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Ind ian S tanda rdSPEC IF ICAT ION FOR

ELECTRIC AXIAL FLOW FANS( First Revision)

UDe 621'638'34

< I > Copyright 1988BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002Gr 6

IS : 3588 - 1987( Reaffirmed 1999 )

D e ce m be r 1 9 38

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IS: 35881981

Indian StandardSPECIFICATION FORELECTRIC AXIAL FLOW FANS

( F irst R evisio n)O . FOREWORD

0.1 This Indian Standard (First Revision) wasadopted by the Bureau of Indian Standards on27 August 1987, after the draft finalized by theElectric Fans Sectional Committee had beenapproved by the Electrotechnical DivisionCouncil.0.2 The axial flow fans covered by this standardare capable of working against pressures and aredistinct from the table, ceiling or pedestal typefans which also are considered to be axial flowfans. The main difference between these two isthat latter category works under free flow condi-tions and the pressure developed is very low, ofthe order of 0'5 mmH,Q.0.3 This standard was originally published in1966. The present revision has been undertakento take into account the experience gained sincethen and to align some of the safety requirements

with the provisions of IS: 302-1979*. The amend-ments issued to the previous edition of the stand-ard have also been incorporated, to the extentapplicable.0.4 In preparing this standard, some assistancehas been drawn from BS 848: Part 1 ; 1980'Fans for general purposes: Part IMethods oftesting performance', issued by the British Stand-ards Institution.0.5 For the purpose of deciding whether a parti-cular requirement of this standard is compliedwith, the final value, observed or calculated,expressing the result of a test, shall be roundedoff in accordance with IS : 2-1960t. The numberof significant places retained in the rounded offvalue should be the same as that of the specifiedvalue in this standard.

General and safety requirements for household andsimilar electrical appliances (fifth r dv is io n ) .tRule!l for rounding ofI'numerical values ( re vise d ).

1. SCOPE1.1 This standard covers the requirements andtests for axial flow fans having impellers directlycoupled to the shaft of electric motors or in-directly driven by electric motors. In the case ofindirectly driven fans, the electric motor shallconform to the relevant Indian standard.1.2 The fans for use under free flow conditionsare excluded from the scope of this standard.1.3 Axial flow fans for use in mines and hazard-ous atmospheres may require additional require-ments to be met, not covered by this standard.2. TERMINOLOGY2.0 For the purpose of this standard, the follow-ing definitions, in addition to those given in IS :1885 ( Part 55 )-1981 * shall apply.2.1 Axial Flow Fan - A fan having a cylindri-cal casing inwhich the air enters and leaves theimpeller in a direction substantially parallel to itsaxis.

"'Electl'otechnical vocabulary: Part 55 Electric fans.

2.2 Fall - A rotary machine which maintains acontinuous flow of air at a pressure ratio notnormally exceeding 1.3.2.3 Air - The term air has been used as anabbreviation for 'ai_r.or any other gas' exceptwhere referred to as 'atmospheric air'.2.4 Stalldard Air - Atmospheric air having aspecific weight of 1'2 kg/mll which is dry air at2000 and 50 percent relative humidity with abarometeric pressure of 760 mm Hg.2.5 Multi-Stage Fan - A fan having two ormore impellers working in series.2.6 Wet Volume - The volume per unit timeentering the fan ( Qv ) expressed in mS/h.2.7 Air Power (Total) - That part of theenergy, per unit time, imparted by the fan to theair in increasing its total pressure from that at theinlet to that at the outlet.2.8 Air Power ( Static) - This is equal to theair power ( total ) less the nominal kinetic energyper unit time at the outlet.

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IS : 3588 19872.9 IDlpeUer Power - The energy input perunit time to the fan impeller.2.10 Shaft Power - The energy input per unittime to the fan shaft including the power absorbedby such parts of the transmission system as con-stitute an integral part of the fan, for example,fan shaft bearings.2.11 Fan Duty (Total) - The inlet volumedealt with by the fan at the stated fan totalpressure.2.12 Fan Duty (Statie) - The inlet volumedealt with by the fan at a stated fan staticpressure.2.13 Net Fan Total Efficiency - The ratio ofthe air power ( total) to the impeller power.2.14 Net Fan Statie Efficiency - The ratio ofthe air power ( static) to the impeller power.2.15 Fan Total Efficiency - The ratio of theair power ( total) to the shaft power.2.16 Fan Static Efficiency ~ The ratio of theair power ( static) to the shaft power.2.17 Side Tube or Statie Pressure Tube - Atube which allows air to flow without disturbance,past one or more small orifices having their axisat right angles to the direction of air stream inwhich it is placed.2.18 Side Tapping or Static Pressure Tapp-ing - A small opening in the wall of an airwary,having its axis at right angles to the wall and soconstructed as to allow the air to flow past with-out disturbance.2.19 Facing Tube or Total Pressure Tube -An open ended tube, the axis of which is coinci-dent with the direction of the air stream in whichit is placed, the open end facing upstream, that is,against the direction of flow.2.20 Pitot Tube - A combination of side tubeand facing tube as one unit.2.21 Cooling Air TeDlperature - The tern-perature of the surrounding atmosphere in whichthe fan operates.2.22 Type Tests - Tests carried out to prove

