Weld overlay dimensional tolerance

[sree60]

Hello Members

We have a 3in forged nozzle ASTM A 105 Clad with 3 mm SS316L attached to the shell of clad vessel HP separator.
The clad thickness specified is 3 mm.As per approved drawing the bore of base metal of forged nozzle is 73.66 mm and inside dia after cladding is 67.66 mm (73.66-6mm).

My questions are

1)What is the tolerance on the bore dimension 67.66 mm after cladding.
ASME B 16.5 specifies Flange Bore ( without cladding)Tolerance AS +1MM AND -0.0 MM.There is no under size tolerance .The clad thickness is usually more than 3 mm and the surface in our case will be as clad and not machined.An excessive clad thickness will result in reduction of bore size and there can be process issues due to restricted flow turbulence etc

2) What is the surface finish requirement for as clad surfaces?

The design considers 3mm overlay only for corrosion protection and not for strength calculations.

Thanks in advance

Sree60

 

[weldtek]

In my experience, these issues are ones you would normally resolve with your customer.

 

[stanweld]

The Purchaser/Engineer must define tolerance.

 

[vesselfab]

3mm is the thickness of the overlay that meets the chemistry requirements.

you have to add on the "butter" pass thickness.

if we have a 3mm requirement, the weld overlay would wind up 3/15" to 1/4" thick

 

[sree60]

The thickness OF WELD OVERLAY is more than 3 mm and close to 5 or 6 mm. This rsults in reduced bore than specified in the drawing.This is out of permissible tolerance for the bore as per ASME B 16.5.We would ask purchaser/ engineer.
Thanks for the inputs
sree60

 

[JohnGP]

ASME B16.5 provides tolerances for the base flange, and not for add-ons such as cladding. If there are process considerations that require tight control of fitting ID, then this needs to be specified on the drawings - if not initially, then as a comment to be addressed before being "approved".

 

[petronik]

I have this job in my in hand project. I know your problem exactly:1- if you don't increase the overlay thickness you will not find the chemical composition in PMI test because you need minimum 6mm thickness for get the composition (3mm overlay with 309 and 3mm overlay with 316 filler) 2- if you machining the base metal you will deviate the drawing

solution 1: you shall check the nozzle neck calculation with thickness 3mm less than drawing, if the new thickness is approved you can revise the drawing and do the overlay after machining else you shall ask your client to accept 3mm of the overlay thichkess as buttering in your calculation because actually you will do 6mm buttering and half of it can be consider in calculation instead of base metal (forge)

solution 2: process designer shall check ID 67.66 mm for flow rate of this nozzle and give you the approval.

if the overlay will accept visually (after PMI test) normally no machining is necessory but you must get the client approval.