Bolt hole orientation 3

[ssreekylm]

HIII Guys,

All Flange Bolt Holes Straddle the Center lines that is for a vertical flange face (the flange face in the vertical and the line is horizontal) the bolt holes want to be orientated to straddle the vertical and horizontal center lines and also for the horizontal one the bolt holes want to be orientated to straddle the Plant North center lines.

What is requirement of straddle the holes from center line?

If we found one tank man way with bolt hole is on exact center line,what action will take?

 

[LittleInch]

Bolt holes straddling the centerline is not a mandatory action, but to be able to standardize, all fitting (Ref ASME B 16.5) are made with bolt holes straddling the centre line. Hence all valves, flanged components and other items which arrive with flanges already welded or forged will be vertical / horizontal when connected to pipework.

For items such as manways, there is only the mating flanged plate, therefore in practice it might just look a bit strange, but otherwise is technically acceptable.

See what the specification or data sheet said and if it says staddle the centerline then ask them to cut it off and rotate.

Depends on whether you can handle the schedule delay and possible claim from the vendor.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pennpiper]

LittleInch is correct with all he writes. However, there could be a problem if you have Davited manholes depending how the Davit mechanism is attached to each of the two flanges (Nozzle Flange and the Cover Flange). You should discuss this specific issue with someone from the Client's Maintenance Department.

Sometimes its possible to do all the right things and still get bad results

 

[rconner]

While perhaps of some less relevance for a manway, there is likely a good bit of history behind at least the straddle vertical centerline convention. In the Renaissance or “Age of Enlightenment”, applications of pumping technology as well as exposed pressure pipeline design and installation were expanded. In the period from 1650-1664 I understand a significant pipeline system consisting of 35 km of flanged cast iron piping was designed and installed for the “Sun King” Louis the 14th of France, working with the famous scientist Edme Mariotte and others to carry water to the gardens and fountains of the Chateau de Versailles (Antaki 2003 and Baridon 2012) .
As exhibited in the attached photograph of an exposed portion of the Versailles pipeline, presumably designed by Mariotte more than 350 years ago (and that I understand is mostly still in service after three and a half centuries), it appears that the original installation was with the flanged/bolted joints installed with the bolt holes/locations “straddle the vertical centerline” (or “two-holed”). While I guess I shouldn't attempt now to explain Mariotte's thinking, I do believe maintaining such convention in design, manufacture and installation of at least bolted flanged piping probably facilitates constructability (e.g. with spirit levels etc. laid across bolt holes), provides a frame of reference for adjoining fitting and other specials directions (when drilling is purposefully rotated etc.) and orientations, makes the bolts easier to reach from the sides of the pipeline (or manway?)with wrenches working below and above the line, and also makes for a uniform and altogether not unpleasant appearance as pictured.