Lafarge Process Kit - Air flow rate - Pitot V2.pdf

Lafarge Process Kit - Air flow rate - Pitot V2.pdf

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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 1/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres SUMMARY 1. PURPOSE............................................................................................................................. 1 2. FIELD OF APPLICATION...................................................................................................... 1 3. PRINCIPLE ........................................................................................................................... 1 4. SAFETY................................................................................................................................. 2 5. EQUIPMENTS....................................................................................................................... 2 6. WORKING INSTRUCTIONS ................................................................................................. 3 6.1. Location of the measurement hole.................................................................................. 3 6.2. Evaluation of the number of measurement points........................................................... 5 6.3. Measurement of air flow with Pitot tube .........................................................................10 6.4. Calculation of the air flow rate........................................................................................12 1. PURPOSE Measure the air flow rate inside an air duct using the Pitot tube. 2. FIELD OF APPLICATION All LAFARGE Gypsum Division production sites. 3. PRINCIPLE Determine the average gas velocity through a pipe section using the Pitot tube. To measure relevant figures, the section of the pipe or air duct should have uniform velocity repartition and should not present any vortex zone or return flow. Furthermore the measurement is usually considered difficult when the gas velocity is lower than 5 m/s. Dynamic Pressure = Total Pressure – Static Pressure Total Pressure Static Pressure
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 2/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres Reminder: - Do not use the Pitot tube in a corrosive and dusty environment. - If the relative humidity is high, some water could jam the Pitot Tube. In this case, remove the tube and shake it. 4. SAFETY For the measurement of air flow, the technician in charge of the test must wear safety gloves. 5. EQUIPMENT Equipment recommendations Equipment Supplier Price estimation Pitot tube (ref: NPL), Length: 1000mm, Diam.: 8mm KIMO (France) 400 Euros Manometer MP 200 (datalogger) KIMO (France) 600 Euros
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 3/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres 6. WORKING INSTRUCTIONS 6.1. Location of the measurement hole The pipe section must be located on the straight part of the pipe in order to have uniform shape and a constant diameter. The location of the measurement hole has to comply with the following conditions : 1. The upstream distance should be at least equal to 5 times the hydraulic diameter (Dh). 2. The downstream distance should be at least equal to 5 times the hydraulic diameter (Dh) when the pipe outlet is not connected (stack) or when the downstream perturbations can have an important influence on the measurement. About the angled pipe, this distance is twice the hydraulic diameter from the angled pipe. 5 x Dh minimum 2 x Dh distance minimum measurement distance section 5 x Dh 5 x Dh minimum minimum distance gas gas distance When the downstream perturbation When the downstream perturbation has an important influence has a slight influence
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 4/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres Hydraulic diameter: Dh Dh : hydraulic diameter S : pipe section P : pipe perimeter P S 4 h D × = • In the case of a circular pipe which diameter is noted “D”; it is easy to verify that : D circular h D = • In the case of a rectangular pipe which length is noted “L” and width is noted “l”; it is easy to verify that : ) l L ( l . L 2 gular tan rec h D + × = • In the case of a square pipe which side is noted “L” ”; it is easy to verify that : L square h D =
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 5/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres 6.2. Evaluation of the number of measurement points Circular pipe The method to follow is the “Log-Tchebycheff method” : • “n” is the number of measurement points per radius (total number of points = 2n) • “i” appoints one measurement point (1 ≤ i ≤ 2n) diameter 'D 1st radius 2nd radius i 1 Y1 2n Yi Y2n There is n measurement points per radius and thus 2n measurement points per diameter. Those points are symmetric to each other from the center of the pipe. There’s no measurement on the center of the pipe. “Yi” is calculated as per the equation : Yi = Ci x D using the table presented here under. Due to the symmetry from the center of the pipe : Ci+ C2n+1-i = 1 n 1 st radius 2 nd radius 3 C1 = 0.0320 C2 = 0.1375 C3 = 0.3125 C6 = 0.9680 C5 = 0.8625 C4 = 0.6875 4 C1 = 0.0240 C2 = 0.1000 C3 = 0.1940 C4 = 0.3345 C1 = 0.9760 C2 = 0.9000 C3 = 0.8060 C4 = 0.6655 5 C1 = 0.0240 C2 = 0.1000 C3 = 0.1940 C4 = 0.3345 C4 = 0.3565 C1 = 0.0240 C2 = 0.1000 C3 = 0.1940 C4 = 0.3345 C4 = 0.6435