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6.7 Protective Measures - An earthing termi-nal of adequate current-carrying capacity con-veniently located and easily accessible shall beprovided. In the cese of fans for use on three-pha5e~ two separate earthing terminals shall beprovided.7" GENERAL AND SAFETY REQ,UIRE ..

MENTS ... .. __ .._ ..,... COl" __ .. T_~I.J. rrOl:ecl:u.u~ agaJ.D.Sl: .oJ.e4;:l:r~c.,n04;:H;- 111

the assembled fan, Jive parts shall not be accessi-ble to the standard test finger (see IS : 1401-1970* ). This requirement is applicable for allpositions in the normal use.7.2 Electric Insulation - Wben measuredaccording to the method specified in 10.5, theinsulation resistance shall be not less than 2 Mi.l.7.2.1 Leakage Current - Requirements of rele-vant Indian standards on motors shall apply,

The leakage current which may flow from the1;~1"'" ......' J : . . tC J . . . n 1-hA ~""""A..n::!a",l~ T'l'CllT+a . t: lI 'n r l . ., ., . .. .. e l fn.;l nn_ . . _ , . Y t ', .. . ., . . . ,,; :J ~ '- " '" - "" '''- '~ ''':' '''''''' ''''''- ' t" "' _ ~. -""'"external insulating material connected togethershall not exceed 300 p.A ( peak )! that is 210 p.A( rms ).7.2.2 There shall be no breakdown of the

insulation when the fan is subjected to highvoltage test as given in 10.3 or flash test ( 10.4 ),as the case may be.7.3 Insulating Materials - Windings of fansand regulators ( where provided) shall be insula-ted with either Class A, Class E or Class Binsulating materials which comply with the limitsof temperature-rise specified in 7.4. These insulat-ing materials are detailed in IS : 1271-1985t.7.4 Temperature-Rise - The fan motor shallbe tested at any cooling air temperature notexceeding 40"C, but whatever may be the valueof this temperature, the permissible temperature-rise when measured as described in iO.i4.2 shallnot exceed the limits given in Tab1e 1.

* Specification for accessibility test probes (firstr ev j$ i~ n ) .tTberma! evaluation and classification of electricalinsulation ( fi r st r ev is io n ).

IS 13588 .19817.5 Finish - All the surfaces of the assemblyand mechanism of both fan and regulator, if any,shall be of corrosion resisting material or shall besuitably and durably protected against corrosion.7.6 Speed Regulators7.6.1 It is not usual for fans covered by this

specification to be provided with regulators.However, if regulators are required, this shall be..... TYk .::._ ...... r ~ . . ,. .. .. . ..a..........."''t- .:..t-'t.lr~~1"1 ' the. r..1I1- ....r-ho::l;oPI" o:!I .nAaJ.J.JUI- .l. 'LI.L "51.~....l.L.L._..i.J.Lo v...... '--"L f, . " . y"-"''''-'-'..L'' ................._ ............the supplier.7..6.2 Enclosure - Enclosures of the fan regula-

tors shall either be of the ventilated type or thetotally-enclosed type.7.6.3 Where a regulator is provided with a

capacitor not permanently connected across themotor terminals, provision shall be made for thecapacitor to be discharged when the regulator isin the '011" position.7.6.4 The regulator handle or knob shall eitherbe of insulating material Or of metal. Ifof metal,

it shall be adequately insulated electrically andth ..r-mall v. All mp.tallic narts associated with it~h;li-b~-p~~t~~t~d-ir~~-a~cidental contact, - ---- -_7.6.5 The rt>.gulator handle or knob shall be so

