2015

Assembly and Disassembly procedure for Screw type Fuel Gas Compressor

Prepared by

Md. Shaha Jalal Mechanical Maintenance Technician

450 MW Combined Cycle Power Plant

OVERALL CONSTRUCTION

The screw compressor is a sort of rotary positive displacement compressor, and a machine in which

successive volumes of gas are confined within a closed space form by two rotors and casing, and

elevated to a higher pressure as the volume of the closed space is decreased by rotation of rotors.

The mechanism of the screw compressor consist of two screwed teeth rotors which are

i8ntermeshed in parallel within the casing.

The rotor which has five lobes is called “male rotor” and the other which has six lobes is called

“female rotor”.

The tow rotors are supported y bearings at each ends so that they can rotate with keeping a

constant small casing. These bearings are type of sleeve and are required durability against the radial

or thrust load forced by the compressed gas to the rotors.

ROTOR

In its construction the screw compressor closely resembles the well-known rotary lobe blower. It

differs, however, in its peculiar rotor profile and its very large helix angle (the wrap angle of a mail

rotor is 300 degrees in most cases).

The rotor profile is the unsymmetrical type as shown in Fig-1.2 having both convex and concave

faces.

MECHANISM of COMPRESSION

Gas is drawn through the suction port into grooves of rotors.

As rotation continues, the groove spaces are cut off from the suction port and gradually reduce the

starting compression of entrapped gas.

Compressed gas flows smoothly out of the compressor.

Remember

1. Check all spare parts required are available. 2. Proper hoisting and transport are available and ready for use. 3. Sufficient room space and appropriate tools are available. 4. Select skill manpower those who are obey safety for him and equipment. 5. It is important that all personnel observe safety precautions to minimize chances of injuries.

The following should particularly be noted. 6. Maintenance and repair shall be performed by authorized, trained personnel only. 7. Take care and follow appropriate procedures in handling, lifting, installing, operating and

maintaining the equipment. 8. Lifting tools such as eye bolts are designed to lift individual parts only. 9. Specially instructed, never lift the assembled parts with the tools.

Use spark free tools in

compressor shad.

DISASSEMBLY PROCEDURE FOR FGC

Take the permit from control room. Check the proper isolation. (all electrical components, gas and oil line) Purging by N2 (check O2 label by O2 meter) Connection the hose pipe with drain line. Take out all oil from compressor. (use Empty drum and keep it proper area) Remove all noise hoods. Take out all pipe line from compressor. Remove the coupling and keep it proper place ( please don’t missing coupling bolt, nut and

washer) Loosen the all base bolt Take out the compressor and shift to the workshop (before shift the compressor please

keeps it on the stand and blind compressor discharge line)

Pay attention: - Please care with handle.

Oil Draining from hydraulic cylinder

Remove the four drain plug under the hydraulic cylinder (K 82) and the plug of Vi end cover (B18) to drain oil from inside.

Then remove the end cover (B18) by removing the hex bolts. If compressor has a fixe Vi block, remove the Vi block from slide stop (D01).

Indicator

Proceed with disassembly of the indicator only after all wiring is disconnected from the compressor.

Loosen the hex bolts and remove the indicator cover (F05) Loosen the bolts (J12) and grub screws in the potentiometer coupling (F02), then remove

the potentiometer (F10). Remove the potentiometer terminal block (F1x1) by loosening the hex bolts.

Cylinder Head

Remove the bolts connecting cylinder head (D32) and cylinder (D31). Use of jack screw bolts to separate the cover from the cylinder. The indicator spindle ((D34), pin (D10) and ball bearing (D31) can be removed with the

cylinder.

Hydraulic Cylinder

Remove the lock nut (D09) after bending back the claw of bearing lock washer by using licking spanner.

Use 8mm eye bolts to remove the slide to remove the slide valve piston (D05) then remove the pin (D10) from slide valve rod (D03)

Suspend the cylinder by nylon ropes. Remove the bolts connecting the cylinder (D31) and the cylinder fixture (B06). Apply jack screw to cylinder to separate it from the cylinder fixture. Slide the cylinder horizontally away from the compressor.

Caution: care should be taken not to damage the slide valve rod (D03)

Remove “C” retaining ring (L11) in the removed hydraulic cylinder by using snap-ring pliers. Remove the stopper plate (D33) which separate slide valve cylinder and slide stop cylinder. Loosen the hex bolts that connect the cylinder fixture (B06). Inlet casing (B01), remove the

cylinder fixture (B06). Loosen the lock nut (K32) with a locking spanner. Remove the slide stop piston (D04) with eye bolts from the slide stop (D01). Pull out the piston stopper (D06) with eye bolts.

