If you're behind a greenside bunker pitching isn't always essential. In actual fact chipping over bunkers can be a more effective alternative. I myself have chipped over bunkers, but you can't be too far away from the green.
To chip over a bunker you should be very close to the greenside bunker. The closer you are the closer you'll be to green, and thus the ball will more likely make it over the bunker and land on the green. If you're more than 10 yards behind the bunker then it's best not to chip over.
In addition to this, the greenside bunker itself has to be a small one. A small greenside bunker should leave only a few yards for your chip to clear, preferably between five or ten yards. The bunker should also be a shallow one.
You'll also need to select a suitable club for the chip. The wedges are the most suitable clubs for the the bunker chip, because they have the most loft to provide the carry over the bunker. The sand and loft wedge could be the most suitable if you require minimal roll on the green. If more roll is needed a pitching wedge could be more effective. But the most essential thing is that the ball makes the green.
The advantage of greenside chips are that they can be more accurate. But then of course, if they don't make it over the bunker the sand wedge will be required. Check out the YouTube video for further details.