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TUTORIALS/ REFERENCES
TUTORIALS/ REFERENCES
SCFM to Mass Flow Rate
SCFM to Mass Flow Rate
What exactly does SCFM mean, and what assumptions are baked into it?
What temperature and pressure define “standard,” and who decides?
Why does SCFM not uniquely define mass flow without additional info?
What is the clean, unit-consistent equation to convert SCFM → lbm/hr or kg/s?
When should you not use SCFM at all?
SCFM Data to Different Gases
SCFM Data to Different Gases
Why can’t you directly reuse air SCFM data for another gas?
When does specific gravity scaling work—and when does it fail?
How do molecular weight and compressibility factor affect conversion accuracy?
What assumptions do vendors usually make (and not tell you)?
What level of error is acceptable for early design vs. final sizing?
Why This Is So Confusing
Why This Is So Confusing
Why do vendors publish SCFM instead of mass flow?
How do mixed unit systems (psi, ft³, lbmol) make this worse?
Why do engineers argue about “standard conditions” endlessly?
What is the single safest way to communicate flow unambiguously?
US vs. Imperial Gallon
US vs. Imperial Gallon
What is the numerical difference between US and Imperial gallons, and why does it exist?
In what industries does this mistake most commonly show up (fueling, HVAC, chemical dosing)?
How big is the error if you mix them up in a mass or energy balance?
Why does this matter more for liquids than gases—but still matters for gases?
How do codes and standards specify which gallon they mean (if they do at all)?
What valve types behave like orifices vs. flow elements?
What is Cv, and what does it physically represent?
When is Cv-based sizing valid, and when does it break down?
How does choked flow occur in valves?
How do gas properties change valve flow compared to liquids?
Why is ΔP-based sizing dangerous near sonic conditions?
Model Selection
Model Selection
How do you decide whether a flow problem is compressible or incompressible?
What Mach number is the real dividing line?
When is Darcy–Weisbach appropriate?
When do you need Fanno flow instead?
When does isothermal flow make sense physically?
Incompressible Flow
Incompressible Flow
What assumptions make a flow truly incompressible?
When does gas flow act incompressible even though it isn’t?
How much density change is “small enough” to ignore?
Compressible Flow
Compressible Flow
What is the difference between adiabatic and isothermal models?
Which model is conservative for pressure drop?
How does pipe length influence which model dominates?
Why do long, small-bore lines behave differently than short, large ones?
Minor Losses Confusion
Minor Losses Confusion
What actually counts as a minor loss?
Why are minor losses often larger than friction losses?
Why do K-factors vary so wildly between references?
When is it acceptable to lump losses—and when is it not?
Definitions
Definitions
What is the difference between a safety valve, relief valve, and safety relief valve?
Why does terminology matter legally and technically?
Which standards define these terms authoritatively?
3% Inlet / 10% Outlet Rule
3% Inlet / 10% Outlet Rule
What does the 3% inlet pressure drop rule actually protect against?
Why is the outlet rule more lenient than the inlet rule?
When are these rules waived or modified?
What happens if you violate them in real systems?
Fire Case (API 521 / CGA)
Fire Case (API 521 / CGA)
What assumptions go into a fire case calculation?
Why is fire sizing often grossly conservative?
How does insulation or burial change the result?
Why are gas systems treated differently than liquid-filled vessels?
Codes and Standards
Codes and Standards
Which codes govern PSV sizing vs. installation?
When does ASME apply vs. API vs. CGA?
How do jurisdictional requirements override engineering judgment?
OPP for Vaporizers
OPP for Vaporizers
Why are vaporizers especially dangerous from an OPP perspective?
What failure modes dominate vaporizer overpressure?
How do blocked outlet and heat input scenarios differ?
Vessel Modeling
Vessel Modeling
How do you model pressure rise from a leak into a closed volume?
How do you model heat input during a fire case?
When does lumped-capacitance break down?
Gas Temperature Changes (JT Effects)
Gas Temperature Changes (JT Effects)
What is the Joule–Thomson effect in plain language?
When does gas cool vs. heat during expansion?
Why does hydrogen behave differently than most gases?
When is assuming isothermal expansion dangerously wrong?
What can a check valve actually be relied on to do?
What can it not be relied on to do?
Why are check valves not isolation devices?
How does cracking pressure affect system performance?
How do leakage class and backflow rate really matter?
Sizing and Selection
Sizing and Selection
Why does oversized check valves cause chatter?
How does orientation affect performance?
What failure modes dominate in gas service?
What is the difference between droop and lock-up?
Why do regulators behave differently with gases vs liquids?
How does upstream pressure variation affect outlet control?
When do you need a monitor or series regulator setup?
Why do regulators often fail silently?
How does a flat-plate orifice actually measure flow?
What assumptions go into the orifice equation?
When does discharge coefficient matter most?
Why do orifices lose accuracy at low Reynolds numbers?
Selecting Fittings for Gas Service
Selecting Fittings for Gas Service
What makes a fitting suitable for gas vs liquid service?
How do leak paths differ for gases?
Why do torque specs matter more for gases?
SAE J1926 Fittings
SAE J1926 Fittings
What problem does SAE J1926 solve?
How does it differ from NPT and ORB?
Why is it common in high-pressure gas systems?
What are the common failure modes?
What is the difference between MAWP, design pressure, and service pressure?
Why is MAWP not a design target?
How do temperature deratings factor in?
Why do engineers confuse test pressure with operating pressure?
How do particulate size requirements get defined?
Why does oil content matter more than people think?
How does moisture content affect downstream equipment?
How are ISO air quality classes specified?
Dryer Selection Confusion
Dryer Selection Confusion
Why use a desiccant dryer downstream of a refrigerated dryer?
What happens if you don’t?
How do pressure drop and purge losses factor in?
When is this configuration overkill?
What does it mean for a refrigeration system to “balance”?
How do compressor, condenser, and evaporator curves interact?
Why is this an iterative problem?
What assumptions break most spreadsheet models?
What problems is CoolProp actually good at solving?
What inputs are required to avoid garbage outputs?
How do you link CoolProp to Excel safely?
What are the most common unit mistakes?
When should you not use CoolProp?
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