Reciprocating Compressors and Valves Flashcards
When volume of a gas is reduced?
The gas increases in temperature and pressure
What is the purpose of “purging” a compressor?
To remove dangerous gases prior to disassembly
What is the purpose of an aftercooler?
To remove moisture after compression
What must be used to prevent explosive pressures from forming in the event of a blockage in compressed gas piping or vessels?
Pressure Relief Valves
What are the 3 ways that the pressure of a gas can be increased?
Decrease volume, increase temperature and pack more into a confined space
What will happen if gas is heated in a confined space?
It will increase in pressure
What would be used to improved the efficiency of a multi-stage compressor?
add or use an intercooler
Why is it important to make piping connections to the top of a main supply header?
This prevents water and solids contaminants from reaching equipment
Pressure applied to a confined fluid is transmitted equally in all directions and at right angles to the surface, this is known as?
Pascal Law
If the temperature remains constant, the volume changes inversely to the pressure, this is known as?
Boyle’s Law
It is stated that if the pressure on a given volume of a gas is held constant, the volume changes in direction proportions to the absolute temperature, this is known as?
Charle’s Law
If the flow rate is constant, the sum of the kinetic and the potential energy at various points in the system is constant, fluid increases, the pressure decreases?
Bernoulli’s Principle
What is the Combined Gas Laws?
combination laws of Boyle, Charle and Gay-Lussac’s law
What are the name of the positive displacement reciprocating compressors?
- Single acting
- Double acting
- Labyrinth
- Diaphragm
List all the positive displacement rotary/screw compressors?
- Sliding vane
- Liquid Ring
- Single Rotor
- Two Rotor
List some problems moisture has on a compressor or compressed air system?
- causes rust
- harmful to lubricants
- form sludge
- In some cases moisture might freeze
What happens when the bourdon tube gauge pressure goes up?
The tube straighten out
What is a single-acting compressor?
Compression happens on one side of the piston.
What is a double-acting compressor?
Compresses gases on both sides of the piston
Which compressors are the most common used because of the widest range of operating suction and discharge pressure?
Reciprocating Compressors
The term single-acting means what?
Compression on one side of the piston
Can the labyrinth compressor run without oil?
yes, by creating a seal between the cylinder in the piston with a series of grooves machined on the piston and cylinder wall
An integral compressor is what essentially when combined into one frame with one common crankshaft?
An Engine and a compressor combined
What does the Conrod connect to on a diaphragm compressor?
Flexible membrane or a diaphragm
Where is a gas injection compressor most common?
Oil production
What are 3 ways pressure can be increased?
- Heat it
- Reduce the volume
- Add more gas into a confined space
What compressors has a sealed container where pressure is created on the inside surfaces by molecules of gas striking the surface creating a force?
Positive Displacement Compressors
How is gas lifts different than gas injection?
Gas passes through a series of lift valves pushing the oil out of the well.
How many compressors are used for gas gathering?
One central compressor to pull gas from a series of locations into one central pipeline
How many kilometers should a boast station be from one another?
150 - 300 km along pipeline
What kind of compressors used more commonly in the compressor lift station application?
Centrifuge Compressors
Bernoullis principal and the law of conservation of energy apply to what?
All Fluids
Define clearance volume?
Clearance Volume is the space between the piston in the cylinder head when the piston is at top dead center (TDC)
What is the purpose of inter cooler?
To increase efficiency and to draw moisture out
What is the purpose of a receiver?
To store the compressed air and to take up fluctuations in demand and the system pressure to very within reasonable limits
What is the definition of vacuum?
is when the pressure in a building or container is less than the pressure surrounding it which is normally atmospheric pressure
What is special about a labyrinth compressor?
It has a special design that allows it to run without oit
What are the compressors type that can run without oil?
- Labyrinth Compressors
* Diaphragm Compressors
What are the two types of air flows?
- Laminar Flow
* Turbulent Flow
How is the piston connected to the rod?
It is locked against a shoulder or on a taper with a locknut
What is the distance piece?
It houses the crosshead, guides and oil wipers
What are some examples of unloaders?
- Pressure switch unloader
- Start/Stop
- Inlet Valve Unloader
- By Pass
- Variable Volume Pocket
What are the 3 main types of reciprocating compressor unloaders?
- Inlet Valve Unloader
- Pressure Switch Unloader
- Bypass Unloader
What are the 3 types of air dryers?
- Desiccant type
- Deliquescent type
- Refrigeration type
What is the setting on a safety relief valve?
The maximum/highest of the lowest pressure rating of any part of the system
What must you do if a higher than 5:1 compression ratio is needed?
It must be staged
Out of the two valves, intake and exhaust, Which one generally needs to be replaced more often?
Exhaust @ discharge
Dampened disc valves are suitable for _______ applications
High Speeds
What are poppet valves a good choice for?
Well suited to applications where there is condensate or other liquids in the gas stream
Three (3) advantages to synthetic sealing elements?
- Lighter weight
- Limited damage to other compressor components in the event of breakage
- Reduce noise
Four (4) components of a compressor valve are?
- Seat
- Guard
- Sealing elements
- Assembly elements
Added advantages of a V shape sealing element?
- Better Flow
- Smoother flow path
- Less turbulence, does not get dirty
Which valve has the least restriction to flow?
The Ring Valve
What is good practice when one spring in a set shows wear?
Replace the Set
Three (3) measurements on a channel valve?
- Lift Check
- Side Clearance
- End Clearance
What is a common way in the field to check if a valve is sealing?
Leak test with window washer fluid
Define Swept volume?
