5
PREPARATION FOR START UP The following following preparat preparations ions are meant meant for a unit unit start start up after after mainten maintenance ance turna turnarou round nd activ activiti ities. es. Some Some piece pieces s of equi equipme pment nt were were maint maintain ained ed,, fixed fixed,, replaced. The unit is isolated at BL, with closed block valves and/or spectacle blinds, for the process circuits and, possibl, for utilit sstems as well. Befor Before e an an activi activit t can can start start it is neces necessar sar to close close all all work work permi permits ts for for comp comple leti tion on,, remo remove ve from from the the unit unit all all tool tools s and and mate materi rial als s used used duri during ng maintenance, send out of the area all maintenance and contractors workers.
5.1
Plant Ch Check-Ou -Out !or a normal start"up an interdependent sstems should be online or in the appropriate state for this start"up procedure. !or example, if a sstem being started is part of a flow stream, the upstream and downstream sstems should be online or pressuri#ed and read to deliver or receive product.
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Safet issues
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$ork plan
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%alves line"up
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&e"isolation 'blinds list(
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)urge requirements
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)ersonal )rotective *quipment
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+ommon )rotective *quipment
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Safet *quipment
)rerequisites for start"up nspection of the plant can be basicall divided into the following areas. +har +harge ge heat heater er . 0eactors 1. %essels 2. 3eat 3eat *x *xchan change gers rs 4. )umps 5. +ompre mpress sso ors 6. )iping
7. nstrumentation 8. +atalst/+hemicals nventor
On Charge Heater check that: Radant Sect!n •
3eater is clean and free from debris.
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0efractor is in good condition before and after refractor dr"out. 9o refractor is resting on tubes.
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3eater shell is sealed to prevent escape of hot gases and entrance of atmospheric moisture during shutdown.
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:dequate space for tube expansion Tubeskin thermocouples, are located properl and installed so that the have good contact with the tubeskin.
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Snuffing steam connections are not covered b refractor.
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%alves on snuffing steam are located remote from the heater, with drain valves and steam traps upstream of final block valve for condensate removal.
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Soot"blowers are installed and are out of heater.
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$eep holes provided in snuffing steam lines at low points are clean.
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3eater instrument connections and sampling connections are open " not filled or covered with refractor.
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!uel gas, fuel oil and pilot burner tips are clean and oriented properl.
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Burners are properl mounted with clearance for firing and removal.
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&er is free to move full open and closed; its position indicator is correct both at the stack and at the damper control.
C!n"ect!n Sect!n and Stack •
f extended surface elements are allowed, the bottom three or more rows of convection tubes must be bare.
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9o refractor is on the tubes.
E#ternal In$%ect!n •
)latforms for access to all observation ports, instrumentation, sample connections, sootblowers, and damper connections.
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*xplosion doors located such that heater gases will not flow towards process equipment and platforms.
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*xplosion doors located such that doors can open completel.
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nstrumentation and sampling connections.
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&er position indicator visible from damper control; damper control functioning properl.
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)ocketed crossover connections have flanged drains.
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solation valves on snuffing steam are located remote from the heater, with drain valves and steam traps upstream of final block valve for condensate removal. $eep holes provided in snuffing steam lines at low points.
On C!&'u$t!n Ar Fan$ check that: •
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:ll instruments are installed 'including auto starts(. Lube oil sstem is operable.
On Fuel S($te&$ check that: •
!uel lines have batter limit block valves which are remote from the heater and easil accessible.
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!uel oil piping and its steam tracing are correctl arranged.
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!uel lines to pilots and burners can be easil disconnected from burners for burner removal.
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!uel oil lines at burner valves are correctl piped with steam crossovers. :ll steam lines have adequate traps and condensate drains.
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Shutdown solenoids for fuel shutoff valves have been set properl.
On React!r check that: •
The reactor internals are exactl with the design specifications
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The good distribution is to be attained and the catalst migration is to be avoided
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nlet distributors, quench distributors- metallurg, tpe, si#e, opening si#es, freedom to expand
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+atalst support grids- metallurg, grid tpe and dimensions, screen tpe and si#e, supports, welding.