placed that it can be safely and convenientlymanipulated with definite positioning action. Thehandle or knob shall be so designed that it doesnot become loose in use. The 'Running' and 'Off>. . . . . . . . . . . .o : . : _ ,. . . . . . ' " . . . . . ..f + - 1 - . . . : .. . . .. , . .' l : l ~ t . . . .. . .. . . . Q h - " l l l l hA ...-1;(!t-; +1 ' t . , . - ~""H4p . . . . , .. ; J o . . . .. . . .. .vJ.,L,;; .. ,. " ~ 5 1 ; . 4 ;" 'L t < " '. .. ,. . . . .. , .. .. .. .. .!- -,.". . " ' - "U 1h ' " l I < - < I . - I . . o I - " " " " T _ . . . . ._ _clearly marked and the indicator on the operatinghandle or knob shall correctly indicate the posi-tion of the regulator. -7.fij6 The mechanism of the regulator shall be

so designed as to ensure positive contact at eachrunning position. In the case of induction typeI. .,'" ________ L1 __ -'-- __ _ _ __ .L ~ __ , . .1 _regula.Ol', U; IS esserrrrar cnar nu POHIUIl ur tneinduction winding remains permanently shor t-circuited in any of the running positions,7.6.7 The regulators shall have mechanicalstODSfor the rezulator movinz contact to nrevent

ac~idental cont;:ct with the ~etallic body of theregulator in the event of forced overtravel of theknob.

TABLE! PERM!SS!!!LELI~~TTS OF TEMPERATURE-RISE( C la u se s 7.4, 10.14.2 an d 10.14.2.1 )

.:0.., . .No. n.~rn ,r......,.1I..f ....." "# "> . .. .. _ .~... .o,p,.A ._.z, J.T.._....,~VA VJloREQULATOB 4 "f"II_ .. n~__f"...~r. 'l i~4.L,J.Po. ll- .... . I. ., ,~ ,. ' -',...- _ __.o._ ,Class A Class E Class B. , . _ I t _ _ ~ _J,~A.Do-J. n.VlJ v.t!

MEASUREMENT

(I)i)

(2)Insulated windings ofmotors

T~ ___ '_" ,' :: __ T___ .t_ ..!__ T __ '1_~:__,LJ.J;~U.l.aL.l-VJ_J. .I. ..... i:lu..~I..u.u. ..L.JI.QOU.,.:U.l.V,U

(3) (4) (5}60 75 8060 75 80

(6)Change ofresistanceC!~~~:~~T~e_t~Jl1P~r~!~~e-ris~shaJ!~ot,.r~a~h suc;h

4V"llueU"\ LU~t: ." ariSKIjJ UJury I,..Uany insulating material 011 adjacent partsof the regu Iator40 40 40

H) Insulated windings, if any, of. ..pO'Ul~tnr { with ,rnnf;nnnu-z; l : ; ;mi~g-o~~y-~o~ t~ - t ) - - - -Regulator resistance unit (with

con t inuous fiifiuing OIl aLLYcontact)iii)

iv) External surface likely to be tou-ched during normal usage3

Thermometer

Thermometer

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IS : 3588 -19877.7 Starters, if provided, shall conform to therequirements of the relevant Indian standards.7.8 Silent Operation - Precautions shall betaken in the manufacture of fans and regulatorsto ensure a reasonable degree of silence at allspeeds.

NOTE1- The Deedfor specifying limits of noiselevels (acoustical) ofthe fans is recognized. However,it has not bee n found possible to specify these limits atpresent on account of:a) dependency of these limits on the actual locationof the fans,b) lack of data on the acceptable noise levels fordifferent applications, andc) lack of agreed definition ofnoise level and methodof evaluating the same.The criterion of noise level may, therefore, besubject to an agreement between the manufacturer andthe purchaser,NOTE 2 - The values of noise 1evel (acoustical)are under consideration.

8. PERFORMANCE REQ.UIREMENTS8.1 Air Delivery Test;- This test shall becarried out and computations made in accordancewith 10.13.8.2 Fan Characteristics - Fan charactersiticcurves shall be drawn after testing, consideringnot less than three test points determining a shortpart of the fan characteristic at different inletvolume flows and corresponding fan total orstatic pressure.

A system resistance line shall also be drawn,passing through the specified duty point such that

the total or static pressure varies as the square ofthe inlet volume flow ( see Fig. 1 ).The most probable operating point for the fan

shall be at the intersection of the fan characteri-stic and the system resistance line. The differencebetween the inlet volume flow at the intersectionand the specified inlet volume flow ( that is theduty point) shall be recorded as the measure ofdeparture of the fan from the specified perfor-mance. This value shall fall within the range ofspecified tolerances.

