Abstract: In an arrangement for feeding a fluid at a given temperature into a vessel containing fluid at a different temperature from an inlet pipe through an inlet nozzle to feedfluid distribution means in the vessel, a removable thermal isolator arrangement is provided. Spaced concentric sleeves form a series of fluid spaces which thermally insulate the inner surface of the nozzle from the feedfluid and leakage feedfluid is directed away from the nozzle whereby thermal cycling of the inner surface of the nozzle is minimized to eliminate cracking thereof.