BOILERS
SCOPE:
This procedure procedure is intended to give guidance to the plant inspector to check, evaluate, and asses the condition of the water tubes boiler components and recommend any necessary repair.
Function
>> The purpose of the utility boilers is to produce superheated steam for use in the process units. The primary source of boiler feed water is the clean condensate returned from steam users throughout the complex. The makeup water is from the process water after it has been Demineralized. Both the condensate and the Demineralized water enter the deaerators D-6!"#B before reaching the t he boilers. The maximum continuous rating of the boiler bo iler is $%! Ton#h. The The normal operating temperature and pressure are & ' and a nd &&( )pag respecti*ely.
MAJOR PARTS
Economizer: " heat exchanger which is used to reco*er the heat from the fuel gases which otherwise would be lost up to the stack. +t is used to preheat the feed water of the boiler. b oiler. The economizer consists of spiral fin tubes connected to two headers lower and upper. The boiler feed water enters the economizer through the lower header and the preheated water enters the steam drum from the upper header. The The economizer has two set of manholes for cleaning and inspection.
Forced Draft Fan : " fan supplying air under pressure to the fuel burning e,uipment.
Induced Draft Fan : " fan exhausting hot gases fro the heat absorbing e,uipment.
Furnace/Fire Box "n enclosed space pro*ided for the combustion of fuel.
Mud Drum " drum at the bottom of the boiler which is connected to the steam drum by the *ertical bank tubes. The drum is also connected to the furnace wall tubes. +nside the drum an intermittent blowdown pipe is fixed along the drum bottom with 6 mm holes to remo*e any deposits from the drum.
Steam Drum: " drum at the top of the boiler which is connected to the mud drum by the *ertical bank tubes. The drum is also connected to the furnace wall tubes. The drum contains che*ron dryers that are installed at the top to remo*e the moisture.
Strainer etal screen with small openings to retain solids and particles in fuel media which could detrimentally detrimentally affect the operation of the burners.
Superheater The superheater is a con*ection type and it consists of three set of bank tubes secured to two headers by weld /oints. +t is installed between the screen tube zone. The saturated steam from the steam drum is superheated through the three pass superheater.
Wind box " chamber below the grate or surrounding a burner through which air under pressure is supplied for combustion of the fuel. 0ne type called a burner wind box which is a chamber around a burner in which an air pressure is maintained to ensure proper distribution and discharge of combustion air.
SILENCERS Two Two silencers to be checked checked in the boiler, boiler, one is the start-up Vent Silencer, and the second is the SV Silencer for the normal operation.
Stack
!urner
REFERENCES API, Guide for Inspection of Renery
Equipment, Chapter VIII- Direct-Fire Boilers and u!iliary Equipment, "econd Edition #$%&' API 510, (ressure Vessel Inspection Code, )aintenance, Inspection, and lteration, "e*enth "e*enth Edition #$$+' ASME, Boiler and (ressure Vessel Code,
"ection I, (oer Boilers, Edition #$$+' ASME, Boiler and (ressure Vessel Code,
"ection VIII, Recommended Guidelines For the Care of (oer Boilers, Edition #$$+'
BOILER INSPECTION
>> "ccording "ccording to "12 standard section + and 3+++ Boiler has to be inspected annually. "4+ 'hapter 3+++ does not specify any inspection inter*al. 5rom " "742T experience it has been decided that the boiler shall be down for inspection e*ery two years. There are two types of inspection during operation and during outage inspection.
DURING OPERATION INSPECTION
"" The inspection during operation should be done to ensure that the outside surface and parts are in good opera table condition. #t also to ensure no leaks, hot spots, corrosion, nor settlement are exist. The external inspection may be done during the operation of the boiler, however, the main foundation and supports of the $re box shall be done during the boiler outage.
