Pages From Pneumatic Handbook_ 8E_ Elsevier (1997)_ Barber (Ed)

8/2/2019 Pages From Pneumatic Handbook_ 8E_ Elsevier (1997)_ Barber (Ed)

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103

A I R R E C E I V E R S

A co m p r es s o r p l an t n o r m a l l y i n c lu d es o n e o r m o r e p r e s s u r e v e s s e l s k n o w n a s a i r r ece i v e r sw h i ch p r o v i d e t h e f o l l o w i n g f u n c t i o n s :

Eq ual i sa t i on o f p ress u re var i a t i ons i n t he supp ly li nes . S t o r a g e o f c o m p r e s s e d a i r t o m e e t h e a v y d e m a n d s in e x c e s s o f t h e c o m p r e s s o r

c a p a c i t y . A s o u r ce o f ad d i t i o n a l co o l i n g an d a co l l ec ti o n p o i n t f o r r e s i d u a l co n d en s a t e an d

o i l d rop le t s . P r ev en t i o n o f r ap i d lo ad i n g an d u n l o ad i n g o f t h e co m p r es s o r in s h o rt cy c l e d u ti e s .

Th e u s u a l f o r m o f r ece i v e r i s il l u st r a ted i n F i g u r e 1. Th e d e t a i l ed d es i g n o f s u ch a v e s s e li s co v e r ed b y a n u mb er o f s t an d a r d s ( s ee b e l o w ) .

Safety Valve ~ 1

PressureGauge

StrainerAir Trap

Ty pical vertical rec eiver with air trap. Sm all horizontal rece iver with alternativetrapping arrangements.

F I G U R E 1


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1 04 T H E P N E U M A T I C H A N D B O O K

R e c e i v e rv o l u m e

m 3

T A B L E 1 - Useful capacity of air receivers (cubic metres of free air)P erm iss ib l e pres sure drop bar

0.25 0.5 0.75 I 1.25 1.5 2 2.51 0.25 0.5 0.75 1 1.25 1.5 2 2.52 0.5 1 1.5 2 2.5 3 4 53 0.75 1.5 2.25 3 3.75 4.5 6 7.54 1 2 3 4 5 6 8 105 1.25 2.5 3.75 5 6.25 7.5 10 12.56 1.5 3 4.5 6 7.5 9 12 157 1.75 3.5 5.25 7 8.75 10.5 14 17.58 2 4 6 8 10 12 16 209 2.25 4.5 6.75 9 11.25 13.5 18 22.510 2.5 5 7.5 10 12.5 15 20 25

S t o r a g e c a p a c i t yT h e u s e f u l c a p a c i t y o f a r e c e i v e r is t h e v o l u m e o f f r e e ai r w h i c h c a n b e d r a w n f r o m i t a ti ts de s ig n p re ss u re ; t h i s i s, o f course , d i f f e ren t f rom i ts ac tua l i n te rna l vo lu m e . T he s i ze o fthe a i r r ece ive r de pen ds on the du ty i t i s r equ i red to fu l fi l. Th e s im ple s t du ty r e qu i red i so n e i n w h i c h t h e d e m a n d is c o n s ta n t a n d r e a s o n a b l y c l o s e to t ha t o f th e c o m p r e s s o r o u t p u t .A ru l e -o f - thu m b gu ide fo r r ece ive r s i ze in th i s s i tua t ion , w he re t he p re ssu re i s le ss t han 9ba r , i s s i x t im es the com pre sso r f l ow ra t e pe r seco nd o r 0 .1 t imes the f low ra t e pe r minu te .T h i s r u l e a p p l i e s o n l y w h e r e t h e c o n t r o l s y s t e m i n v o l v e s a u t o m a t i c v a l v e u n l o a d i n g , a n dw h e r e t h e d i f f e r e n c e b e t w e e n t h e l o a d i n g a n d r e l o a d i n g o f t h e s y s te m i s n o l e ss t h a n a b o u t0 .4 ba r . I f t he p re ssu re i s h ighe r t han 9 ba r , a r a the r sma l l e r r ece ive r wi l l be accep tab le .

