chapter 2 : piping materials
TRANSCRIPT
ME444 ENGINEERING PIPING SYSTEM DESIGN
CHAPTER 2 : PIPING MATERIALS
LAST SESSION
1. INTRODUCTION 2. STANDARDS3. BASIC UNITS4. BASIC FLOW IN PIPE5. QUICK LOOK AT PIPE DRAWINGS
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CONTENTS
1. PIPES2. VALVES3. ACCESSORIES4. PUMPS
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1. PIPES
PIPE SELECTION:• MATERIAL • SIZE• THICKNESS
CONSIDERATIONProperties of the fluid° Corrosive or scale-forming properties ° Unusual characteristics, for example, viscosity or sludgesService conditions° Pressure (including surges and transients)° Corrosive environment for exposed piping or buried piping° Soil loads, bearing capacity and settlement, external load
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PIPE SIZES
NPS = NOMINAL PIPE SIZE (INCHES)DN = DIAMETER NOMINAL (mm.)
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STANDARD SIZES
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STANDARD SIZES (CONT’D)
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STEEL PIPE THICKNESS
A schedule number indicates the approximate value of the expression
1000 P/S,whereP is the service pressure and S is the allowable stress.
Higher schedule number means the thicker pipe.
[SEE TABLE E2.1 IN PIPING HANDBOOK]8
STEEL PIPE TABLE
[SEE APPENDIX ข.8] 9
STANDARD DIMENSION RATIO
SDR = Outside diameter / Thickness
SDR is used mostly in plastic pipes .
For comparison; a DN100 sch.40 steel pipe SDR = 114.3/6.02 = 19
Examples
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PVC PIPE SIZES
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PRESSURE RATING
Class – PSIGPN – BARS
Actual allowable working pressures depend on MATERIAL and TEMPERATURE
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PRESSURE RATING
Temperature (Celcius)
Allo
wab
le W
orki
ng P
ress
ure
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PIPE MATERIALS
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CARBON STEEL PIPES
TYPES:SEAM/SEAMLESSBLACK/GALVANIZED
JOINTS:THREADEDWELDEDFLANGED
APPLICATIONS:GENERAL PRESSURE PIPING
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STAINLESS STEEL PIPESStainless steel pipes have Cr, Ni and Mo content.
1.Ferric type: resist corrosion, magnitic response, cannot be harden: ASTM 430
2.Austenitic: corroded under chloride, non-magnetic response: ASTM 304 – Most popular, ASTM 316, general purpose: food-drug, chemical, etc.
3.Superaustenitic: high corrosion resistance4.Martensitic: high temperature applications,
magnitic response: ASTM 4105.Duplex (1+2)
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CAST IRON PIPES
TYPES:CAST IRON/DUCTILE CAST IRONPLAIN/COATED
JOINTS:CAULKED
APPLICATIONSSOIL, WASTE, DRAIN
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COPPER PIPES
TYPES:HARD (ANNEALED) / SOFT (DRAWN)THICKNESS: K (THICK), L, M (THIN)
JOINTS:SOLDEREDFLAREDFLANGED
APPLICATIONS:COMPRESSED GAS, MEDICAL GAS
Copper pipes don’t like ammonia18
OTHER METAL PIPES
ALUMINUM – Light weight, low thermal inertia
BRASS (Cu+Zn) – General sanitary pipe, valves.
LEAD – Radioactive waste
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PLASTIC PIPESADVANTAGES1. Resistance to a very wide range of sanitary and chemical effluents2. Resistance to aggressive soils3. Availability in long lengths4. Light weight5. Low resistance to fluid flow6. Generally low initial cost
DISADVANTAGES1. Poor structural stability requiring additional support2. Susceptibility of some types of plastics to physical changes resulting from exposureto sunlight3. Generally low resistance to solvents4. Poor fire resistance
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MAJOR TYPES
PVC, CPVCPP, PP-RPE, HDPE, PB
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OTHER PIPE MATERIALSCONCRETE
NON-REINFORCE/REINFORCE CLASS I TO 5GENERAL WASTE AND DRAIN
GLASSFOR CORROSIVE LIQUIDS i.e. ACIDS.