The fan characteristic may be extended to zeroinlet volume and to zero static pressure conditionsbut the portion of the characteristic which isbeyond the range specified by the supplier shallnot be taken into account for the purpose of per-formance detailed in Appendix B .8.3 Tolerances on Ratings - The observedresults expressed as percentage of the ratingsassigned by the manufacturer shall be within thefollowing limits:

Characteristic ToleranceVolume flow -5 percentStatic or total efficiency -5expressed as a percentageTotal power input +10 percentSpeed 10 percentWhere a tolerance in one direction is omitted,

there is no restriction on the value in thatdirection.

UJa::;:)(fI(fIILla:Q....J. . . . .o. . . .2u, " ' .. .O > ~

~"CHARACTERI-STiC ERROR

SYSTEM RESISTANCELINE

INLET VOLUME FLOWP = Pressure

Qv ~Inlet volume flow

FIG. 1 EXAMPLE OF FAN CHARACTERISTIC CURVE AND TEST FOR A SPECIFIED DUTY4

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9. MARKING9.1 Each fan shall be indelibly marked with atleast the following information:

a) Manufacturer's name, trade-name of fan,if any, and serial number;

b) Rated voltagets) or voltage range andnumber of phases;c) Input in watts;

d) Size of fan;e) Rated speed of fan in rev/min;f) Frequency of power supply;g) Direction of rotation and direction of air

flow (marking should be of permanentnature );

h) Air delivery at test voltage and statedduty; and

j) Country of manufacture.9.1.1 Fans shall be marked in a legible andindelible manner on or adjacent to these termi-

nals with the symbol J.. .9.2 For additional information that the manufa-cturer may be requested to supply, see Appen-dix A. .9.3 For additional information that the purchasermay be requested to supply, seeAppendix C.9.4 Axial flow fans may also be marked with theStandard Mark:

NOTE - The use ofthe Standard Mark is governedby the provisions of the Bureau of Indian StandardsAct 1986and the Rules and Regulations made there-under. The Standard Mark on products covered by anIndian Standard conveys the assurance that they havebeen produced to comply with the requirements of thatstandard under a well defined system of inspection,testing and quality control which is devised and super-vised by BIS and operated by the producer. Standardmarked products are also continuously checked byBIS for conformity to that standard as a further safe-guard. Details of conditions under which a licence forthe use of rhe Standard Mark may be granted to manu-facturers Or producers may. be obtained from theBureau of Indian Standards.

10. TESTS10.1 Categories of Tests

10.1.1 Type Tests - The tests specified belowshall constitute type tests and shall be carried outon three sumples of same type and rating selected,preferably, at random from a regular productionlot:

a) High voltage ( 10.3 ),b) Insulation resistance ( 10.5 ),c) Earthing continuity ( 10.6 ),d) Electrical input ( 10.7 ),e) Fan speed ( 10.8 ),f) Power factor ( 10.9 ),

IS : 3588 1987g) Starting ( 10.10 ).h) Moisture proofness (for regulators only)( 10.1I ),j) Mechanical endurance ( for regulatorsonly) ( 10.12 ),k) Air delivery ( 10.13 ), andm) Temperature rise ( 10.14 ).10.1.2 Acceptance Tests - The following shallconsitute the acceptance tests:a) High voltage ( 10.3 ),b) Insulation resistance ( 10.5),c) Earthing continuity ( 10.6 ),d) Electrical input ( 10.7 ). ande) Fan speed ( 10.8).10.1.2.1 Sampling Plan for acceptance testsis given in Appendix D.

10.1.3 Routine Tests - The following shallconstitute routine tests:~) flash test ( lOA ),b) Insulation resistance ( 10.5 ), andc) A simple running test to determine thatthe fan mechanism is in working order.

10.2 General Conditions of Test10.2.1 Test Voltage and Frequency - Unlessotherwise specified, the tests shall be carried outat rated voltage and frequency.

10.2.1.1 When a rated voltage is indicatedon the name plate, the tests shall be conductedat the rated voltage. Ifthe fan is specified for twoor more distinct rated voltages with three or moresupply terminals, the tests shall be carried out atthe most unfavourable voltage. In case of doubt.the tests shall be carried out at all voltages.

10.2.1.2 When a rated voltage range isindicated on the name plate, the test shall beconducted at the mean of the upper and lowerlimits of the range provided that the upper limitdoes not exceed the lower limit by more than 10percent.If the upper limit exceeds this value, the test

shall be conducted at the voltage corresponding toeither the upper limit or the lower limit which-ever is more unfavourable to the particular test.

