is 10431 (1994): measurement of air flow of compressors ... · is 10431 : 1994 6.4 the minimum...

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है”ह”ह

IS 10431 (1994): Measurement of air flow of compressors andexhausters by nozzles [MED 22: Compressor, Blowers andExhausters]

Indian Standard

MEASUREMENTOFAIR FLOW OF COMPRESSORS AND EXHAUSTERSBY NOZZLES

( First Revision / Fi 1st Reprint JUNE 1996

UDC 621.51 : 621.639 : 621.647.31 : 533-6

0 BIS 1994

BUREAU OF INDIAN STANDARD~S MANAK RHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

September 1994 Price Croop 8

Compressors, Blowers and Exhausters Sectional Committee, HMD 22

.

FOREWORD

This Indian Standard ( First Revision ) was adopted by the Bureau of Indian Standards, after the draft finalized by the Compressors, Blowers and Exhausters Sectional Committee had been approved by the Heavy Mechanical Engineering Division Council.

The accurate measurement of the air flow of the compressors and exhausters form the basis for the rating and specific power consumption of the air compressor which in turn are the deciding factors for the selection of a particular air compressor unit.

This Indian Standard was first published in 1982 and had superseded IS 5538 [ Part 1 ) : 1969 ‘Measure- ment of air flow of compressors and exhausters : Part 1 Nozzles’. The standard flow nozzles included in this standard were the ISA 1932 nozzles conforming to the general recommendatiang made in ISO/R 541 : 1967 ‘Measurement of safety flow by means of orifice plates and noezles’ issued by the Interna- tional Organization for Standardization ( IS0 ). IS 5538 ( Part 2 ) : 1969 ‘Measurement of the air flow compressors and exhausters : Part 2 Orifice plate’ was also withdrawn and it was considered to formulate a separate standard for the measurement of air flow by the crifice plates. Later on the Sectional Committee, decided that there was no need to have a separate standard for the measurement of air flow by the orifice plates as this system was not being followed presently.

In this revision considerable assistance has been taken from the following IS0 Specifications:

IS0 1217 : 1986 (E) Displacement compressors - Acceptance tests IS0 5 1674 m: 1991 (E) Measurement of fluid flow by means of pressure differential devices : Part 1

Orifice plates, nozzles and venturi tubes inserted in circular cross-section conduits running full

In this revision, following important modifications have been made:

9 ii)

iii)

iv)

v) vi)

Arrangement of the test equipments; Nozzle sizes of 6, 10 and 16 mm included for measurement of air capacity below 60 ms/h;

The diamensions for the nozzles;

The diamensions of the flow nozzle arrangements;

The table for flow coefficient for ISA 1932 nozzles; and

Equation for the free air delivery alongwith sample calculation given in Annex B.

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded ofi in accordance with IS 2 : 1960 -Rules for rounding off numerical values ( revised)‘. The number of significant places retained in the rounded off value shal! be the same as that of the specified value in this standard.

Is 10431: 1994

Indian Standard

MEASUREMENT OF AIR FLOW OF COMPRESSORS AND EXHAUSTERS BY NOZZLES

( First Revision)

This standard prescribes a method of measurement of air flow and free air delivery of positive displacement compressors and exhausters, both reciprocating and rotary types.

1.1 This standard deals with measurement of air flow by using standard flow nozzle in order to obtain consistent and generally acceptable results, within a specified tolerance.

1 SCOPE 3.1.3 Relative Humidity

It is the ratio of actua~l vapour pressure and the saturated .vapour pressure ( diamensionless ).

3.1.4 Specific Humidity

It is the ratio of the mass of water vapour to the ( kg/kg of dry

1.2 This standarddoes not deal with the compressors, giving a pressure rise of less than 0.01 MPa and greater than 6 MPa.

total mass of moist air sample air + associated water vapour ).

3.2 Unless otherwise specified, symbols shall be used:

the following

Unit

2 REFERENCES

2.1 The following Indian Standards are necessary adjuncts to this standard:

Roman Letters

B

d

Description

Barometer reading Orifice diameter of the measuring device at operating conditions Internal diameter of measuring pipe at operating conditions

Mass flow rate

bar m

IS No.

1821 : 1987

3601 : 1984

3624 : 1987

5456 : 1985

5727 : 1981

Title

Dimensions for clearance holes for bolts and screws ( third revision )

Steel tubes for mechanical and general engineering purposes (first revision )

Pressure and vacuum gauges ( second revision )

Code of practice for testing of positive displacement type air compressors and exhausters (first revision )

Glossary of terms relating to compressors and exhausters (first revision )

3 TERMINOLOGY AND SYMBOLS

3.1 For the purpose of this standard, in addition to the followlng, the definitions as given in IS 5727 : 1981 shall apply.

3.1.1 Absolute Humidity

It is the ratio of the mass of water vapour to the total volume of sample ( kg/m8 ).

3.1.2 Humidity Ratio

It is the ratio of the mass of water vapour and the mass of dry air contained in the sample ( kg/kg of dry air ).

