1. Introduction

Recently, much attention is paid to preserving the environment, and build systems that prevent pollution of the environment. Thermal power plants are one of the biggest environmental polluters. In the process of electricity production as coal combustion products occur large amounts of waste material. Transportation and disposal of fly ash and bottom ash are among the vital technological systems of each power plant that burns coal. The system of transport of fly ash and bottom ash in the thermal power plant can be: transportation by belt conveyors, transportation with dumper-trucks, hydraulic transport and pneumatic conveying [5,9].

The pneumatic transport involves the transportation powder, granular and piece of material and is based on the phenomenon that at the appropriate velocity of air in the pipeline, the solid particles are brought in the desired direction. Selection and efficiency of pneumatic transport depends of physical and chemical characteristic of the fly ash [2,11].

Compressors are mechanical devices used for raising the pressure of gas or vapour either by lowering its volume (as in the case of positive displacement machines) or by imparting to it a high kinetic energy which is converted into pressure in a diffuser (as in the case of centrifugal machines). The selection of compressors for different applications is a crucial issue in the process industry. It is usually the most expensive piece of equipment and has dominant influence on cycle efficiency. The common types of compressors used in industry are reciprocating, twin screw, single screw, centrifugal, scroll and rotary vane. In this paper is explained calculation cooling compressors. For properly system sizing ability, it is important to know the system function condition, pipe network, equipment position, and conveying medium characteristics (in this case compressed air) [3,6,10].

In this paper is presented a system of preparation and distribution of compressed instrument air to the consumer in the system of internal pneumatic transport of fly ash under the electrofilter, flues and steam air heaters and calculation cooling compressors. System of compressed air for electrofilter is an integral part of a whole, the pneumatic transport of fly ash for the silo. The quantity of fly ash shown in table 1 and list of design input data are shown in tables 2 and 3.

2. Technical description

2.1. Compressed air distribution

Compressed air is distributed by seamless steel galvanized pipelines. Distribution pipeline is oriented towards consumers, apropos to all valves on pneumatic drive which are located under electrofilter (EPS) of unit 1 and unit 2, and to the consumers in pump stations 1 and 2. In function of assigned pressure, complete pipeline is dimensioned, apropos diameters of certain sections are specified.

2.2. Compressed air consumers

Compressed air is used for manipulation and control in pneumatic transport process as well as for manipulation of pneumatic valves which are within automatic control of pneumatic transport. Locations which are supplied with compressed air: pressure vessels for pneumatic fly ash transport, air transport pipeline, armatures of ash receiver (plate gate valves), ash transport pipelines and pneumatic valves in bager station. Consumers, apropos places which are needed to be supplied with compressed air, altogether there are 226 pieces. Function of these valves is in program control of fly ash transport process which is managed by PLC. Safe operation of installation, apropos maintaining pressure in installation within limitations of minimal and maximal permissible pressure is supplied with regulation system which is located in the compressor. Compressor is in mutual automatic operation with reservoir of instrumental air where pressure should be between 6,3-7,5 bars. When pressure in reservoir drops under 7,5 bars, and reaches value of minimum permissible operation pressure pmin = 6,3 bars, automatically one compressor activates until maximal wanted pressure is not reached [4].

3. Selection of compressor for compressed air under electrofilter

* Air consumption by consumer for transmition in block 1: [Q.sub.1]= 53 [m.sup.3]/h.

* Air consumption by consumer for transmition in block 2: [Q.sub.2]= 53 [m.sup.3]/h.

* Air consumption by consumer for transmition in pump stations 1 and 2 like consumers on air preheaters and under channel of flue gases: [Q.sub.3]= 15 [m.sup.3]/h.

* Total air consumption increased for 20%: Q= 1,2 x ([Q.sub.1] + [Q.sub.2] + [Q.sub.3]) = 1,2 x 121 = 145,2 [m.sup.3]/h.

On the basis of calculated consumption of 145,2 [m.sup.3]/h compressor of firm Atlas Copco is selected:

Type: [GA15.sup.+], Capacity: 160 [m.sup.3]/h, Operation pressure: 7,5 bara, Power of electromotor: 15 kW, Noise level: 64 dB, Dimensions 1400 x 1225 x 650 [1,4].

On the base of selected compressor and according to Atlas Copco recommendation absorption dryers type CD 44 (2 piece) are chosen (Fig. 1). And on the base of experience in designing system of compressed air, instrumental air reservoir is selected, volume V = 2 [m.sup.3].

