the temporary increase able to be achieved in the cavity 6 by closing the locking element 13 in the line 7 makes it possible to temporarily increase the thermal transfer coefficients of the components surrounding the cavity 6 after the desired pressure and temperature level is achieved the locking element 13 and thereby the line 7 can be fully opened again so that the pressure in the cavity 6 falls again for steady state operation of the steam turbine the two delimiting parts 1 2 have flange connections through which the attachment screws 14 are routed as an alternative or in addition to the preheating hole 12 there can be provision for the seal allowing thermal expansion 10 to have a specific leakage through which a defined quantity of hot steam can flow continuously into the cavity 6 the shielding of the joint 3 reduces the danger of a leakage at the joint 3 furthermore the result of lowering of the pressure is a reduction of the forces acting on the attachment screws 14 especially the axial forces if two delimiting parts 1 2 are provided these are connected to each other at a joint 3 three delimiting parts form a butt joint and four delimiting parts form a cross joint fig2 shows a further variant of the sealing of a joint 3 or of a cross joint between at least two delimiting parts 1 2 of a steam turbine the variant differs from the variant shown in fig1 in that the seal 10 allows thermal expansion.