LCC Quick Notes, Governor Valve Steam Chest Lift Bar Alignment

    Some new instrumentation technology helps solve an old problem of leveling steam chest governor valve lift bars.  For a very modest tool investment both good results and repeatable settings can be achieved.

    A row of sequential lift poppet valves which are raised off their seats by a common lift bar by two lift rods (Fig. 1) is a common governor valve steam chest design which has been used by many manufacturers.  By setting increasing lift clearances between the valve stem nuts and the lift bar a relatively linear progression of steam admission is theoretically possible.  One assumption, that the lift bar is level, has traditionally been difficult to confirm short of proof in operation with nozzle port pressure measurements.  If the lift bar is not level the steam admission rate with stroke will be accelerated at valve lift points and proper control can be compromised.

   This Quick Note illustrates an easy way to adjust and confirm a level bar using a digital protractor with an RS232 output cable to a laptop for remote display.


                Figure 1, Fulcrum-Lift rack Side View (of course with an electric actuator... this is on the LCC site!)




With the steam chest cover off, install a digital protractor with RS-232 output on the lift bar at center, then run the cable out the cover flange.  Place a set of at least four level blocks of 0.500-inch thickness (or precision bolt spacers) on the flange at each side so as to allow the digital protractor cable egress to a laptop.  Now set the cover and secure the flange bolts, maintaining the cover alignment, albeit slightly raised.  The lift rod/s may now be adjusted for a perfectly level lift bar as read on the digital protractor program readout on the laptop.







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