4. Calculation cooling compressors

Compressors (Fig. 2) of compressed air are water cooled, while compressors of control air are air cooled. Water for cooling of compressed air and compressors is used in secondary circuit which is closed. A water tank will be used to supply additional water should any losses of water occur during circulation. Water from primary circuit is supplied from unit 1 and flows to bager station. Circulation pump, heat exchanger and pipeline were selected in accordance with calculation.

4.1. Calculation of quantity of water for cooling of compressor and compressed air of secondary circuit

Calculation of quantity of water for cooling of compressor and compressed air of secondary circuit be calculated according to the following:

[Q.sub.uk] = 5[Q.sub.k1] + 2[Q.sub.k2] (1)

where [Q.sub.K1] = 11,5l/s = 41,4[m.sup.3]/h is quantity of water for cooling of compressor and compressed air (Q=5600[m.sup.3]/h) and [Q.sub.K2] = 4,66l/s = 16,7[m.sup.3]/h is quantity of water for cooling of compressor and compressed air (Q=940[m.sup.3]/h).

[Q.sub.uk] = 5 x 41,4 + 2 x 16,7 = 240[m.sup.3]/h

Reserve of water for one compressor is applied in above (Q=5600 [m.sup.3]/h).

4.1.1. Determining dimensions of secondary circuit pipeline of cooling water

Determining dimensions of secondary circuit pipeline of cooling water is given by:

d = [square root of [4 x [Q.sub.uk]]/[[pi] x v]], (2)

where v= 2 m/s is assumed water velocity in cooling pipeline.

d = [square root of [4 x 240]/[[pi] x 2 x 3600]] = 206mm

Nominal diameter DN 200 ([empty set]219,1 X 5,9) is selected.

4.1.2. Calculation of actual water velocity in pipeline

Actual water velocity in pipeline be calculated according to the following:

v = [4 x [Q.sub.uk]]/[[pi] x [d.sup.2.sub.p]] = 1,97m/s, (3)

where is [d.sub.p]= 219,1 - 2 x 5,9 = 207,3 mm = 0,2073 m.

Water velocity in cooling pipeline:

v = [4 x 240]/[[pi] x [0,2073.sup.2] 3600] = 1,976m/s.

4.1.3. Pipeline features and local losses

Length of pipeline is L= 60m. List of pipeline features and local losses is shown in table 4.

4.1.4. Calculation of pressure drop in secondary cooling circuit

Pressure drop in secondary cooling circuit can be determined by:

[DELTA][p.sub.u] = [DELTA]p + [DELTA][p.sub.k] + [DELTA][p.sub.i], (4)

where [DELTA]p = [DELTA][p.sub.1] + [DELTA][p.sub.2] is pressure drop in pipeline ([DELTA][p.sub.1]--pressure drop in straight pipe and [DELTA][p.sub.2]- -pressure drop due to local losses), [DELTA][p.sub.k] = 0,55 bar is pressure drop through compressors and [DELTA][p.sub.i] = 0,45 bar is pressure drop through heat exchanger.

Pressure drop in straight pipe should be calculated according to the following:

[DELTA][p.sub.1] = [lambda][L/[d.sub.p]] x [[v.sup.2]/2g], (5)

where [lambda]=0,0144+0,00947/[square root of n]=0,0211 is coefficient of air friction using Weissbach method.

[DELTA][p.sub.1] = 0,12 bar.

Pressure drop due to local losses should be calculated according to the following:

[DELTA][p.sub.2] = [[v.sup.2]/2g] x [xi], (6)

where [xi] = 25,6 is local losses and pressure drop in pipeline is given by:

[DELTA][p.sub.2] = 0,528 bar

and pressure drop in pipeline

[DELTA]p = 0,12+0,528 = 0,648 bar.

Pressure drop in secondary cooling circuit can be determined by (4):

[DELTA][p.sub.u] = 0,648 + 0,55 + 0,45 = 1,65 bar.

4.1.5. Selection of circulation pump in secondary circuit

Pump power is given by:

N = [[Q.sub.uk] x [H.sub.p] x [rho] x g]/[367 x [eta]], (7)

where [rho] = 1000 kg / [m.sup.3] is water density in secondary circulit, [eta] = 0,7 is coefficient of device usage, [Q.sub.uk]--total water flow in secondary circuit and [H.sub.p]--pump head.