D

G

h

k

l

P P

4 r

R

m

kg/s

s-1

kW

bar

bar

ms/s Dimensionless

J/kg.K Dimensionless

Height of liquid column

Roughness value Shaft speed Power

Pressure, gauge Pressure, absolute Volume flow rate

Pressure ratio

Gas constant Reynold’s number ( Referred to pipe dia D )

Temperature Thermodynamic temperature, absolute temperature Exponent for polytropic process Velocity Volume Condensate Humidity ratio

mm

“C K

Dimensionless

m/s ms

kg/h kg/kg of dry gas

1

IS 10431: 1994

Greek Description Unit Letters

a ( Alpha ) Flow coefficient Dimensionless

B ( Beta ) Diameter ratio Dimensionless ( w 1

s ( Epsilon )

r(Mu) P ( Rho ) 7 ( Tau )

9 ( Phi )

x ( Chi )

A ( Lamda )

subscripts

0 Z

2

3

4

a av

C

m Max Min

V

W

Expansion factor Dimensionless

Dynamic viscosity Pa.S

Mass density kg/m3 Tolerance Dimensionless

Relative humidity Dimensionless ( Fraction ) Differential pres- Dimensionless sure ratio Friction factor Dimensionless

MeanSg

Refers to ambient condition Refers to condition at standard inlet point Refers to condition at standard discharge point

Refers to condition at upstream of measuring device Refers to condition at downstream of measuring device

Refers to air Refers to average value

Refers to contract value Refers to measured value Refers to maximum value Refers to minimum value Refers to vapour Refers to water.

4 PRE-TEST CHECXS

4.1 Preliminary Checks

It is recommended that a preliminary check be made of the test arrangements and instruments to ensure their proper working

4.2 General Conditions for Conducting Tests

The general conditions for conducting tests shall be according to IS 5456 : 1985.

4.3 Precautions

The precautions, while conducting tests, shall be taken according to IS 5456 : 1985.

4.4 Initial calibration of the instruments shall be available prior to the test. Recalibration after the test shall be made for those instruments of primary importance which are liable to variations in their calibration as a result of use during a test.

4.5 Only those observations and measurements need be made which apply and are necessary to attain the object of the test. Instrument indica- tions or readings shall be recorded as observed. Corrections and corrected values shall be ente- red separately in the test record. The test shall be reported in the prescribed form.

5 MEASURING INSTRUMENTS

The instruments and apparatus for measurement of air flow and free air delivered by compressors are iucluded in the following list:

a) Barometer - Fortin type

b) Thermometers or thermocouples and associated instruments

c) Pressure gauges or manometers d) Differential pres’sure gauges or manome-

ters

e) Standard nozzle, and f) Psychrometer - Sling type. ~

6 ARRANGEMENT OF TEST EQUIPMENT

6.1 The arrangement of test equipment and measuring device usually conform to Fig. 1 to 3. These arrangements are intended to accommodate different compressor types and operating conditions:

a)

W

6.2 A

The arrangements of Fig. 1 and 2 shall be used for air compressors where the discharge pressure is sufficient to provide throttling as required ( see 6.3 ) and where the-air compressed may be dischar- ged to the atmosphere.

The arrangement of Fig. 3 shall be used for vacuum pumps, or exhausters, where the inlet pressure is low enough to provide throttling as requir-ed in 6.3 and where the test may be made on atr.

receiver and a throttle valve arrangement _ _ ~- shall be used between the standaid flow nozzle and the compressor. It necessary, a by pass valve across the throttle valve may be used to control the receiver pressure accurately.

The schematic arrangement of this apparatus is illustrated in Fig. 1 to 3.

6.3 The pressure drop through the throttle valve shall be equal to or greater than twice the pressure beyond the throttle, except in the case of low pressure blowers, for which the minimum drop through the throttle shall be at least half the pressure rise ( that is, discharge pressure minus intake pressure ) through the blower, but in no case less than 0.35 bar ( gauge.).

NOTE - In case the requiremtnts laid down in 6.3 cannot be met on disCharge side, the measurements shall be taken on the suction side.

2

IS 10431 : 1994

HEAT EXCHANGER

b-P4 L FLOW STRAIGHTENkR

k - PASS

FIG. 1 SCHEMATIC DIAGRAM OF ~TESTING ARRANGEMENT FOR COMPRESSORS WITH AFTER-C• OLBR ( WHEN PROVIDED )

hPASS

FIG; 2 SCHEMATIC DIAGRAM OF TESTING ARRANGBMBNT FOR COMPRBSSORS WITHOUT AFTBR-COOLBR

PRESSURE T

D=NOT LESS

TION NOZZLE

/ DRAIN

FIG. 3 TBSTING ARRANGEMBNT FOR VACUUM PUMPS AND EXHAUSTERS

3

IS 10431 : 1994

6.4 The minimum volume of the air receiver, which is used for the test in case of reciprocating compressors shall be as given by the following formulae:

a) V, 0 40 Vc

b) V, = 100 -5 r

where

Vr = Volume of air receiver ( my ),

v, - Volume of one side of piston of last stage cylinder/cylinders ( m3 ), and

I‘ = Compression ratio of last stage

Absolute discharge pressure of last stage = Absolute intake presstire of last stage

The higher value should be taken as the minimum volume for the air receiver.

6.5 The pipe connecting the discharge end of the compressor and the air receiver shall, as far as possible, be free from bend or contraction of area which may be the source of causing 10~s of pressure.

7 STANDARD FLOW NOZZLE

7.1 Nozzle profile with dimensions shall be as shown in Table 1.

7.1.1 General Design

The part of the nozzle inside the pipe is of revolution symmetry. The nozzle comprises a convergent portion with a rounded profile and a cylindrical throat.

