HOME OFFICE

CODE OF PRACTICE

FOR THE STORAGE OF

LIQUEFIED PETROLEUM GAS

AT FIXED INSTALLATIONS

LONDON

HER MAJESTY'S STATIONERY OFFICE

197 I

SBN 11 340365 8

F O R E\\O RD

THIIiI Code providc3 J general guide to ... are practice In 3toring and handling liquefied petroleum gas (LPG) at fixed storage Inslallalions where tanks are filled on site. I t has been prepared primarily as a gUIde for any bodies which may be given the task of enforcing safely reqUIrements at these installations. I1 IS, howc\cr. recogm<;ed that each ,a\e must be con!.ldercd on liS merits. and �pcclal ClrcumStances may ncccssllate \3riallons of the requirements here recommended 11 1\ nOI mtended to preclude the use of alternative designs. materials and methods where these provide eqUivalent standards of safety. Further 11 I ') nOl the mtentlon that the recommenda­tions of the Code :,hould be applied rigidly to e'l(151111g pi cmises, where for a variety of reasons It may not be practicable to comply with them. Only such alterallons as 3re considered to be reasonable, or essential for the public safety should be made.

The Code IS divided mto four parts; Part I gl\oe"i general information on LPG; Part 2 covers the larger storage facilities at refinenes. bulk plants for distribution of LPG and gas work"i: Part 3 coven. the �maller �torage facilities at industnal. commercial and domestic premises. but if the storage at these premiSes IS large reference IS made to Part 2 of the Code; Part 4 gl\es recommendallons for safe operating pracllce. Installations are co\oered only up to the mlet of first stage line pr��ure reduction.

The design and construction of plant and eqUipment for the storage and handllOg of LPG in bulk should be carned oul only by experienced people. Personnel responsible for operations should understand the physical characteristics of the products and should be trained 10 the use of the LPG eqUipment and the action to be taken In an emergency. Attention is dra\\'T1 to the recommendallons 10 the Code on commiSSIOning ne\\ facllllles. on the care nece�sary In draining water or dra\\lng samples from tanks and on product transfer operations.

The Code does nOI include detailed guidance on the design. construction and maintenance of LPG eqUipment. For such gUidance reference should be made 10 the Codes of Pracllce lI\ted 10 AppendIx A .

. . . '"

COI,TENTS

PART I GENERAL

1.1 LIQUUIED PETROLEUM GAS (LPG)

1.2 CIIARACTERISTICS A'ID HAZARDS

PART 2 STORAGE AT REFINIoRIES AND BULK PLANTS

2.1 scoPr

2.2 STORAGE TAt-;K LOCATION AND SAfETY DISTA'ICES

2.2.1 Pressure Storage 2.2.2 Low Pressure Refngerated SlOrage

2.3 PRI:.SSURE STORAGE

2.3.1 Design 2.3.2 Tank Fillings 2.3.3 Tank Connections 2.3.4 Pressure Relief 2.3.5 Capacity of Relief Valves 2.3.6 Relief Valve Informal Ion 2.3 7 Relief Valve Inslailallon 2.3.8 Shut-off Valves and Emergency Shut-off Val"cs 2.3.9 Filling Capacity 2.3.10 Insulation and Heating of Valves 2.3.11 Protection Against Corrosion 2.3.12 Maimcnance 2.3.13 Marking of Tanks

2.4 LOW PRESSURE REFRIGERATED STORAGE

2.4, I Scope 2.4.2 Design 2.4.3 LIquid Level 2.4.4 Capacity of Refrigeration System 2.4 S Tank Fillings 2.4.6 Pressure/Vacuum Relief 2.4.7 Insulation 2.4.8 Protection Against Corrosion 2.4.9 Marking or Tanks

2.5 PIPING, VALVES AND fiTTINGS

2.05.1 PIPing 2.05.2 Materials 2.5.3 Pipe Joints 2.5.4 Valves

v

Poge

I

I

2

2 2 5

6 6 6 7 7 7 7 7 8 8 9 9 9 9

10 10 10 10 10 10 10 I I 11 I I

11 11 12 12 12

2.5.5 2.5.6 2.5.7 2.5.8 2.5.9

Thermal Prc\<iure Relief In.,tallauon and TC!ltmg Imulation Ho')c., Arllculalcd Pipe Connections

2.6 SUI'PORTS tOR TANKS AND PIPING

2.6.1 Tank Support!> 2.6.2 PIPC Supporh

2.7 LOADI'G AND UNLOADING .... CILITI£S

2.7.1 Pumps 2 7.2 Compressors 2.7.3 Meters 2.7.4 Tram.rcr Systems 2.7,5 Protection

2.8 \ APQRISERS

2.8. I General 2 8.2 Construction 2 8.3 Prcs\ure Rchcf 2.8 4 Liquid Control 2.8.5 Heat Inpul Control 2.8.6 Maintenance

2.9 lLECTRICAL

2.9.1 Area Clas'i.,k3tion 2.9.2 Electrical Apparatus, Earthmg and Bondmg

2.10 nRE PROTECTIO'

2.10.1 General 2 10.2 Commumcallons 2,10.3 Waler Supply 2.10.4 Fir�I-Ald Fire EXllngulshers 2.10.5 Access 2.10.6 IsolallOg Valves 2.10.7 Drains and Blow-otT Lines 2.10.8 Grass and Weed Removal 2.10.9 Warning Signs

PART 3 INDUSTRIAL, COMMERCIAL AND DOMESTIC BULK STORAGE

3.1 seo!'1:.

3.2 STORA(.I TANK LOCATION AND SAn.IT DISTANCES

3.2.1 Location and Spacing 3.2.2 Spillage 3.2.3 PrOlCClion

v,

Page

11 12 13 13 13

13 I 3 14

14 14 14 14 14 15

15 15 16 16 17 17 I 7

17 17 17

19 19 19 19 19 20 20 20 20 20

20

20 20 22 23

Page 3.3 STORAG£ TA ........ S

23 3.3.1 De�lgn 23 3.3.2 Filtlng' 24 3.3.3 Pressure Relief 24 3.3.4 Capacity of Relief Valves 24 3.3.5 Relief Valve Information 24 3.3.6 Rellcf Valve In">tallatlon 24 3.3.7 Shut-off Valves and Emergency Shut-off Valves 25 3.3.8 Filling Capacity 26 3.3 9 Tank SUPPOrlS 26 3.3.10 ProleCllon Against Corrosion 27 3 3.11 Installation of Underground Tanks 27 3.3.12 M:lIntenance 27 3.3.13 Marking of Tanks 27

3.4 r'IPING, VALVES AND IITTINGS 27 3.4.1 Matenals 27 3.4.2 Pipe Jomts 28 3.4.3 Valves 28 3.4.4 Thermal Pressure Relief 28 3.4.5 Installation and Testing 28 3.4.6 Hose\ 29

3.5 PUMPS, COO,1PRESSORS AND METERS

3.5.1 Pumps 3.5.2 Compressors 3.5.3 Metero; 3.5.4 ProteCllon

3.6 VAPORISERS

3.6.1 General 3.6.2 Con,,>truction 3.6.3 Pressure Relief 3.6.4 Liquid Control 3.6.5 Heat Input Control 3.6.6 Maintenance

3.7 I:L[CTRICAL

3.7.1 Area Classification 3.7.2 Eleclrlcal Apparatus, Earthing and Bonding

3.8 rtRE PROTECTION

3.8.1 General 3.8.2 Water Supply 3.8.3 First-Aid Fire Extinguishers 3.8 4 Access 3.8.5 Isolaung Valves 3.8 6 Gra">s and Weed Removal 3.8.7 Warnmg Signs

'I'

29 29 29 29 29

29 29 3J 3 J 3J 3J 3J

J2 32 J2

J2 32 J2 34 34 34 34 34

PART 4 OPERATIONS

4.1 TRAINING

4_2 SFGREGATION OF PRODUCTS

4.3 PURGIr-.:G AND FILLING TANKS AND SYSTEMS

4.4 DRAINING OF TANKS

4.5 PRODUCT TRANSFERS

4.6 ATTENDANCE DURING OPERATIONS

4.7 At' I ION IN EMERGENCY

4.8 LlGHTlf'o.;G STORAGE AND OPERATING AREAS

TABLES

Table 2_2.1 Location and Spacmg for Pressure SlOrage at

Page

34

35

35

36

36

37

37

37

Refineries and Bulk Plants 3

Table 2.2.2 Location and Spacing for Low Pressure Refrigerated Storage 5

Table 2.8.1 (i) Safety Distances between Vaporisers and Storage Tanks 16

Table 2.8.1 (ii) Safety Distances between Vaporisers and BUildings 16

Table 2.9.1 Classlficalion of Dangerous Areas 18

Table 3.2.1 Location and Spacing for Tanks for lnduslrial, Commercial and Domestic Bulk: Storage 21

Table 3.6.1 (i) Safety Distances between Vaporisers and Storage Tanks 30

Table 3.6.1 (11) Safety Distances between Vaporisers and BlIildings 30

Table 3.7.1 Classification of Dangerous Areas 33

APPENDICES

Appendix A References

Appendix B Reference Temperatures

viii

38

39

PART I GE:\ERAL

I I LlQUEHED PETROLEU M GAS (LPG)

Q. "Liquefied Petroleum Gno;' or 'LPG' is a generic term, used 10 dc')cnbe liquefiable gase� consi!Joung predommantly ofC] .tnd C" hydrocarbons.

h. Th�c hydrocarbon ... C\I.,t a ... ga')o at normal almo�phenc temperatures and pre�sure but the)' can be liquefied under moderate pressure. I f the pres­'iure is sub!Jcqucmly relea\ed. the hydrocarbons ;lgnm become gaseous.

c. As liquids they occupy only about l/no1h oflhe .,pace they would need If they were stored as gases. From a commerCial !>Ollll of view It IS therefore more practicable to store and convey the hydrocarbons as liquid'i than as ga�e�.

d, The 1\\ 0 liquefied petroleum gases In gener.1I u .. e are kno,", n as 'Com­n�erclal Butane' and 'Commerclal Propane" The characterlstlc� and com­posllion of thc3c products arc sct OUI In SS 4250'.

(>. LPG may be slorcd a'i n liqUid eITHER at amblcllI lcmpcralurc under moderate pressure OR In a refrigerated condulon at a lower pressure. If the temperature of storage IS !.ufficlcntiy low. the LPG may be ... tored at substantlall) atmospherit: pres\ure.

f At 15 C commercial butanc has a vapour pre .. ,ure of about 25 psig and commercial propane has a vapour pressure of about 105 psig.

1 . 2 CHARACTERISTICS AND HAZARDS

a. LPG I!. colourless. and II'. ..... elght as a liquid 1\ onl) just over half that of an equivalent volume of watcr,

b. LPG vapour IS denser than air. commercial butane being about I\\ICC as heavy a) air and commcrclal propane about onc ,lIld a half time ... as heavy 33 air. Because of this. the vapour may flow along the ground 'lIld Into drall1s, Sinking to the lowc3t IcvcI of the )urrOundlngs. In suit air condi­tions any accumulallon of vapour will lake limc to disperse.

c. When ml\cd WIth air 111 ccrtall1 proportlon\, LPG form) an Inflammable mixture. The inflammable range extend.:. bet\.\ccn approxlmatcl} 200 of the vapour In air 31 113 lower bmlt and approximately 10"'", oflhe vapour III air at 11 ... upper Itmlt. Outside thl) range. any mixture 1\ clther too weak or too rich to propagate flame. Within the range there I.., the risk of explo\ion. Small quanlltles of the liquefied gas can give rise to large volume ... of vapour/air ml;c.ture and thus cause considerable hazard. A SUitable. prop­erly calibrated exploslmeter mOl} be used for tc\ung the conccnlrallon of LPG m air. On no account should a naked flame be u�ed to dclet:1 a leak.

