safety factor and joint efficiency
safety factor and joint efficiency
(OP)
I have a non-code vessel, SA-36 material, I am increasing the allowable stress to 23200 psi decreasing the safety factor to 2.5, I'm not performing any RT, so I'm using 70% efficiency, but with the thks I have my MAWP is still below my DP, can I increase my Efficiency to reach my DP keeping my Safety factor over 2.5?





RE: safety factor and joint efficiency
Efficency is based on weld profile/type and the amount of NDE you wish to preform. Minimum thickness required for vacuum design will not be effected by weld efficiency.
I would say if you are already using SA-36, which is for non pressure parts, and reducing the safety factor to 2.5:1; just overlook the MAWP calculation. You are already demonstrating a disregard for ASME rules. Why is this calculation required for non-code?
RE: safety factor and joint efficiency
Where will this device be installed ?
RE: safety factor and joint efficiency
As per innovation2, since you have fully disregarded ASME VIII design rules, why are you asking the question? Now you really must consider toughness at the design conditions to avoid fracture during service or pressure testing.
Should you plan to pneumatically test, contact your rescue responders to pick up the human remains.
RE: safety factor and joint efficiency
So in conclusion if i want 2.5 SF I can use the following stress in ASME formulas:
Smodified=S*E/2.5 with E=0.7 (NO RT)
RE: safety factor and joint efficiency
RE: safety factor and joint efficiency
Some body could help me!
RE: safety factor and joint efficiency
RE: safety factor and joint efficiency
RE: safety factor and joint efficiency
RE: safety factor and joint efficiency
Yes you can perform NDT on in-service vessels. It is done all of the time and is a matter of proper scheduling.
RE: safety factor and joint efficiency
RE: safety factor and joint efficiency
Simply calculate the induced stresses based on the pressure, diameter, thickness and joint efficiency of the actual vessels and compare to the minimum specified ultimate tensile strength of the material to determine the actual factor of safety.
RE: safety factor and joint efficiency
hey guys any other thoughts
RE: safety factor and joint efficiency
Efficency should be accounted for in the formulas used to calculated stress.
Actual component safety factor can be determined by taking minimum allowable tensiles and deviding by calculated stress.
Try not to cut corners in your design...stick to the rules, that is why they are there.
Honestly you will not save a terrible amount of money on an atomospheric or low pressure tank by using a reduced S.F.
RE: safety factor and joint efficiency
A couple of thoughts on this. First, I'm not that familiar with ultrasonic testing, but could it be done from the outside while a tank or vessel was in service?
Secondly, the calculation of a particular factor of safety per one code or another also assumes that the vessel was otherwise constructed in accordance with the code. So if you're designing a vessel with 70% joint efficiency due to not having any radiograhy, you're still assuming that the weld procedures and welders were properly qualified and that the welds were full-penetration and that some degree of visual examination was done on them. On the other hand, if you look at a weld after the fact and don't know how it was welded or by whom, you don't know any of those things. You may also find that nozzle reinforcement is what actually limits the pressure rating rather than shell thickness itself. A lot of the non-code vessels that I see also have heads that don't comply with the knuckle radius requirements of ASME, so you don't really have a good basis for design of them.