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 6/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres Example : n= 3 with a 300 mm pipe. In that case the total measurement points is 6 (Y1 to Y6). The hereunder table presents the results of calculation : 1 st radius 2 nd radius i Ci Yi (mm) i Ci Yi (mm) 1 C1 = 0.0320 10 6 C6 = 0.9680 290 2 C2 = 0.1375 41 5 C5 = 0.8625 259 3 C3 = 0.3125 94 4 C4 = 0.6875 206 D = 300 mm Y1 = 10 Y2 = 41 Y3 = 94 Y4 = 206 Y5 = 259 Y6=290 1 2 3 4 5 6
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 7/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres Rectangular pipe The equal areas are represented on the drawing here under : L/2n l/2n l n points N p o i n t s L • “N” is the number of measurement points on the length “L”. • “n” is the number of measurement points on the width “l”. The number of equal areas is : N x n The smaller distance from one measuring point to the wall is n 2 L for the length. The smaller distance from one measuring point to the wall is n 2 l for the width. The following tables are presenting some examples for the values of : N, n, n 2 L , n 2 l . For different square pipes : 1 l L = and for different rectangular pipes : 1 l L
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 8/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres For a square area 1 l L = L (m) N L/2n (cm) l (m) n l/2n (cm) 0.5 2 12.5 0.5 2 12.5 1.0 4 12.5 1.0 4 12.5 1.5 5 15.0 1.5 5 15.0 2.0 6 16.7 2.0 6 16.7 2.5 7 17.9 2.5 7 17.9 3.0 8 18.8 3.0 8 18.8 For a rectangular area 5 . 1 l L = L (m) N L/2n (cm) l (m) n l/2n (cm) 0.75 3 12.5 0.5 2 12.5 1.50 5 15.0 1.0 4 12.5 2.25 7 16.1 1.5 5 15.0 3.00 8 18.8 2.0 6 16.7 3.75 8 23.4 2.5 7 17.9 The curve here under is a resume of those results : Number of measuring points as a function of L and l 0 1 2 3 4 5 6 7 8 9 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 L or l (m) N or n
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 9/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres Example : Rectangular pipe length L = 50 cm width l = 40 cm Considering the curve here above : For the length : N = 2 For the width : n = 2 The distances between each point are presented in the table here under : L (m) 0.5 L (m) 0.4 N 2 n 2 L/2N (mm) 125 l/2n (mm) 100 The drawing for the measurement points location is the following one : 500 400 100 125 The total measurement points is : N x n = 4 x 4 = 16
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 10/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres 6.3. Measurement of air flow with Pitot tube • Connect the plastic pipe to the Pitot tube to measure the Static Pressure as shown on the attached picture. • Connect the plastic pipe to the Pitot tube to measure the Total Pressure as shown on the attached picture.
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 11/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres • Measure the Static Pressure in one location. Protect the measurement hole on the air duct with a card board. • Record the value from the display • Measure the Total Pressure. Protect the measurement hole on the air duct with card board. • Record the value from the display (averaged value (minimum integration time : 30s*, 3 values per location, the highest one is kept). • Move the Pitot tube on the section pipe according to the defined location of measurement points.**
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 12/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres * :For the Pitot tube measurement, the dynamic pressure is measured at 6 different locations per diameter and with 30seconds at least as integration time. In the following example, more than 30 seconds is not necessary as the cumulative mean is quite stable (see following chart, to be checked for each casewith the datalogger, the signal can be less stable than that sometimes). D ata / C u m u lative m ean and stand ard d eviation 30 35 40 45 50 55 60 65 70 0 20 40 60 80 100 120 140 160 180 200 Data / Cumulative mean 0 1 2 3 4 5 6 7 8 9 10 Cumulative standard deviation D ynam ic pressure C um ulative m ean C um ulative standard deviation ** : Some specific connections (with plastic electrical fittings…) can be done in order to avoid movements of the Pitot tube and to make safely the measurement :
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  Lafarge Process Kit Methods Version2 Direction Industrielle Direction Assistance des Procédés MEASUREMENT OF AIR FLOW RATE WITH PITOT TUBE Page : 13/13 Date : Dec 01, 2008 © Copyright 2006, Lafarge Plâtres All rights reserved. No part of this document may be reproduced, stored in a retrieval system, translated, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Lafarge Plâtres. CONFIDENTIAL The information contained herein is confidential and proprietary to Lafarge Plâtres. It may not be disclosed or transferred, directly or indirectly, to any third party without the explicit written permission of Lafarge Plâtres 6.4. Calculation of the air flow rate To calculate the value of the air flow, use Thermicalc software as shown below: Key in the “yellow cells” the following figures: - Dynamic pressure (calculated with Total Pressure and Static Pressure figures measured with the Pitot tube following the above test method) - Static pressure (measured with the Pitot tube following the above test method) - Dry temperature (following the method from the Lafarge Process Kit) - Wet Bulb temperature (following the method from the Lafarge Process Kit) - Diameter of the section - O2 and CO2 content (if you cannot measure those figures, do an assessment of the figures according to the location of the air flow measurement) - Atmospheric pressure (according to the location of the plant)