Total water flow in secondary circuit can be determined by (1):

[Q.sub.uk] = 5 x 41,4 + 2 x 16,7 = 240[m.sup.3]/h,

where [Q.sub.K1] = 11,5l/s = 41,4[m.sup.3]/h is quantity of water for cooling of compressor and compressed air (Q=5600[m.sup.3]/h) and [Q.sub.K2] = 4,66l/s = 16,7[m.sup.3]/h is quantity of water for cooling of compressor and compressed air (Q=940[m.sup.3]/h).

Pump head should be calculated according to the following:

[H.sub.p] = [DELTA][p.sub.i] + [DELTA][p.sub.k] + [DELTA]p, (8)

where [DELTA][p.sub.i] = 0,45bar is pressure drop in heat excanger, [DELTA][p.sub.k] = 0,55bar is pressure drop in compressor and [DELTA]p = 0,65bar pressure drop local losses.

[H.sub.p] = 0,45 + 0,55 + 0,65 = 1,65bar

Pump power can be determined by (7):

[mathematical expression not reproducible], (9)

where [mu] = 0,9 is coefficient of device safety,

[N.sub.m] = 16,8kW.

Standard pump motor with N= 18,5 kW will be used.

The characteristics of the pump:

Firm: WILO, Type: IL150/260-18,5/4, Flow range: 216 [m.sup.3]/h, Motor power: 18,5 kW and Weight 309 kg [7].

4.2. Selection of circulation pump in primary circuit

Total water flow in primary circuit can be determined by:

[mathematical expression not reproducible], (10)

where are:

[[??].sub.dv] = 60,02l/s = 216[m.sup.3]/h--total water flow in secondary circuit,

[i.sup.ul.sub.2] = 209,34 kJ/kg (t = 50[degrees]C)--enthalpy secundary circulit water at outlet heat excanger,

[i.sup.iz.sub.2] = 167,53 kJ/kg (t = 40[degrees]C)--enthalpy secondary circulit water at outlet heat excanger,

[i.sup.ul.sub.1] = 117,37 kJ/kg (t = 28[degrees]C, p = 3,5bar)--enthalpy primary circulit water at inlet heat excanger,

[i.sup.iz.sub.1] = 142,25 kJ/kg (t = 35[degrees]C, p = 3,5 bar)--enthalpy primary circulit water at outlet heat excanger.

[mathematical expression not reproducible]

4.2.1. Determining dimensions of primary circuit pipeline of cooling water

Determining dimensions of primary circuit pipeline of cooling water is given by:

d = [square root of [4 x [[??].sub.tv]]/[[pi] x v]], (11)

where v= 2 m/s is assumed water velocity in cooling pipeline.

d = [square root of [4 x 360]/[[pi] x 2 x 3600]] = 252,3mm

Nominal diameter DN 250 ([empty set]273 X 6,3) is selected.

4.2.2. Calculation of actual water velocity in pipeline

Actual water velocity in pipeline be calculated according to the following:

v = [4 x [[??].sub.tv]]/[[pi] x [d.sup.2.sub.p]], (12)

where is [d.sub.p]= 273 - 2 x 6,3 = 260,4 mm = 0,2604 m.

v = [4 x 360]/[[pi] x [0,2604.sup.2] x 3600] = 1,88m/s.

4.2.3. Pipeline features and local losses

Length of pipeline is L= 700m. List of pipeline features and local losses is shown in table 5.

4.2.4. Calculation of pressure drop in primary cooling circuit

Pressure drop in straight pipe should be calculated according to the following (5):

[DELTA][p.sub.1] = 1,02bar

where [lambda]=0,0144+0,00947/[square root of v] =0,0211 is coefficient of air friction using Weissbach method.

Pressure drop due to local losses should be calculated according to the following (6):

[DELTA][p.sub.2] = 0,3bar,

where [xi] = 16,7 is local losses and pressure drop in pipeline should be calculated according to the following:

[DELTA]p = 1,02 + 0,3 = 1,32 bar.

Pressure drop in secondary cooling circuit can be determined by (4):

[DELTA][p.sub.u] = 1,32 + 0,55 + 0,45 = 2,32 bar,

where [DELTA][p.sub.k] = 0,55 bar is pressure drop through compressors and [DELTA][p.sub.i] = 0,45 bar is pressure drop through heat exchanger.

