The steam lock release (SLR) consists in a needle valve integrated in the steam trap body. Its aperture is tunned manually, with a screwdriver, to allow constant bleeding of steam, just enough to prevent steam locking. This option is not retrofittable!
In siphon drip tubes connected to rotating cylinders or long drain lines a steam pocket may form and so the condensate does not reach the trap. This condition is normally known as steam locking and when float and thermostatic steam traps are used it is necessary to prevent the problem. The SLR - Steam Lock Release should be requested to bleed away that steam.