Compressors - Basic Types & Operations

Select the cooling medium that cools a compressor that has metal fins on its casing. Water Air Ice Refrigerant

Air

The total energy of a flowing gas is a function of its: Pressure All Three Variables Velocity Temperature

All Three Variables

Which of the below statement is/are correct with respect to Critical Speed? Vibration is very high All the above Compressor will not be operate at critical speed Shaft rotational speed at which the rotor bearing support system is in a state of resonance

All the above

_______ motion is end-to-end movement along the axis of the shaft.

Axial

Before starting the compressor, you must: Complete a final inspection and walk-around. Load engines and turbines. Load the packing.

Complete a final inspection and walk-around.

What is the function of compressor? Move fluids Compress gas and air Remove contaminant Move liquid

Compress gas and air

The ratio of the absolute discharge pressure to the absolute suction pressure is referred to as the compressor's ______ ______.

Compression Ratio

are the four factors that determines compressor capacity.

Cylinder diameter Length of the piston stroke Number of cylinders Speed

When the total energy of a gas stays the same, and energy in the form of pressure increases, energy in the form of velocity: Stays the same Decreases Increases

Decreases

Which device in a centrifugal compressor slows down the gas flow and helps prevent radial thrust? Suction plate Shaft bearing Diffuser vanes Impelle

Diffuser vanes

Characteristics commonly used to rate a compressor are _______________ & _____________

Discharge pressure Flow rate

The _______ ______ allow gas to flow out of the cylinder, but prevent it from flowing back in.

Discharge valves

Your tasks to ensure safe operations include: Making periodic inspections. Each of the task listed. Observing the equipment carefully. Taking prompt corrective action.

Each of the task listed.

Rotary compressors have pistons that rotate inside the cylinders. True False

False

Throttling a compressor decreases discharge pressure. True False

False

Unlike mechanical efficiency, volumetric efficiency is always equal to 100. True False

False

Select all of the devices that may be used in a compressed air system to clean or dry the compressed air.{multiple selections required} Intercooler Filter Desiccant dryers Oil separators

Filter Desiccant dryers Oil separators

An air compressor typically has some type of _________ in the intake line. Filtering device Cooler Heating element Lubricator

Filtering device

Which of the devices listed is typically found in an air compressor's intake line? Cooler Heating element Lubricator Filtering device

Filtering device

elect all of the types of drive mechanisms that can be used with compressors.{multiple selections required} Steam turbines Gas turbines Electric motors Gasoline engines

Gas turbines Electric motors

Which one of the following does not require shutdown of the Reciprocating compressor? High Gas discharge Temperature High Level in Suction Separator High Oil Filter Differential Pressure High Vibration

High Oil Filter Differential Pressure

Displacing the gas into a smaller volume __________ the pressure of the gas. Decrease Increases Does not effect

Increases

Within a confined system, when volume decreases, gas pressure: Increases Stays the same Decreases

Increases

A [_____] is a device commonly used in large compressors to control the amount of gas that is delivered to a receiver.

Inlet valve unloader

What type of seal that consists of a series of ridges that create an intricate path that makes it difficult for leakage to get through the seal? Electric seal Basin seal Labyrinth seal Mechanical seal

Labyrinth seal

Centrifugal force can separate liquids from gases because ___________.

Liquids are heavier than gases

Suction valves open when cylinder pressure is Higher than the discharge line pressure. Equal across the valves. Lower than the suction line pressure. Higher than the suction line pressure.

Lower than the suction line pressure.

In a compressor _______ ______ is the percentage of work energy output compared to the amount of energy input.

Mechanical efficiency

The centrifugal tendency of a rotating object is its tendency to: Move toward the center of rotation Travel in a straight line Move away from the center of rotation

Move away from the center of rotation

Which of these statements is the reason why the operation of an oil separator is possible? Gas and oil weigh approximately the same. Oil is heavier than gas. Gas is heavier than oil.

Oil is heavier than gas.

