Module 2 - Selection & Sizing

Module from the Instrumentation Engineering Curriculum curriculum.

INSTRUMENT SELECTION & SIZING · Learning Objectives · 1. Apply selection criteria based on process conditions (pressure, temperature, corrosion, hazardous area) 2. Size orifice plates using beta ratio and flow coefficient 3. Select materials of construction for process wetted parts 4. Specify instrument ranges with proper turndown and overrange · Selection Guide by Service Condition

Service Condition	Pressure	Temperature	Flow	Level	Analytical	Material Notes
Clean hydrocarbon liquid	DP transmitter, gauge	RTD or Type K TC	Orifice, vortex, or Coriolis	DP, radar, or displacer	Density (Coriolis)	316 SS wetted parts standard
Dirty / slurry service	Diaphragm seal transmitter	Thermowell (heavy wall)	Magnetic (if conductive), Coriolis	Radar (non-contact), nuclear	Sampling + lab analysis	Hastelloy C-276 or ceramic
High temperature (>600°F)	Remote seal with capillary	Type K or N TC, thermowell Alloy 600	Orifice with remote seal taps	DP with remote seals, radar	Extractive sampling + cooling	Alloy 625 or 800H thermowells
High pressure (>1500 psig)	Monoflange DP, integral manifold	TC in heavy-wall thermowell (Schedule 160)	Orifice with 1500# flanges, Coriolis	DP with monoflange, GWR	Special sampling system	NACE MR0175 if sour (SSC risk)
Corrosive (acid/caustic)	Teflon-lined diaphragm seal	Tantalum or Hastelloy thermowell	Magnetic (PTFE liner), Coriolis (Hastelloy)	Radar (PTFE antenna), ultrasonic	pH, conductivity (specialty electrodes)	Match alloy to corrodent
Cryogenic (<-50°F)	Low-temp rated transmitter, seal fill rated for cryo	Type T TC (best accuracy at cryo), RTD	Coriolis, ultrasonic	DP, GWR, radar	Composition (GC, IR)	304/316 SS (avoid CS — brittle)
Hazardous area (Zone 1/Div 1)	Explosion-proof or IS transmitter	IS barriers for TC/RTD signals	All types — must be rated for area class	Same technologies — explosion-proof or IS	IS analyzers or remote sampling	FM/CSA/ATEX approval required
Source: IPE Engineering Practices Sec_12 (51 docs), Control Valve Handbook, Orifice_Flow_Calculator_v1.xlsx

Source: Instrumentation_Engineering_Curriculum_v1.xlsx · Sheet: Module 2 - Selection & Sizing

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