FOUNDATIONS >>The important of foundation can not be o*eremphasized. "ny "ny o*erlook of the foundation fou ndation deterioration might lead to e,uipment bearing failures refractory failures steam leaks and.....etc. Ta Tapping the concrete with a hammer will re*eal deterioration or unsound conditions. 5oundation should be checked for8 A)- 1ettlement which is caused by water wash or high *ibration. 1ettlement of the foundation can be detected by cracks in the concrete brick walls and ad/acent flooring. 1ur*eyor9s le*el or transit or transparent hose water le*el can be used to check the settlement. Boiler manufacturer often put le*el marks on drums or other parts that can be used to check settlement.
B)- 1palling usually caused by excessi*e heat
mechanical shock the corrosion of reinforcing steel. C)- 'racks in concrete which may be caused by
excessi*e heat poor design material mechanical shock or une,ual settlement. D)- 1oundness of the anchor bolts.
LADDERS, STAIRWAYS, PLAT PL ATFO FORMS RMS & WA WALK LKWA WAY YS "" The ladders, stairways, platforms, platforms, and walkways should be checked carefully by visual inspection aided with light hammering and scraping the oxide scales and other corrosion products. They should be checked for% &racks. •!roken !roken parts. par ts. • Tightness Tightness of bolts. •Wear of ladder rungs and stair treads. • The The condition of of the platforms platforms 'ooring. •&orrosion beneath painted surfaces which will be •
PIPING
The piping and their connections are items may be affected if any *ibration settlement earth,uakes and fire damages occur to the boiler. They should be checked for8 :;igh *ibration. :
INSULATION
The insulation and cladding of the boiler components is considered as one of the ma/or items that it should be in good condition due to the fact that any defect or loss of insulation will cause loss of heat and may sub/ect personnel to heat burns. The insulation should be checked for8 :;ot spots may indicate hidden defects in the insulated parts. :=n-secured parts of cladding. :1ign of leaks may indicate a hidden problem. :Deterioration and general defects.
AUXILLARY EUIPMENT
"uxiliary e,uipment such as gauges connections sight glasses and safety *al*es may be inspected *isually for8 :=ndue *ibration. :'orrosion and breakage. •eneral deterioration .
DURING OUTAGE INSPECTION #nspection will be carried out when the boiler is out of service either in planned shutdown or an emergency shutdown. The emergency emergency shutdown shutdown usually in short short period of time, therefore, complete inspection could be di(cult. )owever, it is considered a good chance for checking the critical areas and*or the areas with previous problems. !efore starting internal inspection, the results of the recent external inspection and the previous internal inspection should be used as a guide for the current internal inspection, e. g. a hot spot on the casing
CONTINUATION!
+ preliminary inspection of the inside of the boiler shall be carried out before the boiler is cleaned. The location, amount, physical appearance, and analysis of mud and sludge or scale deposited on the inside of tubes and drums will provide information relative to the eectiveness of the feed water treatment, treatment, blowdown operation and method of cleaning needed. The preliminary inspection may also be helpful in determining determining which part of tubes or drums reuire close inspection.
FIRE BOX The fire box ?furnace@ is the main and ma/or component of the boiler. The fire box is constructed of water wall tubes backed up by firebricks ? refractory@ block insulation and steel plate casing. The fire box should be inspected internally by checking the following items *isually and#or by using any of the 7DT methods. TUBES:
"ll tubes should be checked for 8 : Blistering and Bulging. : 'racks.
:Bowing and 1agging. :'orrosion. :Deposit that will effect the heat transfer. :etal loss may be done by checking the wall thickness of the tubes using =ltrasonic as per A.$. :1oot and dirt shall be remo*ed and area below it should be inspected.
verheating. • Tube Tube may be x-rayed to to check the internal internal deposit and wall thinning. •
"ll the tubes should be inspected for signs of o*erheating corrosion and erosion. =sually o*erheating is caused by deposits or excessi*e scale on the water side of the tube. The nearest tubes to the burners are susceptible to o*erheating and should be closely examined for bulging blistering ,uench cracking sagging and bowing. Blistering and bulging is easily accomplished by shining a flashlight parallel to the length of the tubes so that bulges or blisters will cause shadows.
