Chapter 9: Piping Equipment and Systems

9.1 What factors are considered in selecting pipe size for fluid flow?

Flow rate, allowable pressure drop, velocity limits, pipe material, and cost; tradeoff between energy (pumping) and installation cost.;

9.2 What differentiates turbine pumps from centrifugal pumps? How used?

Turbine pumps use multiple stages to generate high head at low flow; used in HVAC for high-pressure, low-flow applications like boiler feed.;

9.3 What differentiates positive displacement pumps from centrifugal pumps? How used?

Positive displacement pumps move fixed volume per cycle (constant flow regardless of pressure); used for precise flow (e.g., chemical dosing).;

9.4 If 50 ft head → 30 gpm, what head for 60 gpm?

Head ∝ flow² → (60/30)² = 4 → 50×4 = 200 ft head.;

9.5 Parallel vs series pumps?

Parallel: increases flow (same head); Series: increases head (same flow).;

9.6 Advantages/disadvantages of plastic vs steel piping?

Plastic: corrosion-resistant, lightweight, cheaper; Steel: stronger, handles higher temps/pressures but can corrode.;

9.7 What limits max/min velocities in piping?

Max: noise, erosion, pressure loss; Min: air pockets, poor heat transfer, sediment settling.;

9.8 Differences in insulation types (calcium silicate, fiberglass, foam rubber)?

Calcium silicate: high-temp, rigid; Fiberglass: general-purpose, good insulation; Foam rubber: flexible, best for condensation control.;

9.9 Difference between control valve and balance valve?

Control valve modulates flow dynamically; balance valve sets fixed flow for system balancing.;

9.10 When use three-way vs two-way valves?

Three-way used when constant flow is needed (older systems, pump protection) despite higher cost.;

9.11 Purpose of a check valve?

Prevents backflow → protects equipment and maintains system direction.;

9.12 Limitations of open expansion tanks?

Air contact causes corrosion, evaporation losses, contamination, and maintenance issues.;

9.13 Expansion loops vs slip joints?

Loops: durable, no moving parts but require space; Slip joints: compact but need maintenance and may leak.;

9.14 Provisions for air control in hydronic piping?

Air separators, vents, proper piping slopes, expansion tanks → remove trapped air.;

9.15 Provisions for condensate control in steam piping?

Steam traps, proper slope, drip legs → remove condensate and prevent water hammer.;

9.16 Why is reverse-return piping better than direct-return?

Self-balancing → equal pipe lengths reduce need for manual balancing.;

9.17 Advantage of closed-loop vs open-loop system?

Closed-loop reduces contamination, corrosion, and water loss → more efficient and reliable.;

9.18 Is a cooling tower system open or closed loop?

Open-loop (water exposed to air → evaporation and contamination).;

9.19 1 psi = 2.31 ft of water head?

True (standard conversion between pressure and head).;

9.20 Calculate WHP for 100 gpm, 30 ft head.

WHP = (Flow×Head)/3960 = (100×30)/3960 ≈ 0.76 hp.;

9.21 Calculate BHP if pump efficiency = 75%.

BHP = WHP/efficiency = 0.76/0.75 ≈ 1.01 hp.;

9.22 What are the two types of fluid heat exchangers?

Direct-contact and indirect-contact heat exchangers.;

9.23 Which heat exchanger is best for low temperature difference?

Direct-contact → more efficient heat transfer.;

9.24 Grooved-pipe joints used only for steel?

False (also used for other materials like ductile iron).;

9.25 Grooved-pipe joints are extremely rigid?

False (they allow some flexibility and movement).;

9.26 Soldered joints used for type-K copper?

True (commonly used for smaller copper piping).;

9.27 Why is air venting needed in hot-water systems?

Air causes reduced flow, noise, corrosion, and poor heat transfer.;

9.28 Approximate latent heat of steam?

~970 Btu/lb (used for calculations).;

9.29 Purpose of a strainer upstream of pump/valve?

Removes debris → protects equipment from damage.;

9.30 Purpose of a suction diffuser?

Smooths flow into pump, reduces turbulence, and protects pump.;

9.31 Three functions of a triple-duty valve?

Isolation, balancing, and check valve functions.;

9.32 Advantages of district heating vs individual systems?

Centralized efficiency, reduced maintenance, less equipment in building; but less control.;

9.33 Advantages/disadvantages of high-pressure steam distribution?

Adv: smaller pipes, less flow needed; Disadv: higher losses, safety concerns, more complex controls.;

9.34 Why insist on isolation valves?

Allows maintenance/repairs without shutting down entire system → critical for reliability.;

9.35 Why repair leaky steam traps quickly?

Leaks waste energy, reduce efficiency, and can damage system.;

9.36 Key considerations for refrigerant piping design?

Proper sizing, oil return, pressure drop, leak prevention, and maintaining correct refrigerant velocity.