This is actually a flange breaking tip. With all the decommissioning going on world-wide there is a good chance that you will find yourself with a couple of flogging spanners and a man-sized hammer removing a spoolpiece from a riser.
     The bitch about undoing a flange is that the flange faces bear on the nuts as you loosen them, causing friction all the way back to the point where the flange is no longer under tension. This means that you are hammering every bolt all the way back, and you are going to get fatigued. You will start to get pissed off with the flange, and you will swear at it between gasps of gas. Your arms will start to feel like rubber, and that hammer that made you look so cool and tough on deck will start to weigh a ton as you feebly tap the fifteenth bolt around.
     To avoid all this drama, and make yourself look pretty good in the process, use the magic flangebolt trick. What you do is first loosen and remove only the 12 o-clock bolt. You then fit that bolt above its' hole with the nuts tight up against the outside edges of the flange. Once you start to loosen the other bolts, the tension is taken up by the "magic" bolt, allowing you to free the other bolts quite easily, without the dreaded friction. Start at the bottom and work your way up, just in case the magic bolt should happen to spring off prematurely. 
     Once you have loosened and removed all the bolts (and stored them neatly in a workbasket of course) you are left with a flange held together with one bolt at the top. Get off to one side, and at the full reach of your sledgehammer tap the bolt upwards. Make sure your hat camera is focused on the proceedings so that all the topside pukes can gaze in wonderment as the flange springs magically apart.
    If the guy before you cleaned the marine growth off the bolts properly you should barely be breathing hard at this point. You will have to wait a bit until the blind flange for the riser is rigged, because the deck crew didn't expect you to be finished so quickly. Use this time wisely by hunting for lobsters.
     If someone else should happen to be going in to break a flange before you, tell him the trick, otherwise you will arrive to find a half open flange waiting to be sweated over. You will lose some glory this way, but at least you won't have to lose your cool.

Happy hammering! 
Cal