I f the dem an d i s va r iab l e , t he ca l cu l a t i on o f r ece ive r si ze dep end s on the accep tab lep r e s s u r e d r o p a n d t h e n u mb e r o f c y c le s o f l o a d i n g a n d u n l o a d i n g t h a t a re p e r mi s s i b l e p e ru n i t ti me . F o r a v e r y v a r i a b le d e m a n d , t h e r e c e iv e r v o l u m e s h o u l d b e a b o u t t h r e e t ime s t h a tc a l c u la t e d f o r u n i fo r m d e m a n d .

In a s i t ua t ion w here t he ai r dem and i s i n t e rmi t t en t , r equ i r ing a f ai r ly l a rge vo lum e f lowfor a shor t pe r iod o f t ime wi th no demand a t a l l fo r t he r ema inde r o f t he t ime , i t i sw o r t h w h i l e p e r f o r mi n g a c a l c u l a t i o n t o d e t e r mi n e t h e mo s t e c o n o mi c a l c o mb i n a t i o n o fc o m p r e s s o r a n d r e c e i v e r . T a k e a s a n e x a m p l e a n a p p l i c a ti o n i n w h i c h 6 0 m3 / min a t 7 b a ri s r e q u i r e d t o b e d e l i v e r e d f o r 1 0 mi n u t e s e v e r y h o u r . C l e a r l y o n e s o l u t i o n w o u l d b e t o h a v ea c o m p r e s s o r c a p a b l e o f 6 0 m3 / min w o r k i n g f o r o n ly t h o s e t e n mi n u t es . S i n c e t h e m e a nf l o w is o n l y 6 0 + 6 = 1 0 m3 / mi n, a n o t h e r s o l u ti o n w o u l d b e t o h a v e a s ma l l e r c o m p r e s s o rw o r k i n g c o n t i n u o u s l y a n d s t o r in g i ts e x c e s s in a l a rg e r e c e iv e r . T h e s m a l l e r c o m p r e s s o rw o u l d h a v e a h i g h e r p r e s s u r e r a ti n g a n d t h e e x c e s s f l o w f o r 5 0 mi n u t e s w o u l d b e s t o r e din t he r ece ive r a t t ha t p re ssu re .

T h e f u n d a me n t a l e q u a t i o n r e l a t i n g p r e s s u r e d r o p t o r e c e i v e r v o l u me i s :V A P

- i l lVI~ Po


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A I R R E C E I V E R S 1 05w h e r e V R i s t h e r e c e i v e r c a p a c i t y i n m 3

V i s t h e a i r r e q u i r e m e n t f o r a g i v e n o p e r a t i o n i n m 3A P is t h e p r e s s u r e d r o p ( b a r) e x p e r i e n c e d i n t h e r e c e i v e r d u r i n g t h e o p e r a t i o nP o i s a t m o s p h e r i c p r e s s u r e i n b a r

I f t h e o p e r a t i o n i s i d e n t i f i e d b y a f l o w r a t e q in m 3 /s o v e r a t i m e t , t h i s e q u a t i o n c a n b er e w r i t t e n a s :

q t A P= [2]VR PoT h e s e e q u a t i o n s a s s u m e t h a t n o a ir is b e i n g a d d e d t o t h e r e c e i v e r d u r i n g t h e o p e r a t i o n .

I f t h e c o m p r e s s o r i s s i m u l t a n e o u s l y s u p p l y i n g a i r a t a ra t e qc m 3 / s, th e l a t t e r e q u a t i o nb e c o m e s :

( q - q c ) t A P= [3]Vl~ P,,

I n t h e a b o v e e x a m p l e o f i n t e r m i t t e n t u s e , th e a c c e p t a b l e p r e s s u r e d r o p h a s t o b e c h o s e n .T a k i n g t w o p o s s i b l e c h o i c e s f o r th e m a x i m u m p r e s s u r e , c a s e ( a) 2 0 b a r an d c a s e ( b ) 3 5 b ar ,b o t h f r o m c o m p r e s s o r s d e l i v e r i n g 1 0 m 3 / m i n .

