PWHT Method Options

[weeeds]

UW-40(a)(4) permits "heating the vessel internally by any appropriate means ...".
Sect. I PW-39.4 does not specify internal or external heating.
There are companies who perform PWHT by shooting a flame into the interior of a vessel in order to obtain the required temperature. I have also heard of chemical exothermic reactions from the inside as well.
Some large consultants do not accept any method other than heating the entire vessel in a furnace but I suspect that alternatives are used successfully.
Does anyone have experience with these alternate methods?
Are there other methods that are used?
Any problems with such alternate methods?
Thank you.

 

[unclesyd]

There are several threads on Eng-Tips where direct internal heating has gone from bad to worst. Not to say it isn't done successfully, but the expertise and experience of company undertaking the work would be my primary concern.

The only thing we have used direct fire burners for heating is the drying and curing refractory and heating boilers for chemical cleaning. Even this has given me a few moments of anxiety due to problems with getting the project going.

The only exothermic type reaction I’ve seen is on ceramic lined vessels where ceramic weld repairs are made

 

[metengr]

I would recommend not using any of the alternative heating methods you mentioned above. Your Authorized Inspector (AI) must also review and approve of any heating method to assure adequacy of PWHT.

The key to PWHT is to provide control of heat input, and most importantly, to provide uniformity of heat to prevent harmful gradients in and adjacent to the zone of PWHT.

 

[LSThill]

Team Member Please comment

If the work for a Vessel is fabricator in India?

Vessen is too large for the Farnce in this case will require two PWHT and One weld.

SDDR has been Issued by the fabricatior.

Oh! with the current rain of 24"-30" this past Wed, Thru. FRI, it is sitting on the truck in the Mud.

 

[metengr]

The ASME B&PV Code permits local PWHT using a band of heating, and multiple cycles (if necessary).