I

d. Because or the characteristics outlined in Clauses 1.2b. and 1.2c. any vapour/air mixture arising rrom leakage or other cause may become Ignited some distance rrom the point or escape, and the flame may travel back 10 the onglnal source of leakage.

e. LPG vapour is slightly anae�thetic and may also cause suffocation if present in �umcienlly high concentrations.

f. LPG is normally odorised before dl�tnbution, by the addition of an odorant such as ethyl mercaptan or dimethyl sulphide, enabling detection b} smell of Ihe ga:) at concentrations down 10 one fifth of the lower limit of mflammabllity (i.e. approximately 0 4% of the gas in air). However, in some cases where, for example, the odorising mllerial mlY be harmful to a process or does not serve any useful purpose as a warning agent, the LPG is not odorised.

g. Esc.,pe of LPG may be noticeable otherwise than by smelt. When the liquid evaporates, the cooling effect on the surrounding air causes conden­sation and even freezing of water vapour in the air. This may show itself as frost at the point of escape and thus make it easier to detect an escape of LPG.

h. OWing to its rapid vaporisation and consequent lowering of tempera­ture, LPG can cause severe frost burns if brought into contact with the skin. Protective clolhing such as gloves and goggles should be worn if exposure to this hazard is likely to occur.

i. A container which has held LPG and is 'empty' may SI ill contain LPG in vapour form and is potentially dangerous. In this state the intern2.1 pressure is approximately atmospheric and if a valve is leaking or left open, air �an diffuse into the con tamer, forming an inflammable mixture and creating a risk of explosion while LPG can be displaced to the atmosphere.

PART 2 STORAGE AT REFINERIES AND BULK PLANTS

2.1 SCOPE

2.1.1 This Part of the Code covers LPG storage installations at refineries, bulk plants for distribution of LPG and gas works. Where the total LPG storage at a gas works does not exceed 30,000 gallons waler capacity the recommendations of Part 3 should be followed. Part 3 covers storage at industrial, commercial or domestic premises, unless storage at these premises involves tanks of individual capacity greater than 30.000 gallons water capacity or group storage greater than 100,000 gallons water capacity, when the recommendations of Part 2 should be followed.

2.2 STORAGE TANK LOCATION AND SAFETY DISTANCES

2.2.1 Pressure storage

o. Location and :.pacing

1. The djstanc� given in Table 2.2.1 are minimum recommendations for above·ground tanks and refer to the horizontal distance in plan be­tween the nearest point on the storage tank and the nearest poim of a

2

specified feature (e.g an adjacent storag'! tank. building, boundary). The distances are for both spherical and cylindncal tanks.

11. Wi th the provi�ion of radiation walls or ad�quate fixed water spray systems, separation di<;tances may be reduced but specialist advice should be obtained.

Table 2.2.1

Location and spacing for pressure storage at refineries and bulk plants

Factor Recommendations for LPG stored in pressure tanks

J. Between LPG pressure Onc quarter of the sum of the diameters of the two storage tanks adjacent lanl.s. but not less than 5 rt

--

2. To tanks contamlng 50 rt from the top of the bund surrounding tanks Inflammable liquids contaming inflammable liquids with a flash-pomt with a nash-point belo" 150 F below 150 F

3. To low pressure refrig- One dIameter of the largest low pressure refngerated crated LPG tanks storage tank. but not less than 100 fl. The pressure

storage tank should be not less than 50 re from the top of the bund surroundmg the refngerated storage tanl.

4. To process unit. office Water capacity of MaXimum total SeparatIOn bUilding, workshop, largest single tank water capacity dIstance laboratory. ""rehouse, m a group of all tanks in a In fect boundaf). busy mternal group road carrYing uncon-trolled tramc. or any Gallons Gallons fixed source of IgnitIon Over 250-500 1500 10

O\er 500-2000 6000 25 Olicr 2000-30.000 100.000 50 O\er 30,000-75,000 225.000 75 O,er 75,000 500.000 100

b. Spi llage

t. The provision of conventional bunds (see Clause 2.2.2h. around LPG pressure storage tanks deSigned and constructed tn accordance with Clause 2.3.1 is not reqUIred (but sce Clause 2.2.lb.iii for separation kerbs).

11. The ground beneath tanks should either be concreted or compacted. and so sloped as to:

o. prevent the ae-cumulatlon of any liquid beneath them; and

h. ensure a flow away from the tanks and any important areas.

3

.Voln. I Where all thc connection ... of Ihe ve�')el are groupell at one end the above pro'o';,)lons need only be requIred beneath the con· !lcction..,.

2. Pro'o'l<;lon ... hould also be made for a no .... away from the tanks and any important areas of coolmg water applied under fire conlll t lon�.

Ill. Separation kerb'), 10\\ to avoid ga!) traps. with a ma,\lmum height of 2 f, may be reqUired to dIrect �plllage to suitable places away from the tank ... and other Important areas.

IV. To prevent the formlllg of gas pockets, which might affect the safety of the timk, the \'icinIlY of LPG storage tanks should be free of pits and depres'ilom, other than those nccc!)sarlly required for the contaLn­men! of ",plllage.

v. LPG 'itorage tanks should be installed well away from tanks contain­Ing liquid oxygen or other hazardous substances and III such cases speciah'it ad\u.:e should be obtamed on spacing. In any case, no pressure �toragc lank for LPG should be located In any bund where there ... any permanent source of heat (c.g. steam mams) or within the bunded enclo<.ure of:

Q. a tank cOlltainlllg an mflammable liquid with a flashpoint below 150 F;

h. a !;.Ink contalnlllg liqUid oxygen or any other hazardous sub­stance;

c. lov,,-pressure refrigerated LPG tanks:

d. any healed storage tank (e.g. fuel oil tank).

c. Lay-out of tank ..

The lay-oul and grouplllg of tanks, as disllnct from spacing, should recei"e careful com.lderauon so as to ensure accessibility for fire-fighting and the aVOidance of spIllage from onc tank flowing towards any othcr tank or towards a nearby Imporlant area. The number of storage lanh In one group \hould not e,ceed 6, !lubject to the ma-..;imum total capaClly of a group given III Table 2.2.1. Any tank III one group should be at least 25 ft frolll an) tank III another group unle ... s a radiation wall is erected bcl\\een the group').

tI. Fencing

To prevent trespa ... <;lIlg or tampering. the area whIch includes tanks, pumping cQulpmenl and loading and unloading facitities should be endo\cd by an IIldu<;lrial type fence at least 6 fl hIgh at a distance of not le ..... than 5 fl from the Installation unless the fence is a boundary fence, when the dIstance ... given In Table 2.2.1 will apply. Where necessary. fence ... should have <lt least t\\O meal1') of e-..;it, not adjacent to onc another. Gate ... should open outwards, should not te self locking, and should provide ea ... y mean') of escapc from \\rithm.

4

2.2.2 Loy,·pressure refri�('raled �Iorage

a Locallon and Spa':lng

The di')lam;e; gl\en III Table 22_2 arc minimum rec:ommendJlion'lo and refcr to the hon/onlal dbtanl'C 10 plan bet",een the ne<lre,t pOint on the .. torage tank and the neare'il pOlOt of a spcr.:lfied feature (e_g an adJJcent Slor:lge tank. bUIlding, boundary ).

TlIblc 2.2.2

Location and spacing for la¥! pr�surc refrigerated ;Iorage

Factor

Bct .... een refrigerated I PG storage tanks

1. To lan"s containing mOammablc liqUids with a Oash·polnl below 150 r

3. To pressure slorage tanks

Recommendations for I o .... ·Pressure Refrigerated LllG Storage

One half of the sum of the diameters of the t .... o adJacent tan"s

The diameter of Ihe largest refngerated storage tank but not less than 100 r,

The diameter or the largcst rerngerated storage tank but not less than 100 n The pressure storage tan"'­should be not less than SO ft from Ihe lOp of Ihe bund surrounding the rerrlgerated storage tan"

4. To process unit, offii.:e 150 feel building, ",or""hop, laboratory, .... arehouse. boundaT). busy Internal road carrying uncon-trolled traffic. or an) fh.ed source of Igmtlon

h. Bund or Impounding Basin

I. A bund should be prOVided around all 10 .... pre!.surc lanh containing refrigerated LPG. The lank\ \houtd be completely surrounded by the bund, unlc)) Ihe topography of the area I .. .. uch, either naturally or by con"tructlon. Ihal "plllag� ... can be dlre(.:lcd qUldl)' and safely. by gravity dramage and dl\er';,lon .... all .. If reqUIred. to a depre ..... lon or Im­pounding ba .. m localed ""lIhm the boundary of the plant. Bunds ,hou Id be deSigned 10 be of .. ufliclent .. I rcngl h to WII h,land I he pre')sure 10 which they would be subjected If the volume \ ... lthm the bunded en· clm.ure ""ere filled .... lIh ..... aler The area .... llhm Ihe bund, dcprc!.';,ton or Impoundmg ba ... m .. hould be I .. olated from any oUblde dramage s)":,lem by a valve. normally closed unless the area IS bcmg drained of waler under coni rolled condllion<;,.

11. Where only- onc lank i; .... lIhm the bund, lhe nel capaclly ofthe bunded cnclo)urc. mcludulg thc carmcllY of any depre:,slon or Impounding ba')m, �hollld be nOI lcs!. Ihan 75 per cenl of the lank capacity. Where

5

more than onc tank is within the main enclosure, intermediate bunds should be provided, so as to give an enclosure around each tank of 50 per cent of the capacity of that tank, and the minimum effective capacity of the mam enclosure, includmg any depression or Impound-1I1g basin, should be 100 per cent of the capacity of the largest tank, nJter nllowing for the volume of the enclosure occupied by the re. maming tanks. It is desirable for the required capacity to be provided by bunds not exceedmg an average height of 6 ft as measured from the outside ground level.

Ill. The number of storage tanks within a main enclosure should not exceed three.

IV. The area within the bund should be graded to levels which ensure Ihat any spillage has a preferential flow away from the tank.

v. No tanks other than low pressure tanks for refrigerated LPG should be \\lIhm the bund.

c. Lay-out of Tanks

The lay-out and grouping of tanks, as distinct from spacing, should receive careful consideration so as to ensure accessibility for fire fighting.

2.3 PRESSURE STORAGE

2.3.1 Dco:;ign

u. Storage tanks should be designed, fabricated and tested in accordance With a recogOlsed pressure vessel code for static chemical plant.

b. The de�ign pressure of the tank should be not less than the vapour pressure of the actual LPG to be stored, at the highest temperature that the contents of the tank will reach in service (see Appendix B).

Nore: The vapour pressure is dependent on the surface temperature of the Contents (cr. Clause 2.3.9)

c. Careful con:,ideration should be given to the materials used for con­strucllon. bearing in mind the minimum temperature that the material of the tank wilt reach in service. In the case of smaller tanks with high draw­off rates, thiS may be below the minimum ambient temperature.

d. Slorage tanks for refrigerated pressure storage should be designed in accordance with the low temperature requirements of the Code referred 10

in Clause 2.3.lu. Storage tanks for low pressure refrigerated SlOrage of LPG should be designed in accordance with Section 2.4 of this Code.

e. For refrigerated pressure SlOrage, the capacity of the refrigeration system or the means of vapour dispo:,al should be adequate to maintain the LPG in the lank at a temperature such that its vapour pressure is below the pres�ure setting of the relief valves on the tank..

2.3.2 Tank fWings

a. Each tank should be provided wilh at least one each of the following fitllngs, all of which should be suitable for use with the LPG at a pressure

6

I

not le')� than the de')lgn pre')')urc of the tank to which they arc filled and for temperatures appropriate to the charactenstlcs of the LPG and worio..ln8 condlllons:

I. Pres:,ure rehef valve connected directly 10 the vapour space.

11 Drain, or other means of remO\lOg the liquid conlents.

Ill. Conlen!'. gauge or ma"mlUm le\'el Inou.:ator.