10.2.1.3 Limits oj uoltag variation - Thevariation in the test voltage shall not exceed 2percent of the test voltage during air deliverytests. While taking the current and watt readingsduring these tests, however, the voltage shall bemaintained at the test vo]tagg..10.2.2 For a fan rated with a range of frequ-ency. the test shall be made at the frequencywhich gives the most unfavourable results. Toler-ance on frequency shall be 1 percent.

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IS : 3588 198710.2.3 Limits of-Error of Electrical Instruments-

The ammeters, voltmeters and wattmeters usedfor type tests shall have a Class index 0'5 orbetter [see IS: 1248 (Part I)-1983*]. Forroutine and acceptance tests, instruments of Classindex 2 may be used.10.3 High Voltage Test10.3.1 The source of supply for high voltagetest shall be not less than 500 VA.10.3.2 The high voltage test shall be applied

to all new and completed fan motors in normalworking conditions with all parts in place exceptthe capacitors which should be disconnected. Astype test; this test should preferably be doneimmediately after the temperature-rise test.

10.3.3 An ac test voltage at any convenientfrequency between 40 to 60 Hz of approximatelysine wave-form shall be applied and maintainedfor one minute without showing any kind ofbreakdown or flashover. The voltage should beapplied starting with one-third of the full value,gradually increasing it to the full value whichshould be maintained for specified period afterwhich the voltage should be gradually reduced.

The test voltage shall be applied as follows:a) F or f an m oto rs:

i) Between line parts and 1 500 voltsbody in the case of motorsintended to be earthedii) Between live parts and 1 500 volts

other inaccessible metalparts (that is, over thefunctional insulation) inthe case of double Insular-ed motorsBetween the inaccessiblemetal parts and the body( that is, over the supple.menrary insulation ) inthe case of double insulat-ed motorsBetween live parts and body( that is, over the reinforc-ed insulation) for reinfor-ced insulated motor

iii) 2 500 volts

iv) 4 000 volts

b) For regulators:i) Between any terminal and 1 500 volts

the bodyii) Between the terminals with I500 voltsthe regulator in the 'OFF'

position10.3.4 At the end of one minute, the test

voltage shall be removed and the insulation-resistance test conducted as in 10.5.

Spedfication for direct acting indicating analogue-etectrical measuring instruments and their accessories;Part 1 General requirements ( se cD n d r eD is io n ) .

10.3.5 If this test is required to be repeated.the test voltage levels shall be reduced to 85 per-cent of the original value.10.4 Flash Test10.4.1 Every fan and regulator ( if provided)

shall withstand the voltage 20 percent higherthan that specified in 10.3 for one second whenit is applied instantaneously.10.4.2 Any other test similar to the one speci-fied in 10.4.1may be carried out as a routine testprovided itwill ensure the fan passing the highvoltage test covered by 10.3.10.5 Insulation Resistance Test10.5.1 Insulation resistance test shall be carri-

ed out on fans and regulators immediately afterconducting the high voltage or flash test, as thecase may be.10.5.2 The insulation resistance shall be not

less than 2 megohms when tested with a devoltage approximately 500 V applied between thepoints used for high voltage test or flash test.10.6 Earthing Continuity Test - For fansintended to be earthed, the resistance shall notexceed 0'1 ohm between any exposed metal partsexcept the rotating parts supported by metalbearings, and

a) the free end of the earthing conductor ifthe fan is fitted with a flexible cord, dueallowance being made for the resistance ofthe earthing conductor of the flexible cord,or

b) the earthing terminal or contact, when thefan is supplied without a flexible cord.

The resistance measurement shall be madewith a current of lOA with a dc voltage notexceeding 6V.10.7 Electrical Input Test - The electricalinput to the fan in watts shall be determined byrunning the fan at the test voltage and at thehighest speed.10.8 Fan Speed Test - The speed of rotationof the fan shall be determined by running thefan at the test voltage and its rated frequency.The method of measurement of the speed of fanshall be such that the speed of the fan is notappreciably affected.10.9 Power Factor Test - The power factor ofthe fan when tested at the test voltage and thehighest speed of the fan shall not be less than:

a) 0'90 for capacitor type fans, andb} 0'60 for non-capacitor type fans.

10.10 Starting - The fan shall be capable ofstarting up from rest at the lowest speed stepwhen 85 percent of the rated voltage or 85 per-cent of the lowest voltage in the voltage range isapplied.