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The vessel has been hdrostaticall tested.
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0eactor skin thermocouples are located properl and installed so that the have good contact with the wall.
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nlet and outlet lines are connected.
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!langes on catalst withdrawal no##les are installed.
)e$$el$ •
%essel tras- spacing; levelness, orientation and dimensions of weirs, downcomers, accumulators, drawoff and trap tras, seal pans, distributors, baffles, no##les, tra contact devices; metallurg of tras, contact devices, clips, bolts, nuts and gaskets; freedom of movement of valve caps or other contact devices; number, si#e, and distribution of tra contact devices or perforated plate holes; proper fit of all internals and proper welding of support rings or other support devices; liquid tightness of drawoff tras, seal pans and accumulators, all bolting and clips tightened.
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=esh blankets and outlet screens- si#e, location, levelness, suitabilit of fit 'no bpassing allowed(, metallurg of blanket, support, tie wires, and grids.
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%ortex breakers- tpe, si#e, and orientation.
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Baffles- tpe, orientation, levelness.
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nstrument no##les- location, orientation, cleanliness, thermowell length and metallurg, baffle si#e and tpe.
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nlet distributors- tpe, si#e, orientation, levelness, freedom to expand.
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nternal ladders and other devices- location, si#e, orientation, properl secured..
*eneral •
The vessel should be clean 'free from trash( and should not have excessive mill scale.
E#ternal In$%ect!n •
=anwas and no##les- location, si#e, flange rating and finish, metallurg, with proper gaskets, nuts and bolts.
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Ladders and platforms- correctl positioned, secure and free to expand.
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nsulation and steam tracing- provided as specified and has expansion >oints as required.
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%essel grounded correctl.
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+orrect vessel elevation.
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%alves and instrumentation- easil accessible from grade or platform.
P%ng: •
:dequate supports and guides for all connecting lines.
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Level and pressure instrument connections drain to a safe location.
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%ents to atmosphere or blowdown provided as specified.
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0elief valves have been bench tested.
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+heck valves exist on utilit line connections where hdrocarbon backup could occur.
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+onnections available for steaming/purging of the vessel.
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!ireproofing of structure and supports is complete.
Flter$ !or filters, the same checking as for the vessels must be completed. n plus, check if"
: complete set of filters cartridges and gaskets are purchased as commissioning spare parts-
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The isolation is in according with the pro>ect specification and with the vendor requirements.
On Heat E#changer$ check that: •
*xchanger is free to expand. Slot length of sliding plates adequate for expansion. *xchanger should not be tied down at both ends. +heck sliding ends of exchangers with regard to expansion of exchangers and connecting pipe.
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%ent and drain connections are installed.
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&esign temperature, pressure and pressure"drop ratings.
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9o##le si#e, flange tpe, rating, facing and metallurg; vent and drain connections.
On Ar C!!led e#changer check that: •
?:uto"variable? or ?standard"pitch? fans, as specified.
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=otor switches accessible from grade and located near the exchanger.
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!an pitch set correctl as determined b fan amperage draw.
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%ibration switch on each fan.
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)roper motor/fan rotation. =otors properl grounded.
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)roper elevation and distances from connecting equipment.
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Belt tension on motor drive pulles is equal and correct.
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=otor amperage can be easil checked.
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*xchanger free to expand.
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=anifold piping arrangements as shown on *!&s.
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Split header design where specified.
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!ree draining requirements, as shown on *!&s.
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Tube fin surfaces are in good condition with no construction debris on top of the fins.
Pu&%$ general check$. The +!ll!,ng te&$ $h!uld 'e checked +!r all %u&%$: •
Suction strainer easil removed for cleaning.
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&ischarge pressure gauge readable from discharge block valve.
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Suction/discharge valves easil accessible and operable, and near to the pump. :ccessibilit of auxiliar piping and controls.
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$arm"up lines provided across discharge check valve when pumping hot fluids.
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@rounding devices.
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Steam tracing and insulation provided on suction/discharge lines, pump casing, and process seal flush lines.
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=inimum flow lines 'with restriction orifice(, if required. :dequate means for venting and draining the pump casing.