It refers to the volume of air that is swept or pushed out of the cylinder on the compression stroke
Why is rod reversal necessary?
To allow oil to flood around the crosshead pin and connecting rod bushing
What is the best flowing valve?
Concentric Ring Valve
What is a common type of piston?
Trunk Style (Single acting only)
or
Trunkatted
Is the ring land diameter smaller or larger than the skirt?
Smaller
Valve lift refers to what?
How far the lift is away from the ceiling element
What pressure are cylinders hydro tested to?
1.5 times their maximum allowable working pressure
Which rider ring is used if it passes over a valve port?
The Uncut Rider Ring
What should be done to a cylinder that has been honed or deglazed?
Should be washed with soapy water
Name the type of Cylinders;
- Cast Integral
- Wet Liners
- Dry Liners
Name four (4) types of Packing Rings;
- Pressure Breaker
- Radial Cut
- Tangental Cut
- Back-Up Ring
Which Ring does the most sealing?
Tangental Cut
Which ring is the only one used singly?
Pressure Breaker Ring
What ring combination is used on a double acting cylinder?
Two Tangental Cut Rings dowels together
In lubricated packing where is the oil distributed?
It enters through the flange at the top and isdirected near the pressure side, but not all the way to the pressure breaker
Where does liquid coolant enters to cooled the packing?
at the bottom, so no air can get trapped
Where is the oil wiper packing found?
on the Crank side of the distance piece
What is proper ratio when setting clearance in piston and cylinder head?
2/3 on head end
1/3 on Crank end
*This allows for expansion from heat
What is the purpose of the distance piece?
It allows access to the oil wipers
What is the purpose for multiple compartment distance pieces?
In applications where a complete sealing of an explosive gas from the compression chamber must exist
What are some ways to balance an opposing throw compressor?
use different metal pistons, balance nut, larger piston made of aluminum
What is the most common system of cooling in industrial compressor?
Circulated liquid cooling
What are the two (2) styles of connecting rods?
- Bias
* Straight Cut
What are the four (4) main jobs of lubricants?
- Prevent corrosion
- Reduce Wear
- Cooling or Carry away heat
- Sealling
What type of lubrication system is commonly found on small compressors?
Splash lubrication system
What must be the temperature of the cooling liquid at the cylinder be, and why?
5.5° degrees more warmer than the gas, so it doesn’t condensate inside the cylinder
Name some causes of low oil pressure?
Increased clearance in bearings, air enters the oil lines, plugged oil filter, (Crankshaft main bearing)
What are the two (2) common systems for supplying metered amounts of oil?
Pump to a point to point system
and
Divider block valves
Which system allows for individual adjustment to each point?
Pump to a point to point system
what is the operating pressure of the divider system above the last stage cylinder pressure?
10% or higher
What must be done after servicing the divider lubrication system?
You must bleed the air out of the lines after servicing
Paper element filters down to what microns?
3 - 5 microns
Before locking out a compressor what two things must be done?
- Purged first with inert gas or sweet gas
* then Vented
After any kind of work or service on the compressor is done, what must always be done before starting up again?
Bar the compressor over on complete revolution.
Two is better but one is a must
When would you find an articulating rod?
In an Integral type compressor
When torqueing bolts on rods what is the minimum numbers of steps used?
3 steps or 3 stages
What is a bump check used for?
A method to determine whether a bearing is worn enough to warrant further dismantling of main bearings
When sizing a compressor foundation what are the four (4) things to take into consideration?
*The Size
*Weight
*Vibration characteristics
The type of Driver
What is a wire alignment used for checking?
Bearing location measurement
What are the three (3) things every air receiver must have?
- Gauge
- Drain
- Safety Relief Valve
When referencing bouncing as a rule the greater number of compressing cylinders the?
Fewer the number of vibrational forces will occur
When performing a crank deflection test in the dial has reading of five mills, what might be the cause?
- Soft Foot
- Bent Crankshaft
- Improper installation of compressor
Why do we need bearing spread?
We need it for location and to keep in place during installation
Bearing crush is used to?
For good seating and good heat transfer
What are dowels and locking tabs used for?
Anti-rotation devices or to keep bearing element from rotating with journal or shaft
Why do we have clearance pockets on the compressors and where are they located?
They are used to control the output to meet demands, they are located at the head end.
What is the main reason for keeping rod runout within limits
To limit wear and increase sealing
Which rider ring is used if it passes over a valve port?
The uncut rider ring
Which ring is used by itself and where is it located?
The Pressure Breaker Ring
It is located closest to the cylinder or pressure end
What are liquid cooled packing case is normally used for?
Oil free applications
What happens if the surface of the piston rod is scratched or damage?
it will ruin the seal of the packing
We inspect and measure cylinders to see if they are?
- Straight
- Round and
- Within specified dimensions
What is the purpose of the connecting rod?
To convert rotating motion to reciprocating motion
Where are cracks likely to be located on the crank?
The corner of the fillets, and around oil holes
How does a dynamic system make pressure?
It restricts flow to get pressure
When does valve flutter or multiple impacting occur and what do you do to correct it?
It occurs at high speeds and is fixed by using a dampening disk
What should be done to the valve chair bolt when removing the valve?
The valve chair boat should always be backed off before removing the valve cover
Is compressor rotation the daily check?
No, only when a major service is done
What are some examples of daily checks?
- Oil levels
- Fluid levels
- Water temperature
What is the purpose preload?
Is used to compensate for thermal expansion so the rod runs true at operating temperature
In lubricated packing where is the oil distributed?
It enters through the flange at the top and it is directed near the pressure side, but not all the way to pressure breaker