7.1.2 Upstream Surface

This surface may be described as under:

a) A flat portion perpendicular to the axis,

b) A convergent portion defined by two areas of a circumference, and

c) A cylindrical throat.

7.1.3 Downstream Edge of Throat

The downstream edge of the throat shall be square, with a sharp edge. The edge shall be protected from damage by a lip.

7.1.4 Throat Diameter

The throat diameter d shall be taken as the mean of the measurements of at least four diameters situated in meridian planes distributed at approximately even angles to each other.

7.1.5 Profile of Ctlrved Surface

The profile of the convergent inlet shall be checked by means of a :emplate.

two diameters of the convergent inlet in the same plane perpendicular to the axis shall not differ among themselves by more than 0.001 d.

7.1.6 Upstream Face

The surface of the upstream face shall be polish- ed so as to keep the maximum roughness, that is peak-to-valley height under lo-” d.

7.1.7 Material

Nozzles shall be made of brass, bronze, alloy, cast iron or stainless steel.

7.1.8 Dimensions and Tolerances

In case of recommended nozzle sizes, the dimensions and tolerances of the measuring device shall conform to those shown in Table 1. For any other size of nozzle, the proportions as given in Tables 1 and 2 shall be employed.

8 STANDARD FLOW NOZZLE PIPINGS ARRANGEMENT

8.1 Standard flow nozzle piping arrangement for the recommended nozzle sizes is shown in Fig. 4 and 5 with dimensions as per Table 2. 8.2 The pipe containing the standard nozzle shall :be straight and co-axial for a suitable distance before and after the nozzle as specified in 8.3 and 8.5.

8.3 The upstream distance shall be such that any disturbances of the flow have had time to subside before the measuring position is reached and the downstream distance sufficient to pre- vent any reaction being propagated back to the pressure ~difference device. Table 2 gives the dimension’s for flow nozzle arrangement shown in Fig. 4 and 5 with the straight lengths necessary for the standard nozzle on the upstream and downstream sides in terms of the internal diameter of the pipe D.

8.4 Straightener vanes with the perforated baffle plate shall be used at the upstream end of the nozzle arshown in Fig. 4.

8.5 Condition and Tolerance on Internal Diameter of Pipe

8.5.1 The inside surface of the pipe shall be clean, free from pitting and deposit and not encrusted. However, it may be either ‘smooth’ or ‘rough’.

8.5.2 The pipe shall be considered straight when it appears so on visual inspection. 8:5.3 The inside of the pipe shall be fairly circular over the entire distance of the required miaimum straight lengths shown in Fig. 4.

8.5.4 The cross section shall be considered to be circular when it appears tion, with the exception approach to .he nozzle.

so on visual inspec- of the immediate

4

. lS10431:l9!U

Table 1 Dimesions of Nozzles

( CIauses 7. I rend 7.1.8 )

All dimensions in millimetres.

DIRECTION OF

FLOW

Throat Dia d 6 10 16 22 33 50 go 125 165

To1 + O’tMtO5 d f0’0030 fO’OftS0 &0’00SO-f0’0110 &CO165 f0’0250 fOXMtJ0 fft-062. fg-0825

( 0‘75 d )

( O-604 d )

50

4’50

3’624

-

E ( 0’2 d 1 1’2

G ( 0’304 d ) 1’824

H ( 0’1 D Max ) 2’60

K ( 0‘833 d 1 4’998

R Max 2’058

Mill 1‘938

r Max 1’236

Min 1’164

ar, Min ( 0’03 d 1 0’18

nr. Max ( 0‘03 d 1 018

Tolerance on profik of - curved surface

R = 0’333 d + 0’010 d

r = 0’2 d f 0006 d

50 75

7’50 12’00

6’040 9’664

-

2’0 3’2

3’04 4‘864

2’60 4’00

8’330 13’328

3’430 5’488

3’230 5’168

2’060 3’296

1’940 3’104

0’30 0’48

0’ 30 0’48

-

f 0’08 f 0’08

100’00 10000

16’50 24’75

13’290 19’930

f 0’08 f. 0’1

4’4 6’6

5’688 10’032

5’45 5’45

1 g-326 27’490

7’546 11’319

7’106 10’659

4-532 6’798

1’268 6’402

0’66 0’99

0’66 0’99

5 0’175 f 0’175

f 0’20 f 0’25

15000 250’00

37‘50 6000

30’200 48’320

f 0’12 _t 0’12

10’0 16’0

15’20 24’32

8’25 15’43

41’650 66’640

17’150 27’400

16’150 25’800

10’300 16’480

9-700 15’520

1’50 2’40

1’50 2’40

f 0’200 f 0’250

fo-30 f 0‘40

3SoOO 415’00

93’75 123‘75

75’StM 99660

+ 0’15 fO’M

25‘00 33’0

38’000 SO-160

20’79 26’00

104‘125 137’445

42’875 56‘595

40-375 53295

25’750 33’990

24’2SO 32010

3’72 4’9s

3’75 4’9s

f 0’250 f o-2So

NOTE - The curved surface shall not depart from the nominal profile by more than the tolerances giver-in the table at any point between cylindrical throat and the upstream face of the nozzle.

l!310431:l994

Table 2 Flow Nozzle Arrangemeot

( Clauses 7.1.8, 8.1 and Fig. 4 and 5 )


d 6 10 16 22 33 50 80 125 165

0 26.0 26’0 40’0 545 54.5 82’5 154’3 207’9 2660’0

dlD

A’)

c

E

F

G

8’)