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0otating parts protections between pumps and drivers.
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+heck valves are installed in the correct direction.
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:ll drains from pumps and associated piping and instrumentation should be routed to a safe location.
On Centr+ugal Pu&%$ check that: •
Sight flow indicators, inlet/outlet shutoff valves on cooling water lines are installed.
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Thermometers/pressure gauges for gland seal and flushing oil manifolds are installed.
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0estriction orifices 'if required( present in seal flush manifold piping are correctl installed.
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+ooling water to mechanical seals on pumps operating at high temperature is fitted.
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)roper direction of rotation has been controlled. :uxiliar lube oil sstem 'if provided( is read for operation. Temporar strainer is installed.
On Rec%r!catng Pu&%$ check that: •
+ooling/lubrication sstems are installed.
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)ump stroke ad>ustment device is available.
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)ulsation suppression devices, if required, are fitted.
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0elief valves are installed.
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=eans for calibrating the pump flow rate are fitted.
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Temporar strainer is installed.
On Rec%r!catng C!&%re$$!r$ check that: •
:cidi#ing requirements have been met and acidi#ed piping is not in contact with the atmosphere 'under nitrogen blanket(, includes both process and lube oil piping. =ill scale must be removed from the compressor section b +hemical +leaning in order to reduce the possibilit of solids entering the compressors. The exact procedures to be followed are supplied b the compressor vendor. The following items must be chemical cleaned- all gas piping including spillback lines, compressor suction drum gas coolers and intercoolers.
!ield nspection The following items should be checked in the field•
=aterials of construction; flange tpe, rating, finish, gasketing.
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nstrumentation
for
conformit
to
pro>ect
specifications,
location,
operabilit and access. •
Lube oil sstem/cooling water piping, including sight flow indicators.
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&istance piece/packing vents piped correctl.
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:dequate and accessible drains which are routed to a safe location. Single strand steam tracing on the bottom of suction lines and snubbers,
as specified; insulation as specified for heat retention and personnel protection. •
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:utomatic suction valve unloader operation. Two compartment distance pieces, if required 'greater than 1A mol percent hdrogen in process gas(.
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:cidi#ing requirements have been met and acidi#ed piping is not in contact with the atmosphere 'under nitrogen blanket(, includes both process and lube oil piping.
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)rovision for suction strainers, if required.
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Buffer gas lines are fitted
In$tru&ent$: :ll instruments should be checked as soon as possible so that an malfunctions or other faults can be detected earl. The instrument checkout should include the following items•
)ressure test of instrument air lines
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+ontrol valve action and calibration
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)ositioner calibration
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Board calibration and loop check
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Thermocouple calibration and identification
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Level instrument calibration
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Thermometers, pressure gauges, etc.
:ll orifice plate bores should be measured, recorded and compared with required si#es. The orifice plates should also be checked to see if the were counterbored wherever required. :fter hdrotesting and water flushing have been completed, the orifice plates can be installed.
P%ng •
The unit must be constructed in accordance with *ngineering !low &iagrams '*!&s(, including all details, elevations, dimensions, arrangements, and other notes on the *!&s.
ect design. :lso, piping for special procedures such as dr"out, special materials preparation, regeneration and/or alternative flow schemes ma have been incorporated into the units design, and the unit should be able to operate in all of these modes with piping as designed and constructed.
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!or the connections to other process facilities, adequate means must
be provided to receive feed from or send products to these facilities without contamination of these streams, and minimi#e as much as possible the effects of upsets of other process units especiall where contamination of feed or product stream might occur. +heck all tankage interconnections to minimi#e the possibilit of stream contamination outside of the batter limits. •
+heck that adequate means of measuring flows, pressures, and temperatures, and sampling of all process streams has been provided.
The following items must be checked to ensure conformit to the pro>ect design specifications•
!langes- rating, facing, and metallurg; tpe 'tpicall, ? and smaller are socket weld, C? and larger are weld neck flanges(.
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@askets- tpe; metallurg 'materials of retainer, >ackets, winding, filler, etc.(; thickness, ring si#e, etc.
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!ittings, connections and couplings- rating and metallurg.