The locations of the thickness measurements shall be identified so next shutdown the readings will be taken in the same locations for comparison.
REFRACTORY The refractory should be inspected for8 :'racks. :2rosion. :elting. :Bulging. :5all down.
&racks in the refractory are common and are to be expected but if the cracks is severe, then repairs should be made. #f the erosion and melting are present, then the refractory has to be carefully evaluated before putting the boiler back into service. /etal shell and insulation
BURNERS "ll burners should be checked for8 •'orrosion. •2rosion of tips. •Burning and elting. •1palling. •'racks. •eneral deterioration.
STEAM DRUM
The drum should be inspected internally for8 :1eam welds cracks. :'orrosion. :4itting. :roo*ing. :1cale deposits and sludge accumulation in shell and tubes. :Tightness. :Deterioration. :1oundness. :1tructural stability. :etal loss
MUD DRUM
The mud drum ?water drum@ should be checked for8 :'orrosion. :4itting. :roo*ing. :'racking. :1cale deposits and accumulation of sludge in shell and tubes. •etal loss as
Special attention should be paid to all seam welds and should be examined for cracks and a nd corrosion. &orrosion ad0acent to the seam weld is more serious than a similar amount of corrosion in the solid plate away from the seams. &racks along the seams is likely to occur when the material is highly stressed.
SUPER"EATER
The superheater should be checked for8 :'orrosion and paint defects. :1igns of leaks. :'racks at weld /oints. :all loss of headers and tubes thickness check to be taken in fixed points as per :elting burning and#or heat damage to the internals. :1ign of insulation and refractory deterioration at the walls. :eneral damage or breakage.
ECONOMI#ER
The economizer should be checked for8 :'orrosion and paint failure. :'racking at weld /oints. :1igns of leaks. :all loss of header and tubes thickness check to be taken in fixed points. :Damage to the structural and *ane plates. :Tightness of bolts and clips of header and tubes. :1ecurity and cleanness of *ents.
BANK TUBES C"ANGER
The bank tubes chamber should be checked for8 :'orrosion and paint failure. :'racking at weld /oints. :1igns of leaks. :all loss as per :Damage to the structural and *ane plates. :Tightness of bolts and clips of header and tubes.
SIDE WALL TUBES
The side wall tubes should be checked for8 :'orrosion and paint failure. :'racking at weld /oints. :1igns of leaks. :all loss
WIND BOX AND F$D$ FAN
They should be checked for8 :'orrosion and paint failure. :2rosion due to ash particles. :Thinning and holes in the fan blades. :eneral deterioration. :Damage of the lou*ers near the burners. •"ny damage deterioration or paint failure on the burners *isible parts
STA ST A
The stack should be checked for8 :Cefractory damage :'orrosion on the stack metal parts. :2rosion. :0*erheating. :2xternal 4aint damage.
STRAINERS
Two Two strainers for the gas and the diesel fuel to be checked in the boiler shutdown. They are located at the top platform in the inlet lines to the boiler. They should be checked for8 :Breakage in the screen. :;ea*y deposit. :'orrosion. :5oreign materials. •Deterioration in the screen or the body
%AL%ES
During the boiler shutdown there are two *al*es to be checked one is the boiler feed water non-retaining *al*e and the other is the superheater non-retaining *al*e. They should be checked for8 :2rosion. :'racking in the seat and seat ring. :'orrosion. :eneral deterioration.
SILENCERS
Two Two silencers to be checked in the boiler one is the start-up 3ent 1ilencer and the second is the 413 1ilencer for the normal operation. The smaller one is for the start-up. They should be checked for8 :'orrosion internally or externally. :'racking in the weld /oints or the body. :Deterioration in the internals. :Damage to the connecting fittings. :'orrosion or deterioration of the inlet piping.
