Lantern Ring:

It is not always probable to use a standard stuffing box to seal the shaft of a centrifugal pump. Pump suction might be under a vacuum so which outward leakage is impossible or the fluid might be too hot to gives adequate cooling of the packing. Those conditions need a change to the standard stuffing box.

One techniques of adequately cooling the packing below these conditions is to involve a lantern ring. The lantern ring is a perforated hollow ring situated near the middle of the packing box which receives associatively cool, clean liquid from either the discharge of the pump or from an external source and distributes the liquid uniformly around the shaft to gives cooling and lubrication. The fluid entering the lantern ring could cool the lubricate the packing, shaft and packing, or seal the joint among the shaft and packing against leakage of air into the pump in the event the pump suction pressure is less than in which of the atmosphere.