PRODUCTION TRAINING PACKAGE 11.1 RECIPROCATING COMPRESSOR THIS TRAINING PACKAGE IS DEVIDED INTO TWO PARTS PTP 11.1 : PRINCIPLES & COMPONENTS PTP 11.2 : OPERATION & ACCESSORIES

PRODUCTION TRAINING PACKAGE 11.1 RECIPROCATING COMPRESSOR PTP 11.1 : PRINCIPLES & COMPONENTS

Reciprocating Compressor Principles Why Compressors are used in PDO Operations? - To increase the Natural gas pressure Consequently To utilise the Gas in the process To Export or to Sale the Gas To inject or to lift to Enhance the oil production DIFFERENT TYPES OF COMPRESSORS ARE USED IN PDO

Reciprocating Compressor Principles Types of Compressors:

Reciprocating Compressor Principles

With the help of Cylinder and Piston Reciprocating Compressor Principles Principles: Positive Displacement compressor Operates by volumetric displacement Most operates with reciprocating- back and forth or up and down - motion Some with rotary motion PRESSURE INCREASES WHEN THE GAS IS FORCED TO OCCUPY A SMALLER VOLUME. Greater the reduction in volume - Greater the increase in Pressure With the help of Cylinder and Piston These are High Head and Low Throughput Machines

Reciprocating Compressor Principles Depends on its Function it is categorised: 1. Single Acting Reciprocating Compressor: DISCHARGE CYLINDER PISTON SUCTION One revolution: One forward stroke & one back ward stroke or One suction stroke & one discharge stroke. One discharge per revolution Compression taking place on one side of the piston

Reciprocating Compressor Principles 2. Double Acting Reciprocating Compressor: One revolution: Two suction stroke & Two discharge stroke Suction stroke and Discharge strokes are simultaneously Two discharge/Two suction per revolution- Crankcase end and head-end Compression taking place on both side of the piston

Reciprocating Compressor Components External Components: FLYWHEEL CROSSHEAD COMPARTMENT FRAME/CRANKCASE DRIVER PULSATION DAMPENER SUCTION VALVE SEAL COMPARTMENT DISCHARGE VALVE CYLINDER

Reciprocating Compressor Components Internal Components:

Reciprocating Compressor External Components: 1. Driver: May vary with the size of the machine Availability of energy source. Commonly Electric motor - run at constant speed, require capacity control Another - Gas Engine - Speed controller available, require more maintenance than Electric motor. Gas/Steam driven turbines are the last alternative. 2. Fly Wheel: To avoid any surge of power due to reciprocating action 3. Frame/Crankcase: To provide high strength at a reasonable weight. In the side walls - Saddles are machined for the crankshaft main bearing shells The frame serves as a reservoir for lubricating oil On non-drive end, the main lub oil pump is fitted.

Reciprocating Compressor External Components: conti- 4. Cross Head Compartment: Consist of the shoe and cross-head guide Access through side door to carry out alignment and clearance checks. 5. Seal Compartment: consists of the gas and oil scraper seal. Access through side door to carry out leakage checks. 6. Cylinder: Are cover with water jackets for cooling purpose. Piston travels To and Fro with a liner. 7. Pulsation Dampener: To absorb the intermittent pulsation due to reciprocating action. Surge the gas pulses. Each on suction and discharge

Reciprocating Compressor External Components:conti- 8. Suction / Discharge valves: Acts as Non return valves. Let the gas enter / discharge at specific pressure. Suction valves fitted on top and discharge valves are fitted on bottom of the cylinder. Consists of valve seat, valve guard, valve plates etc.

Reciprocating Compressor External Components:conti- Across Section of a Discharge Valve A worn or damage valve allows gas to back leak. Sudden chilling on hot valve can break valve plate. Gas should be free of liquid.