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%alves- rating and metallurg 'bod, trim, seats, etc.(; packing; seat inserts; bonnet gaskets; grease seals; socket"weld or flange tpe, rating and facing; installed in correct direction of flow; lubricant provisions; gear operators; extended bonnets; stops; ease of operation.
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Bolting- stud or machine bolts; bolt and nut metallurg; bolt si#e.
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The hdrotest connections for process lines are seal welded.
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)ipe- metallurg, thickness; seamed or seamless; lining.
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Tubing- si#e and thickness; metallurg; seamed or seamless.
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@auge glasses-
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Through"view tpes should have rear"mounted lights.
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&esign pressure and temperature.
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Special materials of construction.
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&rains to safe location.
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%isible from grade 'or platform, if required(.
)ressure relief valves•
Si#e and stle.
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Lever requirement.
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nlet/outlet flange material, facing and rating.
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Set pressure " must be bench tested.
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=etallurg of no##le, disc, spring, etc.
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Tpe 'pilot operated, balanced, etc.(.
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nlet/outlet block valves car"sealed open; valve stems installed in hori#ontal or below.
@eneral•
Dtilit sstems within the batter limit should follow all relevant pipe class specifications in the same detail required for process lines.
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)ackage sstems 'modular units, etc.( shown on the *!&s should follow all relevant pipe class specifications in the same detail required for other process lines.
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*xpansion- review the phsical installation to ensure that no expansion problems will occur when the unit gets hot and that•
+olumn overhead, reflux, feed and other lines are free to
expand. •
0otating equipment will not be pulled out of alignment.
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Sufficient expansion loops have been provided on long hot
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)ipe shoes are free to move in one direction, and are
lines. resting on supports of sufficient si#e that the shoe will not fall off the support. •
3igh point vents and low point drains should be installed where necessar.
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Spectacle blinds should be provided where required.
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+ar"sealed valves should be locked in proper position.
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Spring hangers should have locking pins removed 'after hdrotesting( and necessar ad>ustments should be made for hot/cold position after startup.
Catal($tChe&cal In"ent!r(
+atalst t must be verified that sufficient quantities of catalst, catalst support material, and other materials 'such as ceramic fibre rope, etc.( are on site, in good
condition, and properl stored 'for example, in drums, indoors, and on pallets to prevent contact with moisture(. t must be verified that all equipment required to load the catalst is on site and in good condition. +onsider estimated quantities and detail spec +hemicals t must be verified that the proper tpe and quantit of chemicals 'such as inhibitors, sulfiding agent, soda ash, etc.( are on site and properl stored.
5.1.1
Operational Checks The plant operator has to make several checks-
Act!n
+onfirm that all construction and repair work on the sstem is completed. +onfirm that sstems are isolated from an of the maintenance activities.
+onfirm that all permits and maintenance checklists are closed out.
1
+onfirm that the drain, vent, and bleed valves are in the closed position.
2
+onfirm that the blinds and flanges are removed and documented. +onfirm that energ isolation has been removed. !ollow the Safe $ork )rocedures =anual 'Lock
4 5
+onfirm that the safet and fire fighting equipment is in place, operational, and read for use.
6
+onfirm that the status of each temporar defeat is correct
7
+onfirm that housekeeping has been properl carried out.
5.1.2
Maintenance Checks
Act!n
+onfirm that control and shutdown loops are functional.
*nsure that the control valves, Blow &own %alves, Shut &own %alves and *mergenc Shut &own %alves are stroked to confirm that the valves are operating correctl.
1
+onfirm that 0estriction
2
+onfirm that all instruments are lined up and calibrated.
4
+onfirm that electrical power is connected and tested for an necessar equipment.
5
+onfirm that insulation is replaced on equipment where appropriate.
5.
E$ta'l$h&ent !+ Utlt( Ser"ce$ :fter maintenance and before purging, all the utilities must be prepared, in order to be available before starting up the process equipment. The various utilit lines should be tested and placed into service as soon as the construction schedule allows. )ressure tests should be carried out on the steam, condensate, air, fuel gas, fuel oil, flare, and nitrogen lines. The steam lines should be warmed up graduall to prevent damage b water hammer. :t the same time, all steam traps and condensate lines should be placed into service. Scale and construction debris can be convenientl removed from the steam lines b blowing them as long as necessar with steam. The other utilit lines can be cleaned b blowing with steam or air, or b water flushing if possible. :ll utilit lines, with the exception of fuel and flare, can be put into service as soon as the construction schedule allows.
