1 ME444 ENGINEERING PIPING SYSTEM DESIGNCHAPTER 13 : COMPRESSED AIR PIPING

2 CONTENT INTRODUCTION AIR COMPRESSOR PIPING SYSTEM PIPE SIZING

3 1. INTRODUCTION COMPRESSED AIR SERVES MANY PURPOSESDELIVER MECHANICAL ENERGY (PNEUMATIC SYSTEM) PROCESS AIR SUPPLY (MIXING, AGITATION) DRYING AND CLEANING (NOT RECOMMENDED) ETC.

4 AIR Cp = 1.01 kJ/kg.K Cv = 0.72 kJ/kg.K k = Cp/Cv = 1.4AT STP (0 °C and kPa), dry air has a density of ρSTP = g/L

5 COMPRESSION CYCLES P  k 1 PVn = Constant n = 0 ISOBARICn = 1 ISOTHERMAL n = k ISENTROPIC n =  ISOCHORIC n = 0 V

6 ISENTROPIC COMPRESSION PROCESSFully insulated cylinder No heat exchange with the surroundings. Constant entropy

7 2. COMPONENTS

8 DISPLACEMENT COMPRESSOR

9 ACTUAL COMPRESSION CYCLE

10 ROTARY DISPLACEMENT COMPRESSORSSCREW SCROLL

11 DYNAMICS COMPRESSORS

12 ACCESSORIES FILTERS DRYERS SILENCERS REGULATORS VALVES

13 TYPICAL AIR COMPRESSOR ASSEMBLY

14 COMPRESSOR ROOM

15 AUTOMATIC DRAIN

16 PNUMATIC EQUIPMENTS

17 3. PIPING SYSTEM General practice Tap from top of main pipeSlope toward automatic drain V < 6 m/s Use ring loop for large system Consider 5% minimum leakage

18 PIPING SYSTEM DESIGN SEQUENCESLocate and identify each process, work station, or piece of equipment using compressed air. This is known as the total connected load. These elements 2. Determine volume of air used at each location. 3. Determine pressure range required at each location. 4. Determine conditioning requirements for each item, such as allowable moisture content, particulate size, and oil content. 5. Establish how much time the individual tool or process will be in actual use for a specific period of time. This is referred to as the duty cycle. This information will help determine the simultaneous-use factor by eliminating some locations during periods of use at other locations.

19 PIPING SYSTEM DESIGN SEQUENCES6. Establish the maximum number of locations that may be used simultaneously on each branch, main, and for the project as a whole. This is known as the use factor. 7. Establish the extent of allowable leakage (2%-5% for good system). 8. Establish any allowance for future expansion. 9. Make a preliminary piping layout, and assign preliminary pressure drop. 10. Select the air compressor type, conditioning equipment, equipment and air inlet locations making sure that consistent scfm (scmm) or acfm (acmm) is used for both the system and compressor capacity rating. 11. Produce a final piping layout, and size the piping network.

20 COMPRESSOR SELECTION Flow rate Pressure Survey the requirementConsider use factor Account for leakage Apply margin of safety Pressure

21 ABOUT AIR PRESSURE AND FLOW RATEACFM – ACTUAL MEASUREMENT OF COMPRESSED AIR SCFM – EQUIVALENT TO FREE AIR AT 0 PSIG PSIG = 100 X ( ) / 14.7 = 780 SCFM 1 psig X = kPa. 1 cfm X = m3 / min. FAD = Free Air Deliverly

22 AIR REQUIREMENT

23 AIR REQUIREMENT

24 AIR REQUIREMENT

25 LABORATORY OUTLET USE FACTOR

26 SLOPE DOWN AND TAP FROM TOP

27 LAYOUT A C B D

28 4. PIPING SIZING ESTABLISH THE PIPE LAYOUT DETERMINE THE LONGEST RUNDETERMINE THE EQUIVALENT LENGTH (150% OF THE ACTUAL LENGTH IS PRACTICAL) ALLOW PRESSURE TO DROP UP TO 10% VELOCITY OF AIR SHOULD BE LESS THAN 6 M/S

29 PRESSURE DROP Qc in litre per second (FAD) l in metre d in mm.p in bar (absolute)

30 PRESSURE DROP CHART P-drop (bar/100m) AIR FLOW RATE (LPS – FAD)

31 PRESSURE DROP AND PIPE SIZEEXAMPLE

32 PRESSURE DROP IN FITTINGS

33 PRESSURE DROP IN FITTINGS

34 INLET PIPE SIZE

35 SIZING THE RECEIVER 20 l/kW10S of compressor capacity for constant load 20S of compressor capacity for fluctuated load

36 EXAMPLE

37 FINAL NOTES 1. DESIGN PROCESS START FROM THE END USEREND USER REQUIREMENT SOURCE PIPING SYSTEM 2. SOME SYSTEM ARE NOT INCLUDED SUCH AS FIRE FIGHTING SYSTEM (SEE EIT STANDARD) HIGH PRESSURE STEAM OIL PIPELINE MUNICIPALITY WATER DISTRIBUTION NETWORK 3. PIPING SYSTEM COST 7-8% OF A CONSTRUCTION PROJECT OPERATING COST IS MUCH MORE DO NOT UNDERSIZE THE PIPE