Pipefitter Pipe Systems and Fluid Mechanics

Question 1

Bernoulli's principle states that as the velocity of a fluid increases in a pipe section, the static pressure in that section will:

Accepted Answer

Decrease

Answer

Also increase proportionally

Answer

Remain constant regardless of velocity

Answer

Double if velocity doubles

Question 2

In a piping system, what does 'NPSH' stand for and why is it critical for pump operation?

Accepted Answer

Net Positive Suction Head — the pressure available at pump suction above the vapor pressure of the liquid, required to prevent cavitation

Answer

Net Pressure System Head — the total head available at the pump discharge

Answer

Normal Pipe System Hydraulics — the standard flow calculation method

Answer

Net Pump Static Head — the elevation difference between suction and discharge

Question 3

What is the function of a strainer (Y-type or basket type) installed upstream of control valves and pumps in a piping system?

Accepted Answer

To remove particulates and debris from the fluid stream, protecting downstream equipment from damage

Answer

To reduce fluid velocity before entering sensitive equipment

Answer

To act as a check valve preventing backflow

Answer

To measure fluid pressure drop across the system

Question 4

What does the term 'deadleg' refer to in process piping, and why is it a concern?

Accepted Answer

A section of piping that is connected to an active system but has no through-flow, allowing stagnant fluid, corrosion, or bacterial growth

Answer

A horizontal pipe section without adequate slope for drainage

Answer

The dead-end cap at the end of a piping header

Answer

A pipe that has been permanently removed from service

Question 5

What is the purpose of a pressure gauge 'snubber' (pulsation dampener) installed on instruments in pump discharge piping?

Accepted Answer

To dampen pulsating pressure oscillations from reciprocating pumps or compressors, protecting instruments from fatigue damage

Answer

To amplify pressure signals for easier reading

Answer

To reduce the pipe pressure by throttling flow to the instrument

Answer

To isolate the instrument during maintenance without shutting down the process

Question 6

Under ASME B31.3, what variables are included in the minimum required wall thickness formula for straight pipe under internal pressure?

Accepted Answer

Pressure (P), outside diameter (D), allowable stress (S), weld joint quality factor (E), and temperature coefficient (Y)

Answer

Pressure (P), inside diameter (d), yield strength (Sy), and weld factor (E) only

Answer

Pressure (P), outside diameter (D), and safety factor (4.0) only

Answer

Wall thickness is looked up in a table; there is no formula