Bolting Requirements in Code
Bolting Requirements in Code
(OP)
For years I have been doing Pressure Vessel Inspections and have gone by what was taught when i learned. I was taught to assure that all bolted joints had at least three exposed threads beyond the nut. Where does this come from. I have been looking but not found it yet. Is there a place in any code applicable to API that requires this? If so what and where. I am writing a proceedure and want to put it down by chapter and verse.
Thanks in advance for any help
Thanks in advance for any help





RE: Bolting Requirements in Code
RE: Bolting Requirements in Code
"108.5.1 General
(A) Bolts, bolt studs, nuts, and washers shall comply with applicable standards and specifications listed in Table 126.1 and Table 112. Bolts and bolt studs shall extend completely through the nuts."
The 2004 ASME B31.3 states:
"335.2.3 Bolt Length. Bolts should extend completely through their nuts. Any which fail to do so are considered acceptably engaged if the lack of complete engagement is not more than one thread."
Every decent pipefitters book I've ever seen shows the number, diameter and length of studs required for any given class of flange, and these studs are commercially available in these lengths. The published standard lengths also leave enough "extra" length to allow for blanks to be installed. Why would anybody use shorter? They sell these by the pound - the money saved by having them a little short is the square root of nothing.
RE: Bolting Requirements in Code
RE: Bolting Requirements in Code
Corrosion of excess threads can hinder joint
disassembly. A practice that facilitates joint disassembly
(see para. 15) is to fully engage the nut on one
end (no bolt projection beyond the nut) so that all
excess threads are located on the opposite end; the
excess threads should not project more than 13 mm
(½ in.) beyond the nut, unless required for the use
of hydraulic bolt tensioners [see para. lO.l(c)]
RE: Bolting Requirements in Code
RE: Bolting Requirements in Code
Excessive extension beyond the nut can be a corrosion issue as mentioned earlier and can also be a safety issue.
I certainly hope no one is out there counting exposed threads. Gee, if they are are they counting from the vanishing point of the threads, from the nut face, from the bottom of the chamfer in the nut...?
Paul Ostand
www.ostand.com
RE: Bolting Requirements in Code
RE: Bolting Requirements in Code
Who is cutting the threads off?
Paul Ostand
www.ostand.com
RE: Bolting Requirements in Code
RE: Bolting Requirements in Code
Paul Ostand
www.ostand.com
RE: Bolting Requirements in Code
The nominal length unless modified by the order is from tables using ANSI flange dimensions with a 1/8" gasket. The most common modification for the length is if the stud is to be installed with washers, either one or two.
The standard cut length is nominally ±1/16" but with automatic saws it will be around ±1/32".
About 25% of the orders will call out a non-standard length with can vary up to 3/4" from the nominal length.
I've seen several orders that narrow the limits to ±0.010" on length and a very specific call out on chamfer. This particular customer also uses ground washers and torques every fastener on site.
In the fastener industry there are a lot of nuts.
RE: Bolting Requirements in Code
When I see studs that looking a "little short", it's a situation like the crew didn't have the 4-1/2" long studs they needed for the 4" Cl 300, but they had some 4-1/4" (for 3" Cl 300) in the shop or truck - "We'll use them up." Or somebody just grabbed the wrong ones on the way out the door - it's pretty easy to do.
The supplyhouse we normally use will routinely ship us flanges "dressed" - whatever gasket we call for, B7 studs & 2H nuts - when we ask for it. We don't have to tell them the number, diamteter or length of studs. They don't cut them either - the various standard diameter & length combo's are on the shelf.
There are always exceptions to any given rule, but under normal conditions, why would anybody spend the time to spec studs shorter (or longer) than an industry standard length? And using standard lengths eliminates the "how many threads past the nut" discussions like this. You'll be left with 2 or 3 threads showing, so it'll meet B31.1 or B31.3 and the inspector can see that from a distance.