I am sorry if this is long, but please bare with me.
We are currently facing a slight problem with one of the vessels that we have manufactured for a ýclient. The problem lurks in the results of heat treatment performed in a way where the vessel ýturned into an egg shaped object. ý
For your information, because the vessel is so long, we converted the vessel into a furnace. The ývessel size is the following: Inside diameter 4,877mm X 48,768mm tangent to tangent in length X ýý44 mm thickness. ý
The plates used are supplied by the mill with simulated PWHT.ý
The vessel was treated in the horizontal position with four units high velocity burners. Two on ýeach head end, and the other two from the top spaced equidistantly on the remainder of the ýshell with heat being diverted horizontally by means of a specially made 22 degrees diversion ýelbow. ý
We have placed 13 units outside saddle supports with none inside and started firing. Upon ýcompletion @ 50 degrees Celsius an hour for a total temperature of 610 degrees Celsius areas ýof the top third of the vessel fell to about 210mm from its own weight and nozzles. Maximum out ýof roundness per code is 48mm. ý
I kindly seek your expert opinion for a method statement and or a repair procedure to resolving ýthe current situation so as to bring this vessel back to code compliance requirements. ý
The code is the latest version and addenda of ASME section IIIV Division 1.ý
Our engineering manager stated the following:ý
The dimensional reports attached with NCR P01-1432/02 (Q11-D-204) for out of roundness of ýthe vessel after heat treatment indicates the following:ý
ý1.ý The heating in my opinion was not uniform at 4 burners as the result of this there may ýbe thermal pockets generated due to differential expansions at the burner’s locations. ý
ý2.ý This report does not indicate shifting of TRUE VESSEL center line of vessel towards 90° ýor 270°. The vessel might have bent like Banana or at some portion bent towards 90° ýand remaining portion bent towards 270°. If the vessel is bent towards one fixed degree ýthen turning the vessel by 90° say and doing heat treatment would reduce out of ýroundness. If the top half portion is bent and maximum deflection is at the center of ývessel length and towards one fixed degree than it indicates the introduction of internal ýspider supports. These spider supports shall be inter-connected so that it acts as a ýhomogeneous structure. This is one of the possibilities. Complete readings have to be ýtaken at 1 meter interval or at the shell course weld joints. ý
ý3.ý Jacking of shell would not help unless vessel is jacked beyond yield strength. To yield ýý44 mm thick shell, it requires a very big jack. Jacking of vessel would lead to jacked ýspots and it is not recommended by the writer. ý
ý4.ý Heating rate and cooling rate shall be faster as to avoid prolonged thermal stresses. ý
ý5.ý How this material behaves at 1100° F (HEAT TREATMENT) temperature is very difficult ýto assume. ý
ý6.ý Cutting the shell weld joint would be one of the disliked alternatives. ý
ý7.ý It is ad visible to take expert opinions particularly from metallurgical engineers pertaining ýto support etc before it is too late. ý
ý8.ý It is beyond my engineering capacity to deal with thermal expansion calculations, ýstiffeners outside or inside the vessel. ý
ý9.ý This problem may be new to us, but definitely not a new problem for thick vessel ýmanufacturers or thick vessel inspectors and they may give vital information about ýarrangement of internal stiffeners. We do not want to do it wrong this time. ý
I would appreciate any and all assistance you could provide, ý
We are currently facing a slight problem with one of the vessels that we have manufactured for a ýclient. The problem lurks in the results of heat treatment performed in a way where the vessel ýturned into an egg shaped object. ý
For your information, because the vessel is so long, we converted the vessel into a furnace. The ývessel size is the following: Inside diameter 4,877mm X 48,768mm tangent to tangent in length X ýý44 mm thickness. ý
The plates used are supplied by the mill with simulated PWHT.ý
The vessel was treated in the horizontal position with four units high velocity burners. Two on ýeach head end, and the other two from the top spaced equidistantly on the remainder of the ýshell with heat being diverted horizontally by means of a specially made 22 degrees diversion ýelbow. ý
We have placed 13 units outside saddle supports with none inside and started firing. Upon ýcompletion @ 50 degrees Celsius an hour for a total temperature of 610 degrees Celsius areas ýof the top third of the vessel fell to about 210mm from its own weight and nozzles. Maximum out ýof roundness per code is 48mm. ý
I kindly seek your expert opinion for a method statement and or a repair procedure to resolving ýthe current situation so as to bring this vessel back to code compliance requirements. ý
The code is the latest version and addenda of ASME section IIIV Division 1.ý
Our engineering manager stated the following:ý
The dimensional reports attached with NCR P01-1432/02 (Q11-D-204) for out of roundness of ýthe vessel after heat treatment indicates the following:ý
ý1.ý The heating in my opinion was not uniform at 4 burners as the result of this there may ýbe thermal pockets generated due to differential expansions at the burner’s locations. ý
ý2.ý This report does not indicate shifting of TRUE VESSEL center line of vessel towards 90° ýor 270°. The vessel might have bent like Banana or at some portion bent towards 90° ýand remaining portion bent towards 270°. If the vessel is bent towards one fixed degree ýthen turning the vessel by 90° say and doing heat treatment would reduce out of ýroundness. If the top half portion is bent and maximum deflection is at the center of ývessel length and towards one fixed degree than it indicates the introduction of internal ýspider supports. These spider supports shall be inter-connected so that it acts as a ýhomogeneous structure. This is one of the possibilities. Complete readings have to be ýtaken at 1 meter interval or at the shell course weld joints. ý
ý3.ý Jacking of shell would not help unless vessel is jacked beyond yield strength. To yield ýý44 mm thick shell, it requires a very big jack. Jacking of vessel would lead to jacked ýspots and it is not recommended by the writer. ý
ý4.ý Heating rate and cooling rate shall be faster as to avoid prolonged thermal stresses. ý
ý5.ý How this material behaves at 1100° F (HEAT TREATMENT) temperature is very difficult ýto assume. ý
ý6.ý Cutting the shell weld joint would be one of the disliked alternatives. ý
ý7.ý It is ad visible to take expert opinions particularly from metallurgical engineers pertaining ýto support etc before it is too late. ý
ý8.ý It is beyond my engineering capacity to deal with thermal expansion calculations, ýstiffeners outside or inside the vessel. ý
ý9.ý This problem may be new to us, but definitely not a new problem for thick vessel ýmanufacturers or thick vessel inspectors and they may give vital information about ýarrangement of internal stiffeners. We do not want to do it wrong this time. ý
I would appreciate any and all assistance you could provide, ý