4.2.5. Selection of circulation pump in primary circuit

Pump power is given by:

N = [[[??].sub.tv] x [H.sub.p] x [rho] x g]/[367 x [eta]], (13)

where [rho] = 1000kg/[m.sup.3] is water density in secondary circuit, [eta] = 0,7 is coefficient of device usage, [H.sub.p]--pump head and [mathematical expression not reproducible]--total water flow in primary circuit (99l/s = 360[m.sup.3]/h).

Pump head should be calculated according to the following (8):

[H.sub.p] = 0,45 + 0,55 + 1,32 = 2,32bar,

where [DELTA][p.sub.i] = 0,45bar is pressure drop in heat exchanger, [DELTA][p.sub.k] = 0,55bar is pressure drop in compressor and [DELTA]p = 1,32bar pressure drop local losses.

Pump power can be determined by (13):

N = [360 x 2,32 x 1 x 9,81]/[367 x 0,7] = 31kW,

and

[N.sub.m] = 31/0,9 = 35kW,

where [mu] = 0,9 is coefficient of device safety.

Standard pump motor with N = 45 kW will be used.

The characteristics of the pump: Firm: WILO, Type: IL200/320-45/4, Flow range: 360 [m.sup.3]/h, Motor power: 45 kW and Weight: 512 kg [7].

4.3. Calculation of area heat exchange

4.3.1. Characteristics of water in secondary circuit

[p.sub.1] = 100 kPa--water pressure in secondary circuit,

[t.sup.ul.sub.2] = 50[degrees]C--inlet water temperature in secondary circuit exchanger,

[t.sup.iz.sub.2] = 40[degrees]C--outlet water temperature in secondary circuit exchanger and

[[??].sub.tv], = 66l/s--mass flow of water.

4.3.2. Water performance in primary circulit

[p.sub.2] = 3,5 bar = 350 kPa--pressure water of primary circulit,

[t.sup.ul.sub.1] = 28[degrees]C--inlet temperature water in heat exchanger primary circulit and

[t.sup.iz.sub.1] = 35 [degrees]C--outlet temperature water in heat exchanger primary circulit.

4.3.3. Heat quantity which recive primary circulit water

Heat quantity which give in secondary circulit water be calculated according to the following:

[Q.sub.d] = [[??].sub.tv] ([i.sup.ul.sub.2] - [i.sup.iz.sub.2]) (14)

where are:

[i.sup.ul.sub.2] = 209,34 kJ/kg (t = 50[degrees]C)--enthalpy secundary circulit water at outlet heat excanger,

[i.sup.iz.sub.2] = 167,53 kJ/kg (t = 40[degrees]C)--enthalpy secondary circulit water at outlet heat excanger and

[Q.sub.d] = 66 (209,34 - 167,53) = 2759,46 kW.

Heat quantity which recive primary circulit water be calculated according to the following:

[Q.sub.tv] = [eta] x [Q.sub.d], (15)

where [eta]=0,985 is coefficient of used heating.

[Q.sub.tv] = 2759,46 x 0,985 = 2718kW

4.3.4. Calculation of area heat exchange

Flow of technological wather through heat exchanger can be determined by:

[mathematical expression not reproducible]. (16)

Area of heat exchange is given by:

[A.sub.tv] = [[Q.sub.tv] x K]/[DELTA][T.sub.log], (17)

where [Q.sub.tv] is heat quantity which recive primary circulit water (tehnical water), K =1/R is coefficient of resistance of heat passage, R = 4,5 W[m.sup.2]/K is resistance of heat passage and [DELTA][T.sub.log] is middle logarithmic temperature.

Middle logarithmic temperature be calculated according to the following:

[mathematical expression not reproducible], (18)

[mathematical expression not reproducible]. (19)

Area of heat exchange should be calculated according to the following (17):

[mathematical expression not reproducible]

The characteristics of the plate heat exchanger: Firm: Alfa Laval, Test pressure: 13 bar, Design pressure: 10 bar, Min. temperature: 0 [degrees]C, Netweight: 941 kg and Operating weight: 1117 kg [8].

5. Conclusion

The selection of compressors for different applications is a crucial issue in the process industry. It is usually the most expensive piece of equipment and has dominant influence on cycle efficiency. In this paper is presented a system of preparation and distribution of compressed instrument air to the consumer in the system of internal pneumatic transport of fly ash under the electrofilter, flues and steam air heaters and calculation cooling compressors. System of compressed air for electrofilter is an integral part of a whole, the pneumatic transport of fly ash for the silo.

