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Mecha20 (Mechanical) (OP)
8 Jul 09 10:53
Does anyone have a copy of the bolting sequence for a 280 bolt fllange?
it's tiresome to manually work out this sequence.
jOHn10 (Mechanical)
8 Jul 09 13:24
Start at 1 then 2 (at 180deg from 1) then 3 90 deg from 2 then 4 (180 deg from 3)and so on. Scale up the procedure from the following link till you reach your max torque.

Mecha20 (Mechanical) (OP)
8 Jul 09 15:01
whilst your information is valuable, to come up with a sequence for 280 bolts is very tedious. one mistake, and the whole thing goes wrong.
racookpe1978 (Nuclear)
8 Jul 09 15:27
You need to clearly label EVERY bolt hole on the pressure vessel head, and have a check chart kept of every nut at each torque point:  Nope, there is NO shortcut.   

What is tedious from the specification standpoint?  The foreman of the millwright/mechanical crew tightening the bolts might get tired writing every bolt on the checkoff drawing, and each intermittent torque value - remember, as shown above in the procedure you must NOT fully tighten any bolt by itself.  Each bolt must be partially torqued in alternating sequence around the bolt circle:
12 Bolt Flanges and More

    * First round – 20% of final torque (flange sequential order)
    * Second round- 40% of final torque (flange sequential order)
    * Third round – 80% of final torque (flange sequential order)
    * Fourth round – 100% of final torque (sequential order)
    * One final time - clockwise or counter clockwise sequentially around the flange.  

So, you have 280 bolts times five rounds of torquing in sequence.  Tell the crew to get busy.  Give the foreman a calibrated torque wrench and the chart of all 280 bolts with the proper sequence of each bolt drawn on it and five blanks by each bolts.  

Tell the foreman to come back when the chart is filled in.   By the way, check him and the crew two or three times as he completes the chart.

Make sure he  
SnTMan (Mechanical)
8 Jul 09 15:28
Well, a lot of stuff we do is like that:)


Mecha20 (Mechanical) (OP)
8 Jul 09 15:37
280 bolts is not very common though...its the chart i'm searching for. i did the sequence once already manually, but doesn't line up. need to redo!!, unless someone has it their archives.  
rb1957 (Aerospace)
8 Jul 09 15:52
? the way i read the directions it looks like 1, 140, 70, 210, 2, 141, 71, 211, ... 69, 209, 139, 279 ... excel can produce a list of numbers like that.

does it matter if the flanges have stiffening webs (extending across the tighening flange) ? i'd've thought it did.
telecomguy (Mechanical)
8 Jul 09 15:57
Looking at the example for a 24 bolt pattern, wouldn't it be more like 1, 140, 70, 210, 35, 175, 105, 245, ...

TGS4 (Mechanical)
8 Jul 09 17:01
With a flange that big, couldn't you have multiple crews working on bolts 90° apart simultaneously?
LOUDOG (Mechanical)
8 Jul 09 18:57
Thats very true. If you could have 4 guys starting 90 degress apart and moving counter clockwise. That way you would only have to mark the starting points.
Mecha20 (Mechanical) (OP)
8 Jul 09 19:27
What are your thoughts about the following.

 I would imagine that this would be no different than a 4, 8 or 24 bolt sequence.  Number the bolts consecutively (clockwise) 1 through 280 starting with any bolt.  Then tighten in this order:  1, (1+n/2), (1+n/4), (1+3n/4) where n is the number of bolt holes.
Start at bolt number one, locate the bolt 180° from bolt #1.  (In your case it will be bolt number 141). Now go to bolt 71 and rotate to 211.  Now to bolt 2, 142, 72, 212.  3, 143, 73, 213. etc.
Cuemaster64 (Mechanical)
8 Jul 09 19:32
I came up with this pattern based on a 20 bolt sequence with 14 itterations spaced sequentially on a 16 bolt pattern(if that makes sense).  If I was to do this I would probably do it in this manner.  See if it makes logical sense.  The form is on worksheet 2 and my calculations are on the first sheet.


Mecha20 (Mechanical) (OP)
9 Jul 09 13:14
Your sequence looks good. would try and see if it lines up!...
Adalius (Mechanical)
9 Jul 09 15:54
The way I've usually seen it done, and a method thats taught in some apprenticeship programs, for the common bolt patterns that are divisible by 4, is as follows.

Take the number of bolts and divide by 4.
Consider this your 'max' number.
Start at the 12 o'clock position and number this bolt '1'.
Going clockwise, mark each bolt as the prior bolt's #, plus 4.
If the number you're about to write is greater than your max number, mark it '3', and continue the pattern by adding 4 to get the next bolt number.
The next time you reach your max number, mark that bolt '2', continue again, and then when you max out again, that bolt is '4'.

Then you just tighten in sequence, in as many passes as called for. It's basically the same idea as above, but you're numbering the bolts via tightening sequence rather than position, and it's simple enough you can remember how to do it in the field.
Continue marking bolts until you reach #1.

SnTMan (Mechanical)
9 Jul 09 16:49
Mecha20, this might help ease things for your field guys, ASME PCC-1, "Guidelines For Pressure Boundary Bolted Joint Flange Asembly" recommends tightening in groups of 4 or 5 bolts for flanges with large numbers of bolts, and I'd say yours qualifies. I have used this method on rectangular flanges with over a hundred bolts and it really speeds things up.

My apologies for not thinking of something useful for you in my earlier post:)



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