The preparation work of extraction steam check valve before maintenance includes the following contents:
After the equipment is out of service, the protection, power supply and air source are cut off, loosen the air inlet and air outlet connector of the air control control seat, remove the pin connecting the piston rod of the control seat with the check valve lever, loosen the fixing bolt of the control seat, remove the control seat and place it in a fixed quantity. Then, do the following.
1、 Valve disintegrates
(1)First, mark the fitting of the cover and valve body with marker pen, then loosen the cover bolt and remove the cover.
(2)Remove the bearing, oil retaining ring and lever on the connecting side of lever shaft and air control control seat and place them in a fixed position.
(3)Loosen the big cover nut and remove the big pressure ring.
(4)After making the matching mark, loosen the fixing bolt of the big bracket, remove the big bracket and place it in place.
(5)Remove lever shaft and bushing, place in place.
(6)Remove the small bracket and accessories on the side of the rocker arm shaft and place them in place.
(7)Loosen the nut on the small pressure ring, remove the small pressure ring and place it in a fixed quantity.
(8)After making the matching mark, loosen the fixing bolt on the flange cover, remove the flange cover and place it.
(9)Remove rocker arm and valve spool and place them in place.
(10)Take out the rocker arm and valve spool and place them in a fixed position.
2、Clean and inspect valve
(1)Check the valve spool and valve line on the valve body, the valve line should not affect the sealing performance of the groove, hole and cross the sealing surface trace, should contact all week without interruption. If the defects that affect the sealing performance are found, they should be ground.
(2)Check the connection between valve butterfly and rocker arm, adjust the gap between shim and rocker arm between 1 ~ 1.2mm, should not be too big or too small, otherwise should be adjusted. The fastening nut of valve butterfly and rocker arm should be connected firmly, the welding spot of positioning should be complete without cracks, the clearance between valve butterfly shaft and rocker arm ring should meet the requirements.
(3)Check the gap between lever shaft, rocker arm shaft and size bushing and seeding arm. The surface of each shaft and the inner surface of the bushing should be smooth and clean without pits.
(4)Check the packing in the big sealing cover and flange cover, should be complete, if any damage should be replaced.
(5)Check the valve cover and sealing surface of the valve body should be complete, without affecting the sealing effect of grooves, sand holes and through scratches.
(6)Clean and inspect the sealing surface of the joint of bracket, flange cover and valve shell. Clean and remove the old gasket sticking to the sealing surface. The sealing surface shall have no defects that affect the sealing effect.
(7)All keys and keyways shall be cleaned and well connected.
3、Valve reinstallation
Before the valve is reinstalled, the surface of each shaft and bushing should be rubbed hard with molybdenum disulfide powder until shiny. The assembly and reconstruction should be carried out according to the reverse sequence of disassembly according to the assembly mark. During the assembly and reconstruction, the following points should be noted:
(1)After connecting the valve butterfly with the rocker arm, the thickness of the adjusting gasket can be adjusted to ensure that the Angle of the valve butterfly switch reaches the Angle required by the manufacturer. After that, the locking nut should be spot welded firmly with the valve butterfly.
(2)When the lever shaft, rocker arm shaft and rocker arm are assembled, the gap between the lever shaft and the rocker arm end, the adjustment shim of rocker arm shaft and the rocker arm end shall be 1 ~ 1.20mm.
(3)In the rocker arm shaft, the lever shaft and the valve shell outside the bracket and flange cover installation, pay attention to keep the two shafts concentric, in order to prevent the valve butterfly switch not loose or stuck.
(4)In both ends of the packing compaction process, should ensure that the shaft (lever shaft, rocker shaft) action is flexible, not stuck.
(5)All gaskets should be renewed.
4、Control seat disassembly
(1)After the assembly marks are made between the upper cover of the control seat and the cylinder body, and between the cylinder body and the base, remove the short bolts in the fastening double-head bolts of the upper cylinder and the base and place them in a fixed position.
(2)Loosen both until the bolt in place.
(3)Separate the upper cover of the control seat, the cylinder block and the base, take out the piston, door rod and spring, and place them in a fixed position.
(4)Remove the split pin and hexagon socket nut to separate the piston rod from the piston and place them in place.
(5)Check and clean the control seat.
1)Check the inner wall of piston cylinder should be smooth.
2)Check the cylindrical compression spring and record the length of the spring in the free state for comparison with the previous (last) overhaul.
3)Check piston rod and piston surface should be smooth.
4)Check the sealing surface of upper cover, cylinder block and base connection should be intact, and clean.
(6)Mounting of control seat. The reinstallation of the control seat is carried out according to the reverse step of disintegration, and the following points should be noted:
1)Each sealing o-ring are replaced with new, replace the temperature resistant rubber, sealing ring;
2)The inner wall of the cylinder and the surface of the piston should be coated with silicone grease to ensure lubrication;
3)After the air control control seat is installed again, the empty stroke of piston rod should be checked with compressed air, which should meet the requirements of the manufacturer.
(7) Global check. Fix the control seat on the valve body and connect it with the lever of the valve to connect the compressed air joint for overall check. Requirements:
1)After assembly with the extraction check valve, the travel of the pass compressed air switch shall conform to the travel specified by the manufacturer.
2)In the process of switching, the whole action should be continuous activation, no jam phenomenon.
3)Valve opening indication should be checked correctly, action switch together with thermal control check. The open and close display is in accordance with the actual position indication of the valve.