6.4　Steam Valve and Its Driving Device

6.4.1　Installation of the steam admission section of automatic MSV，single-seated governor valve and CRV shall comply with the following provisions:

1　Alloy steel parts shall be inspected according to provisions in 3.1.8 of this part.

2　The pore size of steam strainer shall be correct，for a strainer with unequal pore sizes，the part with small pores or no pore shall be aligned to the steam admission direction of steam chamber.

Between the strainer and steam chamber there shall be an expansion gap and the device to prevent the strainer from rotating，and the expansion gap should be:

Radial clearance at peripheral points　1.0mm-1.5mm

End axial clearance　1.5mm-3.0mm

3　The steam chamber drain holes shall be well through.

4　The tooth shaped steel gasket of bonnet and valve housing joint surface shall be in a sound condition，without through groove；for joint surfaces without packing，continuous contact trace shall be shown in a coloring check.

5　Steam chamber fastening bolts shall comply with the provision in 4.4.3 of this part.

6　The device to prevent disengagement of valve seat shall be in a sound condition.

7　The valve disc and valve seat shall be smooth and free of trace of damage，and the valve disc and valve seat shall be tight when checked with coloring method，as shown in Fig.6.4.1-1.

8　The threads of valve disc and valve disc sleeve shall be tight，and the spot welding on all sides of the contact plane shall be secure.

9　The valve stem shall not bent，the clearance and travel of valve stem and valve stem sleeve or shroud seal ring shall all comply with requirements on drawings，the clearance of valve stem and valve stem sleeve diameter should be 0.30mm-0.40mm，the total clearance of shroud seal ring in rod length direction should be 2mm-3mm，steam vent hole on the steam guide ring and that on valve stem sleeve shall be aligned.

10　The clearance between valve body and guiding sleeve shall comply with requirements on drawings.

11　Deflection shall be prevented when the bolts of MSV and governor valve steam chamber cover and bolts of self-sealing structure small bonnet are tightened，as shown in Fig.6.4.1-2.

12　Bolts of high temperature high pressure steam valve steam chamber shall be hot tightened as per manufacturer requirements.

13　The governor valves shall be installed according to the sequence shown on drawings.

14　The spherical joint surfaces of governor valve clamping ring and frame and the plane joint surfaces with bush shall all be in good contact，and the clearance c between top clamping ring and press washer should be 0.04mm-0.06mm，as shown in Fig.6.4.1-3.

15　After disassembling of valve，valve stem shall be protected against deformation，bending and damage.

6.4.2　Installation of actuator and manipulating base shall comply with the following provisions:

1　Damage must be prevented to any part on piston rod and actuator during installation，the plugs at pipe connections shall not be removed，to prevent intrusion of dust.

2　Special tools such as spring loading bolts shall be used in removing and fitting springs.

3　For the manipulating base with cooling water chamber，the cooling water chamber shall be free of defect such as crack and sand hole，threaded connectors of water inlet and outlet pipes shall be in a sound condition without damage.When necessary，hydrostatic test shall be conducted at 1.25 times the working pressure for the water chamber，and it shall be free of leakage when the pressure is maintained for 5min.

4　In installing the actuator，it shall be ensured that there is a buffer zone between the actuator piston and cylinder bottom when the valve is fully closed.

5　In installing the actuators，the distance from actuator mounting surface to piston rod end shall be measured，and the thickness of shims shall be adjusted，to ensured that there is a buffer zone between the actuator piston and cylinder bottom when the valve is fully closed.

6　After completion of installation of manipulating base and servomotor and valve，the corresponding displacement sensors shall be installed，adjust travel switch，to ensure that all moving parts can operate flexibly and free of jamming.

7　Adjust travel position of the scale dial to ensure correct indication.

8　When the displacement sensor is mounted，the core and sleeve shall be concentric.

6.4.3　Installation of lifting type governor valve shall also comply with the following provisions in addition to the relevant provisions in 6.1.4 and 6.4.1:

1　The lift of each valve disc and the travel of sliding block on lifting rod shall all comply with specification and be recorded；the travel of sliding block on lifting rod shall be such as to ensure that the last valve disc can be fully open.

2　When all governor valve are closed，the clearance between the sliding block on lifting rod and steam chamber cover shall comply with manufacturer requirements，and when there is no requirement from manufacturer，it should be 1mm-2mm，and there shall be surplus travel for the servomotor piston.

3　When the lifting plate is mounted on the steam chamber，the direction of the plate and position sequence of governor valve shall be correct.

6.4.4　Installation of MSV and CRV shall comply with the following provisions:

1　The elevation and centerline position of steam valve shall comply with the requirements on design drawings，the deviation must not exceed 10mm.

2　The steam valve seat and frame shall be in tight contact and firmly connected，and locating pins shall be fitted.

3　When the steam valve is to be moved for cold drawing steam lead pipe，it shall be done according to design value after completion of steam lead pipe installation and weld seam heat treatment，and during cold drawing，the steam valve shall be moved straightly.

4　The fixing method and expansion direction of the HP steam valve mounted on the base shall comply with manufacturer requirements.

6.4.5　Installation of cam driving device shall comply with the following provisions:

1　The location，profile and arrangement sequence of cams shall be correct.

2　In cold state and expansion with shaft heated up，cam shaft and bearing shall have some axial clearance.

3　During centering of cam shafts，the circumference and end deviation shall not exceed 0.10mm，and they shall rotate flexibly.

4　The joint surface and slide groove between casing and cam shaft support shall be flat，allowing free expansion，the locating pin at the dead point shall be secure and reliable；slide groove clearance should be 0.04mm-0.08mm，link bolt washer clearance should be 0.04mm-0.06mm，and there shall be sufficient clearance between link bolt and bolt hole on expansion side.

5　The clearance between governor valve lever roller and cam base circle shall be adjusted in cold state according to manufacturer requirements.After full load operation of turbine，in the hot state with governor valve closed，a clearance of 0.05mm-0.20mm shall still be maintained between cam base circle and roller.

6.4.6　Installation of connecting rod and lever driving device of governor valve shall comply with the following provisions:

1　The opening sequence of valves shall be correct；with the servomotor piston at zero position and both pre-inlet valve and MSV closed，the clearance of all connecting rod pin shafts shall comply with manufacturer requirements.

2　The spherical joint of valve stem and spring support shall keep a moving clearance of 0.10mm and rotate flexibly.

3　When dual springs are assembled，the ends of springs in the inner and outer ring shall be staggered by 180°，to reduce unbalance force.

6.4.7　In mounting the rotary diaphragm rotating device，packing shall be filled into the packing chamber at the end of splined driving shaft；the lower part of the packing chamber shall have a drain hole and be well through.Before turbine covering，the connection of rotary diaphragm and servomotor shall be done according to provisions in 4.7.5 of this part.