to transfer the load to steel structure stoppers/guides are provided.

Pls check with pressure part(Coil) designers, there must be stoppers/restraints provided on the casing.

Generally horizontal as well as vertical restraints attached to casing inside. According to load concentration they decides the stopper regions and no of stoppers per region. Gap is provided to allow the thermal expansion of the coils.

These stoppers transfer the seismic load to the furnace wall. Wall further transfer these loads thro' buckstays and seismic guides provided outside of the furnace wall to the main structural steel frame of the building.

Best Regards_ VH