I (Recommended 1

K ( Minimum I

L ( Approx 1 M N ( Minimum 1

P ( Approx 1

P’

321 Blr)

6G6’0

33’4

38

48

80

44

50

5

I5

9

4.3

1’3

lOl26.0

33.4

38

48

80

44

50

5

IS

9

4’3

1’3

(L

NO. of bolts for ring chamber

S (Recommended 1 T ( Recommended 1 u

Y ( Recommended 1

W

B

No. of bolts for flow straightener flange

Y ( Recommended )

2 ( Recommerllkd )

I-3

La

Ls

46’

4”

1’0 1’0

2’3 2’3

6’5 6’5 -

6 6

64 64

80 80

12 12

64 64

3 3

65 6’5

4 4

2 2

I 1

130 130

I 200 1200

52 52

4’0 4’0

3’6 3’6

Ml0 MI0

Ml2 MI2

-r See IS 3601 : 1984 and clause 8.5

*r Tolerance on H shall be H7.

yrdt&r- ring

Bolts for flanges

16140’0

48‘9

70

90

130

84

90

7

20

11

5’0

2’0

f 0‘08 f 0’25 f 0’25 f 0’30 f 0’40

33154’5 50182’5 801154’3 J25/207’9 1651260’0

1’0

3’0

10’5

6

f 0’08

22154’5

60’3

80

100

170

95

100

5

23

+12

50

2’0

I5

1’0

2’5

12’0

60”

6

60’3 88’9 165’1 219’1 273

80 130 230 320 385

100 150 250 350 415

170 240 340 440 530

95 140 240 340 400

100 150 250 350 415

5 10 10 15 15

23 52 52 80 98

12 20 20 30 30

5’0 9’0 9’0 12’0 13’5

2‘0 SO 5’0 7’0 8’0

15 25 25 40 50

1 .D 1’5 1’5 2’5 3’0

2’5 5’0 8’0 11’0 12’0

12’0 14’0 15’0 15’0 19’0

60” 60” 45” 45” 30” 6 8 8 8 12

115 140 140 200 300 400 480

120 170 170 240~ 340 440 530

14 14 14 16 18 20 22

90 140 140 200 300 400 480

3 3 3 3 4 5 5

12’5 14’0 14’0 18’0 18’0 18’0 18’0

4 4 4 8 8 8 12

2 3

1 3

200 275

1200 850

80 110

5’0 5‘5

3’6 5’0

Ml0 Ml0

3 3 5 5 5

3 3

275 460’.

5 5 5

780 1 050 1 300

850 1 250 2350 3 I50 4000 110 185 315 420 525

7’0 11’0 19’0 24’5 30’0 . 5’0 5’0 7’0 7’0 7.0

Ml0 Ml2 Ml2 Ml2 Ml6

Ml2 Ml2

. a*

Ml2 Ml6 Ml6 Ml6 Ml6

q For d/DCO’CS, Q<O.O3 D, for d/D>0’65, Q lies between 0’010 to O’OZD.

‘1 See IS 1821 : 1987.

5) Thickness of perforated balIIe plus packing thickness of I mm on either side.

6

IS 10431: 1994

Table 3 ISA 1932 Nozzle Flow Coefficient a

( Note given under Table 2 )

_- _ ____~___ ___

\ ROD 2 x 10” 3 x 104 5 x 104 I x 104 1 x 105 3 x 105 1 x 106 2 x 10s P

____.- __ ___- ._

0‘30 - - - 0’990 0 0’990 8 0.991 9 0’992 3 0’992 4

0’32 - - 0’990 3 0 991 2 0’992 6 0.993 0 0 993 0

.0’34 - - - 0’990 7 0’991 8 0’993 3 0’993 8 0’993 9

0.36 - _- _- 0’991 3 0’992 5 0’994 3 0’994 8 0’994 9

0’38 - - - 0’992 2 0’993 5 0’995 4 0’996 0 0’996 1

0’40 - - - 0’993 2 0’994 7 0’996 8 0’997 4 0’997 5

0’42 - - - 0’994 6 0 996 1 0’998 3 0’999 0 0’999 I

0’44 0’980 3 0’988 1 0‘993 9 0’996 2 0.997 9 1’000 2 1’000 9 1’001 0

0’46 ( 0’981 5 0’989 6 0’995 7 0’998 2 0’999 9 1’002 4 l~‘OO3 1 1’003 2

0’48 0.983 2 0’991 7 0’998 0 1’000 5 1’002 3 I ‘004 9 1’005 7 l-005 8

0’ 50 0’985 5 0 994 2 I ‘000 7 1’003 3 1’005 2 1’007 8 1’008 6 1’008 7

0’52 0’988 4

/

0’997 3 1’003 9 1’006 6 1’008 5 1’011 2 1’012 0 1’012 1

0’54 0 992 1 ~1’001 0 1’007 7 1’010 4 1’012 3 1’015 0 1’015 8 1’016 0

0’56 0’996 6 j 1’005 5 1’012 2 1’014 8 1’016 7 1’019 4 1’020 2 1’020 4

0’58 I 1’020 0 1’021 9 1’024 5 1’025 3 1’025 4

y; i

_i:!:i / i/fZ!

