Allowable thickness for restoring wasted wall thickness of pressure vessel
Allowable thickness for restoring wasted wall thickness of pressure vessel
(OP)
Dear Fellows,
We are in process of repairing a pressure vessel which the wall thinning has happened because of corrosion. We decided to restore the corroded area using weld buildup.
I have refereed to NBC and API 510 to find the maximum thickness is allowable to be restored by buildup welding. In other words under which circumstances we must use flush patch or lap patch?
Does anybody knows the limit based on industry practices, regulatory association like ABSA, BCSA, TSSA or code and standard for in service pressure equipment.
Much appreciated for any thoughts and inputs.
Alireza
We are in process of repairing a pressure vessel which the wall thinning has happened because of corrosion. We decided to restore the corroded area using weld buildup.
I have refereed to NBC and API 510 to find the maximum thickness is allowable to be restored by buildup welding. In other words under which circumstances we must use flush patch or lap patch?
Does anybody knows the limit based on industry practices, regulatory association like ABSA, BCSA, TSSA or code and standard for in service pressure equipment.
Much appreciated for any thoughts and inputs.
Alireza





RE: Allowable thickness for restoring wasted wall thickness of pressure vessel
How much area must be restored to original thickness?
Is this one area of destruction, or a wide area? How many sq units (inches or cm) need to be repaired?
What material?
Do you have certified welders and a certified welding process already in place?
RE: Allowable thickness for restoring wasted wall thickness of pressure vessel
RE: Allowable thickness for restoring wasted wall thickness of pressure vessel
RE: Allowable thickness for restoring wasted wall thickness of pressure vessel
Please see answer to your questions:
How thick is the PV? 05"
How much area must be restored to original thickness? 0.4"
Is this one area of destruction, or a wide area? How many sq units (inches or cm) need to be repaired?Around 5" by 5"
What material? A516-70N Sour services
Do you have certified welders and a certified welding process already in place? Yes
TGS4,
Is that correct ande5rstanding that "Thicknesses less than welding consumable diameter is in risk of burn trough"?
RE: Allowable thickness for restoring wasted wall thickness of pressure vessel
My mistake. The corrcet original thickness is 0.5"
RE: Allowable thickness for restoring wasted wall thickness of pressure vessel
But a skilled welder can join or repair almost any thickness metal by choosing the right diameter wire or rod and the right amperage and the right speed. Your "thumb rule" is both correct and incorrect. Do not let it become a "Thumb rule of law" rather than mere guidance.
Other things that he or she can change: "time" of the current => small, short "taps" of the current let the thin metal cool off before the next little bit is melted on. Longer arc distances help. Lower voltages help. Good gas flow helps cool the metal. Applying shield gas as a coolant to the back side of the base metal helps suck heat away from the joint.
On your PV, 1/2 thick wall is a modest thickness that is workable - even for a significantly deep repair over a modestly small repair area. Check that the weld area is preheated carefully, and that the irregular - and probably very dirty ! - bottom and sides of the repair area are ground completely clear of pits and tears and valleys, and are both chemically and mechanically kept clean. Clean about 1-1/2 inch to 2 inches (35 to 50 mm) around the repair area as well.