The flow of gas is least controlled in the ____________ impeller Semi-enclosed Open Enclosed

Open

Reciprocating compressor has to be started with a _____ ______. Closed Discharge Open Discharge

Open Discharge

Select the type of compressor that works by trapping a certain amount of gas and forcing it into a smaller volume. Vacuum Positive displacement Centrifugal Spring-action

Positive displacement

In a reciprocating compressor, the packing rings: Convert rotary motion to reciprocating motion Prevent gas leakage around the piston rod Contain the liquid for cylinder cooling Keeps the piston is alignment

Prevent gas leakage around the piston rod

To reduce pressure fluctuation and Vibration ......... ....... a is used in Reciprocating compressors. Inter-coolers Pulsation Dampener Separator Relief Valves

Pulsation Dampener

To reduce pressure fluctuation and Vibration [______] is/are used in Reciprocating compressors. Relief Valves Separator Pulsation Dampener Intercoolers

Pulsation Dampener

________ motion occurs when the shaft rotates off-center.

Radial

A common positive displacement compressor is a _________ compressor. Centrifugal Reciprocating Dynamic Gas accelerating

Reciprocating

Gas is displaced with an up-and-down motion in a: Reciprocating compressor. Rotary compressor.

Reciprocating compressor.

The gas traveling through an axial compressor follows a: Relatively straight path Spiral path

Relatively straight path

Gas is displaced with a rotary motion in a: Rotary compressor. Reciprocating compressor.

Rotary compressor.

The _____ are the devices that increase the velocity of a gas inside an axial compressor.

Rotor

One type of system that prevents gas from leaking where a compressor's shaft penetrates the casing is a__________________. Pressure reducing system Gas penetration system Seal oil system Gas bypass system

Seal oil system

The ______ ______ allow gas to flow into the cylinder but prevent it from flowing back out.

Suction valves

In Centrifugal Compressors have a minimum flow point called ______ below which the operation of the machine is unstable. Off Rated Point Overload Stone wall Surge

Surge

As the compressor reaches operating temperature, which is likely to expand more? The piston and rod. The cylinder.

The piston and rod.

Select all of the choices that are correct when harmful gases are present in a compressed gas system.{multiple selections required} Their presence is usually noted with a warning sign. Wearing a respirator may be required. An area may have to be tested before work can begin there

Their presence is usually noted with a warning sign. Wearing a respirator may be required.

Select all of the characteristics that gases in compressed gas systems may have.{multiple selections required} They may be flammable They may be explosive. They may be toxic They may displace air

They may be flammable They may be explosive. They may be toxic They may displace air

Why is moisture removed from compressed air?

To prevent damage to equipment that uses compressed air

Select all of the hazards that may exist around a compressed gas system.{multiple selections required} Toxic gases Airborne dust and dirt Excessive noise Hot surfaces

Toxic gases Airborne dust and dirt Excessive noise Hot surfaces

The gas moving through a centrifugal compressor: Pulsates Travels in a straight line Travels in a spiral path

Travels in a spiral path

A balance drum is generally mounted on the shaft after the last impeller. It is used to balance the total thrust produced by the impellers. True False

True

Because there is always some energy lost due to heat or friction, mechanical efficiency is always less than 100% True False

True

Compressed air released from a nozzle near a human ear can cause severe damage. True False

True

Compressed gases produce heat because of molecular friction. True False

True

Debris with 40 pounds of air pressure behind it can travel in excess of 40 MPH. True False

True

In certain environments, compressed air can contribute to conditions that are potentially explosive. True False

True

One of the most common dangers of compressed air is particles and debris flying back into the face of the operator. True False

True

Throttling a compressor reduces volumetric efficiency. True False

True

While most compressors are capable of running at near 100% capacity, a compressor may be run at a lower capacity to reduce fuel consumption or for other reasons. True False

True

The single-acting reciprocating compressor has __________ stroke(s) per revolution. One Six Two Four

Two

Which valve is open during pre-startup? Suction valve. Discharge valve. Vent valve.

Vent valve.

From the list provide, select the component that is not found in an axial compressor. Inlet guide vanes Volute Stationary blades Rotating blades

Volute

When the gas leaves the diffuser, it enters the: Eye Discharge Volute Impeller

Volute

[_______] compressors works by spinning gas to increase the speed of the gas flow.

centrifugal

A _________ is a piece of equipment that takes in air (or other gases) and increases its pressure so the compressed gas can do work.

compressor

_____________ & ___________ are devices that remove moisture from the compressed gas in a compressed gas system.

demister desiccant dryer

A compressor that works by trapping a certain amount of gas and forcing it into a smaller volume is called a(n) [ ] compressor.

positive displacement

Axial compressors contain _________ and ___________ blades.

rotor stator

Positive displacement (PD) compressors operate by displacing a ________ volume of gas in each compression cycle.

specific

The _____ are the devices that decrease the velocity of a gas inside an axial compressor.

stator