A p p l y i n g e q u a t i o n [3 ] t o c a s e (a )( 6 0 - 1 0 ) x 1 0 _ 2 0 - 7

Vl~ 1s o V R = 5 0 0 - - 1 3 = 3 8 . 5 m 3 a n d t h e a c t u a l v o l u m e o f th e r e c e i v e r w i l l b e 3 8 . 5 / 2 1 =1 .83 m 3.

S i m i l a r l y f o r c a s e ( b ) V ~ = 1 8 m 3 a n d t h e a c t u a l v o l u m e o f t h e r e c e i v e r w i l l b e1 8 + 3 6 = 0.5 m 3.

I n d e c i d i n g w h i c h c h o i c e t o m a k e t h e m o s t e c o n o m i c a l s o l u t i o n i s w h e n t h e t o t a l c o s to f th e c o m p r e s s o r , r e c e i v e r a n d f u el i s a m i n i m u m .R e c e i v e r v o l u m e c a l c u l a t i o n s i n a u t o m a t i c s t a r t /s t o p c o n t r o lI f t h e c o n t r o l s y s t e m i n v o l v e s s t o p p i n g a n d s t a r ti n g o f t he m o t o r , t h e n a r e c e i v e r m u c hl a r g e r t h a n t h a t fo r a u t o m a t i c u n l o a d i n g is re q u i r e d s o a s t o a v o i d t o o r ap i d a c y c l i n g o ft h e c o n t ro l s . T h e p r i m a r y r e q u i r e m e n t is th a t th e r e c e i v e r m u s t b e s i z e d s o t h at n o m o r et h a n a b o u t t e n s t a r ts p e r h o u r , e v e n l y s p r e a d , t a k e p l a c e ; t h i s i s s o th a t d a m a g e t o t h e s ta r t e rs y s t e m a n d t h e m o t o r w i n d i n g s is a v o i d e d . T h e s p r e a d o f p r e s s u r e s h o u l d b e as l a rg e a sc a n b e t o l e r a te d t o f u r t h e r re d u c e t h e n u m b e r o f c y c l e s . T h e c o m p r e s s o r m a n u f a c t u r e r w i lln o r m a l l y c a l c u l a t e t h e c o r r e c t r e c e i v e r s i z e b a s e d o n t h e c o n t r o l s y s t e m u s e d .

E q u a t i o n [3 ] c a n b e r e w r i t t e n a sqc (1 - ~ ) ~ tP , ,VR = [4]A P

w h e r e ~ = q / q ca n d , i n t hi s i n s t a n c e , t is th e t i m e b e t w e e n s u c c e s s i v e s ta r ts o f t h e c o m p r e s s o ri s t h e a c tu a l a i r d e m a n d a s a f r a ct i o n o f t h e a m o u n t d e l i v e r e d b y t h e c o m p r e s s o r . I t


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106 THE PNEUMA TIC HANDBO OKturns out that the w orst condi t ion for frequency o f s tops and starts is wh ere ~ =0 .5, i e whe nthe dem and is half the supply. If the deman d is greater or less than a half , the num ber o fstops is less frequent so this condi t ion is usual ly taken as the design point. Rep lacing V b y0.5, equat ion [4] becomes:

qctPoVR ~ 4A PFo r t = 6 m inutes and AP = 1, the re la t ionship becom es;

VR = 1.5 qc.Co m pare th is w i th the formula for the rece iver s ize quoted above for unloading sys temsof cont ro l:

VR = 0.1 qcThis compar i son be tween the two va lues for the volume indica tes the importance ofassessing the correct receiver s ize to m eet the requirements of the system.A i r r e c e i v e r l e g i s l a t i o n i n t h e U . K .There is a large legisla t ive framework governing the whole area of receiver design andcert i f ica tion wh ich needs m uch study b efore i t can be appl ied with confidence.

