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flanges
- lee1255
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16 years 7 months ago - 16 years 7 months ago #8746 by lee1255
flanges was created by lee1255
Why are the holes of flanges never positioned on the vertical line
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- Jop
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16 years 7 months ago - 16 years 7 months ago #4171 by Jop
Do it once and Do it Right
Replied by Jop on topic Lee1255, You have asked a question
Lee1255,
You have asked a question that I am sure that no one knows the actual answer. It is what it is and there is nothing you or I can do about it.
The following is from the article I wrote about flanges. the complete article can be found on the "Training" page of this web site.
Bolt Hole Location:
The ASME B16.5 has a standard for bolt holes that in used by all (US) manufacturers for flange sizes up through 24" For instance; the number of bolt holes required varies with the size and rating of the flange. But the number and size is the same no mater the type of flange. The bolt holes are evenly spaced around the flange on a concentric bolt circle. There will always be an even number of bolt holes, in graduations of 4 (i.e., 4, 8, 12, 16, etc.).
Unless specifically noted otherwise by the piping designer (and then only if for good reason) all flange bolt holes shall straddle the "natural" centerlines. This is the flange bolt hole orientation rule. This "natural" centerline rule for flange is known, understood and followed by all responsible equipment manufacturers and pipe fabricators. The rule is:
• For a vertical flange face (the flange face in vertical and the line is horizontal) the bolt holes shall be oriented to straddle the vertical and horizontal centerlines.
• For a horizontal flange face (the flange face is horizontal and the line is vertical up or vertical down) the bolt holes shall be oriented to straddle the (plant) north/south centerlines.
Care must be taken to check all equipment vendor outlines to identify any flange orientations that do not match this rule. When an exception is found the vendor can be requested to change his bolt hole orientation. This is not always successful and if not then the piping designer must insure that the piping fabrication documents call for the correct orientation.
This rule of bolt holes straddling the natural centerlines is sometimes referred to as "Two-Hole" the flange. This means that the two of the holes straddle the centerline. To "One-Hole" a flange means that the flange has been rotated so that one hole is right on the natural centerline. I assure you that 99.999% of the time that to "One Hole" a flange is a mistake and will add cost to the field. It also makes the piping foreman very unhappy.
Please consider this much as you would gravity. You don't know why gravity works but you accept it.
You have asked a question that I am sure that no one knows the actual answer. It is what it is and there is nothing you or I can do about it.
The following is from the article I wrote about flanges. the complete article can be found on the "Training" page of this web site.
Bolt Hole Location:
The ASME B16.5 has a standard for bolt holes that in used by all (US) manufacturers for flange sizes up through 24" For instance; the number of bolt holes required varies with the size and rating of the flange. But the number and size is the same no mater the type of flange. The bolt holes are evenly spaced around the flange on a concentric bolt circle. There will always be an even number of bolt holes, in graduations of 4 (i.e., 4, 8, 12, 16, etc.).
Unless specifically noted otherwise by the piping designer (and then only if for good reason) all flange bolt holes shall straddle the "natural" centerlines. This is the flange bolt hole orientation rule. This "natural" centerline rule for flange is known, understood and followed by all responsible equipment manufacturers and pipe fabricators. The rule is:
• For a vertical flange face (the flange face in vertical and the line is horizontal) the bolt holes shall be oriented to straddle the vertical and horizontal centerlines.
• For a horizontal flange face (the flange face is horizontal and the line is vertical up or vertical down) the bolt holes shall be oriented to straddle the (plant) north/south centerlines.
Care must be taken to check all equipment vendor outlines to identify any flange orientations that do not match this rule. When an exception is found the vendor can be requested to change his bolt hole orientation. This is not always successful and if not then the piping designer must insure that the piping fabrication documents call for the correct orientation.
This rule of bolt holes straddling the natural centerlines is sometimes referred to as "Two-Hole" the flange. This means that the two of the holes straddle the centerline. To "One-Hole" a flange means that the flange has been rotated so that one hole is right on the natural centerline. I assure you that 99.999% of the time that to "One Hole" a flange is a mistake and will add cost to the field. It also makes the piping foreman very unhappy.
Please consider this much as you would gravity. You don't know why gravity works but you accept it.
Do it once and Do it Right
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- matthew0421
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16 years 7 months ago - 16 years 7 months ago #4173 by matthew0421
Replied by matthew0421 on topic Another flange question...when and/or why
Another flange question...when and/or why are class 250 flanges used? Class 125 flanges seem to be standard throughout the water and wastewater industry.
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- 11echo
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16 years 7 months ago - 16 years 7 months ago #4174 by 11echo
Replied by 11echo on topic matthew0421 ...Class 125# & 250#
matthew0421 ...Class 125# & 250# are all cast iron spec., cast iron is a major "pain" to deal with, but it does have some endearing qualities. It's easy to machine and it stands up to corrosion very well ...i.e. you see alot of it in the water handling sectors. The answer to you question is pretty simple actually (IF I under stand it correctly). As with 150# & 300# spec steel flanges, higher pressure/temp.s require "stronger" fittings, hence the 250# class.
Because cast iron is so easy to fabricate equipment from (as I listed above) you'll see alot of equipment with 125# & 250# suction and discharge connections (especially on pumps) in steel pipe spec systems. You probably already know that the mating dimensions of the flanges in both cast iron and steel are the same in both spec.s, so you can "bolt-up" the 150# steel flange to a 125# cast iron flange (same with 300# to 250#). BUT ...ALL cast iron flanges come with flat faces, and you should NOT bolt up a cast iron flat face to a steel raised face flange!!! What "MAY" happen is then the mechanics bolting it up can over tighten the stud bolts and break off an ear of the cast iron flange, major problem if it on a new piece of equipment! So you ALWAYS mate up a cast iron to steel with a flat faces on the steel flange! My $0.02 anyway, Good Luck! …Mark
Because cast iron is so easy to fabricate equipment from (as I listed above) you'll see alot of equipment with 125# & 250# suction and discharge connections (especially on pumps) in steel pipe spec systems. You probably already know that the mating dimensions of the flanges in both cast iron and steel are the same in both spec.s, so you can "bolt-up" the 150# steel flange to a 125# cast iron flange (same with 300# to 250#). BUT ...ALL cast iron flanges come with flat faces, and you should NOT bolt up a cast iron flat face to a steel raised face flange!!! What "MAY" happen is then the mechanics bolting it up can over tighten the stud bolts and break off an ear of the cast iron flange, major problem if it on a new piece of equipment! So you ALWAYS mate up a cast iron to steel with a flat faces on the steel flange! My $0.02 anyway, Good Luck! …Mark
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- matthew0421
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16 years 7 months ago - 16 years 7 months ago #4175 by matthew0421
Replied by matthew0421 on topic Thanks! It looks like Class
Thanks! It looks like Class 125 flanges are rated for a maximum working pressure of 250 psi per ASME/ANSI B16.1, but I cannot determine the max working pressure of a Class 250 flange. Any ideas?
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- 11echo
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16 years 7 months ago - 16 years 7 months ago #4176 by 11echo
Replied by 11echo on topic matthew0421 ...I'm looking at ASME
matthew0421 ...I'm looking at ASME B16.2 for Class 250# it states ..."Class 250 fittings are recommended for max. working saturated steam press. per sq. inch of 250Lb.s for sizes 1 to 12 inch., 200Lb.s for sizes 14 to24 inch., and 100Lb.s for sizes 30 to 48 inches. Sizes 12 & smaller maybe used for liquid & gas service over 300Lb.s max. at 150Deg. F " ...found this in my NAVCO piping datalog book. Hope it helps!?? ...Mark
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