Pipe Systems and Fluid Mechanics Flashcards

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

Answer: Decrease

Bernoulli's principle states that in a flowing fluid, an increase in velocity corresponds to a decrease in static pressure, as total energy (pressure + kinetic + potential) remains constant in an ideal frictionless system.

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

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

NPSH (Net Positive Suction Head) is the pressure available at the pump suction above the liquid's vapor pressure. If NPSH available falls below NPSH required, the liquid flashes to vapor at the impeller, causing cavitation.

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

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

Strainers remove solid particles, scale, weld slag, and other debris from the flowing fluid, preventing damage to pump impellers, control valve seats, and heat exchanger tubes from particle impingement and erosion.

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

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

A deadleg is a branch or stub section of pipe connected to a flowing system but with no continuous flow through it. Stagnant fluid in deadlegs causes corrosion, microbiologically induced corrosion (MIC), heat loss in steam systems, and product contamination in food/pharmaceutical piping.

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

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

A snubber is a small restriction device installed at the gauge connection to dampen the rapid pressure pulsations from reciprocating pumps and compressors, preventing gauge needle flutter and fatigue failure of the Bourdon tube.

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

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

ASME B31.3 para. 304.1.2 gives the minimum wall thickness for straight pipe as t = PD / (2(SE + PY)), where P is design pressure, D is outside diameter, S is allowable stress, E is weld joint quality factor, and Y is a material/temperature coefficient.