IV, Pre')')urc gauge connected to Ihe vapour c;pace.

v. Where a maximum level indicator is not filted, means of meac;unng the temperature of Ihe conlenl\ of the tank

b. Since LPG IS non-corrOSi\C,1I h normall} unnece<,c;ar} to subJccI small lanb 10 mternal e"ammatlon; manholes and hand-holes are nOI ther�fore normally reqUired. HO\H�\er, manholes or hand-holes should be provided on tank!:. e,ceedlng 1100 gallon'!> "ater capaclt), 10 facilitate flCriodlc examination.

2.3.3 Tank connections

Tank connections should be deSIgned and attached to the tank m accor­dance with the requirements of the Code referred to III Clause 2.3.10.

2.3.4 Pressure relief

The reqUirements for pressure rehef In the Code referred to In Clause 2.3.10. should be follo\\.cd. Rellef vahe!l should be direct spnngloaded or pi lot-opera led.

2.3.5 Capacity or relier lahes

The full now capacity of pressure rehef valves should be sufficient 10 pro­lecl the lank under fire exposure conditions.

2.3.6 Relief vaht inrormation

Every rellef valve should incorporate permanent markings as follows :

Manufacturer's Idenllfication. IIlcludmg manufacturer's name and calalogue or type number. Slart 10 discharge pressure Certified capacity in terms of a1r at 60 F (15'6 C) and 14·7 psia.

2.3.7 Relief lahe installation

a. In the case of multiple safety rehef valvc'!>, If provision is madc to isolale any one rchef valve for testing or servicing. it !>hould be ensured that the remaining relief \alves connected 10 the tank provide the full capacity required by Clause 2.3.5. In the ca<,e of tank\ fitted with single relief valves, provision may be made for their removal for testing or !>ervicing by Ihe uc;e of an automatic shut-off valve, provided this valve is retained In the fully open posItion by the presence of the relief valve and will close when Ihe rehef valve I� rcmoled. In carr)lO& out ItHS procedure. I t is es!tential lhat the storage vessel IS nOI left unprotected and a replacement relief valve should be ImmedIately filled.

7

h. for tJn� ... over 1100 gallon� water capaclt), the relief vahe� should be liued with "cnt pipe ... adequately sUJ1Poned and haVing oUllet:) at lea�t 6 rt 'lbove the tClp of the tank to,� hlch Ihey arc fitted and at least 1 0 rt above ground le\el. Vent plpC,> .. hould be dC'>lgned 10 allow for drainage of water and 10 cmure thill, III the ca ... e of Ignition of discharging product<;, flame 111lplllgcment on the tan!.., or on any adjaccnt tank, pipmg or equipment ., avoided Vent pipe,> rna) be prO\ H.led \vllh loo<;e-filllng ram caps. In the c .. he of '>mallcr lank,> filled ..... nh valve protecting I:overs, a venl or vent!) ... ufficlcnt to pcrmll thc free d .... chargc of LPG rrom [he relier valve or from an) proteCllon cap fittcd to 11 should be prO\ Idcd. The vent or vent" should be In such a position as not to sprcad the LPG over the lank shell.

2.3.8 Shut-ofT \ ahcs and emergency 'ihut-olf \-ahcs

fI. All liquid and vapour connection'> on tank-.. wllh the exception of tho,>c for relief valve,> (see Clau<;e 2.3.70.), plugged openings, and Ihose '1,-'here the connectIOn through the tank shell is not greater than No 54 !Horse dnll "'Ie should have '>hut-off vahes located a<:. clo'ie to the tank as

pracllcable. Pre ...... ure gauge mounting connection<; should be protecled Internall) by a tapping reduced JIl[crnally to a bleed hole not largcr than a No 54 morse drill size or b) a suilable excess flow valve.

b. Emergency ... hut-off \al",,:,> (c.g_ an exce\ ... 00\\ val1,-c, an automatically opcrn[cd valve or a remotely comroJled \ahe) should bc fitted 10 liquid connet.:llons on tank ... (except dramage and samplmg connections or ... mall diameter).

c. Dram connection,> should be pro\ Ided ''',Ih a �hu[-off vahc m accoru· ance With Clau,>e 2.3.80., and should preferably be nOI more than 2 m. 11011111131 Size. ThiS ,hut-on· \ah'e should be provided with a length or piping tenlllnat1l1� ",lIh a second shut-off valve, preferably nOI more than I m. nommal <'izc. The first \'ahe ,>hould be a qUlc!.. shut-off t}PC: the

second \ahe '>hould be a throllllOg t)pe. The length or plpmg bct\\een Ihe \ah"es �hould be such that the risk of 'iimultancous ob'ilrucllon of both vahes by the rreezing of any waler prc!)cnt In the LPG IS IllminllSed. A <;ufficlent length or piping should be provided do ..... nstream or the ,>ccond valve 10 ensure that dIscharge Will not tal..e place beneath [he tanl... The second vahe and the plpm£ should be adequately '>upport;!d and secured to prc\cnt mechanical damage or breakage b) Jet rorec\ Both \alves on the drain \}'stcm should have a means or actu,ltlon \� hlCh cannot be readily removed or moved from the closed POSI[lon except by Intentional operation.

d. The additional pipc\\ork and manual valve called for by Clause 2.3.8c. may be fit ted at the [lllle of dra I nmg pro\ Ided that the drai n valve requi red by Cia u,>e 2.3 .8c. I� protected by an emergency '>hut-ofT valve (c.g. an excess now \alve, an automatlcalty operntcd valve or a remotel) controlled va[\c) fitted up�treal11.

2.3.9 filling capacil) The maXllllUm quantity or LPG which �hould be filled into any lank '>llOUld be .... ur.;h that the wnl.. \\ III become no morc than 97° 0 liquid futl due

8

to c"pan�ion of the content.) \�Ith n�e of temperature 10 the highc�t temperature \�hjch the content" \\111 reach In senlce* (See Appendl\ B).

Vole: The volume of the product b depcndent on the bulk mean temrcra. ture of the COntents (cr. Clause 2.3.lb.)

2.3.10 In.sulation and heating of \'ahes

a. In')ulatlon. when prmided on refrigerated pre�<;llre tank ... <;hould

l. wllh'.ltand, together with the cladding. dIrect Impingement from ho')e stream� :

11. be Impen IOUS. eHher by a cellular con!)truction or the provi')ion of an efficient vapour barrier, 10 the Ingres<; of " ... ·ater vapour:

Ill. be �uftklently robust so that mlllor Illcchalllcal damage \�dl nOI sigOlficantl) ImpaIr the m�ulatlon:

IV. be protected from. Or be resl�lant to, firc.

b. In')ulatlon. ::.team heaung or othcr mean� �hould be u!>ed to prevent iCing of valvc� or other fittings If product quahty, operating techniques and/or ambIent tcmperatures are favourable to ice formation.

2.3.!! Protection against corrosion

Storage tanks and thclr supports 'i.hould be adcquatel) protected agamst corrosion. by Pdlllong or other means.

NOle: Storage tanks should be finish palntcd III light colour m order to mcreasc rcflectlon from them and minimise temperature rise of their contents.

2.3.12 Maintenance

All tanks should be examined at regular interval:. and the date of the last examination markcd on the tank.

2.3.13 Marking of tanks

Each preS'iure 'ilorage lank should be con,picuou�ly and permanently marked to mclude the folio\\' Ing.

o. The pre'i!oure ves�el code to \\, hlCh 11 is made.

b. The manufacturer"'i name and 'ierral number.

c. The water capacIty In gallons. lilrc\ or cubIC metres.

d. The maximum safe workmg pres<;ure.

e. In the ease or a refngeratcd pre't�ure tank. the minimum temperature for which the tank IS designed.

f The year in which the lank was made.

* The filling rallo should be calculated to allow a guaranteed free space of 30:0 at these reference temperatures. after allo\\ancc for the degree of uncenalnty In the liqUid density data. Ho,,"e\er. to allow for liqUids of hIgh coefficient of expansion. the filling ratio should In no case gl\le nse 10 a liqUid full condlllon at a tempera­lure less than S deg. C abo ... e the filling rallO reference temperature.

9

2.4 LO" PRESSURE REFRIGERATED STORAGE

2.4 I Scope

a, Thic; section of the Code applies to large to\\ pre,:)sure welded steel tanks for the bulk \torage of LPG In a refngerated <;talc.

b. This !.ccllon doe\ not apply to pressure \anks for storage of refrigerated LPG Such tanks �hould be designed and constructed In accordance with Secllon 2.3.

2.4.2 Design

a Tanks for the .. terage of LPG In a refrigerated state and all their fittin� .. hould be designed. con.,tructed and te<;led In accordance ",l1h a recogmsed standard for large welded low pre�sure storage (anks for refrigerated products.

b. The refrigeration system or other sUitable methods of vapour disposal should be de:.igned 10 mamtain the LPG at a temperature such that its vapour pressure does not exceed the deSign pressure of the tank.

c Materiab should be <ielected for their nOlch ductility at design metal temperatures. and should be In accordance "lth matenals listed In the standard referred to in Clause 2.4.2a.

2.4.3 Liquid Ic\cl

The filling level should be such that the tank will not be fuil orliquid at the cquilibrium temperature of the product for the pressure at which the relief valves are set to operatc. Tlm means In practice that the filling level will be sufficiently below the curb angle to allow for liqUid expansion In, for example, the event of a fire Incident or the failure of the refrigeration system.

2.4 4 Capacity of refrigeration system

The refrigeration sy..,tem should be of a capacity adequate to deal with normal bOlI·ofT plus maximum tank filling rate.

2.4.5 Tank fitting .. Each tank should be provided with a pressure and vacuum relief system and a content.., gauge.

2.4.6 Pressure. \acuum relief

(I. Pre!lo!'>ure and vacuum relief valves should be filled to protect the lank under all operatlllg conditions. Emergency \ellllng should be provided 10 protect Ihe tank under fire expO!loure conditions. This may be provided by means of a weak shell-to-roof seam.

b. Where the pressure relief valves discharge to the vent collecting system of a Hare, additional relieving devices, set at n slightly higher pressure,

capable of handling the towl venting reqUirement, may be provided dis­

charging directly to atmosphere.

10

c. Care must be taken to ellmlOate all liquid trap� 10 "ent lines.

d. Precautions should be taken to counter the effect of Icing on relief valves.

e. Relief valves discharging directly to the atmmphere should be designed and l O .. talled so that 10 the event of IglUtlOn of dlscharglOg vapour, Ramc impmgement on the tank 0. liS equipment will be avoided.

2.4.7 Insulation

I nsulation should be:

o. c;tpable of withstanding, along with Its claddmg. direct Impingement from hose streams;

b. ImperviOus, either by a cellular construction or the provision of an effiCient vapour barner, to the Ingress of water vapour;

c. sufficiently robust so that mmor mechanical damage will not signific­antly Impair the Insulallon;

d. be protected from. or be resistant to, fire.

2.4.8 Protection against corrosion

Tanks and their fittmg .. should be adequately protected agamst corrosion.

2.4.9 Marking of tanks

Each refrigerated storage tank should be idenufbd by the attachment of a name plate which should Indicate the following mformatlon:

a. The manufacturers name and serial number.

b. The maximum level to which the tank may be filled with LPG.

c. The liquid volume of the tank when filled With LPG to the maximum level.

d. The maximum deSign pressure.

e. The mlOimum temperature for which the tank is designed.

f The maximum level 10 which the lank may be filled with water for test purposes.

g. The year III which con\tructed and tested.

2.5 PIPI G, VALVES AND FITTI GS

2.S. 1 Piping

a. Piping systems should conform to the provisions of a recognised piping code.

b. Piping for low temperature service should conform to {he relevant low temperature provisions of the code referred 10 in Clause 2.S.la.

I I

2.5.2 I\laterial ..

o. All materials Including non-metallic parts for valvc�, seal�, gJ<;kets and dli.lphragm!-. �hould be re�I'!>talll to the action of LPG under [he service condition, to \\'hlCh they are subjected

h. All piping over � Inch �ile '1hould be made of steel.

c. Ca'lt in)n or other un'!>ullable piping matenals should not be used.

d COPf1er or bra'!>'!> pipe and (ubmg should be ..,eamle'!>� and should only be u\ed for ')IZCS t Inch and under.