1

i:Zi *

( ::;;x; 1’034 1’027 5 7 1’036 1’030 9 3 1’031 1’037 0 6 1’031 1’037 2 8

0’64 1’025 8 1’033 1 1’038 6 1’040 8 1’042 3 1’044 6 1’045 2 1’045 3

0’66 1’036 7 1’043 2 1’048 0 1’050 0 1’051 4 1.053 3 1’053 9 1’054 0

0’68 1’049 5 1’054 9 1’059 0 1’060 6 1’051 6 1’063 4 1’063 9 1’064 0

0’70 1’064 6 1’068 7 1’071 7 1’073 0 1’073 6 1’075 1 1’075 4 1’075 5

0‘72 ’ 1’082 3 1’084 7 1’086 6 1’087 9 1’088 6 I ‘088 8 I.088 9

0’74 1.103 1 1’103 6 1’104 0 i ;:;;:: 1’104 3 1’104 4 1’104 5 1‘104 5

0’76 1’1278 1 1’125 0 1’124 6 1’1240 1 1’123 6 1’123 0 1’122 9 1’122 8

0’78 1‘1572 / 1’152 S 1’148 9 1’147 5 1’146 5 1’145 1 1’144 7 1’144 6

0’80 1’192 4 1’184 3 1’178 2 1’175 7 1’174 0 1’171 5 1’170 8 1’170 6

NOTE -This table is given for convenience. It is not intended for precise interpolation.

8.5.5 Over a length of at least 0.5 D measured upstream from the upstream face of the nozzle, the pipe shall be cylindrical. The value D of the internal diameter of the pipe shall be taken as the mean of the measurements of a number of diameters situated in meridian planes at approximately even angles to each other, and in different cross sections taken over the length or O-5 D. A minimum of four diameters shall be measured.

8.5.6 The pipe shall be considered cylindrical 8.7 The standard nozzle shall be installed so when any diametet at any cross section does that the flow through it is in the proper direction not differ from the mean diameter by more than and the throat shall be concentric with the f 0.3 percent of the mean diameter. bore of the pipe.

8.5.7 The mean diameter of the downstream straight length, when considered over a length of 2 D from the upstream fat shall not differ from the .mean II

of the nozzle, iameter of the

upstream straight length by more than f 2 percent.

8.6 The ,ratio of the downstream to the upstream absolute pressure across the nozzle shall be greater than 0.75.

7

w FIRST PR;SSURE OUTLET IN THIS RING CHAMBER

ROUND RUBBER SECOND PRESSURE OUTLET IN THIS RING CHAMBER

LOW STRAIGHTENER LATE5 WELDED AT

ONVENIENT POINTS

J P$ PRESSURE TAPPING BORED

BETWEEN TWO BOLT HOLES

DETAIL OF PEZFORATION ON BAFFLE

VIEW FROM A

FIG. 4

SECTION XX


STANDARD FLOW NOZZLE ARRANGEMENT

IS 10431:1994

FIRST PRESSURE OUTLET ,

FIG. 5 ENLARGKDSECTION OFNOZZLB AND RING CHAMBER

8.8 Gaskets, rivets and weld seams shall not project into the main pipa near the point of installation.

9 PRESSURE MEASUREMENT

9.1 The upstream pressure shall be measured from static taps with two independent manometers. The taps are spaced 90” circumferentially.

9.2 Pressure below 2 bar ( absolute ) shall be measured with U-Tube manometer filled with suitable liquid. of known specific gravity. The bore of the glass tubes shall not be less than 6 mm. The manometer scales shall be accurately graduated with minimum dimensions of O-5 mm.

9.3 Pressure of i bar (absolute ) and above shall be measured by Bourdon gauges conforming to IS 3624 : 1987.

9.4 The use of Bourdon gauge or W-Tube for measurement of pressure shall be in accordance with IS 5456 : l?S5.

9.5 For measuring the differential pressure across the standard nozzles U-Tube manometers filled with suitable liquid of known specific gravity shall be used.

9.6 The diameter of the standard nozzle, when used with the flow measuring arrangement, shall be such that the Jiffe:,ential pressure is not less than 100 mm or more than I 000 mm of water.

9

9.7 If the differential pressure is varying, it is preferable to use a single-tube well-type manometer, the cross-sectional area of the well being a minimum of 100 times the cross-sectional area of the monometer tube.

9.8 Atmospheric pressure shall be~measured as given in IS 5456 : 1985.

10 TEMPERATURE MEASUREMENT

10.1 The air temperature shall be measured from two stations in the pipe located upstream of the ring chamber at a distance of 3 D. The positions of the temperature taps are shown in Fig. 4.

10.2 For pipe diameter D less than 150 mm, it is sufficient to install one temperature tap.

10.3 If the air temperature in the pipe differs from that of the surrounding atmosphere by more than 24” C, the pipe shall be thermally insulated.

10.4 When two thermometers are used their readings shall agree within 1°C.

10.5 Depending on the operating conditions or convenience, temperatures may be measured by certified thermometers or calibrated thermocouples inserted into the pipe or into wells as given in IS 5456 : 1985. The installation of the temperature measuring device directly into the

IS 10431: 1994

pipe without the addition of a well is desirable for temperatures below 150°C. Whichever mean is employed, the temperature device shall be so chosen that it can be read to within an accuracy of f 1% The average of the instrument readings at .each measuring station shall be taken as the temperature of the fluid. If discrepancies between the individual reading and the average are greater than 0.2 percent of the absolute temperature, they shall be investigated and the discrepancies eliminated.