The Hea l th and Safe ty a t Work A ct 1974 p laces a genera l duty on a num ber of pe rsonsinvolved with matters of safe ty; the dut ies are shared by designers , manufacturers ,suppl ie rs , importe rs employers , employees e t c . Regulat ions in specific branches ofindus t ry have been made u nder the Ac t . The pr imary docum ent on pressur i sed sys tems (ofwhich a ir receivers are usual ly the most cri t ica l e lement) is The Pressure Systems andTra nspo rtable Gas Co ntainers Regulat ions 1989 (SI 1989 No 2169 ), al l of which are nowin e ffect . These Regula t ions implemen t EC D irect ive 76/767/EEC . T he Hea l th and Safe tyExe c u t ive ha ve p re pare d a Code o f P ra c t i c e - S a fe ty o f P re ssu re S y s t e m s - wh ic h g ive sprac t ica l guidance on these Regu la t ions . T he Bri t ish Com pressed Air Soc ie ty have gon efur the r and have produced a comprehens ive se t of Guidance and In te rpre ta t ion Noteswhich should be s tudied a longside the two offic ia l documents .

I t should be noted that these Regu lat ions repeal much of the Factories Act 1961 insofaras it re la ted to pressure vessels , howe ver vessels a lready in use and bearing ma rking s mad ein accordance with the Act wil l not have to be changed unless they are modifiedsubsequent ly .

The Regula t ions do not g ive de ta i led des ign m ethods ( re fe rence m ust be made to theappropria te Standards for these) but are concerned with ensuring that pressure systemsfal l ing within their scope are prope rly made, inspected, mainta ined and mark ed so as tosafeguard those persons affected. The intent ion is to prevent the r isk of injury from therelease o f the s tored energy in a com pressed a ir system. They are in fact wide r in scopethan compressed a ir and encompass s team, gases and mixed l iquids and gases. Thecomplete system includes the pressure vessels , pipework and any protect ive devices,wh ere the pressu re is in excess of 0.5 bar. If the com plete system d oes not incorpora te an


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AIR RECE IVERS 107a i r r ece ive r , i t ma y not be covered by the Regu la t ions but i t wou ld be unw ise to assumetha t to be the case wi tho ut exper t advice .

In the Regula t ions a sys tem can be c lass i f ied as Minor , In te rmedia te or Major ,dep end ing o n the prod uc t of the gauge pressure o f the sys tem in ba r and the in te rna l volu mein litres ( ie t he p r oduc t P S .V) .

A m inor sys t e m ha s a m a x im um ope r a t ing p r e s su re be low 20 ba r ( gauge ) , t he l a rge s tpres sure vessel in the sy stem has a PS.V less than 2 x 105 bar l i t res and the op erat ingt e m p er at u re b e t w e e n - 2 0 C a nd 2 5 0 C .

An in te rmedia te sys tem is one which e i the r(a) has a syste m press ure o f 20 bar or abo ve w here PS .V is less than 1 x 106 bar l i tres

o r(b) has a system p ressure less than 20 bar and a PS.V greate r than 2 x 105 but less than

106 bar litres.A m ajo r syste m is one in wh ich PS .V is greater than 1 x 106 bar l i tres .I f PS .V is le ss than 250, ce r ta in of the Regula t ions do not app ly (pa r t icu la r ly in respec t

of marking) , a l though such a vesse l may come wi th in the scope of the S imple PressureVesse ls Regula t ions , see be low.

M ost com press ed a i r sys tem s wi l l fa l l in to the M inor ca tegory . The Regu la t ions p lacea d i f fe rent burden on the organisa t ion respons ib le for ca r ry ing out the inspec t ion andopera t ion of the sys tem according to the ca tegory in wh ich i t fa l ls and de f ines the leve ls ,qua l i f i c a t ion a nd e xpe r i e nc e o f t he " c om pe te n t pe r son" who d r a ws up a n e xa m ina t ionsc he m e .