6

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lO.U Moisture ProofnesB (for Regulators~nly ) - The regulator shall be subjected to andshall satisfy the high voltage and insulation resis-tance tests immediately after having been placedfor a period of 24 hours without the current beingpassed through the regulator in a closed receptaclein which relative humidity is maintained between90 to 95 percent at any temperature chosen in therange of 40 to 50"C. Whatever temperature ischosen for this test, it shall be maintained const-ant to within 1D C .10.12 Mechanical Endurance Tests ( forRegulators only ) - The regulator shall conn-nue to function satisfactorily after being subjectedto a test of 1 500 operations when connected 10a ian with full load Current flowing through thefan or an electrical load of an equivalent imped-ance supplied at the maximum rated voltage.One operation includes a full cycle of movementfrom the 'OFF' position to the 'Full Speed' posi-tion (or to the other extreme position ) andback to 'OFF'. The test shall be made at the rateof approximately 6 operations per minute.10.13 Air Delivery Test - This test shall becarried OUt with the guard, if any, in poistion,10.13.1 To the fan inlets shall be attached astraight cylindrical airway of diameter.D andminimum Jength 4 D; D may differ from the fan

inlet diameter by not more than 20 percent largeror 5 percent smaller; a conical expander Ofreducer of 150 maximum included angle beingused to connect the fan to the airway.10.13.2 Ifthe fan is fitted with an inlet flare.the outside diameter of the flare may be regarded

as the fan inlet for connection to the test duct. Ifmore convenient, the flare may be removed forthe test.

IS : 3588 - 198710.13.3 The fitting of any additions to the fanfor the purpose of this test shall be subjected tothe following provisions:a) No additions or alterations solely for thepurpose of a test shall be made to the fanas supplied except: that when an additionto the fan that may affect its performancehas been specified, and unless otherwise

agreed to between the manufacturer andthe purchaser, the addition shall be fittedfur the test. Such an addition shall thenbe regarded as a part of the fan.b) An allowance shall be made for losses dueto the friction of air in the airway between

the fan and the point at which the read-ings are taken according to formula (5)given in 10.13.10.c) In any test, the airways shall be madereasonably airtight. When provision ismade for insertion and manipulation bymeasuring instruments, care shall be takento eliminate leakage as far as possible.d) Care should also he taken to avoid anyobstructions which may modify the airflow, either at the inlet or at the outlet ofthe airways.10.13.4 The inlet end of the test airway shall

be fitted with a conical inlet and four side tapp-ings in accordance with Fig. 2 and with thefollowing provisions:a) The proportions and tolerances of theconical inlet are given in Fig. 2 togetherwith relevant notes on manufacture and

installation. The inlet airway diameter Dused in the computation shall be measuredafter manufacture. '

FIG. 2 CONICAL ImET7

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IS : 3588 - 1987b) The four side tappings at plane AA shall beequally spaced at 900 on the cylindricalduct. The bore at the surface of the airwayshall not exceed 4-76 mm in diameter andshall be straight, uniform and at rightangles to the duct for at least 2 bore dia-meters. The openings shall be flushwith the

duct and free from burrs and countersinksThe four side tappings shall be connectedto one limb of the manometer, each con-nection being of the same length, bore andarrangement of tubing to minimize theeffect of flow due to difference of pressureat the tappings. The other limbs of themanometer shall be opened to the ambientatmosphere and the manometer readingshall be taken as equal to the averagestatic pressure in the airway.

c) Coefficient qf disch arg e - The coefficient ofdischarge of the conical inlet installed asabove is given in Table 2. For Reynoldsnumbers of 400 000 and above. the coeffi-cientof discharge is 0'975 and will cover themajority of fan .tests , When the air flow incubic metres per hour, numerically, is lessthan 16 700 times the airway diameter inmeters, then the coefficient of dischargeshall be taken appropriate to the Reynoldsnumber givenin Table 2.

TABLE 2 DISCHARGE COEFFICIENTS FORREYNOLDS NUMBER ( Re )REYNOLDS 20000, 40000, 60 000, 100000,

NUMBER (Re) 200000, 300000, 400000 and aboveDISCHARGE 0'930, 0'940, 0'945, 0'953, 0'967,COEFFICIENT, Cn 0'973, 0'975A conical inlet shall not be used at Reynolds numberless than 20000.