10.6 The temperature measuring device shall extend into the pipe a distance of 100 mm, or one-third pipe of diameter D, whichever is less.

10.7 The temperature measuring device shall not be inserted into a dead space when measuring a flowing medium.

10.8 When measuring temperature with a mercury-in-glass thermometer, the instrument shall have an etched stem. Commercial metal encased thermometers are not acceptable. When the measured temperature differs from the ambient by more than 5°C and the mercury is exposed, an emergent stem correction shall be made as given in IS 5456 : 1985.

10.9 Periodic readings of wet and dry bulb temperatures shall be recorded to determine the relative humidity of the air supply at the ‘intake of the compressor during the test. These readings shall be taken with a sling psychrometer. The relative humidity shall be determined with the help of psychrometric tables. Relative humidity values as obtained from the nearest meteorologi- cal station may also be used.

11 MEASUREMENT OF FREE AIR DELIVERED

11.1 The free air delivered shall be measured by means of the standard nozzle, the profile of which is shown in Table 1. Nozzle with the upstream and downstream piping, together with the flour straightener, shall conform to Fig. 4 and 5.

11.2 The necessary data to be recorded during testing for different types of compressors, with relevant conversion factors, is given in Annex A.

11.3 The free air delivered shall be calculated as per formulae and calculations illustrated in Annex B.

12 RECOMMENDED CAPACITIES

The following sizes of-nozzles are recommended for the range of capacities indicated below:

Nozzle Size (d) Capacity mm ( mVh 1

6 3-9 10 9-30 16 27-90 22 60-170 33 130-375 50 300-950 80 750-2 DC0

125 1 800-5 500 165 3 500-10000

NOTES

1 The other nozzle sizes satisfying the requirement laid down in the standard may also be employed.

2 The above nozzle sizes are applicable only when the nozzles are-discharging to the atmosphere.

ANNEX A ( Clause 11.2 )

PROFORMA FOR RECORDING OF DATA DURING TESTING OF AIR COMPRESSORS

A-l Record of test readings during type testing of reciprocating single stage or multi stage, air cooled or water cooled, single acting or double acting air compressors.

Designation:

1. Date I

IA. Test number 2. Duration of the test 3. Diameter of nozzle

4. Number of readings \

5. Barometric pressure

6.

7. 8.

9.

10. 11.

12. 13.

14. 15A.

Ambient temperature ( Dry bulb temperature )

Wet bulb temperature Load

Discharge pressure

Temperature at suction

Pressure drop across filter Upstream absolute pressure at nozzle Differential pressure at the nozzle

Temperature at entrance to nozzle Mass of condensate in first inter-cooler

10

15B. Mass of condensate in second inter- cooler

15c. 15D. 16. 17A. 17B. 18. 19. 20. 21A. 21B. 22A. 22B. 23. 24. 25. 26. 27.

Mass of condensate in after-cooler Mass of condensate in air receiver Shaft speed Pressure at first inter-cooler Pressure at the second inter-cooler Oil pressure of compressor Temperature of compressor air Temperature after first stage Temperature after first inter-cooler Temperature after second inter-cooler Temperature after second stage Temperature after final stage Depression Relative humidity Pressure after suction Input -power

28.

29. 30. 31.

Inlet temperature of cooling water ( Jacket ) Outlet temperature of cooling water ( Jacket ) Water consumption ( Jacket ) Temperature after after-cooler Inlet temperature of cooling water in inter-cooler

32.

33. 34.

35.

36.

.Outlet temperature of cooling water . . from inter-cooler

Water consumption in inter-cooler Inlet temperature of cooling water to after-cooler Outlet temperature of cooling water from after-cooler Mass consumption in after-cooler

A-2 Record of test readings during routine testing of a reciprocattig single/multi stage air cooled or water cooled, single acting or double acting air compressor.

Designation: 1. Date 1A. Test numbet 2.’ Duration of test 3i Diameter of nozzle 4c Number of readings 5. Barometl’i pressure 6. Aybienti temperature ( Dry bulb

temperature ) 1 mm HI0 = 9.806 65 N/m* ( exact )

W$ bulb temperature 1 N/m* = 0102 mm HI0 ( approx )

,? i $id 1 N/ma 6 0.102x 10-d kgf/cm* ( approx

x ischarge pressure 1 kgf/cm* = 9,806 65 x l@ N/ma ( exact )

’ emperature at suction 1 bar = 105 N/m*

Pressure drop across fllter 1 Nm = 1 Joule

I1

7. 8. 9.

10. 11.

12. 13. 14. 15A. 15B. l-6. 17. 18. 19. 20. 21. 22. 23.

IS 10431: 1994

Upstream absolute pressure of nozzle Differential pressure Temperature at nozzle Mass of condensate in inter-cooler Mass of condensate in air receiver Shaft speed Pressure at inter-coolers Oil pressure of compressor Temperature after final stage Depression Relative humidity Pressure after suction Input power

A-3 Record of test readings during routine testing of a rotary single stage or two stage oil injected.compressor ( vane or screw type ).

-Designation:

1. Date 1A. Test number 2. 3. 4. 5. 6.

Duration of the test Diameter of nozzle Number of readings Barometric pressure Ambient temperature ( Dry bulb temperature )

7. Temperature of wet bulb thermo-

8. 9.