Caution: pay attention not to damage slide valve rod.

Blind plate and Balance piston

Use eye bolts to remove the male blind plate (B04) and female blind plate (B05). Use eye bolts to remove the piston ring spacer sleeve (B08). Remove “C” retaining ring (L01) that holds the balance piston in place Remove “C” retaining ring pull out the balance piston with eye bolts.

Caution: care must be taken not to damage spring pin inside of the male blind plate.

Inlet Suction Casing

Suction casing

Raise the compressor and place shims under the rotor casing feet so that the inlet casing (B01) is slightly raised off the timber support.

Attach wires to the inlet casing (B01). Use a slide hammer (M8) to remove the dowel pins (K51) located on both sides of the

compressor. Loosen the hex bolts connecting inlet casing (B01) and rotor casing (B02) Apply jack bolts to the inlet casing to separate it from the rotor casing. Slide the inlet casing horizontally away from the compressor. Set the inlet casing on the work bench external surface up. Remove the retaining rings (L12) from both the male and female sides. Turn the inlet casing over so that the external surface is facing sown. Hammer out the roller bearings (C01, C02) and nozzle plates (B10, B12) at the same time.

Caution: Do not damage slide valve rod during removal of the inlet casing.

Slide stop and Slide valve

Slide Valve

Remove the slide stop (D01) from the slide valve rod. Next remove the slide valve rod (D02) from the rotor casing.

Caution: Care should be taken so as not to damage the slide valve rod (D03).

Mechanical shaft seal

Loosen the socket head bolts (J11) connecting gland plate (E02) and bearing grand (Co7). Separate gland plate from bearing grand with eye bolts or jack bolts. Remove the mechanical seal box (E01) by placing eye bolts into the threaded holes and

pulling the seal box slowly from the compressor discharge casing (B03) Slowly pull the mechanical seal assembly (E03) from the shaft.

Caution: Pay attention not to damage the shaft during removal. The gland plate (E02) contains the

mechanical seal seat (mating ring) which must be replaced along with the mechanical seal. The

bearing gland is an assembly made up of the bearing gland (C07), lock nut (C09), and lock washer

(C13) remove bearing grand assembly from discharge casing (B03).

Note:-

1. The bearing lock nut (C09) should only be removed from the bearing gland (C07) if the compressor bearings are being replaced. Do not attempt to remove the bearing lock nut during a routine mechanical shaft seal replacement.

2. If proceeding with compressor rebuild, remove the bolt (J12) located on the bearing gland (C07). This will release the lock washer (C13) from the lock nut (C09). Now use the locking tool to remove the lock nut (C09) from, bearing gland C07).

3. Before removing the mechanical shaft seal box (E01) by placing measure the depth that the seal box is recessed from the edge of the compressor. This measurement will be used during assembly.

4. Mechanical seal box contains a lip seal that must be protected from damage if it is not being replaced. Also the male rotor shaft should be wrapped to protect it from any damage.

Discharge Bearing Removal preparation.

a. Male Side Apply “CRC” or other penetrative to the lock nut before removal. Straighten the claw of bearing lock washer (L22) with extended bar. Use locking spanner and spacer guide for spanner, to the lock nut (K31). Strike the cocking spanner with a hammer to loosen the lock nut. When the lock nut bearing to turn, hold the male rotor shaft with a spanner wrench

and continue to loosen the lock nut by hand. Finally remove the lock nut (K31).

b. Female Side Loosen the bolts (J04) and remove the thrust bearing cover (B07), blind plate (C10)

and shims (B25). Slide off the tow pieces of coned disc spring (C12) from bearing folder. Pull out the bearing folder (C08) with eye bolts.

Loosen the hex bolts (J03) and remove end plate (A08) which restricts axial

movement of bearing on the female rotor (A02) Remove end plate from female rotor.

Rotors

Male Rotor &

Female Rotor

Screw threaded rods into the bolt holes in the discharge casing on the male rotor side. Use the press plate on to the threaded rods by using several nuts. Place a hydraulic jack horizontally between the press plate and the female rotor (A02). Press the female rotor out of the discharge rotor casings approximately half way. Place a strap in the middle of the female rotor, and slide it horizontally out of the rotor

casing. Inner race of the roller bearing (C04) will be removed together with female rotor. Place rotor on tow “V” blocks so as not to damage the rotor edge. Repeat the same procedure as female for the male rotor.

