Diaphragm Seals in Impulse Steam Turbines

In impulse steam turbines, a significant pressure differential exists across the diaphragm; coupled with the unavoidable clearance between the diaphragm and the main shaft, a portion of the steam inevitably leaks through these gaps-flowing from the upstream side of the diaphragm into the chamber situated between the diaphragm and the rotor wheel. This portion of the steam, having bypassed the nozzles, not only fails to perform work itself but also disrupts the flow of the main steam stream, thereby resulting in diaphragm leakage losses.

To minimize such losses, designers maintain the clearance of the diaphragm seals within 0.6 mm and incorporate multiple sealing strips. These diaphragm sealing rings are meticulously installed within circumferential grooves located within the diaphragm body, thereby ensuring that the steam flows efficiently through the nozzles to undergo energy conversion.