10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.

meter at intake Load Discharge pressure Temperature after suction ‘Pressure drop across filter Upstream absolute pressure of nozzle Differential pressure at n@zzle Temperature at entrance to nozzle Shaft speed inter stage pressure Compressor oil pressure Compressor oil temperature Discharge air temperature Pressure after suction Input power

A-4 RELEVANT CONVERSION FACTORS

IS 10431: 1994

ANhTX B ( C/nusf? 11.3 )

COMPUTATION OF TEST RESULTS

B-l STEPS ( WITH EXAMPLES ) IN THE CALCULATLON OF THE FLOW RATE ( .TYPE TEST )

B-l.1 Example

Test on a packaged oil-flooded rotary air screw compressor, two stage waster cooled driven by a directly coupled electric motor.

El.2 Basic Data

Nominal pipe size (D) : 150 mm = 0.15 m Nozzle diameter (d) : 80 mm = O-08 m

El.3 Average of Test Readings

61 No. Item Symbol Wnit Observation

1. 2.

3.

4. 5. 6. 7.

%

9. 10. 11.

12. 13. 14. 15.

16. Temperature before nozzle

17.

Date -

Test number -

Number of readings -

Duration of test -

Compressor load ~-

Ambient pressure ( barometric 1 Porn*

Ambient temperature ( dry bulb ) lam

Wet bulb remperature twm

Inlet temperature flm Absolute iolet pressure P am Absolute discharge pressure P rm Discharge temperature trm

Condensate flow rate w

Absolute pressure before the nozzle Psm Differential pressure over nozzle P*m-P4m

Irrn

Shaft speed II

min

9b bar

“C

“C

“C bar bar

“C

k&h

bar

bar

“C

mtn-’

-

01

04

60

100 I ‘05

18’2

16’6 +2

20’0 1’04

8’00 47’0

3’22

1’072

29’7 x IO-’ f0’5

21’10 +_2

2 936 +5

-

02

06

60

100 1’0.5

18’1

16’9 +2

~20’3

1’04

8’00 48’0

3’28

1’072

29.8~ 1O-J f0’5

21’10 L-2

2 936 f5

El.4

1.

ho, p(OI -0.66 .___. ( _~_.__ 1 + 0401 15 twm - - ) ( tom- t,m ) Porn Y 10vs =

P ov

18.2 = 19.11 x0-c - 0.66 ( 1 + 0~001 15 x 16.6 ) ( - 16.6 ) x 1.05 x 10-s 21.1 x 10-s

= 0.852

12

Detailed Calculations for Test No. 01

Humidity content of ‘inlet air

Relative humidity of the ambient air can either be ca!culated from W. Ferrel’s formula or from pychrometric chart.

Saturated Vapour Pressure P,, at 18*2”C = 21.1 x 10-S bar

Saturated Vapour Pressure P ‘ov at 16.6% = 191 x10-s bar

Relative Vapour Pressure~( according to W. Ferrel formula ):

IS 10431:1994

Absolute humidity content on the inlet air is:

0,622 q&,, Pm x P om il -

om -4om Ki

0.622 x 0.852 x 21.1 x 10-3 = 1.05 - 0.852 x 21.1 x 10-s

= 0.010 84 kg/kg

At 20°C the vapour pressure PI, = 23.38 x 10-s bar.

Xl, = x0,

Relative vapour pressure at the, inlet is:

o.olo 84 = 0.622 Y &m x 23.38 x 10-a 1.04 - &m_ x 23.38 x 10-3

c$,~ = 0.762

2. Approximate volume flow rate:

T 41m = ab Zdz ?L?- 2 (Psm-P,rn) (f'sm x & 1 t

4 PI, Tarn 1 Tom = 18.2 + 273.2 = 291.4 K T

T,“,

- 20.0 + 273.2 = 293.2 K

= 21.1 + 273.2 = 294.3 K

R, = 287.1 J/ kg K

R, = 461.5 J/ kg K

Assume ar = 1.000 293.2 q,m = 1 x% x 0.08’ x - 2 x 0.029 7 x 1.072 x 287.1 4

I.04 294.3

= 0.353 m3/s

3. Mass flow rate of water vapour at the inlet:

G 9jm piv lo5 4 m lV=

___-

Rv T,m

0.762 = x ( 0.023 38 x 106 ) x 0.353 461.5 x 293.2

= 0.004 65 kg/s

= 16.74 kg/h

4. Mass flow rate of water vapour at the nozzle:

Gsv = G,, - w

- 16.74 - 3.22

= 13.52 kg/h

5. Approximate mass flow of dry air at the nozzle:

Gas = ( Plm X lo5 - d,m PI,) X 4h.u

Ra Tjm = ( 1.04 x 105 - 0,762 x 0.023 38) x 0.353

287.1 x 293.2

= 0.436 kg/s

13

IS 10431:1994

6. Approximate absolute humidity content at the nozzle:

XJ Gav c Gsa x 3 600

13.52 - 0.436 x 3 600

= 0.008 6 kg/kg

7. Approximate partial pressure of the water vapour at the nozzle:

x3 x Pm ‘sv = ( 0.622 + Xs )

0.008 6 x 1.072 = ( 0.622 + 0.008 6 )

