In steam turbine we sealing steam with two PSV one for sealing HP and LP side and other PCV is supply direct to surface condenser what’s is the purpose of second PCV ?
On condensing steam turbines, it is common to use the leakage from the high pressure packing to supply the sealing steam to the low pressure packing. If the leakage is not sufficient to maintain about 3 psi, a regulator will introduce low pressure steam. If the leakage from the high pressure packing is too much, another pressure control valve will open to bleed the excess off to the surface condenser. This valve will open to limit the pressure to less than about 6 psi.