PURPOSE: To prevent leakage of Si-oil during storage before the practical use by filling the inside of a pipe which has multiple hole son the outer circumferential surface and of which surface is covered with heat resisting paper and heat resisting felt, with Si-oil in a state of foaming.

CONSTITUTION: On the outer circumferential surface 33 of a pipe 30, multiple holes 34 of 1mm approx. in diameter are formed and in addition heat resisting paper 35 such as Nomex paper and heat resisting felt 36 such as Nomex felt are wound from the inside in order. An inside space 37 of the pipe 30 is filled with Si-oil in a state of foaming. That is to inject the Si-oil before shutting the pipe 30 with flanges 31, and at that time the Si-oil is kneaded under the condition of air supply to make the Si-oil a state of foaming. With such method that filling the Si-oil in the state of foaming, leakage of Si-oil during storage before the practical use is prevented.