It's a Local Rule, so check the card. Here's the recommended one:
Immovable Obstructions Close To Putting Green
Rule 24-2 provides relief, without penalty, from interference by an immovable obstruction, but it also provides that, except on the putting green, intervention on the line of play is not, of itself, interference under this Rule.
However, on some courses, the aprons of the putting greens are so closely mown that players may wish to putt from just off the green. In such conditions, immovable obstructions on the apron may interfere with the proper playing of the game and the introduction of the following Local Rule providing additional relief, without penalty, from intervention by an immovable obstruction would be warranted:
â€œRelief from interference by an immovable obstruction may be taken under Rule 24-2.
In addition, if a ball lies through the green and an immovable obstruction on or within two club-lengths of the putting green and within two club-lengths of the ball intervenes on the line of play between the ball and the hole, the player may take relief as follows:
The ball must be lifted and dropped at the nearest point to where the ball lay that (a) is not nearer the hole, (b) avoids intervention and (c) is not in a hazard or on a putting green.
If the playerâ€™s ball lies on the putting green and an immovable obstruction within two club-lengths of the putting green intervenes on his line of putt, the player may take relief as follows:
The ball must be lifted and placed at the nearest point to where the ball lay that (a) is not nearer the hole, (b) avoids intervention and (c) is not in a hazard.
The ball may be cleaned when lifted.
Exception: A player may not take relief under this Local Rule if interference by anything other than the immovable obstruction makes the stroke clearly impracticable.
PENALTY FOR BREACH OF LOCAL RULE:
Match play â€“ Loss of hole; Stroke play â€“ Two strokes.â€
Note: The Committee may restrict this Local Rule to specific holes, to balls lying only in closely mown areas, to specific obstructions, or, in the case of obstructions that are not on the putting green, to obstructions in closely mown areas if so desired. â€œClosely mown areaâ€ means any area of the course, including paths through the rough, cut to fairway height or less.
Doh! Indeed, that sort of relief is in 24-2 that the Local Rule refers to.
I daftly assumed it was for the non-standard (so LR required) interference with line.
There's nothing 'special' about relief for sprinkler heads - just the same as imbedded benches etc anywhere else on the course. They are just a bit more common and 'at ground level'. That's also why no LR is required for relief from sprinkler heads that are in the rough - even though some clubs actually quote the rule as an LR on the card.