Compressor Crosshead & Distance Pieces, crankshaft & frame

Question 0

What is an advantage of the adjustable crosshead?

Answer 0

Manufactures can shim the shoes at the bolt locations in order to alter the clearance between the crosshead and guide.

Question 1

Why do we use the two compartment distance piece?

Answer 1

When a complete sealing of an explosive gas from the compression chamber must be vented.

Question 2

What is the cause if you can fit a feeler gauge anywhere under the crosshead?

Answer 2

Misalignment between the crosshead and guide

Question 3

What is articulating in a connecting rod?

Answer 3

Allows you to mount two pistons on one crankshaft journal in order to help reduce the size of the compressor.

Question 4

Describe two types of connecting rod cuts?

Answer 4

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.

Question 5

What is a bump check used for?

Answer 5

To determine whether the crankshaft main bearing is worn enough to warrant further dismantling.

Question 6

What do you need to take into consideration when sizing and compressor foundation?

Answer 6

Size, weight, vibration characteristics and type of driver.

Question 7

What is the first thing you do when starting a detailed main frame inspection?

Answer 7

Visual inspection

Question 8

What is wire alignment for?

Answer 8

To check bearing location measurement’s trueness

Frame straightness

Question 9

In balancing, what does a greater number of compressing cylinders mean?

Answer 9

A fewer number of vibration forces will occur.

Question 10

What do you need to do after line boring or polishing a crankshaft?

Answer 10

Use a wire brush, scotch brite pad and blow out with air.

Question 11

What are two ways to balance the reciprocating forces of a crankshaft?

Answer 11

Opposed throws and counterweights

Question 12

What are used to locate and prevent rotation on two-piece bearings?

Answer 12

Tangs and dowels.

Question 13

What is the purpose of the Distance Piece?

Answer 13

• 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

Question 14

What is the purpose of the connecting rod?

Answer 14

converts rotary motion of the crankshaft into reciprocating motion.

Question 15

When is the inertial force the greatest on a reciprocating compressor?

Answer 15

When the piston reaches top TDC and BDC

Question 16

What causes drop in pressure?

Answer 16

Increase in bearing clearances

Question 17

Why is it important to keep the connecting rod bearing caps together?

Answer 17

They are machined together as a set so need to stay that way to prevent misalignment.

Question 18

What are non-destructive tests?

Answer 18

There are a liquid penetrant that can reveal hidden flaws or cracks that can’t otherwise be seen.

Question 19

What is the purpose of the deflection gauge?

Answer 19

To measure the inside distance between the webs of the crankshaft which could create misalignment of the main bearings.

Question 20

How efficient is a paper intake filter?

Answer 20

Down to 3-5 microns

Question 21

Why can’t you use an oil bath with compressors with suction valve unloaders?

Answer 21

They can only flow in one direction

Question 22

When is rotation checked on a compressor?

Answer 22

Only at the initial start up, not at daily start up

Question 23

How do you balance a multi-stage compressor?

Answer 23

Balance nuts

Question 24

What is bearing crush?

Answer 24

It forces the shells tightly against the housing and cap when property torqued. Also, allows for efficient heat transfer.

Question 25

What is bearing spread?

Answer 25

Is when the shell appears to be wider than the housing. It helps keep it in place during installation.

Question 26

Two systems for supplying metered oil?

Answer 26

Pump to point - individual adjustments to each point

Divider valve -

Question 27

Operator logs

Answer 27

• temp changes
• press differential
• change in sound
• change in vibration

Question 28

Cylinder name Plate

Answer 28

• shop/serial number
• max discharge press
• piston stroke
• rpm
• max rod loading
• horsepower req.

Question 29

Rolling out

Answer 29

• 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