= 0014 bar

8. Approximate density of the air at the nozzle:

PS - ( Pm - Psv ) 106 + P&V x 105

4, Tam Rv Tsm

( 1.072 - 0.014 ) 105 0.014 x 106 _ 287.1 x 294.3 + 461.5 x 2943

= 1.262 kg/m3

9. Determination of the final value of:

p -_!!Er &tl - ( Psm - P,m ) 1.072-0~0297 ___ P

= --__ = P Pm 3m 1.072

0.972

0.08 = --

0.15 e 0.533

Pa 3: 0.284 4

8' - 0.080 9

E=

where

x=

E

P-

Differential pressure at nozzle Upstream pressure

29.7 x lWS = 0.022 7 1.072

1.4 for air

E - 6.960 66 x 3.5 (0.288 58 ) ( o;;;21j]1"

- 0.983 2

NOTE - Above formula is applicable only if

14

is 10431 : 1994

01. Dynamic viscosity of air:

cc - 17.2 x IO-6 ( 2g2 ) 076

= 17.2 x I 0-6

= 18.2 x 10-s Pas

41m TSrn Porn 4sm = ~m-p--g--

0.353 x 294.3 x 1.04 C 293.2 x

-- 1;072

= ~0.344 ms/s

v8 = 4 X 4sm n x D=

4 x 0.344 = aXO-15’

- 19.46 m/s

R BD = vaD PS -

P

19.46 x 0.15 x 1.262 = 18.2 x 10-s

= 2.03 x 105

a = CE

where

a = Flow coefficient

c - Discharge coefficient

C= [ 0.99 - 0.226 2 p’*r + ( O*OOO 215 - 0~001 1258 t_ 0.002 4984.7 )

= 0971 2

And D - Velocity of approach factor

So from

a=

11. Volume flow rate at the nozzle:

= ( 1 - B4 )-t = 1.043 I

the above formulae,

1.013 1

NOTE - Table 3 gives flow coefficients as a function of B and ROD for conveniena. They are not intended for precise interpolation; extrapolation is not permitted.

1.013 1 x 0983 2

0996 1

4Sm = ac +

[

2 ( Psrn - p4rn 1 l@

Ps 1 *

- 0.996 1 x -I- C

2 x ( 29.7 x 10-s

x 0*08x

) x ( 105 ) 1.26~ 3

8

= 0344 ms/s

15

12 Inlet volume flow rate:

qw %,a Pm, qom - -r,P,,

_ 0.344 x 291.4 x 1.072 294-3 x 1.05

= @348 m*/s

13. Influence of condensed water vapour:

Mass flow rate of condensate

w= 322kg/h

14.

15.

- 416 ms/h

= 0.001 ms/s

40 =4om+qw

-0_348+oM)1

c O-349 ms/s

If the test conditions deviate from contractuavalues and are within the the volume flow rate shall be adjusted for deviation in speed, polytropic pressure ratio as per Appendii D of IS 5456 : 1985.

ed limits, nent and

Tolerance calculation:

2.0 Sn ~-ssoal% ‘.

294-3

5-o 7s ------=@170/,

2936

The errors in 4 D,, A and Pa are negligible.

cI = f [ r.’ + tc* + s+ + 0.25 X ( TTS* + TAP* ) + d ]l”

= f [ I+ + OW + @tW + 0.25 x ( 0*68* + l-68’ ) + 017’ 11’1

= f MO/,

So measured volume flow rate - @349 m’/s f 1.5%

16

IS 10431 : 1994

B-l.5 Simplified Test Evaluation

1. Gas constant of wet inlet air:

R R, ow = _-.._______ ~_ _

l- 0.377 Qom +- om

Saturated vapour pressure PO, at 18*2”C = 21-l mbar

R, = 287.1 J/kg. K

@ o&II = 0.852

287.1’ R -_- “91 =

1 - 0,317 x 0.852 (

2~1.1 x 10-s --iTF-

= 288.9 J/kg. K

2. Volume flow rate at the nozzle:

Mass density of wet air at the nozzle ( change in gas constant due to condensate drainage is neglected ).

P,, x 10-G Psm - Row X Tsrn

1.072 x 105 = m>(g-

-_ 1.261 kg/m3

As calculated in detailed calculation B-1.4, expansion factor

E = 0.983 2

Dynamic viscosity of Wet air

,‘ = 18.2 x 10-e Pa.s

ReyncAd’s number

R 19.46 x 0.15 x 1.261

en = --~~ --- ~~8;j~-~o-6

= 2.03 x 105

Flow coefficient

a = 1.013 1

3. Mass flow rate at the nozzle:

43m = ac $ (I2 [ 2 (Pam- PJm) lo5 Psm Ill2

-; 1.013 1 x 0.983 2 x + x 0.08’ [ 2 x 2 970 x 1.261 11’2

= 0.433 3 kg/s

4. Mass flow rate of condensate:

w = 3.22 kg/h

= 0.000 89 kg/s

17

IS Iu431: 1994

5. Mass density of wet inlet air:

Porn x ‘Orn = R,, To,

1.05 x 105 = 288-9 x 291.4

= l-247 kg/m8

6. Inlet volume flow rate:

(lo = QSm + w

Porn

_ 0.433 3 + O*OOO 89 l-247

= 0.348 2 ms/s

The estimated volume flow rate shall then be adjusted for deviation in speed, polytropic exponent and pressure ratio as per Appendix D of IS 5456 : 1985.

18

Bureau of Indian Standards

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Review of Indian Standards

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This Indian Standard has been developed from Dot: No. HMD 22 ( 5250 )

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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