I have the problem to understand ASME Code - Flange with ring type gaskets
I have the problem to understand ASME Code - Flange with ring type gaskets
(OP)
I have the problem to understand why if I have ASME/ANSI B16.5-1988 flange 18'' 150#, ASME bolts for this flange, ASME gasket B16.20-1998 18'' 150#, the pressure "very high" 0,1 MPa (14,5 psi), temperature 260oC (500F) the ST calculated tangential stress in flange is so high. Using the formula (4) W=0.5*(Am+ab)*Sa I get large values of W. In my project ex. Am = 11,1 in2, Ab=5.56 in2, consequently the value of Mo and ST are high and the condition ST < Sf is not valid. For me it is crazy: the bolts are 2 times better then should be. Sa and Sb values (allowable bolt stresses) must be very low 130MPa (18800psi), if not, it gets worse. What is wrong with my thinking? What am I not understand?





RE: I have the problem to understand ASME Code - Flange with ring type gaskets
However you are not required to calculate a B16.5 flange under Div.1 coverage.
prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
However, by changing the gasket diameter you won't conform anymore to B16.5, but if you succeed with the calculation, then everything is fine.
prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
UG-11(c)(2) Flanges and flanged fittings may be used
at the pressure–temperature ratings specified in the appropriate
standard listed in this Division.
So you may use B16.5 flanges by just selecting proper pressure-temperayure ratings.
Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
These standard flanges are based on end users' millions of proved records, that is why it is used until now without any changes.
It is unwise to mess around the standard flange. Your flange is only 18", and you shall use standard gasket that fits to the code, service and your flange type. Do not waste your time running ANY calculation.
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
You will be struggling on this ridiculous calculations that inspector is asking you to do. Most of them will fail by seating stress. So, what are you going to do ? change bolting load or gasket ?? That is unwise. Tell your inspector no need to run calculations as long as you are using the right type of bolting and gasket, and size and material property ( just property only, not material spec such as A-105. Different country has different spec) fit to B16.5.
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
RE: I have the problem to understand ASME Code - Flange with ring type gaskets
I answered my own question (my opening is too large)