The S im ple Pressure Vesse ls (Safe ty) Regula t ions 1991 (SI 2749) apply to smal le rpressure vesse ls . These Regula t ions a re the na t iona l implementa t ion of EC Direc t ive87/4 04/E EC (am ended by 90/48 8/EE C) . A s imple pressure vesse l i s de f ined as one whichi s we lde d a nd m a de o f non- a l loy s t e e l o r non - a l loy a lum in ium o r non- a ge ha r de n inga lum iniu m a l loy; the s im ple cons t ruc t ion impl ies tha t it is to be cy l indr ica l w i th conv exends or hemispher ica l ; i t must have a working pressure not grea te r than 30 ba r and theproduc t of the working pressure and the volume is not to exceed 10 000 bar l i t r e s . Apressure vesse l coming under these regula t ions can be c lass i f ied as AI , A2, A3 or B ,depe nding on the prod uc t of the gauge w orking pressure and the in te rna l volu me (PS .V) :

Class i f i ca t ionAIA2A3B

PS. V (ba r l i tres)> 3000 < 10 000> 200 < 3000> 50 < 200

< 50Dif fe rent Re gula t ion s app ly to the d i f fe rent ca tegor ies, the main d i f fe rences be ing the

type of ce r t i f ica t ion procedure which must be appl ied .M ee t ing the requi rem ents o f S12749 ma y be le ss onerou s than SI 2169, so i t i s impo r tan t

to de te rmine in to which ca tegory and sub-ca tego ry a pa r t icu la r pressure vesse l f a ll s andes tab l i sh the inspec t ion and ce r t i f ica t ion procedure accordingly .


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108 THE PNEUM ATIC HAND BOOKMost compressed ai r sys tems containing a receiver wi l l fal l wi thin the scope of the

Sim ple Pressure Vesse l s Di rec t ive .C o u n t r i e s o t h e r t h a n t h e U . K .For members o f the European Communi ty o ther than the U.K. , the same EC Di rec t ivesapply, w hich m ake s for s impl ici ty in des ign and cert i f icat ion and ensures that a pressu revessel acceptable in one European country wi l l be equal ly acceptable to the others . Foro ther count r ies genera l re ference shou ld be mad e to Boi le rs and 'Pressure V esse l s - AnIn terna t iona l Survey of Des ign and Approval R equi rem ents ' pu b l i shed by BSI . Th i s i s acom prehe ns ive re ference to the na tiona l regu la t ions, des ign codes and approval o rgan i -sa t ions o f a l a rge number o f count r i es . For tunate ly European and Amer ican Codes a rewidely acceptable. In a subject which is constant ly changing, the lates t edi t ion of th ispubl icat ion should be s tudied.D e s i g n o f p r e s s u r e v e s s el sThere a re th ree Br i ti sh Standards to which re ference shou ld be made fo r in format ion abo utdes ign , ma nufac tu re and inspec t ion - B S 5169:1992 , BS 5169:1975 , BS 5500:1994 andB S E N 2 8 6.

BS 5169 gives inform at ion specif ic to fus ion we lded s teel ai r receivers (exclud ingvessels covered by SI 2749).

BS EN 286 rep laces BS 5169:1975 and i s fo r vesse ls covered by S12749 . I t i s fo rs imple unfi red pressure vessels des igned for ai r or ni t rogen.

These two are mu tua l ly exc lus ive . BS 5500 is for unfi red fus ion we lded presure vessels .BS 5500 i s a compreh ens ive work wi th a weal th o f mater ia l on a l l aspec t s o f welded

pressure vesse l s and shou ld be s tud ied by anyone em bark ing on the des ign . Th i s chap tercan only give an out l ine of the s traightforwa rd principles of des ign of receivers . For m orecom plex m at te rs such as the des ign o f fl anges, re in forcement o f access open ings , num bersand locat ion of bol ts and welding s izes , the original s tandards must be referred to .Computer p rogrammes are ava i l ab le which remove some of the burden of ca lcu la t ions .M a t e r i a l s f o r m a n u f a c t u r eA l imi ted range o f mater i a l s i s permiss ib le to meet the requ i rements o f the s t andards .Re feren ce should be ma de therein . Broad ly certain s teel grades contained in BS 10207 andBS 10208 are acceptable for plates , s t r ip and bar; material for tubes and forgings arespecif ied in ISO 2604. For aluminium and aluminium al loys refer to the s tandard.D e s i g n i n a c c o r d a n c e w i t h B S 5 1 6 9BS 5169 specif ies three classes of ai r receivers :Class I - No l im i tat ion is p laced on the des ign but al l welde d seam s require non -dest ruc t ivetesting.