LUBE OIL COOLER The cooler usually opened during the scheduled boiler shutdown for cleaning and inspection. +t should be checked for8 :Tube plugging. :'orrosion. :2rosion in the channel co*ers or heads. :'racks or damage. +f leak is suspected the cooler should be hydrotested from the shell side to $.% times the design pressure of the shell and obser*e any leaks through the tubes this test should be done when all co*ers and heads are remo*ed.
T"ICKNESS MEASUREMENTS The thickness measurements shall be taken at se*eral locations ?"ttachment +++@ at the boiler as follows8 FIRE BOX:
"ll four sides of the wall tubes shall be co*ered by the thickness check at fixed locations. The thickness shall be checked at $.% . from the floor on the following selected tubes8 NORTH WALL: $ tubes first & from east & tubes at the middle ?tube no. %( to 6$@ and the last & tubes at the west side ?tube no. $$6 to$$E ).
CONTINUATION!
SOUTH WALL WALL (SCREEN & BAFFLE TUBES): TUBE S): ! screen tubes at the middle section ?tube no. A to E@. E baffle tubes first three at east side ! at the middle ?tube no. %$ to %!@ and the last ! tubes at west side ?tubes $ to $&@. WEST WALL WALL (BURNER SIDE): & tubes tubes at the center ?tube no. ( and E@ of both north and south sections. EAST WALL (MAN-WAY SIDE): E tubes first ! tubes at 7orth corner and ! tubes ?tubes no. to &@ at the center and the last ! tubes at south corner ?tubes n. &% to &A@.
STEAM DRUM: DRUM:
The thickness shall be checked on the steam drum at the following locations8 HEADS: Both heads shall be checked at !6E and $ 09clock positions. SHELL: The shell shall be checked at the top and the bottom sections and the thickness shall be checked Fat three locations east middle and west sides. The top section shall be checked from outside.
MUD DRUM: DRUM:
The thickness shall checked on the mud drum at the following locations8 HEADS: Both heads shall be checked at !6E and $ 09clock positions. SHELL: The shell shall be checked at the top and bottom sections in three locations east middle and west sides.
CONTINUATION! SUPERHEATER:
The thickness shall be checked on the superheater at the following locations8 TOP CHAMBER: TUBES: $ tube in each of the east middle and west banks tube no. $ counting from east of each bank. HEADER: ! locations east middle and west.
BOTTOM CHAMBER: TUBES: $ tube in each of the east middle and west banks tube no. $ counting from east of each bank. HEADER: ! locations east middle and west.
ECONOMIZER: ECONOMIZER:
The thickness shall be checked on the economizer at the following locations8 TOP CHAMBER: TUBES: $ tube in each of the east middle and west sides ?tubes no. $ $A and ! counting from east@ of both south and north ends.
CONTINUATION! 3 locations east, middle and west side plus one point at the bottom side of each branch.
HEADER: HEADER:
BOTTOM CHAMBER: TOP SECTION TUBES: $ tube in each of the east middle and west sides ?tubes no. $ and ! counting from east@ of the north end. BOTTOM SECTION TUBES: $ tube in each of the east middle and west sides ?tubes no. $ and ! counting from east@ of the south end.
CONTINUATION! BANK TUBES TUBES CHAMBER: CHAMBER:
The thickness shall be checked on $ tube in each of the north middle and south sides ?tubes no. $ $A and ! counting from north@ at $.% from the floor. SIDE WALL TUBES: "ll 6 tube shall be checked one point each.
"YDROS "YD ROST TATIC TEST
"" +fter completing the inspection, the boiler shall be hydrostaticly tested to a pressure eual to 1.2 times the maximum allowable working pressure 3/+W4, thus the testing pressure shall be 5567 8a9. The pressure shall be increased gradually, max. :;; 8a9 per minute and shall be held for at least :; minutes. Then the test pressure shall be reduced to the /+W, 6<=7 8a9 and shall be maintained at this pressure until the #nspector certify that there are no leaks or other apparent defects.