{' Ma(enah for 1o\\, temperature service should conform to the low temrerature '!>ervice reqUlrelllents of the code referred to m Clause 2.5.1.

2.5.3 Pipe joints

a Pipe jOlnh over 2 Inches nominal size �hould be welded or flanged. Jomts of 2 Inches nominal ,Ize or smaller may be \\/elded, Hanged or .. cre ..... ed.

h. Scre\\edJolnts 'Ihould not be u'!>ed In piping for low temperature service, except for small diameter Imes such as lIlSlrument l i nes and pressure gauge connCCllon'l.

2.5.4 \'ahcs

o. The pnmar} shut-oIT valves for a tank \\'Ith a water capacity i n excess of 2000 gallons should be made of steel or of nodular Iron made to BS 27899 or an equivalent standard.

b. Other valves should be of steel or forged brass, except that valves of nodular Iron made to BS 27899 or an equivalent standard may be used.

c. Cast iron valves '1hould not be used, other than those of nodular iron made to SS 27899, or an eqUivalent standard.

2.5.5 Thermal pressure relief

Plpellncs I n which Ilquid rna} be (rapped, for example between shut-off valve'!>, should be protected against e\cessi\ e pressure caused by thermal expansion of the contents. If pressure rc.llc\mg devices discharge to atmo�phere, the dl')chargc ')hould be to the open air and should be directed '!>o a') not to endanger per'!>onncl or equipment.

2.5.6 Installation and tc-.tjll�

a. Liquid and \apour pipeline!> should be properly supported and in­'!>talled .. 0 a .. to ha\e adequate flexibility to accommodate any settlement of tanks or other eqUIpment, thermal expan;;ion or contraction or any other strc!>'!>c') which may occur 10 the plpe\ \ork sy'!>tem. Flexiblltty should not be provided by the Introductlon of fleXIble hose into the pipelme s}''1tcm.

b. All pipeline sy .. tcms should be te,ted after installation. and proved free from leak'!> at nOI le .. s than Ihe ma\lmum operating pressure.

12

c. Plpmg .. hould be protected again .. t phY,>l\;al dJmage_

2_5.7 Insulation

PiflCilnc m.,ulatlon requIred for refrigerated ... y .. tems. or \\11Ich may be required for vapour lme ... or drain ... of non·rcfngerated sy)tem.,. \hould be in accord;)ncc with the provblom of the codt: referred 10 in O"u"e 2.5. 11l.

2.5.8 Hoses

a. The dC'>lgn, material and construction of ho,>c\ "hould be "'lIItable for the grade of LPG whICh t hey arc to handle They should be dc.,lgncd to wuh"land a mJOlInUIl1 bursting pre\',>urc of four lime .. the maXlmUI1l pre�surc thcy \\-111 carry In "en'icc.

b. Ho,>e ... for refrigerated LPG should be .. ullable for the lo\\-�t opera ling temperatures 10 .... hlth the)' will be .. ubJected III "ervice.

c. Ho"e" should be exammed \.Isu.l lly e\-ery day If used contlOually "nd at each tlmc of usc If used intermittently They \hould be replal.:ed when Ihey show viSible signs of delerioralJon, and 10 any case at mtervab not c'(cccd· ing lhe year:,.

d. Ho:,c<.:., when 1101 111 use, should be protected from deterioration.

e. Emergency "hUI·off vahes should be In .. talled III pIpeline,> to \ \ Im:h ho'>es are connectcd, to prevent dl"l.:hargc of LPG III the e\-enl of failure of the ho .. e.

2.5.9 Articulated pipe connections

The de-.Ign. material., and constructIon of articulated plpc connecllons should be sUllable for the LPG \\hlch they arc to handle. They should be capable of .... Ithstandmg a test pre" .. ure of twice the maXlnlUm pressure they will carry m ,>ervice.

2.6 SUPPORTS FOR TANKS AND PIPING

1.6.1 Tank supports

a. Tank .. "hould be supported on concrete. masonry or �tructural steel suppon". The"e .. upports (e\cludmg supporting feet 1 8 inchC'i or leli') In height. tank :,addle ... or �kirt\ of verlll.:al tank .. ) ... hould be $0 conlitructed or protected as to have a standard of fire rec; .... tance of at lealit 2 hours.

b. The de�lgn of .. up ports should follow the recommendations In the code to which the tank I'> constructed.

1'. Support\ o:;hould permit movemem of the tank due to change ... in temperature.

d. Tank ... upport., ... hould be de .. igned to prevent or to drain any accumula· tlon of water.

�. Where pler� are u\ed a� part of the lank support for horizontal tank" of "-ater capa\.:lt} e"l(ce�dlllg 1 1 00 glllon<.:.. provi.,lon should be made for securmg the tank at onc end. the other being free to mQ\.-e as required III

I J

Clause 2.6.1c. The end so secured should be that to which the principal liquid and the vapour pipelines are attached. Where saddles are not welded 10 the tank, their support should be shaped to conform with the tank shell. Supports for honzontal tanks. normally two, should be located to give minimum moments and deflections to the tank shell. Additional supports may be reqUIred to meet special circumstances.

f The lank should be securely anchored or \\.eighted or adequate pier heighl provided 10 avoid flotation due to flood waler.

g. SklTls for veTllcal tanks should be provided with vents to prevent accumulation of vapour and with inspection openings.

2.6.2 Pipe supports

Supporb should be adequately designed. spaced and secured 10 suit the plpework configuration and 10 withstand anchorage and guide fricllon forces. In the case of pipe supports In the Immediate vicinity of the tanks, consldcnHion should be given to their construcllon or protection so as to !!ecure a standard of fire resistance of al leasl 2 hours.

2.7 LOADING AND UNLOADING FACILITIES

2.7.1 Pumps

a. The de!!ign, materials and construction of pumps should be suitable for the grade of LPG WhLCh they arc to handle, and they should be de­signed for the maximum outlet pressure to which they will be subjected in operation.

b. Positive displacement pumps should have a by-pass or olher suitable prOleC110n agamst over pressure. discharging 10 the pump suction or 10 a safe place.

2.7.2 Compressors

a. The design, materials and construction of compressors should be suit­able for the grade of LPG which they are to handle, and they should be designed for t he maximum outlet pressure to which they wil l be .l>ubjected in operation.

b. Positive displacement compressors should be equipped with pressure rellcvlng dcvices, discharging to the compressor suction or to a safe place.

2.7.3 Meters

The design, materials and construction of meters should be suitable for the grade of LPG which they are to handle.

2.7.4 Transfer Systems

a. Transfer systems should be designed so that risk by operating error of LPG of hIgher vapour pressure being transferred to equipment deSigned for LPG of lower vapour pressure is aVOided.

b. E).cess now valves, automatically operated valves or remotcly con­trolled valves should be installed in pipelines to which hoses or flexible

14

pipe connections arc connected to prevent discharge of LPG i n the event of failure of the hose or connection.

c. In the case of transfers between storage and ship or pipeline external to the site:

I. There should be positive means of rapidly shulling off flow. located at a safe distance from the storage which is being fil led or emptied.

1 1 . Automatic alarm devices to II1dicate approach to maximum permis­sible filling height. automatic shut-oft· valves or comparable devices to prevent overfilling should be used.

2.7.5 Protection

Pumps, compressors and meters should be protected against accidental damage by SUitable poslllonlng and/or protection. Pumps. compressors, meters and similar equipment should not be s1led beneath tanks.

2.8 V A POR ISERS

2.8.1 General

a. i. Vaporisers can be low pressure steam heated. hot water heated, electrically heated. or direct gas fired Iype.

11. Vaporisers should be of sufficient capacity to supply the latent heat of vaporisation necessary 10 conven the liquid into vapour at the maxi­mum offtake reqUired from the installatIon.

111. Where necessary. precautions against the accumulation of condensate in the vapour discharge line should be taken. This may require insula­tion and heat tracing of the vapour discharge line, with the provision of condensate pockets capable of containing the quantity likely to be condensed during a plant shut-down.

IV. With hot water heated vaporisers, anti-freeze may be added to the water to prevent freezing.

b. Vaporiser systems should be equipped with a means of safe removal of any heavy products which may collect in .he LPG pan of the system. The point of discharge should not be directly beneath the vaporiser.

c. Heating coils should not be instal led inside a storage tank to act as a vaporlser_

d. Valves should be installed to shut off the liquid and/or the vapour con­nection between the storage tank and the vaporiser.

e. Vaporisers, other than direct fired and non-flameproof electrical types, should be installed at a minimum distance of 5 ft from the nearest storage tank. Direct fired and non· flameproof electrical vaporisers should be in· stalled a t minimum safety distances. in accordance with Tables 2.8.1 i. The miOlmum distance between a vapOriser and the nearest important building or line of adjOining property is set out in Table 2.8.1 I t .

15

Table 2.8.1 i

Walt'r clIpacir.r of SIorage rallJ.

Caftons

O .. er 250-500 Over 500 2000 O .. cr 2000 lO.OOO Ovcr ]0.000 ·75,000 Oiler 75,000

Table 2.H.1 I1

Capacity o/ '·(lpori.ler

Ih hr

Up 10 80 80 500 O'cr 500

A1ill;1I111111 di/ifance 0/ �'aporis('r from SIoroge lallk

Fur

1 0 25 50 75

100

\ ll11ll11l1m djl(allce o/ l'tlpOrift'r from nearest imporral/l bllildim: or lille of adjoinillg property

Feet

1 0 25 50

/. Vaporisers should nOI be installed i n a buddmg except where tbe build· ing is u.locd exclusively for ga.lo manufacturing or distribution. Such build· ing'> �hould be of non-combustible construction and v.cll·\'enlllated near the Hoor line and roof.

g. Particular care should be laken with the design and location of direct fired vaporisers to minimise the effects of any failure.

2.8.2 Con'itructiOIl

a. Vaporisers should be designed, fabricated and tested in accordance with a recognised pressure vessel code.

b. Each vaporiser should be marked 10 Include the foIlO\\lng:

The pressure vessel code to v. hich il hi made.

The manufacturer's name and serial number.

The maXlIllUm working pressure and temperature.

The v�lporjsing capacity In pounds per hour.

The year m which made.

2.8.3 PrC!'Isure retid a. Vaporisers should be filled With a rehef valve or \alves. Prcs"ure relief should be 10 accordance wllh Ihe code referred to i n Clause 2.8.20.

b, The full now capnClty of preS"ure relief valve ... ,hould be :,uflicicOl to protect the vaporber under fire exposure condwon5.

16

2,8 4 Liquid control

a. VaporISers should be provided with �ul[able aUlOmalic means 10 pre· vent liquid LPG passmg through the vaporiser to the gas dbcharge piping under all operating conditions.

b. The liquid level control, If filled, may be integral with the vaporiser vc!.�el or filted immediately adjacent to it.

2.8.5 Heat input control

a, The heal input should be suitably controlled to prevent the pressure in the vaporiser \c�sel rcaching the starHo-discharge pressure of the pressure rehef valve or valve� m the vaporiser sy�lem.

b. Direct fired and elcctncally heated vaporiser') �hould be filled \\ lIh an automatic control to prevent overheating of the equipment.

c. Direct fired vaporisers .. hould be filled \\I\h �Ullable flame failure device').

2.8.6 i\1aintenance

Vaponsers should be examined at regular intervals.

2.9 eLECTRICAL

2.9.1 Area classification

Britbh Standard Code of Practice ep 1 0037 and the I n�titutc of Petroleum electrical Safety CodeS glvc recommendations for the installation of elec­trical equipment in area� m which an mnammablc atmosphere which could be ignited b) an electrical source may be pre�cnt (dang�rous areas). The areas detailed m these Code� include the followmg Divisional classlf'i­cation� which are dependent on the probability of a dangerous atmosphere being present, I.e. an atmo!.phere contammg a Significant Quantity of in· flammable gas or vapour III a concentration capable of Ignition.

