1_214_boilersafetyvalveregulations.ppt

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Singapore Maritime Academy/ Singapore Polytechnic Kalyan Chatterjea/June 20051

Boiler>Safety v/v>Regulations

Boiler Safety Valve Regulations

Based on ABS Rules

(2005)



Singapore Maritime Academy/ Singapore oltec!nic

"alyan #!atter$ea/%une 2005

2


Number of Safety Valves for Boiler

&ac! 'oiler (including e!aust gas 'oiler) and steam

generator is to 'e fitted it! at least one safety valve

and !ere t!e ater*!eating surface is more t!an

+,-5 m2 (500 ft2). to or more safety valves are to 'e

provided-

!e valves are to 'e of eual si1e as far as

practica'le and t!eir aggregate relieving capacity isnot to 'e less t!an t!e evaporating capacity of t!e

'oiler under maimum operating conditions-






Safety Valves – Size Restrictions

3n no case. 4

is t!e inlet diameter of any safety valve forpropulsion 'oiler and super!eaters used to generatesteam for main propulsion and ot!er mac!inery to'e less t!an mm (6-5 in-) nor more t!an 602 mm(+ in-)-

4 7or auiliary 'oilers and e!aust gas economi1ers.t!e inlet diameter of t!e safety valve must not 'eless t!an 68 mm (/+ in-) nor more t!an 602 mm (+in-)-





+


Safety Valves – for Superheater &

Economizer

Superheater - &ac! super!eater. regardless of

!et!er it can 'e isolated from t!e 'oiler ornot. is to 'e fitted it! at least one safety valveon t!e super!eater outlet-

Economizers- &ac! economi1er. !ere fitted

it! a 'ypass. is to 'e provided it! a sentinelrelief valve. unless t!e 'ypass arrangement illprevent a 'uildup of pressure in t!eeconomi1er !en it is 'ypassed-





5


Minimum Relieving #apacity

for Boiler Safety 9alve

3n all cases. t!e safety*valve relieving capacity is to 'e

determined on t!e 'asis of t!e 'oiler !eating surface

and ater*all !eating surface along it! t!e fuel*

'urning euipment. and is not to 'e less t!an t!at

given in t!e ta'le (see later)-

:!ere certification 'y t!e 'oiler manufacturer of t!e

evaporative capacity of t!e 'oiler under maimumoperating conditions indicates a !ig!er capacity. t!e

!ig!er capacity is to 'e used-





,



for Boiler Safety 9alve





;



for Super!eater Safety 9alve

:!ere a super!eater is fitted as an integral part of a'oiler it! no intervening valve 'eteen t!e

super!eater and t!e 'oiler. t!e relieving capacity of t!esuper!eater safety valve. 'ased on t!e reducedpressure. may 'e included in determining t!e totalrelieving capacity of t!e safety valves for t!e 'oiler as a!ole-

3n suc! a case. t!e relieving capacity of t!esuper!eater safety valve is not to 'e credited for moret!an 25< of t!e total capacity reuired-







for Super!eater Safety 9alve

!e safety valves are to 'e so set and

proportioned t!at. under any relievingcondition. sufficient steam ill pass t!roug! t!e

super!eater to prevent over!eating t!e

super!eater-

Specially designed full*flo super!eatervalves. pilot*operated from t!e steam drum.

may 'e used-





8


ressure Rise =uring Relieving

7or eac! 'oiler. t!e total capacity of t!e

installed safety valves is to 'e suc! t!at t!evalves ill disc!arge all steam t!at can 'e

generated 'y t!e 'oiler it!out alloing t!e

pressure to rise more t!an ,< a'ove t!e

maimum alloa'le oring pressure-





60


ressure Setting 4 Boiler =rums

At least one safety valve on t!e 'oiler drum is to 'e set at or'elo t!e maimum alloa'le oring pressure-

3f more t!an one safety valve is installed. t!e !ig!est settingamong t!e safety valves is not to eceed t!e maimum alloa'loring pressure 'y more t!an <-

!e range of pressure settings of all t!e drum safety valves is noto eceed 60< of t!e !ig!est pressure to !ic! any safety valve

is set- 3n no case is t!e relief pressure to 'e greater t!an t!e design

pressure of t!e steam piping or t!at of t!e mac!inery connectedto t!e 'oiler plus t!e pressure drop in t!e steam piping-





