A mid-turbine frame for a gas turbine engine may comprise a bearing system including a bearing housing. A first tube may define a first fluid passage configured to carry a first fluid to the bearing system. An outer sleeve may be disposed around the first tube and may define a chamber between the first tube and the outer sleeve. A first fitting may be coupled to the first tube and to the outer sleeve. The first fitting may comprise an inner portion having an inner surface further defining the first fluid passage. An outer portion may be disposed around the inner portion and may further define the chamber therebetween. The chamber may be configured to contain a fluid. An outer surface may have a first mating surface comprising a frustoconical shape. A flange may extend radially outward from the outer surface.