Division I-an area In which a dangerous atmosphere is likely to occur in normal operating conditions.

Division 2-an area In which a dangerous atmosphere can occur only in abnormal conditions and not in normal operation.

Safe areas-all areas not classified as dangerous areas.

Table 2.9. 1 Indicates the area classification of various operations.

2.9.2 Eleclrical apparatus, earthing and bonding

Electrical apparatus and Installations, earthing and bonding, telecom· munlcatlons and In�trumenlatlon should comply with the recommenda· lions of the Institute of Petroleum Electncal Safety CodeS and relevant BnllSh Standards71 1l• LPG storage tanks do not reqUire lightning pro­tection.

I 7

Table 2.9.1

Faclor Extent or Classified Area Area ClassIfication

Storage tanks D. Wlthm 5 ft m all directIons rrom the tank connections or shell Division I b. Up to 5 rt above ground level and with· in the dIstances set out ror a fixed source of igmllon in Table 2.2.1 for Pressure Storage or Table 2.2.2 ror LP Rerrlgerated Storage as appropriate Division 2

Reller Valve Q. Withm dIrect path or discharge Fixed electrical Discharge equipment should

not be installed b. Wlthrn 5 rt in all other directions rrom pomt or discharge Division 1 c. Beyond 5 ft but within 1 5 ft ( I O ft 10 the ca� of tanks or \.', a ter CapacHy not exceed· 109 500 galls) m all other directions rrom point or discharge Division 2

Tank Vc hide u. Wllhrn 5 rt m all d,rections rrom a point and Tank Car where connections are regularly made or Loadrng and dlsconnccted ror product transrer Division 1 Unloadmg b. Bcyond 5 ft but wllhm 1 5 rt ( I O ft m the

case or tanks of water capacity not excced· 109 500 galls) from point of connection or dIsconnectIon Division 2

Pumps. Com-pressors and Vaporisers other than Direct Fired Q. Outdoors in Q. Wlthm 5 ft 10 all directions Division I open aIr, al or b. Beyond 5 ft but within 1 5 rl m 311 above ground dlfccl1on'i (10 ft m the case or tanks of level water capacity nOt exceeding 500 galls) Division 2

Note: Where high standards of maintenance or pumps and pump seats obtain, the area \.',lIhin 5 rt in all dircctions rrom the pump may be classified as Division 2

b. Indoor loea· lion wnh adequate vcn· Ilia lion

Enure room and any adjacent room not separated by a vapour-tIght partitIon Division J

Notes: I . Where any arca IS classified under more than one factor the higher c1asslftcalJon should prevail.

2. Any pit, trench or depresSIon fallmg wilhin a DIVision 1 or Division 2 area should be treated as being a Division 1 area throughout.

3. The term 'outdoors In open air' IRcludes pumps. compressors and vaponsers which are covered by a canopy.

18

2.10 F I R E PROTECTIO

2.10.1 Genera I

The POSSibility of a major fire outbreak. leadmg 10 direct flame Impinge· menl on the storage lank, can be mmimlsed by sound engmeerlng I n plant dcslgn and lay-out, good operatmg practice and proper education and tramlng of personnel on both routine operations and on action IQ be taken in an emergency. Consuhation With the fire authority on the provision of fire protection faci lities should lake place In lhe early planning stages. I [ is recommended that the fire authonty should be consulted with regard to fire-fightmg cqUlpmenl, water supplies. means of access for fire bngade appliances. protection of fire-fightmg personnel and arrangements generally to ensure an earl) call 10 Ihe fire bngade In the event of an OU(­break of fire.

2.10.2 Communications

Consideration should be given 10 Ihe provision of an adequate communi· cations <;ystem for summoning the emergency services. ThiS communica· tlon!. sy�tem should be tested at regular mtervab.

2.10.3 Wafer supply

a. Provision should be made for an adequate supply of water for firc protccllon. The applicallon of water m3) be by hydrants, hoses and mobile cqulpment. fi:o:ed momtors or fixed spra) s)-stem ..... , which may be automatic. Wherc\er posslblc automatic fixcd �pray systems, which offer obvious advantage'i. should be Installed. Control of water Oow, including suitable sectionahsatlon of any piped water supplies. should be possible from outside the danger area, and preference should be given 10 walcr eqUipment which can readily be brought Into use and enable personnel to withdraw from the danger area.

b. Hydrants. where provided, should be readdy acceSSible at al l times and so localed as 10 provide for the prOtccllon of all tanks.

c. Sufficient lengths of fire hose should be provided and be readily 3\all· able. I t IS desirable 10 equip the outlet of each hose line with a combma· lion Jet and spray nozzle.

d. Mobile eqUipment. fixed monitors or fixed spray systems should be deSigned to discharge water at a rate sufficient 10 maintain an adequate film of "ater Olver Ihe surface of the lank and supports under fire con· dlllons.

e. Consideration should be given 10 the provision of mobile or fh:ed waler-spray systems glvmg suitable and effeclive prolection for road lank­er and rail tank car loadmg and unloadmg areas where large transfers of LPG arc made frequently.

2.10.4 Firsl·aid fire extinguishers

A suffiClcnt number of firsl-ald fire extinguishers of adequate size, prefer. ably of the dry powder type. should be avallable at strategic locations. Dry po ...... der e"l.tmguishcrs should conform to OS 34656. Foam ext.n­gUI�hers arc nOI suitable for LPG fires.

1 9

2.10.5 Access SUItable access to and around the installation should be provided for fire­fightmg appliances and kept free at all times.

2. 10.6 Isolating vahcs Provision should be made for aUlOmalic or remote control shut-off so that If accidental leakage occurs, the supply of LPG can be slopped. Other shut-off valves should be located at strategic points.

2.10.7 Drnins and blow-ofT lines No dram or blow-otT line should dIscharge into or be in the proximity of any public drainage S)'stem or any other drainage system where this would be ltable to create a hazard.

2.10.8 Grao;;s and \\ccd rcmo\al Weeds, long grass and an)' combustible material should be removed from an area .... J lhln 10 ft of any LPG :.torage tank of up to 500 gallons water capacity and within 20 ft of larger tanks. I f �ecd killers are u:.ed, chemi­cal.:; such a:. .. odIum chlorate which are a potential source of fire danger :.hould not be selected for this purpose.

2.10.9 Warning signs Where ':>moklng and naked lights are prohibited. prominent notices to this effect should be posted, parllcularly at access POints.

PART 3 I N D U STRIAL, C O M M ERCIAL A N D D O M E S T I C B U L K STORAGE

3 I SCOPE

3. 1 . 1 Tlm Part covers LPG bulk �torage installations at industrial, commercial and domestIC consumers' premises. and at gas works where the total LPG storage capaCity is 30,000 gallons water capacity or less. Installations are covered only up to the Inlet of first stage line pressure reduction. TIllS part i':> not i ntended to cover the following:

o. LPG storage 1I1')tallations at refineries;

b. bulk plants for LPG dIstribution;

c. refrigcratcd storage;

d. industrial Installations Involving either tanks of individual capacity greater than 30,()(X) gallons water capacity or group storag� capacity greater than 100,000 gallons water capacity {see Clause 3.2.Je.}

I n these cases the recommendations of Part 2 should be followed.

3.2 STORAGE TANK LOCATION AND SAFETY DISTANCES

3.2.1 Location and spacing a. Storage tanks are normally installed above ground; i f tanks are to be installed underground, reference should be made to Clause 3.3. 1 1 . but storage tanks should not be Installed I n basements. Storage tanks. whether at ground level or underground should be spaced and located i n accord­ance wllh Table 3.2. 1 . The distances given are minimum recommendations,

20

� -

Table 3.2.1

Location and spacing ror lanks ror induslrial, commercial and domestic bulk !iolorage

Maximum .... aler capaclly or Maximum 10lal ..... ater an) single lanJ.. m a group capacity of all tanJ."s 10 a

group

Gallons Gallons

Up to 100 )00 .

O ... er 100-500 1500 .

O\'er 500 ·2 000 6000

O\'er 2000 - 30.000 100,000

·Whether bUIlt on or not.

Mmmwm Separation Distance m Feet

From bUild 109. boundal). property IInc· or fi�ed SQurl,;C or IgOltlon

.

Abo\c ground

. .

None -

1 0 -

25 -

50

Belo\\ ground

Buned portIon

10

1 0

1 0

1 0

. .

-

Vahe MSembl)t and loading unload 109 POInI abo .. c ground

1 0

1 0

25

25

Bet .... ccn lanks

Abo\e Belo .... ground ground

.

None 5 .

) 5

3 5 .

5 5

tThe isolation \lalves, filling \lal\les and pressure relief val\les 10000ted on the manholc cO\ler of the underground lank.

-

and refer to the hOrllontal distance In plan bet"\Ncen the nearest poim on the storage tank and the nearest point of a specified feature (e.g. an adjac­ent storage tank, buddmg, properly line).

b. With the provision of radiation walJs or adequate fixed water spray systems, separation distance for above-ground tanks may be reduced but specialist advice should be obtained. Where separation distances are rcduced. diversion wall::. may be necessary to ensure that the path of gas leakmg from a storage SHe to a building. boundary or source of Ignllion IS not less than that shown In Table 3.2.1.

c. Storage tanks should nOt be installed one abme the other.

d. No LPG storage tanks should be installed nearer than 20 ft to any tank containing an inflammable liqUId with a flash-point below 1 50 F. The minimum distance of separation between an LPG storage tank and the lOp of the bund of any tank containing an inflammable liquid should be 10 ft.

LPG storage tank� should be installed well away from tanks containing liquid oxygen or other hazardous substances and specialist advice should be obtained on spacing.

No LPG storage tank should be located within the bunded enclosure of a tank contaming an mflammable liquid, liqUId o"ygen or any othcr hazard­ou'\ substance.

No LPG storage tank should be located In any bund where there is any permanent source of heat (e.g. steam mams) or within the bunded enclos­ure of any heated storage tank (e.g. fuel oil lank).

i'. The number of storage tanks in onc group should not exceed 6, subjcct to the maximum total capacl!) ofa group given In Table 3.2. 1 . Any tank In onc group should be at least 25 ft from any tank m another group unless a radiation wall IS erected between the groups, or adequate fixed water spray systerru; are provided.

3.2.2 Spillage

o. The provision of bunds around LPG storage I3nks designed and con­structed in accordance With Clause 3.3. 1 IS not required (but see Clause 3.2.2c. for separ<Hlon kerbs).

b. The ground beneath tanks should either be concreted or compacted, and so sloped a� to:

I. prevent the accumulation of an) liquid beneath them. and

ii. ensure a flov. away from the tanl-s and any important areas.

NOli'S: I . Where all the connections of the tank are grouped at one end the above provi'iions need only be reqUIred beneath the con­nections.

2. Provision should al'io be made for a flow away from the tanks and any Important areas of cooling water applied under fire conditions.

c. Separallon kerbs, lo\\' to a\old gas traps. \\'Ith a ma'.:imum heiglll of I S Inches may be required 10 prevent "pillage reachmg Important areas. They will not be required for tanks with no bottom liqUid LPG outlet.

d. To prevent the forming of gas pockets. which might affect the safety of the tank, the VICInity of LPG storage tanks should be free of pits and depressions. other than those necessanly reqUired for the cOnlainmcnt of spillage.