Thrust Bearing and Discharge Casing

Thrust Bearing

Discharge Casing

Remove the thrust bearing, spacer and roller bearing set (C03) from the male rotor side. Remove the spacer ring (A05). Using eye bolts, remove the balance piston (A04) from the male rotor side. Remove the thrust bearing, spacer and roller bearing matched set (C04) from the female

rotor side. Following the same method of removing the dowel pins from the inlet casing, two dowel

pins (K51) should be removed from the discharge casing. Loosen the hex bolts that hold the discharge casing to the rotor casing. Suspend the discharge casing with wires. Apply jacking bolts to the discharge casing and separate it from the rotor casing.. If all bearings have been removed and the labyrinths are in good condition, removal is not

necessary. Place the discharge casing external side down. Use the labyrinth assembly tool to hammer out the labyrinth (B15) in the male port. Repeat this step for the female labyrinth (B16). Screw an eye bolts into one end of the female rotor. Raise the rotor in the air and evenly heat the race on applying heat. Repeat this process for the opposite end of the female rotor and the suction end of the male

rotor.

Caution:

1. Pay attention not to damage labyrinth portion of the balance piston (A04).

2. The discharge casing weight is not distributed evenly. Care should be taken in supporting the

casing so that it does not tip while removing.

ASSEMBLY PROCEDURE

Rotor Casing and Discharge Casing

Place the discharge casing with external side facing up onto a flat surface. Using the labyrinth assembly tool, drive the male (B15) and female (B16) labyrinths into their respective ports.

After the rotor casing is secured is secured on the work bench, apply a layer of silicone base grease to the discharge casing O-ring (B14). Affix the O-ring to the discharge side of the rotor casing.

Apply a generous amount of three bond to the discharge side of the rotor casing and spread evenly across the contact surface.

Care should be taken so that the three bond does not touch the O-ring or O-ring groove. Suspend the discharge casing by wire and align horizontally with the rotor casing. Start

several hex bolts and drive the dowel pins (K51) into the discharge rotor casing. Tighten the hex bolts between two casings.

Note:-

1. Due to the uneven distribution of weight when attaching the discharge casing to the rotor casing it is necessary to clamp the rotor casing onto the work bench.

Installing Suction Bearings

Place the inlet (suction) casing flat onto the workbench with the external side facing up. Install the female suction roller bearing (C02) with special tool into the female cavity of inlet

casing. Place the female oil nozzle plate (B11), directly on top of the suction bearing. Drive the oil nozzle plates into the cavity with the assembly tool. Use snap ring pliers to install the retaining ring (L12) into the female cavity against the oil

nozzle plates. Repeat the procedure for the male cavity of the inlet casing, using the suction bearing (C01)

oil nozzle plate (B10) and retaining ring (L12) with assembly tool.

Caution; - pay special attention for its orientation when placing.

Note:-

Direction of oil nozzle plate is critical. Using eyebolts to install the oil nozzle plate will also insure the

proper orientation.

The male oil nozzle plate (B10) has two oil nozzles a low nozzle facing the bearing (out side) and a higher

nozzle facing the bearing (inner side). Using eyebolts to install the oil nozzle plate will also insure the

proper orientation.

Bearing Inner Races.

Identify the ends of the male and female rotor to place the inner races. Insert the suction bearing

inner races (C01) (C02).Using the same procedure press in the inner race at female discharge end

(C04).

Note:-

1. Do not for get to insert spacer ring (A06) for older model of KS23M/L/LL and KS28M/L/LLNB. If necessary only heat inner race and heating temperature should be less then 248F (120C) degrees.

Slide Valve and Slide Valve Rod

To check the slide valve clearance place slide valve in valve area push into discharge area.

Check clearance between valve guide and contour of discharge with shim (4/10-.004).

Check inside dia to make sure its clean of chips and debris. Check nuts and washers to make sure there are no burrs on thread and slots. Insert

solid end of rod into valve until it stops. Rotate rod until hole in valve and in rod line up. Install dowel pin into both hole.

Secure with set screw using 262lock tite. Using punch make four punch mark around set screw.

Place washer (L21) and nut (D09) on rod and tighten make sure to align tab on washer to slot on nut.

Bend tab up into slit o nut. Place stopper on rod make sure it fits, then remove. Put all plugs into rotor case, discharge case and inlet.

Slide Valve and Slide Stop

Oil the rotor casing slide valve chamber. Inside the slide valve and slide valve rod assembly in to the rotor assembly. Check smooth action by hand and check the clearance between slide valve concave

and discharge by filler gauge ( clearance – 0.0016-0.0049)4 A Teflon piston seal (D42) and O-ring (L56) are located on the inside of the slide stop

facing the suction side of the compressor. Be sure to remove kink before placing onto the slide valve rod.