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JOINTS
CAULKED JOINT FOR CAST IRON PIPES
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JOINTS FOR STEEL PIPES
FLANGED WELDED24
FLANGES
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JOINTS FOR COPPER TUBES
SOLDERED OR BRAZEDFLARED
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OTHER TYPES
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JOINTS FOR PLASTIC PIPES
HEAT-FUSED JOINT
SOLVENT CEMENT JOINT
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FITTINGS
WYE TEE ELBOW
BEND
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FITTINGS (FOR WELDING)
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2. VALVES
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GATE VALVES
Advantages1. Good shutoff characteristics.2. Bidirectional.3. LOW pressure loss
Disadvantages1. Not quick opening or closing valves. 2. Require large space3. High-fluid velocities when near-fully-closed
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GATE VALVES
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Advantages 1. Good shutoff capability2. Good throttling capability3. Shorter stroke4. Available in tee, wye, and angle patterns, 5. Easy to resurface the seats
Disadvantages 1. Higher pressure drop 2. Requires greater force or a larger actuator to seat the valve (with pressure underthe seat)
ApplicationsFlow regulation
GLOBE VALVES
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GLOBE VALVES
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BALL VALVESAdvantages1. Provides bubble-tight service.2. Quick to open and close.3. Smaller in size than a gate valve.4. Multiport design offers versatility5. Required less actuated force
Disadvantages1. Not suitable for sustained throttling applications.2. Suspended particles can settle causing failure.3. Small size
Applications1. Air, gaseous, and liquid applications requiring bubble-tight service2. Low-point drains and high-point vents 3. Instrument root valves4. Cooling water and feedwater systems5. Steam service
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BALL VALVES
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BUTTERFLY VALVES
Advantages1. Compact and light weight.2. Quick acting (quarter-turn) 3. Available in large sizes: NPS 11⁄₂ (DN 40) to over NPS 200(DN 5000).4. Low-pressure drop
Disadvantages1. Limited throttling (low differential pressure)2. Must avoid turbulent:
- Locate 4 to 6D downstream from turbulent source- Orient valve stem carefully…How?
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BUTTERFLY VALVES
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ORIENTATION OF VALVE STEM
CORRECT INCORRECT40
VALVE ACTUATORS
• Pneumatic• Electric
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VALVE PRESSURE DROP
PQCv ∆
=
Q IN GPM∆P IN PSI
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CHECK VALVES
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CHECK VALVES
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RELEIF VALVES
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AIR RELEASE VALVES
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PRESSURE REDUCING VALVESPRV, pressure regulator, pressure regulating valve, pressure control valve
Direct acting
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PRESSURE REDUCING VALVESPRV, pressure regulator, pressure regulating valve
Pilot operated
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OTHER VALVES
DIAPHRAGM VALVESPLUG VALVESNEEDLE VALVES
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3. ACCESSORIES
Water hammer arrestersStrainerPressure guagesFlow metersPIPE HANGERSEtc.
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STRAINERS
WYE STRAINER BUCKET STRAINER
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Y - STRAINERS
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PRESSURE GUAGE
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TEMPERATURE GUAGE
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FLUID FLOW METER
Rotameter
Propeller/turbineDifferential head-Pitot tubeDeflectionVariable area (rotameter)MagneticUltrasonicEtc.
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TURBINE FLOW METER
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ORIFICE FLOW METER
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WATER TANK ACCESSORY
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PIPE HANGERS
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HANGING INSULATED PIPES
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4. PUMPS
DISPLACEMENT PUMPS DYNAMICS PUMPS
CENTIFUGRALTURBINERECIPROCATING ROTARY
High head High flow61
TYPES
Lobe/gearPiston Diaphragm
Positive displacement Dynamics
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RANGE
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CHARACTERISTICS
Dynamics
PositiveDisplacement
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PISTON PUMP
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FLOW FLUCTUATION
Install receiver tank to reduce fluctuation66
DIAPHARGM PUMP
Avoid contact between fluid and pump mechanism67
ROTARY GEAR PUMP
For high viscosity fluid68
ROTARY SCREW PUMP
For very high viscosity fluid69
CENTRIFUGAL PUMP
End suction Split-case70
CENTRIFUGAL PUMP CONSTRUCTION
End suction pump71
IMPELLERS
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LEAKAGE JOINTS
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INSTALLATION
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NEXT SESSION
• Pipe drawing. Symbols. • Cost estimation. • Theory of flow in pipes. • Calculation of pressure drop in pipes. • Energy balance in fluid flow.
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HOMEWORK 21) Design a check valve that can be built easily.
2) Find the weight per meter of a DN150 sch40 steel pipe filled with water.
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