Compressor Crosshead & Distance Pieces, crankshaft & frame Flashcards
What is an advantage of the adjustable crosshead?
Manufactures can shim the shoes at the bolt locations in order to alter the clearance between the crosshead and guide.
Why do we use the two compartment distance piece?
When a complete sealing of an explosive gas from the compression chamber must be vented.
What is the cause if you can fit a feeler gauge anywhere under the crosshead?
Misalignment between the crosshead and guide
What is articulating in a connecting rod?
Allows you to mount two pistons on one crankshaft journal in order to help reduce the size of the compressor.
Describe two types of connecting rod cuts?
Straight cuts have a parting line that is 90 degrees to the rod beam.
Bias cut are used when you must pull the connecting rod out through the cylinder bore. They have a step joint because of the uneven load on them.
What is a bump check used for?
To determine whether the crankshaft main bearing is worn enough to warrant further dismantling.
What do you need to take into consideration when sizing and compressor foundation?
Size, weight, vibration characteristics and type of driver.
What is the first thing you do when starting a detailed main frame inspection?
Visual inspection
What is wire alignment for?
To check bearing location measurement’s trueness
Frame straightness
In balancing, what does a greater number of compressing cylinders mean?
A fewer number of vibration forces will occur.
What do you need to do after line boring or polishing a crankshaft?
Use a wire brush, scotch brite pad and blow out with air.
What are two ways to balance the reciprocating forces of a crankshaft?
Opposed throws and counterweights
What are used to locate and prevent rotation on two-piece bearings?
Tangs and dowels.
What is the purpose of the Distance Piece?
- prevents leaking compression gases from pressurizing the crankcase or main frame
- prevents oil from getting into the cylinder
- allows access to packing
- allows access to piston rods
- access to change oil wipers
What is the purpose of the connecting rod?
converts rotary motion of the crankshaft into reciprocating motion.
When is the inertial force the greatest on a reciprocating compressor?
When the piston reaches top TDC and BDC
What causes drop in pressure?
Increase in bearing clearances
Why is it important to keep the connecting rod bearing caps together?
They are machined together as a set so need to stay that way to prevent misalignment.
What are non-destructive tests?
There are a liquid penetrant that can reveal hidden flaws or cracks that can’t otherwise be seen.
What is the purpose of the deflection gauge?
To measure the inside distance between the webs of the crankshaft which could create misalignment of the main bearings.
How efficient is a paper intake filter?
Down to 3-5 microns
Why can’t you use an oil bath with compressors with suction valve unloaders?
They can only flow in one direction
When is rotation checked on a compressor?
Only at the initial start up, not at daily start up
How do you balance a multi-stage compressor?
Balance nuts
What is bearing crush?
It forces the shells tightly against the housing and cap when property torqued. Also, allows for efficient heat transfer.
What is bearing spread?
Is when the shell appears to be wider than the housing. It helps keep it in place during installation.
Two systems for supplying metered oil?
Pump to point - individual adjustments to each point
Divider valve -
Operator logs
- temp changes
- press differential
- change in sound
- change in vibration
Cylinder name Plate
- shop/serial number
- max discharge press
- piston stroke
- rpm
- max rod loading
- horsepower req.
Rolling out
- process to inspect main bearing shells without removing the crankcase
- insert roll pin in oil hole on crank and pry out the shell by turning the crankshaft