Rotor

Oil the rotor chamber generously. Suspend the female rotor in the center with a nylon strap or clothe belt.

Place the female rotor discharge end first, horizontally into the female dide of the rotor casing.

After the female rotor is approximately halfway release the nylon satrap and push the rotor the entire way into the rotor casing.

The male rotor in the center with nylon strap or clothe belt. Place the male rotor, discharge end first, horizontally into the male side of the rotor

casing same as female rotor insert. Rote the female rotor clockwise facing the rotor casing. Push the male rotor into the rotor casing

Please not to damage discharge labyrinth.

Inlet Suction Casing

Apply suction casing O-ring with a layer of silicon base grease. Fix the O-ring to the suction side of the rotor casing and apply a generous amount of

three bonds to the suction side of the rotor casing and spread evenly across the contact surface.

Spread oil onto the roller bearing inner races located on the rotors. Align the inlet casing horizontally with rotor casing

Care should be taken so that the Three Bond dose not touches the O-ring or O-ring groove.

Total Clearance Check

Set the dial gauge to the discharge shaft end Set jacking tools to suction shaft end. Push the female rotor to discharge side until rotor end contacts to the discharge

casing. Set the needle of dial gauge Zero. Pull the female rotor to suction side until the suction end of the female rotor

contacts to suction casing. Then this reading is Rotor to casing total clearance. Which must be within the

designated range.(1.40~1.61mm)

Discharge Balance Piston and Bearings

Use eye bolts to place the balance piston onto the male rotor shaft at the discharge end of the compressor

Remove the eye bolts and fix a threaded rod into the end of the male rotor. Slide the male jacking tool up0 against the balance piston. Place hydraulic jack on the threaded rod and thread a nut onto the end. Using the jack press the balance piston onto the shaft. Then first place the roller bearing inner race onto the male rotor shaft. Press the roller bearing onto the male rotor shaft. Finally hammer out the pushing tool strongly to confirm the roller bearing fitting. Remove the hydraulic jack and jacking tools. Place the thrust bearing. Then install of male discharge bearing set is completed. Install female discharge bearing and thrust bearing. Repeat the same procedure as

male discharge bearing. Fix end plate apply loctite 222 to the thread portion of the hex bolt. Install lock washer onto the rotor before installing lock nut. Tighten the lock nut as much as possible by hand before finally striking the locking

spanner.

Discharge Clearance Check

Discharge clearance check is preformed to verify the distances in which the rotors travel horizontally

in the rotor chamber after fixing thrust bearing.

Place the thread rod into the suction end of the male rotor. Secure a dial indicator to thee inlet casing and place the indicator point on the end

of the male rotor shaft side. Tighten the outside nut of the clearance tool. This action will push the male rotor to

the far end of the discharge casing until the lobe end contacts to discharge casing then loosen both nuts a little before proceeding.

Verify the contact of the indicator point with the male rotor shaft and set the indicator dial to the zero position.

Loosen the outside nut of the tool. This action will pull the male rotor to the far end of the inlet casing.

Loosen the in side nut a little bit to release elastic deformation of thrust bearing due to excessive force.

Then this reading is Rotor discharge clearance. Which must be within the designated range.(0.10~0.13mm)

Bearing Holder and Blind Plate

Install bearing holder and blind plate without conned disk and O-ring. Be sure that bearing unti-rotation pin fits in the notch on the thrust bearing race.

Pushing the bearing holder to rotor side measure the gap between blind plate and discharge casing machine surface

Calculate and determine shim thickness will keep this gap between 0.02mm to 0.05mm

Disassemble blind plate from discharge casing. Set two pieces of conned disk to the bearing holder with grease. Fit O-ring and pin on the blind plate. Then insert the blind plate. With shim and pin place the thrust bearing cover. Confirm the gap is between above

tolerance then tighten the bearing cover with hex bolts

Suction Balance Piston and Blind plate

Remove the old O-ring located between piston ring and piston ring spacer. Replace the o-ring and hammer piston ring into piston ring spacer. Insert the combination piston ring

Cylinder and Indicator

Arrange the cylinder so that the fixture end is accessible. Reach into the cylinder and use snap ring pliers to remove the retaining ring. Screw eye bolts into the stopper and remove it from the cylinder. Remove and replace the O-ring located inside of the cylinder with new one. Remove the piston seal and O-ring located on the inside of the stopper. replaced o-

ring and Teflon seal

Caution; - Never operate the compressor with AIR, once it has been put into an actual gas service,

because possible remaining flammable impurities could cause a FIRE.

Assembly and Disassembly Drawing

Flow Path Diagram