=-l 'lOMIN0 1 1 1 .U

CO~ lCA l INtE T-----_

Intermediate values of C D may be obtained bylinear interpolation,The Reynolds number for standard air is given

by Re = 23t8 Q . using the notation of 10.13.10and this may be taken to determine the coeffici-ent of discharge with negligible error for allnormal variations in ambient conditions,10.13.5 A resistance comprising a screen hav-ing evenly spaced aperture of uniform size, notexceeding D/20 should be fitted at a distance Dfrom the commencement ofthe cylindrical portionof the inlet, The screen may be composed of oneor more layers of even wire or fabric supportedby a wire guard,10.13.6 The static pressure data can be obtain-ed by changing the screen or adding additionalscreens in the test duct. Ifa ring is secured insidethe test airway to support the screen, or when aring is used to stiffen the periphery of the fabric

Of the other screen, the radial thickness of thering shall not be greater than D /100 ( see Fig. 3 ),10.13.7 At plane BB, distant 2 D downstream

from the resistance screen, there shall be four sidetappings, similar to those in plane AA, and con-neeted to the low pressure limb of a monometer,the other limb being connected to the ambientpressure in the vicinity of the fan discharge,10.13.8 The volume per unit time at plane AAshall be computed by using formula ( 1 ) and

corrected to fan inlet conditions for any changein the air density between plane A A and the faninlet BB,

8RESISTANCESCREEN

,.\ ,%MAX" /--__.-'"A METHOD OF SlJPPORfl !lGRESIS T ANCE SCREEN -

FIG,3 ARRANGEMENT FOR AIR DELIVERY TEST

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10.13.9 Air temperatures in the inlet airwayshall be taken by providing a thermometer withits probe inside the air way near section BE.The inlet volume so compiled shall then be usedto calculate the velocity pressure at plane BBusing formulae (2) and (3). For the purpose of thistest, the algebraic sum ( with the sign reversed)of the static pressure at plane BE, and the velo-city pressure at plane BB, plus a friction allow-ance for all test ducting downstream of plane BB,in accordance with formula (5) shall be takenas the fan total pressure.10.13.10 Formulae and Computation ifResults -The following formulae shall be used for the

computation of results of the tests laid downin 10.13:a) Inlet volume per unit time

Q=12 500 X CD X D2 ~ / /::, p m3jh'V Wt ... (I)whereC D =coefficient of discharge,D =iameter of airway in metres,6P = difference between ambient pres-sure in the vicinity of the inlet

and the average pressure at theside tappings at plane AA in mmH20; andWt =weight of air in airway at the testtemperature t O e , in kg/mB.

b) Weight per unit volume of atmospheric airat test sectionWt =1-205 X B + 0'073 7 Pa X760

293-( : - :2""""7=3--+- , )' - kg /roswhich may be very closely approximated asWt =1'2 X B + 0'073 7 Pa760 X

293 k I 9(273 + t) g m (2)[taking 1'205 kg/ms (approsimated to1'2 kg/ms ) as the weight of standard airat 20QC and 760 mm Hg ] .whereB = barometric pressure in mm Hg atthe time of test, and

P s =static pressure in mm H20.c) Velocity of air at a point...;-p;-V=16000 'V -Wt- mjh (3)d) Average velocity of air in the airway

V =J ? , , _ mJhA (4)whereA is the area of airway in square metres.

IS :.35881987e) Friction loss in airway

LPf = 0'02D P; mmH20 .. (5)whereLand D = length and diameter of air.

way in metre, respectively;andP =velocity pressure in mmHnO.

10.13.11 Method of calculation of efficiency isgiven in Appendix B.10.14 Temperaces-e-Rtse Test10.14.1 Measurement ifCooling Air TemperatureDuring Tests - The cooling air temperature shallbe measured by means of several thermometersplaced at different points around the fan motor

at a distance of 1 to 2 m and protected from allheat radiations and extrangeous draughts. Thethermometers used for this test shall be accurateto O5C.

The value to be adopted for the temperatureof the cooling air during a test shall be the meanof the readings of the thermometers taken atequal intervals of time during the last quarter ofthe duration of test.10.14.2 Measurement of Temperature-Rise - Thetemperature-rise measurements shall be carriedout by the method indicated in Table 1, immedi-ately after the air delivery test or after the fan

has been run long enough to ensure that thetemperature-rise has reached a steady state, usingthe following procedure.

10.14.2.1 AU temperature-rises to be measu-red by thermometer method [items (iii) and (iv)of Table I]shall be taken at the hottest accessi-ble surface of the part, as also on the parts whichare likely to cause injury to any adjacent insulat-ing material.

10.14.2.2 The method of measurement oftemperature-rise by change in resistances is givenbelow:

The temperature-rise Ie - t1may be obtainedfrom the ratio of the resistances by the formula:t2 + 235 R2--::---'-~~-- (for copper windings)tl + 235 Rl

or t2 + 225 R2tl + 225 -= - - : u : - (for aluminium1 windings)where

R2 =esistance of the winding at tempera-ture t2 ( 0 ) at the end of the test,and

Rl = initial resistance of the winding attemperature t1 ( C) (cold).From the above, the hot temperature (t2) canbe expressed as:

R2te = R; (t1 + 235) - 235for the copper windings.