3.2.3 Protection

o. To prevent trespassing or tampenng. the area which mcludes tan� .. and pumping eqUipment should be enclosed by an industrial typc fence at leas! 6 ft high at a dl�tance of not less than 5 ft from the IOstallatlOn unless the fence IS a boundary fence, when the distances gl-.:en in Table 3.2. I will apply. Where necessary, fences .. hould have at least 2 meam of elot not adjacent to onc another. Gatc� should open outwards, should not be self· locking. and �hollld prOVide ea .. y means of escape from W1I11I11.

b. The prOVisions In Clause 3.2.30. need nOI apply to tanks of le .. :. than 2000 gallon .. water capacHY, \� hlch are eqUipped wuh a posHlve means of denYing acce.,s 10 valves and fittmgs (e.g. a domed hmged cover \\, hlch is capable of bemg locked in the clo:.ed pO:'lllon).

c. When damage to LPG systems from vehicular traffic would be a possi. bllIlY, precautions against such damage .. hould be taken.

d. Underground tanks should be protected from above·ground londings due to ""ehlcular traffic or other cause, ell her by fencing off the area under which the tanks arc buned, or by placmg them m a reinforced concrete· Imed pit protected by a rem forced concrete slab or other adequate cover. I f the tank area is nOt fenced off. the tank manhole cover and the tank fillings o;hould be protected agalllst damage and tampering. The penmeter of the area under w hich tanks are buned should be permanently marked.

3.3 STORAGe TANKS

3.3.1 Design

o. Storage tanks should be dcslgned, fabncated and tested in accordance with a recognised pressure \lessel code for static chemical plant.

b. The deSign pressure of the tank should not be less than the vapour pressure of the actual LPG to be stored at the hlghcst temperature that the contents of the tank will reach 10 service (see Appendix B).

No/e: The vapour pressure IS dependent on the surface temperature of the contents (cf. Clause 3.3.8).

c. Careful conSideration should be gl\en to the materials used for construction, beanng In mlOd the mlOimum temperature that the matenal of the tank will reach 10 ser\llce. In the case of smaller tanks With high draw·ofT rates, thiS may be below the mimmum ambient temperature.

23

3.3.2. Hflings

(I. Each tank should be provided with at least one of each of the following fitting." all of ",hlch should be wllable for usc w!lh LPG at pres'.;urc:; not lc!>s than thc dC')lgn prc .. :.urc of the tanks to which they are filled and for temperaturcs appropriatc to the characteristics of the product and operating condition:.'

Prc.,..,urc relief vah·c connected to the vapour space.

Dram, or other means of removing the liquid conlcnts.

Contents gauge or ma,(lmum level mdlcator.

Pre.,..,urc gauge, connected to the vapour space, If thc tank is over 500 gJ.llons waler capacity.

h. Tank connections should be de .... gned and attached to the tanks in accordance with the code referrcd to m Clause 3.3.10.

c. Smce LPG IS non·corrOSl\e, 11 is normall) unncccssary to subject small tank.'.; to Internal examination; manholes and handhole!> are nOI therefore normall) reqUired on abmc·ground tanks. Howe\er. manholes or hand· hole') may be prOVided on mnk'.; cll;ceedlng 1100 gallons water capacity, to facilitate periodiC exammatlon. Undcrground tank:. ,hould be fitted with a manhole of not Ie:;s than 22 Inches Internal dtameter. The manhole :.hould be In the form of an extended nozzle of sufficient length 10 brmg the manholc cover abo\c ground level.

d All lank fittings and connections of undcrground tanks !>hould be on the manhole cover or covers.

3.3.3 Pressure relief

A spnng·\oaded relief ,alve or \·3Ives should be pro\,jdcd Pressure relief should be III accordance With the code referred to In Clau .. c 3.3.10.

3.3.4 Cupacit) of relief \ahes

The full flow capacity of preS'iure valves should be sufficIent 10 protect the lank under fire expo.'>ure conditIon:.. For underground tankc; the full flow capacit) of pressure rellcf vahes may be reduced 10 nOl lc:,:. than 300:>0 of the abo .. c·ground capacity.

3.3.5 Relief Hlhe information

C\cry rchef valve should Incorporate permanent marking!> as follows:

Manufacturer's Identlficallon, including manufacturer's naOle and c3tnlogue or type number.

Start to discharge prec;sure.

Certified capacilY 10 term!. of air at 60 F (15'6 C) and 14·7 psia.

3.3.6 Relief \ahe in:.tallalion

o. I n Ihe case of multiple safet) relief va"�, If pro\lSlon is made to isolate

any onc relief yalve for teSllng or \crYlclIlg, It should be ensured that the

remallllllg rehef vahe!> connccted 10 the tank prmide the full capacity

14

required by Clau::.e 3.3.4. 111 thecaseof tank\ fitted with smglc relief valves, provision may be made for their removal for te.,tmg or servicmg by the u<,e of an automalll.: ::.hut-olf val\e. prO\ Ided thl� valve IS retained In the fully open po..,llIon by the pre .. ence of Ihe relief vahe and WIll close when the relief valve is rcmo\cd I n carrymg out IhlS procedure, 1 1 is essenllal Ihal the ... fOrage \(,..,.,cl i .. nOI left unprotected and a replacement relief vahe should be Immedlalely fitted.

h. For above-ground tank..., over 1 100 gallons water capacity and for al l underground tank .. , the relief vahe ::.hould be fitled \\Ith \Cn! pipes adequately supported and havmg outlets at Ica�t 6 fl above the tOp of the tank to whIch they are fitted and a t least 10 ft above ground level. Ven! pipe., should be de.,lgncd to allow for drainage of water and to ensure thal. 111 the ca."e of Ignlllon of dl.,chargmg products. flame impmgement on the tank. or on any adjacent tank. plpmg or eqUipment IS avoided. Vent pipeS may be pro\·,ded with loo::.c-fittmg ram caps. I n the case of smaller tanks filted With \alve protectmg co\ers. a vent or vents suflklen! to permit the free discharge of LPG from the relief "ahe or from any protection cap fittcd to I 1 �hould be provided The vent or vcnts should be III such a position ao;: not to �pread the LI>G over the tank o;:hcll.

3.3.7 Shu'-off \'ahes and emergency shut-off \'ahes

a. All hqUld and vapour connections on tanks. other than those for relief valves, plugged opening'), and Ihose where the connection through the lank shell IS nOI greater than No 54 morse drill .::.rz.e, should have .::.hut-ofT valves located as close to the tank: as practicable. Pres')ure gauge mounung connections should be protected InternaJl) b) a tappmg reduced IIltcrnally to a bleed hole not larger than a No 54 morse drill size or by a suitable excess flo,", valve.

b. Emergency shut-olT valvc<; (e.g. an e'(cess now valvc. an automatically operated vahe or a remotel) controlled valve) should be fitted to liqUid connections on tanks (c"cpt drainage and !lamphng connecllons of small dlamcter).

c Drain connection .. for larger tanks should be provided with a shut-off valve m accordanl.:e wllh Clau ... e 3.3.7a . . and !!>hould prefcrably be not more than 2 m. nominal size. Till::. !!>hut-off valve should be provided With a length of plpmg terminating with a ')ccond shut-off valve, preferably not more than I 10. nomln31 size. The first valve should be a qUick shut-off t)pe; the ':>econd valve ')hould be a throllhng type. The length of plpmg bet",ccn the valve .. ..,hould be <;;uch Ihat the risk of slmultaneou.!, obstruc­tion of bOlh valve') b) the freezlIlg of any water present m the LPG is minimised A .. ufficient length of piping should be provided downstream of thc sccond valve to ensure that dl<;;charge Will nOt take place beneath the tank. The ..ccond valve and the ptpmg .. hould be adequately supported and secured 10 pre ... ent mechanical damage or breakage by jet forces. Both valves on the: drain S)�lem \hould have a mean ... of actuation which cannot readIly be remo'ved or moved from the closed position except by mlcmional operation.

25

d The additional plpework and manual valve called for by Clause 3.3.7c.

may be fitted at the time of drammg provided that the drain valve re· quircd by Clause 3.3.7c. IS protected by an emergency shut-off valve (e.g. an excess flow valve. an automallcally operated valve or a remOlely controlled valve) filled upstream.

3.3.8 Filling capacity

The maximum quantity of LPG fi l led into any tank should be such that the wnk will become nOI more than 97 % liquid full due 10 expansion of the contents with rise of temperature (Q the highest temperature which the contents will reach in service· (see Appendix B).

Note,· The volume of the product IS dependent on the bulk mean tempera­lUre of the contents (cr. Clluse 3.3.1b.).

3.3.9 Tank supports

o. Tanks should be supported on concrete, masonry or structural steel supports. These supports (e�c1uding supporting feet 1 8 inches or less i n height. tank saddles, or skirts of vcrtlcal tanks) should be so constructed or protected as to have a standard of fire resistance of at least 2 hours.

b. Supports should permit movement of the tank due to changes in temperature.

c. Where piers are used as part of the tank support for horizontal tanks of water capacity excecdmg 1 100 gallons. provision should be made for securing the tank at one end. the other being free to move as required i n Clause 3.3.9b. The end so secured should be that to which the principal liqUid and the vapour pipelines are attached. Where saddles are not welded to the tank, their support should be shaped to conform with the tank shell. Supports for horizontal tanks, normally 2, should be located 10

give mimmum moments and deflections 10 the lank shell. Additional supports may be required to meet special circumstances.

d. Skirts for vertical tanks should be protected with vents to prevent accumulation of vapour and with inspection openings. Such openings should be as few as possible i n number, as small as practicable and rein· rorced where necessary.

/!. Tank supports should be designed to prevent or to drain any accumula· tion of water.

f The tank should be securely anchored or weighted. or adequate pier height provided, to avoid flotation due to Hood water .

• The filling ratio should be calculated to allow a guaranteed free space of 3 % at t hc.sc reference temperalUres. afler allowance for the degree of uncertainty in the liquid density data. However. to allow for liquids of hIgh coefficient of expansion the filling ratIo should In no case give rise to a liquid full condItion at a tempera· ture less than 5 deg C above the filling rallo rderence temperature.

26

3.3.10 Protection against corrosion

Tanks and thclr supports should be adequatcly protected against corro­"ion, by paintmg or other means.

3.3. 1 1 Installation of underground tanks

Q. The surface of the lank should first be prepared by shot blastmg or chemical treatment and then. before being placcd underground, be given a protectl\c coatmg adequate to resist soil corrosion conditions.

b. The size of the excavation should be sufficient to allow for easy installa­tion. The pit should be large enough to permit a clear gap of at least 3 ft between the "Ihell of the tank and the wails before backfil1ing. When lowering the tank mto place. care should be taken to avoid damage to the coating. When the tank is m place. the coating should be checked by suit­able fault detection apparatus and any dlsconunullles repaired.

c. Tanks should be supported on concrete or masonry supports as required in Clause 3.3.9. The badfil1 material should be free from rocks or other abraSive materials and should be carefully consolidated. I t IS recom­mended that approximately 2 ft of cover should be provided over the top of the tank. Where concrete or masonry-lined pitS are not used, adequate provision must be made to prevent migration of the backfill material.

d. I t is recommended that specialist advice should be obtamed on corro­Sion protection of tanks, including coating materials and application. and on whether cathodiC protection i" necessary.

3.3.12 Maintenance

All tanks should be examined at regular intervals and the date of the last examination marked on the tank.

3.3. 1 3 Marking of tanks

Each tank should be conspicuously and permanently marked to include the followmg:

Q. The pressure vessel code to which i t is made.

h. The manufacturer'S name and serial number.

c. The water capacity in gallons, litres or cubic metres.

d. The maximum safe workmg pressure.

�. The year in which the tank was made.

3.4 PIPING, VALVES AND FITTINGS

3.4.1 Materials

Q. All material" mcluding non-metallic parts for valves, seals, gaskets and diaphragms should be resistant to lhe action of LPG under the service conditions to which they are !<tubjected.

b. All pipmg over � Inch size 'ihould be made of !<ttee!.

c. Cast iron or other unsuitable piping matenals should not be used.

27

d Copper or brass pipe and tubing should be seamless and should only be u�ed for SIZes ! Inch and under.

) 4 2 Pipc joints

PlpcJomb o\er 2 Inches nominal �ilC should be welded or Hanged. JOints of 2 Inche� nominal Size or .!Imaller may be welded. Hanged or screwed.

