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#39640 - 12/18/10 08:37 PM Desuperheater
Van Ha Offline
Member

Registered: 07/29/09
Posts: 171
Loc: Ho Chi Minh City, Vietnam
Dear all,

For stress analysis which piping connected to boiler and a inline desuperheater (with bypass), I have some questions as follows:

1. What code should we use, B3.1 or B31.3 ?
2. I dont have experience with desuperheater, so what should be considered for this device (in stress analysis view point)?
3. How to break temperature at desuperheater (with bypass)?
4. Is there any vibration due to desuperheater? Do we need to consider dynamic analysis?

I already use the search function, and it doesn't help so much.

I hope someone can help.

BR.


Edited by Van Ha (12/18/10 08:38 PM)

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#39645 - 12/20/10 01:45 AM Re: Desuperheater [Re: Van Ha]
danb Offline
Member

Registered: 04/22/05
Posts: 1320
Loc: ...
Please read B31.1 Chapter I Scope and Definitions and eventually B31.3 Chapter I Scope and Definitions. This will help you to choose the design code.

Please note that the Piping Material Specification (Piping Class) assigned to the lines should have the same Design Code specified.

Best regards,
_________________________
Dan

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#39649 - 12/20/10 02:55 AM Re: Desuperheater [Re: danb]
danb Offline
Member

Registered: 04/22/05
Posts: 1320
Loc: ...
For the rest of your questions you may search on http://www.eng-tips.com, there are some things that maybe can help you.

Best regards,
_________________________
Dan

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#39650 - 12/20/10 03:19 AM Re: Desuperheater [Re: danb]
salz64 Offline
Member

Registered: 12/29/09
Posts: 25
Loc: Pakistan
Dear Van,

Fig. 100.1.2(C)of Asme B31.1 (2007) clearly shows the code jurisdiction. i.e. If desuperheater is in the main steam line than upto desuperheater ASME Sec I bears the technical as well as administrative responsibility. Where as at downstream of desuperheater the B31.1 has the technical responsibility.

So you can only use B31.3 after the first STOP Valve (installed after desuperheater ofcourse).

Please refer to ASME B31.1, 122.4 section in which you'll see some requirements for desuperheater either in main steam or reheat lines (like between superheaters and bypasses etc).

Any desuperheater manufacturer will guide you for selection and type of desuperheater required. Mostly process engineers are incharge of this. There is also specific requirement of upstream and downstream distances which piping guyz have to maintain in order for spray water & steam proper mixing and achievement of sort of laminar flow. Also in order control the erosion (if in action as per velocities calculated) a sleeve is incorporated in the downstream of desuperheater piping.

Main analysis requirements are to consider the transient effects associated with water spraying on superheated steam. Also the temperature difference of spray water piping and steam piping is also main concern when evaluating expansion stresses.

Hope that helps.

Regards,
Salz


Edited by salz64 (12/20/10 03:26 AM)

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#39716 - 12/22/10 07:21 PM Re: Desuperheater [Re: salz64]
Van Ha Offline
Member

Registered: 07/29/09
Posts: 171
Loc: Ho Chi Minh City, Vietnam
Thank you all for your help. Your comment is really valuable.

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