Compressed air is distributed by seamless steel galvanized pipelines. Distribution pipeline is oriented towards consumers, apropos to all valves on pneumatic drive which are located under electrofilter (EPS) of unit 1 and unit 2, and to the consumers in pump stations 1 and 2. In function of assigned pressure, complete pipeline is dimensioned, apropos diameters of certain sections are specified.

Compressed air is used for manipulation and control in pneumatic transport process as well as for manipulation of pneumatic valves which are within automatic control of pneumatic transport. Locations which are supplied with compressed air: pressure vessels for pneumatic fy ash transport, air transport pipeline, armatures of ash receiver (plate gate valves), ash transport pipelines and pneumatic valves in bager station. Consumers, apropos places which are needed to be supplied with compressed air, altogether there are 226 pieces. Function of these valves is in program control of fly ash transport process which is managed by PLC. Safe operation of installation, apropos maintaining pressure in installation within limitations of minimal and maximal permissible pressure is supplied with regulation system which is located in the compressor. Compressor is in mutual automatic operation with reservoir of instrumental air where pressure should be between 6,3-7,5 bars. When pressure in reservoir drops under 7,5 bars, and reaches value of minimum permissible operation pressure [p.sub.min] = 6,3 bars, automatically one compressor activates until maximal wanted pressure is not reached.

Selection of compressor for compressed air under electrofilter: air consumption by consumer for transmition in block 1 : [Q.sub.1]= 53 [m.sup.3]/h, air consumption by consumer for transmition in block 2: [Q.sub.2]= 53 [m.sup.3]/h, air consumption by consumer for transmition in pump stations 1 and 2 like consumers on air preheaters and under channel of flue gases: [Q.sub.3]= 15 [m.sup.3]/h and total air consumption increased for 20% : Q= 1,2 x ([Q.sub.1] + [Q.sub.2] + [Q.sub.3]) = 1,2 x 121 = 145,2 [m.sup.3]/h.

On the basis of calculated consumption of 145,2 [m.sup.3]/h compressor of firm Atlas Copco is selected: Type: [GA15.sup.+], Capacity: 160 [m.sup.3]/h, Operation pressure: 7,5 bara, Power of electromotor: 15 kW, Noise level: 64 dB, Dimensions 1400 x 1225 x 650. On the base of selected compressor and accrding to Atlas Copco recommendation absorption dryers type CD 44 (2 piece) are chosen. And on the base of experience in designing system of compressed air, instrumental air reservoir is selected, volume V = 2 [m.sup.3].

Compressors of compressed air are water cooled, while compressors of control air are air cooled. Water for cooling of compresed air and compressors is used in secondary circuit which is closed. A water tank will be used to supply additional water should any losses of water occur during circulation. Water from primary circuit is supplied from unit 1 and flows to bager station. Circulation pump, heat exchanger and pipeline were selected in accordance with calculation.

In this paper is explained calculation cooling compressors. Cooling of compressors is going to be done in two cycles. In first cycle technological water circulates by pumps of first cycle. In second cycle "demi" water will circulate and cooled compressors and coolers of compressed air and also will be drived by pumps. Possible water lost through cooling process will be refunded from additional water tank which is connect with supplying water pipe line for cooling. Selection of circulation pump in secondary circuit (the characteristics of the pump): Firm: WILO, Type: IL150/260-18,5/4, Flow range: 216 [m.sup.3]/h, Motor power: 18,5 kW and Weight 309 kg and selection of circulation pump in primary circuit: Firm: WILO, Type: IL200/320-45/4, Flow range: 360 [m.sup.3]/h, Motor power: 45 kW and Weight: 512 kg. The characteristics of the plate heat exchanger: Firm: Alfa Laval, Test pressure: 13 bar, Design pressure: 10 bar, Min. temperature: 0 [degrees]C, Netweight: 941 kg and Operating weight: 1117 kg. Optimized operation of the compressor is becoming increasingly important, especially for larger systems of compressed air depending on the industry. As the production rate in plants grow with plant development, the operating conditions of the compressor will change. It is therefore important that the compressed air supply system is based both on the current needs, and the needs in the future.

