Bypass Stack

[norzul]

Hi,

Anyone got experience with regards to the installation of bypass stack between GTG and HRSG. What are the pros and cons on having this bypass stack.

I was informed by the HRSG vendor that nowadays about 90% of their installation is without bypass stack.

Thanks

norzul

 

[norzul]

any advise...

 

[taylorg]

Pro is obviously your ability to run in open cycle.
Main con is that bypass dampers and duct joints are often troublesome (leaks).

 

[norzul]

Was informed that having bypass will significantly expedite the start-up period. Without bypass for cold start-up, was told it will take about 7 hours to come up to rated capacity. For hot start-up, will take about 3 hours....In my opinion, this is too slow...any advise

 

[taylorg]

For a Frame 5 in combined cycle, average start up times should be about an hour (hot start) and approx 4 hours from cold. With bypass stack you could get the GT up to full load in about 15-20 mins.
The times you quote do seem very slow. Either the contractor is just trying to sell you a bypass stack or you need to closely review the design of the HRSG.

A quick internet search might give you some data sheets etc.