66


ressure Setting 4 Super!eaters

:!ere a super!eater is fitted. t!e super!eater safety valve is to 'eset to relieve at a pressure no greater t!an t!e design pressure of

t!e steam piping or t!e design pressure of t!e mac!ineryconnected to t!e super!eater plus pressure drop in t!e steampiping-

3n no case is t!e super!eater safety valve to 'e set at a pressuregreater t!an t!e design pressure of t!e super!eater-

3n connection it! t!e super!eater. t!e safety valves on t!e 'oilerdrum are to 'e set at a pressure not less t!an t!e super!eater*valve setting plus 0-+ 'ar (0-5 gf/cm2. 5 psi). plus approimatelyt!e normal*load pressure drop t!roug! t!e super!eater-





62


Safety 9alve 4 &asing ?ear

&ac! 'oiler and super!eater safety valve is to 'e

fitted it! an efficient mec!anical means 'y !ic!t!e valve disc may 'e positively lifted from its

seat-

!is mec!anism is to 'e so arranged t!at t!e

valves may 'e safely operated from t!e 'oilerroom or mac!inery space platforms. eit!er 'y

!and or 'y any approved poer arrangement-

S f /





6


Safety Valve – Connection to Boiler & Superheater

Safety valves are to 'e connected directly to t!e

'oiler. ecept t!at t!ey may 'e mounted on acommon fitting-

@oever. t!ey are not to 'e mounted on t!e same

fitting as t!at for t!e main or auiliary steam outlet-

!is does not apply to super!eater safety valves.!ic! may 'e mounted on t!e fitting for t!e

super!eater steam outlet-

B il S f t / R l ti





6+


Safety 9alve 4 &scape ipe

!e area of t!e escape pipe is to 'e at least eualto t!e com'ined outlet area of all of t!e safetyvalves disc!arging into it-

!e pipe is to 'e so routed as to prevent t!eaccumulation of condensate and is to 'e so

supported t!at t!e 'ody of t!e safety valve is notsu'$ected to undue load or moment-

B il S f t / R l ti





65


Safety 9alve 4 =rain ipe

Safety valve c!ests are to 'e fitted it! drain

pipes leading to t!e 'ilges or a suita'le tan-o valve or coc is to 'e fitted in t!e drain pipe-

B il S f t / R l ti





6,


Safety 9alve 4 ressure

Accumulation est

Safety valves are to 'e set under steam and tested it!pressure accumulation tests in t!e presence of t!e Surveyor-

!e 'oiler pressure is not to rise more t!an ,< a'ove t!emaimum alloa'le oring pressure !en t!e steam stopvalve is closed under full firing condition for a duration of 65minutes for firetu'e 'oilers and ; minutes for atertu'e'oilers-

=uring t!is test. no more feed ater is to 'e supplied t!an t!atnecessary to maintain a safe oring ater level-

!e popping point of eac! safety valve is not to 'e more t!an< a'ove its set pressure-

B il >S f t / >R l ti





6;


Safety 9alve 4 ressure

Accumulation est (aiver)

:!ere suc! accumulation tests are impractical 'ecause of super!eaterdesign. an application to omit suc! tests may 'e approved. provided t!efolloing are complied it! 4 All safety valves are to 'e set in t!e presence of t!e Surveyor-

4 #apacity tests !ave 'een completed in t!e presence of t!e Surveyor on eac!valve

4 type-

4 !e valve manufacturer supplies a certificate for eac! safety valve stating itscapacity at t!e maimum alloa'le oring pressure and temperature of t!e

'oiler- 4 !e 'oiler manufacturer supplies a certificate stating t!e maimum evaporation

of t!e 'oiler-

4 =ue consideration is given to 'ac pressure in t!e safety valve steam escapepipe-




Singapore Maritime Academy/ Singapore olt ! i


6


#!anges in Safety 9alve Setting

:!ere. for any reason. t!e maimum alloa'le oring

pressure is loer t!an t!at for !ic! t!e 'oiler and safetyvalves ere originally designed. t!e relieving capacity oft!e valves under loer pressure is to 'e c!eced againstt!e evaporating capacity of t!e 'oiler-

7or t!is purpose. a guarantee from t!e manufacturer t!at

t!e valve capacity is sufficient for t!e ne conditions is to'e su'mitted for approval. or it is to 'e demonstrated 'y apressure accumulation test. conducted in t!e presence ofa Surveyor-

1_214_boilersafetyvalveregulations.ppt

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