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IS : 3588 ~1987APPENDIX A

( C la u se s 6.6 and 9.2 )ADDITIONAL INFORMATION TO BE SUPPLIED BY THE MANUFACTURER

AI. The following additional information inrespect of an electric axial flow fan shal l be supp-lied by the manufacturer on request:

a) Power factor}b) Number of blades,c) Type of regulator and number of runningpositions,

d) Class of insulation,e) Type of bearings,f) Instructions for lubrication of bearings,g) Condenser value (in case of single-phase

fans ), andh) Fan total efficiency.

APPENDIX B( C la use s 8.2 and 1 O .1 3.1 1 )METHOD OF CALCULATION OF EFFICIENCY

R-l. The performance of the fan at a stipulatedair delivery Q and fan total pressure Pt shall beexpressed by the

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~t-.. 11 I !'''' I I I I I I~~ r' - ,--1-. . : : : : ~~ 'Ti"~ ~ ~ K ( > -,h ;.... t--f---f- p -(t'-tj(1.1 ,_f--r-;~ ~ ~I' ~ f : : : : : : : : - -: : - - . : : . ; : : : : : : - . : : : - -"- : - - -: - . . . : I ' - . . : r-, -. . .~ 095iiiV)wCI ' .0-" 090ILo. . .%WQ 08ILILWov

1- 2

T = 11T = '6T "5T = 1-4"1 ; "3'I ; I 2

V A LU E S O F t1- 3FIG. 4 GRAPH FOR DETERMINING THE COEFFICIENT OF COMPRESSIBILITY ( K p ) WHEN THE

GUARANTEED FAN STATIC PRESSURE EXCEEDS 255 mmHlO UNDER NORMAL ATMOSPHERIC CONDITIONS

APPENDIX C( C la use 9,3 )

INFORMATION TO BE SUPPLIED BY THE PURCHASERC-l. The following information in respect of anelectric axial flow fan shall be supplied by thepurchaser on request:

a) Size;b) Electric supply details;

c) Air delivery at stated duty;d) Nature of medium, air or other gases;e) Atmospheric conditions; andf) Altitude of the place where the fan is to beinstalled.

APPENDIX D( C la use 10.1.2.1 )

SAMPLING PLAN FOR ACC EPTANCE TESTSD-l. LOTD-l.l All the fans of the same size and ratingmanufactured from the same material undersimilar conditions of production in a factory shallbe grouped together to constitute a Jot.Dw2. SCALE OF SAMPLINGD.2.1 For juding the conformity of the Jot to therequirements of acceptance tests. sampling shallbe done for each lot separately. For this purpose,the number of fans to be selected at random fromeach lot shall depend upon the size of the lot andshall be in accordance with calland 2 ofTable 3.

TABLE 3 SAMPLE SIZE AND ACCEPTANCENUMBERLOT SIZE SAlIlPLE SIZE AccEP- FIRST SECONDr--..A.-----, TANCE REJEC- REJEC4First Second NUlII:- TION TIONSample Sample BEF. Nu.~NUll-

BEH- EER(1) (2) (3) (4 ) (5) (6)Up to 25 3 3 0 2 226 " 50 5 5 0 2 251 " 100 8 8 0 2 2101 .. 300 13 13 0 2 2301 and above 20 20 0 3 4

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IS : 3588 1987

D~2.2 In order to ensure the randomness of se le-ction, procedures given in IS: 49051968* maybe followed.D-3. CRITERIA FOR CONFORMITYD-3.1 The number of fans selected at random inaccordance with col 1 and 2 of Table 3 shall besubjected to all the acceptance tests. A fan failingto meet any of the requirements of the acceptancetests shall be termed as defective. The lot shallbe considered as conforming to the- requirements

Methods for random sampling.

of acceptance tests if there is no defective in thesample and shall be rejected if the number ofdefectives in the sample is greater than or equalto the first rejection number given in col 5 ofTable 3. Ifthe number of defectives is betweenthe acceptance number and the first rejectionnumber, the second sample of the same size ( asgiven in col 3 ) shall be selected from the lot atrandom and subjected to the acceptance tests. Ifthe total number of defectives in both the samplescombined is less than the second rejection num-ber given in col 6 of Table 3, the lot shall beaccepted, otherwise not.

1 2

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