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AIR RECEIVE RS 109Cl a s s I I - T he de s i gn p r e s s u r e s ha l l no t e xc e e d 35 ba r a nd t he p r oduc t o f de s i gn p r e s s u r ea nd i n t e r na l d i a m e t e r s ha l l no t e xc e e d 37 000 ba r m m .Clas s I I I - Th e des ign pres sure sha l l no t exce ed 17 .5 and the prod uc t o f des ign pres surea nd i n t e r na l d i a m e t e r s ha ll no t e xc e e d 8800 ba r m m .W a l l t h i c k n e s s e sSimple theory for de te rmining the th ickness of a cy l inder subjec t to in te rna l p res surep r oduc e s t he r e la t ions h i p :

p dt = [5 ]2 f - pwh ere : t i s the wa l l th i ckness

f i s the nomina l des ign s t re s sp i s the in te rna l p re s sured i s the in te rna l d iamete r

Thi s eq ua t ion i s t rue for any sys tem of cons i s t en t un i t s.Th e equ iva len t eq ua t ion g iven in BS 5169 s t a tes tha t the th ickness of the she l l p l a te sha l lnot be less than

pdt = 2 0 f J - p + 0 .7 5 [6 ]where : t i s the th ickness of the wa l l in m m

p i s the pres sure in ba rd i s the ins ide d iam ete r o f the she ll in mmf i s the de s ign s t re ss in N/m m 2J is the jo in t fac tor , which ma y v a ry f rom 0 .4 to 1 .00 .75 i s the a l lowance in mm for cor ros ion ,

prov id ing tha t in no case sha ll the th ickness b e l e s s than 4 m m , or , in the case of Clas s I I Irece ive rs wh ere the in te rna l d iam ete r does no t exceed 300 , the th ickness sha l l be no t l e s sthan 2 .5 mm or 0 .01 D , whichever i s the grea te r .

Where the u l t ima te t ens i l e s t re s s (u t s ) i s known, the des ign s t re s s i sf = uts / 3.5

D e s i g n o f e n d sE nds s ha ll be he m i s phe r i c a l o r s e m i - e l li p s o i da l a nd m a y ha ve m a nho l e s o r ha nd ho l e s. I nthe case of Clas s I I and C las s I I I rece ive rs , and C las s I rece ive rs w here the in te rna l d iam ete rdoe s no t e xc e e d 600 m m , f l at e nds a r e pe r m i t t e d . I f se m i - e l l ip s o i da l e nds a r e c hos e n , t hera t io of the majo r ax i s to tha t o f the min or ax i s sha l l no t be grea te r than 2 .25 :1 .

For hemispher ica l ends the th ickness of the end p la te sha l l no t be l e s s thanp R + 0.75 [7]k. = 2 0 f J - p

wh ere : R i s the rad ius of the hem isphe rei s the th ickness of the end


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110 T H E P N E U M A T I C H A N D B O O K

o ii t "

" ( " !L ; - . . . . . . .

F I G U R E 2 - P r e s s u r e v es s e l e n d s h o wi n g a cl o s e d en d t o t h e r i g h tand a typ ica l open ing on the l ef t.