3.4.3 Vahes

(j The primary shul·off valves for tanks wilh a water capacity in excess of 2000 gallons .!Ihould be of �Ieel or of nodular iron madc 10 BS 27899 or an equivalent 'itandard.

b. Other valves should be of steel or forged brass, except that valves of nodular Iron made to BS 27899 or an equivalent standard may be used.

c Cast Iron valves should not be u'ied, other than those of nodular iron made to SS 27899• or an equivalent standard

3.4 4 Thermal pressure relief

Pipelines 10 "hlch liqUid may be trapped, for e'(ample belween shut-off \al\ics, should be protectcd agamst excesSive pressure caused by thermal e .... pansion of the contents. I f pressure relieVing devices discharge to atmos· phere, the discharge should be to the open air and should not endanger personnel or equipment.

3.4.5 Installation and testing

a. LiqUid and vapour pipelines should be properly supported and installed so as to have adequate flexibility to accommodate any settlement of tanks or other equipment, thermal expansion or contraction or any otherslresses which may occur in the pipcwork system. FleXible hose should not be IOtroduced 1010 the pipeline system to prOVide flexibility unless the follow· ing condnions are satisfied :

1. the capacity of the installation should not exceed 1 100 gallons water capacity;

11 . the mintmum necessary length of hose (not. in any case exceeding 9 inches) should be used;

Ill. the bore of the hose should not c�ceed I lOch:

IV. the hose should be fully armourcd and of high quality;

v. the hose connection to the LPG supply/withdrawal point of the tank (measured in plan at right angles to the tan!.. shell) should be at least onc lank diameter from the nearest pari of the tank shell;

VI. the hose should be Inspected and maintained in accordance with the provlsion� of Clau!>e 3.4.6b.

b. All pipeline systems should be tested after installation, and proved free from leaks at not less than the maximum operating pressure.

c. PIPing should be protected against physical damage.

28

3 4.6 "loses

a. The de:.ign, materials and con:.truction or hoses should be suitable ror the grade or LPG which they are to handle. They should be designed 10

WI!lbland a minimum bursllng pressure or rour times the maximum pressure the) .... 111 carry I n service.

b. Ho�cs �hou'd be examined visually every day i r used continually and at each lime or use i r used intermittently. They should be replaced when they show visible !>Ign!> or deterioration, and in any case at intervab not e1l;ceed I ng fi\'e years.

c. Hoses, when not In use, should be protected rrom deterioration.

d. Ernerg!nc) shut-off valves should be Installed In plpelllles to which hose ... are connected. to prevent discharge or LPG III the cvent or railure or the hose.

3.5 PUMPS, COMPRESSORS AND METERS

3.5.1 Pumps

a. The design, materials and con ... truction or pumps should be suitable ror the grade or LPG which they arc to handle, and they should be deSIgned ror the maximum outlet pressure to which they will be subjected i n operation.

h. Posillve displacement pumps should have a by-pass or other suitable protection against over pressure.

3.5.2 Compressors

a. The deSign. materials and construcllon or compressors should be suitable ror the grade or LPG .... hlch they are to handle, and they should be designed ror the maximum outlet pressure 10 which they will be subjected 1 0 operation.

b. Positive displacement compressors should be eqUipped With pressure relieving devices on the discharge Side.

3.5.3 Meters

The design, materials and construction or meters should be suitable ror the grade or LPG which they are to handle.

3.5.4 Protection

Pumps, compressors and meters should be protected against accidental damage by suitable positioning and/or protection. Pumps, compressors, meters and Similar eqUipment should not be sited beneath tanks.

3.6 VAPORISERS

3.6. 1 General

a. i. Vaporisers can be low pressure steam heated, hot water heated, elec­trically heated, or direct gas fired type.

29

11. Vaporisers should be of sufficient capacity to supply the latent heat of vaporisation necessary to convert the liquid InIO vapour at the maxi­mum offlake required from the lIlslallation.

Ill. Where necessary, precautlon� agJlnst the accumulation of condensate 10 the vapour discharge line should be taken. This may require IOsula­lion and heat traclOg of the vapour discharge hne. with the provision of condensate pockets capable of containing the quantity likely to be condensed during a plant shut-down.

IV. With hot water heated vapomers, anti-freeze may be added 10 the wilier 10 prevent freezing.

b. VaporISer systems �hould be equipped with a means of safe removal of any heavy products which may collect In the LPG part of the system. The pOint of dl'icharge should nOt be directly beneat h the vaporiser.

(' I-Ieatlng cOils should nOI be IIlstalled inside a storage tank to act as a vaponser.

d. Valves should be Installed 10 shut off the liquid and 'or the vapour COD­nectlon between the storage lank and t he vaporiser.

f!. Vaporisers, other than direct fired and non-flameproof electrical types, should be IIlstalled at a minimum distance of 5 fl from the nearest �[orage tank. Direct fired and non-flameproof electrical VapOrisers should be mstal led at mlnllllUm safety distances, In accordance with Table 3.6.1 i. The mil11mum distance between a vaporiser and the nearest Important bul ldlllg or line of adjolnmg property IS set out in Table 3.6.1 11.

Table 3.6.1 i

It 'af�r caponl)' of Slorag� rank

GlIllolIS

Over 250 -500 Ovcr 500 2000 Over 2000 ·30,000 O ... er 30,000 ·75,000 O,cr 75,000

Tablc 3.6.1 ii

Cap(I('ily of I'aporij;t'r

Iblhr

Up IQ 80 80-500 Over 500

Almi",,,,,, dislanc� 0/ I'Oporis�r from storage tallJ..

Feet

10 25 50 75

100

;\/111111111111 duranct' 0/ \·llporlj"�r from n('luest import(lf/f building or line 0/ at/foming propt'fty

30

F�et

10 25 50

f. Vaporisers should not be installed In a bUlldmg except where the build­ing is u�ed exclusivel) ror gas manuracturing or distribution. Such build­ing:. should be or non-combustible con!>truclion and well venlilated near the floor hne and roor.

g. Parllcular care should be taken with the design and location or direct fired vaporisers to minimise the cITects or an) railure.

3.6.2 COIl'itrucliolt

a. Vaporisers should be dC!:.lgned, rabrlcated and lested In accordance with a recognised pressure vessel code.

b. Each vaporiser should be marked 10 include the rollowing:

The pressure \essel code to which I t is made.

The manuracturer's name and serial number.

The maximum working pressure and temperature.

The vaporising capacity in pounds per hour.

The year in which made.

3.6.3 Pressure relier

D. Vaporisers should be filled with a reher valve or valves. Pressure relier should be in accordance with the code rererred to i n Clause 3.6.20.

b. The rull How capacity or pressure relier valves should be sufficient to protect the vaporiser under fire exposure conditions.

3.6.4 Liquid control

a. Vaporisers should be provided with suitable automatic means 10 pre­vent liquid LPG passing through the vaporiser to the gas discharge piping under a l l operating conditions.

b. The liqUid level control, ir fitled, may be integral with the vaporiser vessel or fitled Immediately adjacent 10 11.

3.6.5 Heat input control

a. The heat input should be suitably controlled to prevent the pressure in the vaporiser vessel reaching the start-ta-discharge pressure or the pres­sure relier valve or valves in the vaporiser system.

b. Direct fired and electrical ly-heated vaporisers should be fitted with an automatic control 10 prevent overheating or the equipment.

c. Direcl fired vaporisers should be filled with suitable flame failure devices,

3.6.6 Maintenance

Vaporisers should be examined at regular intervals.

3 1

3.7 ELECTRICAL

3.7.1 Area classification

Briu'ih Standard Code of Practice CP] OO37 and the In�titUle of Petroleum Electrical SafclY CodeS gllwC recommendation::. for the installation of clc(.;lrical eqUipment In areas In which an Inflammable atmosphere which could be Igntted bY ::ln electrical source may be present (dangerous areas). The area\ detailed in these Codes Include the (ollo\l"mg DIvIsional classi­fications which are dependent on the probability of a dangerous atmos­phere being present, I.C. an 31mmphere containing a significant Quantity of inflammable gas or \apour in a concentration capable of ignition.

Division I -an area in which a dangerous atmosphere is likely to occur In normal opcrallng conditions.

Division 2-3n area In which a dangerous atmosphere can occur only 10

abnormal conditions and not in normal operation.

Safe area')--all area!> not classified as dangerous areas.

Table 3.7.1 indicates the area classification of various operations.

3.7.2 Electrical :Ipparatus. earthing and bonding

Electncal apparatu\ and installations, earthing and bond 109, telecom­muntcatton,,; and Instrumentatton should comply wllh the recommenda­tions of the Institute of Petroleum Electrical Safety Code8 and relevant British Standards7, 12. LPG !>torage tanks do nOI require IIghtmng protec­tton.

3.8 FI R E PROTECTION

3.8.1 General

The POSSibility of a major fire outbreak, leadtng to direct flame impinge­ment on the storage tank, cal1 be mimn1lSed by sound engineenng in plant design and lay-out, good operating practice and proper education and tratnmg of personnel on both routine operations and on action to be taken in an emerg-;;!ncy. I t I') recommended that the fire authority should be con­:)ulted with regard to fire-fighting equipment, water supplies, means of

acc�s for fire bngade appliances, protcction of fire-fighting personnel and arrangements generally to cmure an early call to the fire bngade in the event of an outbreak of fire.

3.8.2 Wilier supply

(I. Provision should be made for an adequate supply of water for fire pro­teclJon. The application of water may be b) hydrant!>. hoses and mobile eqUIpment, fixed momtors or fixed spray systems. which may be auto­matic. For �rnall lllstnllallon<;, however, a � LOch hose reel installation may be adequatc_ Control of watcr flow. Including <;uitable scctionalisation of an) piped \\atcr supplies, should be pOSSible rrom oUblde any danger area.

h. Hydranh, where provided. should be rcadtly accessible at all times and so spaccd a!> to provide for the protection of all tanks. Sufficient lcnglhs of fire hose �hould be provided and be readily available. I t is desirable (0

equip the outlet of each hose line with a combination jet and spray nozzle.

32

I'

Table 3.7.1

Factor Extent of Classified Area Area Classification

Storage lanks (I, Within 5 fl in all directions from the tank connections or shell 01 vision 1 b. Up to 5 ft above ground level and with· in the distances set oul for a fixed source of Igmtlon m I able 3.2.1 DIvision 2

Relief Valve o. Within direct path of discharge Fixed electrical Discharge equipment should

nOI be Installed b. Within 5 fl In all other directions from point of discharge DIviSIOn I c. Beyond 5 ft butwllhm 1 5 ft ( 1 0 ft m the case of tanks of water capacity not exceed-Ing 500 galls) In all other directions from pomt of discharge Division 2

Tank Vehicle o. Wnhm 5 fl In all dlrcCllons from a point and Tank Car where connecllons are regularly made or Loadmg and disconnected for product transfer Ol\lSIOn I Unloading b. Bc}ond S ft but " ithin 1 5 ft ( I O ft ln lhe

case of tanks of water CaplCI!Y not eXCl cd· Ing 500 galls) from poinl of connecllon or disconnectIon DIvIsion 2

Pumps. Corn· pressors and Vaponscrs other than Direct Fired o. Outdoors ir o. WUhin 5 ft In all directions Division I open air, at or b. Beyond 5 ft but .... uhtn 1 5 fl in all abo\-c ground directions ( 1 0 rt m the case of tanks of level water capactly not exceeding 500 galls) Division 2

Nole: Where high standards of maintenance of pumps and pump seals obtain, Ihe area .... ithin 5 ft in all directions from Ihe pump may be classified as DIviSion 2

h. Indoor loca· Entire room and any adjacen l room not lion wuh separated by a vapour.lIght panition Division I adequate \-en· Ilia lion

Noln: I . Where any area IS classified under morc than onc faclor. the higher classification should prevail.

2. Any pl!. trench or depression falling within a Division I or Division 2 area should be treated as bemg a Division I area throughout.