DOI: 10.2507/27th.daaam.proceedings.030

6. References

[1] Atlas Copco Airpower NV, (2015), Compressed Air Manual 8th edition, Belgium, ISBN 9789081535809

[2] Bloch, H. P., (2006), Compressors and Modern Process Applications, John Wiley & Sons, Hoboken, New Jersey, ISBN 0-471-72792-X

[3] Bloch, H. P., (2006), A Practical Guide to Compressor Technology, 2nd Ed., John Wiley & Sons, Hoboken, New Jersey, ISBN 0-471-727930-8

[4] Hadziahmetovic, H., Dzaferovic, E., Hodzic, N., (2012), System of compressed air for electrofilrer in thermal power plant, Annals of DAAAM for 2012 & Proceedings of the 23rd International DAAAM Symposium, Volume 23, No. 1, ISSN 2304-1382, ISBN 978-3-901509-91-9, Ed. B. Katalinic, Published by DAAAM International, Vienna, Austria

[5] Mills D., (2004), Pneumatic Conveying Design Guide, Second Edition, Butterworth-Heinemann, ISBN 0750654716, UK.

[6] Seshaiah, N.,(2006), Experimental and Computational Studies on Oil Injected Twin-Screw Compressor, Doctoral Thesis submitted to National Institute of Technology, Rourkela

[7] Wilo Product Catalog (2014), Pumps and systems for Building Services, Water Management, and Groundwater, Dortmund, Germany

[8] http://doc.texnikoi.gr/ylikadata/rtfs/laval4.pdf (2016), Alfa Laval plate heat exchangers, A product catalogue for comfort heating and cooling

[9] Hadziahmetovic, H. & Dzaferovic, E., (2009), Ash pneumatic conveying from existing silos no. 4 to two new silos and ash loading in autocisterns--The 20th INTERNATIONAL DAAAM SYMPOSIUM "Intelligent Manufacturing & Automation: Theory, Practice & Education", 25-28th November 2009, Vienna, Austria

[10] Bogovic, I-N., Barisic, B., Katalinic, B., Krsulja, M., Car, Z.,(2011), Digitizing system ATOS--measuring turbo compressor housing, Annals of DAAAM for 2011 & PROCEEDINGS of the 22nd International DAAAM Symposium / Katalinic, Branko (ur.).--Vienna : DAAAM International Vienna, 2011. 1367-1368 (ISBN: 978-3-901509-83-4)

[11] Bibire L., Ghenadi A., Topliceanu L., (2011), Maintenance -Reliability Duality For A 40 Bars Compressor From A Pet Bottling Line, The 22nd DAAAM World Symposium "Intelligent Manufacturing & Automation: Power of Knowledge and Creativity", Vienna, 23-26th November 2011, ISBN 978-3-901509-83- 4, ISSN 1726-9679, pag. 0029-0030

This Publication has to be referred as: Hadziahmetovic, H[alima] (2016). Calculation Cooling Compressors, Proceedings of the 27th DAAAM International Symposium, pp.0203-0212, B. Katalinic (Ed.), Published by DAAAM International, ISBN 978-3-902734-08-2, ISSN 1726-9679, Vienna, Austria

Caption: Fig 1. Compressor

Caption: Fig 2. Compressors

Table 1. The quantity of ash produced by one unit

            Input data                     Value

             Fly ash:                 165 - 232,2 t/h

   Ash from boiler hoppers and        14,0 - 17,8 t/h
   air preheater hopper: (this
  ash is included in the sum for
             fly ash)

Table 2. Design data

            Input data                    Value

     Bulk density of fly ash         0,74 t/[m.sup.3]
      Specific mass density         2,22 g/[cm.sup.3]

Table 3. Capacity data of the system

            Input data                      Value

      Long distance fly ash      260 t/h per unit (including
       pneumatic conveying               15% reserve)

Table 4. pipeline features and local losses

      Pipeline features                Local losses

 10 elbows 90[degrees] R= 3D           10 x 0,5 = 5
 10 elbows 45[degrees] R= 3D           10 x 0,5 = 5
          20 valves                   20 x 0,6 = 12
         6 T- pieces                  6 x 0,6 = 3,6
                                  [summation][xi] = 25,6

Table 5. Pipeline features and local losses

      Pipeline features                Local losses

 15 elbows 90[degrees] R= 3D          15 x 0,5 = 7,5
  2 elbows 45[degrees] R= 3D           2 x 0,5 = 1
  2 elbows 30[degrees] R= 3D           2 x 0,5 = 1
           6 valves                   6 x 0,6 = 3,6
         6 T- pieces                  6 x 0,6 = 3,6
                                  [summation][xi] = 16,7