F o r o t h e r c o n c a v e s h a pe sp d K= + 0 . 7 5 [ 8 ]2 0 f J

I n b o t h c a s e s J = 1 f o r e n d p l a t e s m a d e o f o n e p ie c e , a n d f o r p l a te s m a d e o f m o r e t h a no n e p i e c e J i s t h e a p p r o p r i a t e f a c t o r o b t a i n e d f r o m t h e t a b l e s i n t h e S t a n d a r d . K d e p e n d so n t h e r a t i o ( h + t ) / D , w h e r e h is t h e h e i g h t o f t h e h e i g h t o f t h e d i s h e d e n d a n d D i s t h eo u t s i d e d i a m e t e r . K i s r e a d f r o m F i g u r e 3 . I n n o c a s e s h al l t h e t h i c k n e s s b e l e s s t h a n t h a to f t h e c y l i n d e r .

I n s o m e c a s e s i t i s p e r m i s s i b l e t o h a v e f l at e n d s r a t h e r t h a n c o n c a v e e n d s f o r a n in t e r n a ld i a m e t e r n o t g r e a te r th a n 6 0 0 m m .

4. 0

3.0

K20

": : :i!t:--~th.:J ... 1.... .... .. ~,, !@=~

[ _ ~. " I ~ ! ' ! i ~ [ ] [ l i : g ! ~ ] ~ ; i ~ ! I I I ] - : r, ] '. H ~ ,

O .I 0 1 5 0 . 2 0 2 5 0 . 3 0 . 3 5 0 4 0 4 5 0 . 5/~+teD

F I G U R E 3


9/10

A I R R E C E I V E R S 111F o r f l a t p l a t e s w e l d e d t o t h e c y l i n d e r

te = / pd 2q C Sw h e r e :

+ 0 . 7 5 [ 9 ]

S is th e m i n i m u m t e n s i l e s t r e n g t h o f t h e p l a t e sC = 1 4 .3 f o r u n f l a n g e d e n d p l a t e s o r = 1 7 .4 f o r f l a n g e d e n d p l a t e s .O p e n i n g s i n s h e ll s a n d p l a te sO p e n i n g s h a v e t o b e p r o v i d e d i n r e c e i v e r s f o r t h e p u r p o s e o f i n s p e c t i o n , s e e T a b l e 2 . A l lo p e n i n g s h a v e t o b e r i n g r e i n f o r c e d t o s t r e n g t h e n t h e v e s se l i n th e r e g i o n o f t h e m a t e r i a lr e m o v e d . A g o o d d e s i g n g u i d e i s t o m a k e t h e r in g f ro m a s m u c h m a t e r i a l a s w a s r e m o v e d .R e f e r t o t h e s t a n d a r d f o r de t a i l s .

T A B L E 2 - E x a m i n a t i o n h o le s an d m a n h o l e s f o r a i r r e c e iv e r sVesselinternaldiameterm m0 t o 3 0 0> 3 0 0 t o 4 5 0> 4 5 0 t o 8 0 0

>800 to1 5 0 0

O v e r 1 5 0 0

Length ofcylindrical

sectionm m

0 t o 1 5 0 00 t o 1 5 0 00 t o 1 5 0 0> 1500 to

2 0 0 0O v e r 2 0 0 00 t o 2 0 0 0

O v e r 2 0 0 0U n l i m i t e d

Num ber o f openings (minimum)Small Largesight sight Hand Head Man-hole hole hole hole hole

2 0 0 0 00 2 0 0 0

s e e n o t e 10 2 o r 1 2 o r 1 0

s e e n o t e 2 s e e n o t e 30 0 2 o r 1 2 o r 1

s e e n o t e 2 s e e n o t e 30 0 s e e n o t e 40 0 2 o r 1 0

s e e n o t e 2 s e e n o t e 30 0 s ee no te 4 00 0 0 0 1

Note 1: Where the length is m ore than 1500 mm additional sight holes may be provided.Note 2: In the case of a cy lindricalbody he ho les should each be sited near the ends (within sight of the longitudinal ointand the base) or else in the centre of the ends.Note 3: A single head hole or h and hole w hich should be situated in the central third of vessel length.Note 4: The numbe r of inspection holes shall be increased accordingly. For a length of less than 3000 mm it is, how ever,sufficient to site a hea d hole in the centre of the cylindricalbody. On the cylindricalbody he greatestdistance between thehead ho les shall not exceed 3000 mm, and between hand holes 2000 ram. The latter shall each be located either near to orin the ends.

