i'm encountering a new problem now, i the Piping class given, for a 400 NB wafer check valve, the length of bolt is 330mm, bolt size is 1" and number of bolts is 16.
for the same 400NB. flange to flange connection is given as 140mm length, 1" dia, and 16 number of bolts.
the face to face length of wafer check valve is 191mm.
PDMS calcualtes as follows ,
default bolt length of 400NB flanged conn with 1 gasket = 140mm
face to face lenght of wafer check valve = 191mm
Thickness of a extra gasket = 3mm
__________
total length of bolt = 334mm
___________
so my company needs that to be 330mm, still due to lack of time we are still using old bolting method,
So basically you need to lose 4mm from the calculated length using old method.
Old method works by taking 1/2 length of flange1 boltref + 1/2 length of flange2 boltref + wafer + extra gasket.
solution
Create new flange in the spec identical to the normal flange but add :wafer to the speco name. (The :wafer will be stripped off by Isodraft)
Give this flange a different STYP and a Boltref with the correct No & Dia bolt but a length of 132mm
Replace one of the flanges in design with this new flange
Bolt calculation should then be 70mm + 66mm + 191 + 3 = 330
how about new method, weather it takes the length of bolt specific for each case, example.
for wafer check valves
for spectacle blinds,
for orifice plates.
can we specify like that.
i fear that already we have flanges based on insulation, i.e material breaks, i'm worried that the designer should select the correct flange for each case.
Your problem is that your company does not want to use the calculated bolt length.
No matter which method you use, if calculation is 334mm that is what PDMS will use (or 335mm to be correct).
If your company wants to use 330mm then you will have to find a way to trick PDMS into getting that answer.
It is not the bolt method that is causing the problem.
If you really want everything to be correct the go to ASME B16.5 and read up on how bolt lengths are calculated. Then do your own calculations to find out what the lengths should be. Then make your bolt tables match your calculations.
I would advise you not to use third party length calculations as being correct.
If you compare a number of different sources (Trouve, Pipedata pro, ASME B16.5, plus manufacturers) you will find that they do not all agree with each other on bolt lengths.
Some calculate in inches. Some calculate in inches then convert to mm.
Some do all the calculations in mm but disagree on rounding up/down on conversions.
All seem to use 1/16" (1.6mm) gaskets in the calculation which may or may not give the correct answer if a 3mm gasket is used.
In all cases the given bolt length is more likely than not going to be too short as they use the flange thickness as given in 16.5, but the manufacturing tolerance is something like -0mm to +6mm.
Pitch you are exactly right... for a Butterfly valve when i refer pipe data it is 420, and a manufacture standard says 425 and PDMS calculates as 405, and the PAper Spec of the client says 400.
i cannot arrive a conclusion on this... if i adapt new bolting method can i arrive at specific bolt lengths based on client spec, especially i face problem with wafer connections.
I agree with Mr.Pitch. Pdms calculates the Bolt length based on your Input, it doesn't matter to use either New or Old bolting method.
Now you have to decide which STD to be followed for Bolt length. If you follow the manufacture's STD, then you will not have problem in erection or
If you follow the Client STD then you will face the short bolt length problem.
Yes you can achieve the Client Std Bolt length by creating more no of flange Spco, but the output of Bolt length???.:baffled:
Better you convince your client for STD Bolt length.
baski,
thats the problem here, the client is telling "we are following this standard for more than 25 Years, now how you can change this,?" he wants PDMS to give the Desired output, and he adds that if it is not giving the required output its not a good tool...
then i went to the top of anger, as he insulted PDMS... so i want to acheive this by adding another flanges, but the isometric is not appending...