3. The term 'outdoors in open air' includes pumps, compressors and vaporisers which are covered by a canopy.

33

c. Mobllc equipment, fi'(ed mOnltor� or fixed spray sy�tems should be de .. igned 10 dlscharg! water at a rate sufficient to m:lIntam an adequate film of water over the surfac� of the tank and supports under fire condl­I ion').

cl Where large deliveries are made frequently, conslderallon should be gpoIen 10 the prO\ISIon of mobile or fi)r;.ed water-spray system .. giving suit­able and effective protection for road tanker and rail tank car loadmg and unloading areas.

3.8.3 First-aid fire eXlinguishers

A <;ufficlcn I number of fi rst-a Id firc extinguishers of adeq Ui t ! size, suitable for LPG fLres. preferably of the dry powder tyP<', should be available a t \trateglc locations. Dry powder fire e\ungUlshers should be t o BS 34656. Foam e"(tmgUlsher<; are not sutlable for LPG fires.

3.8.4 Access

Sutlable access to and around the mslallatlon should be proVIded for fire­fightmg eqUipment and kcpt free at a l l t imes.

3.8.5 Isolaling rah'es

Shut-off valves, which may be automatic or remotely controllcd. should be provldcd at the tank. so that If accidental leakage occurs the supply of LPG can be stopped. Olher shut-off valves may be prOVided al StrategiC pomts.

3.8 6 Crass and l'eed remoHl1

Weeds. long grass and any combustible material should be removed from an area with 10 ft of any LPG tank of up to 500 gallonllj water capacity, and within 20 ft o f larger tanks. ( f weed k i l lers are used, chemicals such as sodium chlorate which are a potential source of fire danger should nct be selected for Ihis purpose.

3.8.7 Warnin� signs

Where smoking and naked lights are prohibited, promincnt notices to this effect should be posted, partlcul:uly at access points.

P A R T 4 O P E R A T I O S

4. 1 TRA INING

a. PerlJonnel respon .. iblc for the operation of cquipment and the handling of LPG should undcrswnd the physical characteristics of the product and be fanll llar with the relevant secllons of Ihis Code appertaining to their spheres of responsibIlity.

h. All persons concerncd wllh the storage and handling of LPG should be fanuhar WIth the fundamentals of fire-fighting and fire control with

34

•

particular reference to fires Involving LPG. They should also be familiar with the correct handling of any fire-fightlllg and fire-control equipm�nt

provided and. where appropriate, should be exercised In this respect at frequent mlcnals. The location of all ga� and liquid piping and valves

should be known and their u�e understood.

c. At the larger plants a proper emergency procedure should be laid down and clearly posted. R�ponslbllltles should be adequately defined and all personnel tramed 111 handling emergency situations.

4.2 SEGREGATION OF PRODUCTS

a. All lanh, and \�here necessar)' pipelines and other equipment, should be clearly marked 10 show the grade of LPG for which they arc sUlIable.

h. Where more than one grade of LPG is handled, the mter-connecting systems should be double-checked 10 ensure that a grade of LPG is nOI charged mto tanks. plpchnes or equipment not designed to handle it and that unacceptable product contammatlon will not occur.

4.3 PURGING AND FILLING TANKS AND SYSTEMS

D. When new tanks and system') are to be taken into commission. or tanks and system� which have been gas-freed arc filled, they should first be

cleared of air.

b. Air should be removed by e\'aCuallon or replaced by water, mert gas or lPG, dependent on circunl')tances.

NolI's: i. Evacuation ThiS method is only suitable for tanks designed for full vacuum conditions. Tanks should be evacuated down to 20'" of mercury vacuum ( 10" of mercury absolute).

ii. Waler Provision should be made for the complete removal of the water. Water should not be used m the case of storage for refrigerated LPG.

iii. Inert gas Admit sufficIent men gas until the oxygen content of the residual mixture is less than 10°'0 by volume (i.e. inert gas of free volume equal to the tank capacity). I f the source of mert gas IS In liqUid form, precautions should be taken to ensure complete vapOflsat!on and that no liquid enters the tank or system.

iv. LPG If LPG vapour is used to replace the aIr, then the lank and system will for a peflod of I1me contain an Inflammable mixture and an inflammable mixture will be ... ented from the tank and system; adequate precautIons to prevent ItS IgnitIOn are essential.

THIS METHOD SHOULD !';OT 81; USEt} UNLF.s5 UNDER THE STRICT CON­TROL OF COMPETENT AND I;'\PERIENCED PERSOSNEL.

35

c. I n filling the tank and �y�lem, care �hould be taken to prevent exce�sive chilling by the too rapid evaporation of the LPG pumped into it.

4.4 DRAINING OF TANKS

Particular care should be e'(crLlsed when dralnmg water from tanks in order to prevent e'Jcape of LPG. There .. hould be 2 dram valves as recom· mended m Clauses 2.3.8c. and 3.3.7('. The valve nearer the tank should be opened fir!:.t to an e\:tent �ufficienl to mamtaln a liquid full condilion on the downstream side. and drammg controlled by gradually opening the val"c furl her from the tank On completion of the draimng operation, the valve fUrlher from the tank. should be closed first, then the valve nearer to the tank ('lee also CJaus� 2.5.5 and 3.4.4).

4.5 PRODUcr TRANSFERS

a. Before LPG IS transferred from a tank to any other tank. whether it is a storage tank, road tanker or rail tank car, the followmg procedure should be followed:

1. The receivmg tank should be checked to ensure that it is in safe work· 109 condilton and that It I� not \0 be filled with a grade of LPG for which It IS not designed.

11. The receiving tank should be ched.ed to establish the quantity that it can safely receive.

I l l . The mter·connectll1& system (i.e. pipe work. fittll1gs. valves, hoses etc.) should be checked to ensure that \1 is 10 safe working condition.

b . Before and dunng LPG trnnsfers from lank 10 lank and on completion of the operation the receiving tank should be checked to ensure that it is not being overfilled and on cornplellon IS not filled abo\e liS safe working level.

c. In the case of road tankers and rail tank cars the following procedure should also be followed:

1. The vehicle should be prevented from accidental movement during the transfer operation. The parking brake of a road tankcr or the hand brake of a rail tank car should be on, and where necessary wheel chock blocks should be used.

11. Any driving Untt or electrical equipmenl nOI required and not specifi· cally designed for the transfer operation should be SlOpped and isolatcd.

Ill. Any accumulated slatlc electricity on a road tanker :;hould be dis· charged to earth and then the tank of the road tanker should be elcctrically bonded 10 the fixed Installation before any LPG transfer operation is carned oul.

IV. Before the vchlde is moved the liquid and vapour connections should be dLsconnected; the electrical bonding connections should then be broken.

36

• I

4.6 ATTENDANCE DURING OPERATIONS

a. A responsible per!<.on �hould rCm311l 10 atlendance dUflng all transfer opernllons.

b. No drain \ahe. bleed ,alve, pipeline elc In the LPG system v. h ich commUnicates dlrectl) 10 the OUlSlde air lohould be left open without an operator In attenaance.

c. I f It .'" necessary 10 dlsconlll1ue a lran",fer operation temporanly and return to complete It later, the loadmg hose :,hould be disconnected.

d. The person In charge of operations should ensure that transfer opera­tions arc stopped and all valves closed If an) of the following occur;

I. Uncontrolled leakage

11. A fire in the vicinity

Ill. An electrical storm In the viciOlty of an operation involving venling of LPG.

4.7 ACTION I N EMERGENCY

In any emergency SHuatlon H is of paramount imporlance to aVOid endangenng human life. I t IS almosl Impossible to lay down a definite procedure to follow m all cases, but the following aClions are indicated:

a. Summon help and fire-fightmg services.

b. Wherever possible. turn off all \'all,-cs to cut off or reduce the source of gas escape.

c. Evacuate all persons. except those neces�ary 10 deal with the emer­gency, from the danger area, especially from any area which IS In the path of the gas cloud.

Always approach any fire or gas leak from upwmd. Gas fires should normally be controlled but nOt extinguished until Ihe source can be CUI olf.

4.8 LIGHTING STORAGE AND OPERATI G AREAS

Operations should nOI be carned out durmg the hours of darkness unless adequate safe artificial lighting IS used.

37

A P P E .'1 D I X A

J . Liquefied Petroleum Gas S.lfclY Code' The I nSlItuteof Pe'ro'eum [967.

2. ' In .. lallalion of Fixed Bulk Storage at Consumer�' Premises': LPGITA 1 969.

3 . . laintcnancc of fixed Bulk LPG Vcs�el5 at Consumers' Premises': LPGITA 1 969.

4. 'Recommendallon, for prc\'enllon or control of fire involving LPG'; LPG ITA 1963.

5. SS 4250: 'Specificatlons for Commercial Butane and Propan'!' : British Standard .. Institution 1968.

6. BS 3465 : 'Dry powder portable fircc'\'tingui:)hers': British Standards Institution 1 962.

7. ep 1003: Pan 1 : 'Cholce, InstallatIon and Mamtenance of Flame­proof and Intrinsical!) Safe [lenrica1 Equipment': British Standards Institution 1 964.

8. Electrical Safety Code ' The I nstitute of Petroleum 1965.

9. as 2789; ' I ron castings with l>pheroidal or nodular graphite': British Standard .. Inl>tltutlon 1 96 1 .

10. BS 1 500: 'Fu::'lOn welded pressure vessels for general purposes' : BrIIll>h Standards InStitutIon 1958.

1 1 . BS 1 5 1 5 ' 'Fusion \\clded pressure vessels for use in the chemical, petroleum and allied mdustnel>': Bntlsh Standards I nstitullon 1 965 ( l'arl 1 ) and 1968 (Part 2).

1 2. ep 1 0 1 3 : 'Earthmg' : Bnmh Standards In::.titulion: 1 965.

Note: Acceptance of the above Codes relates only to the edition of the Code as noted.

38

A P P E N D I X B

REFERENCE TEMPERATURES

I. Reference temperatures for design

I n accordance with current practice in the United Kingdom. tanks should be designed and constructed 10 SS 1 50010, OS 1 5 1 51 1 or other recognlscd pressure vessel codes for the follOWing minimum design working pressures :

COlltel/IS Alill. desig" working presSlIre Commercial Butane 70 psig Commercial Propane 2 1 0 pSlg

However. British Standards based on the Reporl of the Home Office Gas Cylinders and Containers Committee (Apnl 1 968) 3rc currenlly being prepared. For tanks designed and constructed in accordance " u h these reqUirements, the temperature referred 10 In Clause 2.3. I .b. and 3.3. I .h. may be taken as:

50 C for lanks having a capacity exceeding 1 30 lures (approximately 28 gallons) but not exceeding 1 m) (approximately 550 gallons)

47·5 C for tanks having a capacity exceeding 1 ml but nOI exceeding 5m3 (approximately 1 100 gallons)

42 5 C for tan.ks having a capacity exceeding Srn} but not exceeding JOm} (approximately 6600 gallons)

41 C for tanks having a capacity exceeding 30m3 but not e1(ceedmg 100m3 (approximately 22.000 galLonos)

40"C for tanks having a capacity exceeding l OOm).

2. Reference lemperatures for filling ratio

In accordance with current pracllce in the United Kingdom, the highest temperature which the contents of the lank Wil l reach in service should be taken as 38 C for tanks above 3 fl in diameter and 4.5 C for tanks of smaller diameter. However, British slandards based on the Report of the Home Office Gas Cylinders and Containers Committee (April 1 968) are currently being prepared. For tanks designed and constructed in acccrd· ance With these requirements, the temperature referred 10 i n Clauses 2.3.9 and 3.3.8 may be taken as:

42·5 C for tanks having a capacity not exceeding 5m3 (approximately 1 100 gallons)

38 C for tanks having a capacity exceeding 5m3 but not exceeding 30m3 (approximately 6600 gallons)

37 C for tanks having a capacity exceeding 30m3 but not exceedlllg l OOm) (approximately 22,000 gallon!»

36 C for tanks having a capacity exceedmg lOOm)

39

Printed In �n,lond r .... Het �.jestr·' Sto'�on .... , Offiu by Hobbo ll\e PT,n'." Lld . Soul/'ornp'"'' ( 1 l94) D I o09U Klo 9 "