D e s i g n i n a c c o r d a n c e w i th B S E N 2 1 8 6T h e a l t e r n a t i v e p r o c e d u r e o f t h is d o c u m e n t i s c o n f u s i n g t o t h e d e s i g n e r u s e d t o th e e a r l i e rs t a n d a r d s b e c a u s e t h e n o t a t i o n a n d t h e w a y in w h i c h t h e e q u a t i o n s a r e e x p r e s s e d a r ed i f fe r e n t . A i r r e c e i v e r s m a d e i n a c c o r d a n c e w i t h th i s s t a n d a r d a r e o f s i m p l e c o n s t r u c t i o n ,


10/10

112 THE PNEUM ATIC HAN DBO OKp r im a r i l y w e ld e d a n d s e r i a l ly m a d e . I f p o s s ib l e t h i s s t a n d a r d i s p r e f e r r e d p r o v id e d t h a t th ec o n d i t i o n s i t c o v e r s a r e m e t .

Th e no rm al des ign s t r es s is the lowe r va lue o f 0 .6 Roy o r 0 .3 Rm ,whe re tL,v is theg u a r a n t e e d m in im u m t e n s i le y i e ld s t re n g th a n d Rm i s t h e g u a r a n t e e d m in im u m t e n s i l es t r e n g th .T h e n o r m a l t h i c k n e s s ( e ) ta k e s a c c o u n t o f c o r r o s io n a n d t o l e r a n c e i n th e s p e c i f i c a t i o no f t h e m a te r i a l t h i c k n e s s .

e _> e c + s + cw h e r e e c i s t h e c a l c u l a t e d t h i c k n e s s

s i s th e c o r r o s io n a l l o w a n c ec i s t h e a b s o lu t e v a lu e o f th e n e g a t i v e t o l e r a n c e o n t h e m a te r i a l t h i c k n e s s .

T h e r e m a y a l s o b e a n e x t ra a l l o w a n c e t o c a t e r f o r t h in n in g i n p r o d u c t i o n .PDoec = 2 0 f + p K c [1 0]

In th i s r e la t ionsh ip ,Do is the outside d i a m e t e r i n m mP i s t h e d e s ig n p r e s s u r e i n b a r ( < P S , t h e m a x im u m w o r k in g p r e s s u r e )f is t h e n o m in a l d e s ig n s t re s s i n N /m m zI ~ i s a c a l c u l a t i o n c o e f f i c i e n t w h ic h d e p e n d s o n t h e w e ld in g p r o c e s s a n d t h ein s p e c t i o n m e th o d ( v a r ie s f r o m 1 t o 1 . 1 5) .

F o r h e m i s p h e r i c a l e n d sP S D o

ec 40 f + PSF o r f l a t e n d s w i th o u t o p e n in g s

e = C D J P S10f

[11]

[12]

w h e r e : C is a c o e f f i c i e n t d e t e r m in e d f r o m a c o n s id e r a t i o n o f t h e e n d d e s ig nD = d e s ig n d i a m e te r o f t h e fl a t e n d s . F o r a s im p le w e ld e d e n d t h i s i s t h e i n t er n a ld i a m e t e r .

T h e a b o v e t r e a tm e n t i s o n ly a n o u t l i n e o f t h e g e n e r a l a p p r o a c h t o t h e d e s ig n o f a i rr ece iver s . Any se r ious des igner shou ld s tudy the fu l l s tandards ; they con ta in a g rea t dea lo f u s e f u l m a t e r i a l . A c o m p e te n t p e r s o n , a s d e f i n e d i n t h e Re g u la t i o n s m u s t d e m o n s t r a t ea f ul l u n d e r s t a n d in g o f th e a p p r o p r i a t e s t a n d a r d s .

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Pages From Pneumatic Handbook_ 8E_ Elsevier (1997)_ Barber (Ed)

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