Reciprocating Compressor External Components:conti- Valve internals: Valves must be properly installed Means: - Suction valve: you can depress the plate in toward the centre of the cylinder. - Discharge valve: you can depress the away from the cylinder. When a valve leaks: -The gas returning through the valve is hotter and valve become hotter. - Detected by measuring skin temperature of valve cover. - To be checked by operator in morning hours

Reciprocating Compressor Internal Components: 1. Crank Shaft: To convert rotary motion from driver to reciprocating motion to the piston through connecting rods and cross-head. Oil holes are drilled for the lubricating purpose. Non driven end gear wheel drives the main lube oil pump.

Reciprocating Compressor 2. Connecting Rod: Connect the crank shaft and the cross head. Both ends are equipped with heavy duty sleeve bearing. Big end bearing and Small end bearing.

Reciprocating Compressor 3. Cross Head: Connects the connecting rod and piston rod. Made of cast steel and have white metal surfaces. Lubricated through main oil system. Moves on the cross head guides. Shims are installed at the cross-head shoes for vertical alignment.

Reciprocating Compressor 4. Cross Head Guide: Housing is provided with inspection holes and covers. Easy access through this doors for maintenance/inspection. Where no gas leakage is allowed, two distance pieces are built between the cylinder and cross-head guide. 5. Piston Rod: Made of high quality steel alloy. Are heat treated to provide a harder and stronger finish. Heavy chrome plated to protect against H2S.

Reciprocating Compressor 6. Stuffing Box: Used for separation of the compressor cylinders to the atmosphere as well as between the cross-head section and distance piece. Each section consist of two PTEF rings and a back-up ring Numbers of sections depends on differential pressure between compressor discharge pressure and the atmosphere. Stuffing boxes can be lubricated or non-lubricated, water cooled or non-water cooled according to deferent design. 7. Packing: Prevents compressed gas leak along the piston rod. Mostly used metallic rings. Rings are arranged in pairs in each cup and are made in segments. The segments held against the piston rod by garter spring. Could be of fibre, plastic or metal. Carbon or Teflon - used when packing must be free of lubricant

Reciprocating Compressor Gas leakage of Packing: - Have sets of rings scraper or wiper near cross-head Single-acting wiper either prevent oil leak from crank case to cylinder or to either side. Double-acting wipers removes both cylinder oil and crankcase oil from the rod. Wipers scrapes the oil into the distance piece and get drained. A rising temp. at the vents indicates excessive leakage. The gland packing has connections for CW, LO and a vent.

Reciprocating Compressor 8. Piston: Solid and Hollow Piston Hollow Made of Cast iron - usually made solid Low-speed compressor(up to 330 rpm. High-speed compressor(330 - 600 rpm) More than 7” in dia. Usually made hollow.. Manufacturers specify the amount of clearance required. To assemble cold piston, make the piston end clearance greater at the head-end of the cylinder.( 1/3 on the crank case end and 2/3 at the head-end)

Reciprocating Compressor 9. Piston ring: Provide a seal to minimise a leak. Also carry heat from the cylinder. Compressor’s cooling system carries most of the heat. Rings are made of material that wears more rapidly than cylinder or liner. Made of bronze, cast iron, bakelite, teflon etc. Material cause low friction. Ring grooves should be very accurate. Minimum allowable clearance 0.3 mm9between piston and cylinder walls.

Reciprocating Compressor 10. Cylinder assembly: Cylinder bore and Liner - to reduce reconditioning cost. Worn liner needs to be replaced. Due to the weight of the piston, wear is usually at the bottom of the cylinder. Misalign liner: Oil holes in the liner always aligned with the lubricator inlet. Misalign liner can cause plug or close the inlet.

Reciprocating Compressor 11. Bearings: Bearing shell should be inspected for cracks, chips, scratches and wiping. Typical cause for high temperature- - blockage in the oil supply. - Inadequate oil flow. - tight bearing clearance. - Crankshaft misalignment 12. Oil wiper Rings: To prevent crankcase oil from passing into the cylinder. To prevent condensate from entering the crankcase. Normally two or three wiper rings are used in an oil seal. Two types - Designed to turn back a large volume of oil along the rod. - Oil wiped from the rod drains into an annular and back into the crankcase.