5.2.1
Instrument Air =ost often, during maintenance activities, nstrument :ir sstem is kept in service with the specific instruments working.
5.2.2
solate all users turning closed the spectacle blinds or using removable blinds where required
0emove !T"A6 orifice plate. .'if some piping work has been done on the line upstream !T(
1
Turn open BL spectacle blind and remove the final blind flange of the header
2
nform nstrument :ir Dnit responsible of air usage
4
5
Blow the header until the air coming out from the end flange is clean
6
0einstall !T"A6 orifice plate and final blind flange of the header
7
)ressuri#e the sstem and check )@"2AA
8
Blow all branches to users before feeding them
Plant Air =ost often, during maintenance activities, )lat :ir sstem is kept in service as it might be useful for maintenance works.
5.2.3
0emove !T"A6 orifice plate. 'if some piping work has been done on the line upstream !T(
Turn open BL spectacle blind
1
nform )lant :ir Dnit responsible of the air usage
2
4
Blow the sstem until the air coming out from hose connections is clean
5
0einstall !T"A6 orifice plate
6
)ressuri#e the sstem 'check pressure via )@"22(
Nitrogen =ost often, during maintenance activities, nitrogen sstem is kept in service even if isolated 'blinded( at equipment connections.
Act!n
5.2.4
solate all users turning closed the spectacle blinds or using removable blinds where required
0emove !T"A54 orifice plate.'if some piping work has been done on the line upstream !T(
1
Turn open BL spectacle blind and remove the final blind flange of the header
2
nform 9itrogen )roduction Dnit responsible of nitrogen usage
4
Blow the header until the nitrogen coming out from the end flange is clean
5
0einstall !T"A54 orifice plate and final blind flange of the header
6
)ressuri#e the sstem and check )@"24
7
Blow all branches to users b disconnecting, if necessar, at the spectacle blinds before the user connections
Utilit !ater Dtilit water is ver seldom put out of service as it ma be functional to maintenance activities. n case of isolation and maintenance act as followsAct!n
5.2.5
0emove !T"A64 orifice plate 'if some piping work has been done on the line upstream !T(.
Turn open BL spectacle blind.
1
$ash header and lines from BL to all hose connections until water is clean
2
0einstall !T"A64 orifice plate
4
)ressuri#e the sstem
"rinking #ater &rinking water should never be put out of service as it feeds safet showers and eebaths. n case of isolation and maintenance act as followsAct!n
0emove !T"A65 orifice plate 'if some piping work has been done on the line upstream !T(
Turn open BL spectacle blind
1
$ash header and lines from BL to showers and eebaths until water is clean
2
0einstall !T"A65 orifice plate
4
)ressuri#e the sstem
5.2.$
Cooling !ater +ooling water suppl and return headers are seldom put out of service. n case of isolation for maintenance act as followsAct!n
5.2.%
0emove !T"A55 orifice plate .'if some piping work has been done on the line upstream !T(
Turn open +S and +0 BL spectacle blinds.
1
solate all user inlets and outlets 'coolers, pumps and compressors cooling sstems(
2
0emove both headers '+S and +0( end blind flanges
4
nform +ooling $ater Dnit responsible of the water usage
5
$ash headers from BL to their end flange until water is clean
6
0einstall !T"A55 orifice plate and headers terminal blind flanges
7
$ash lines to each user from the headers to drains
8
*stablish circulation through users as needed
&oiler 'ee( !ater HP /!ler Feed 0ater 3) B!$ header is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as followsAct!n
Turn open BL spectacle blind
+lose user valves 'line block valve upstream of 11"!%"A2 and, 11"T%"21 assembl(
1
nform B!$ Dnit responsible about water withdrawal
2
Slowl open BL valve and pressuri#e the sstem
4
&rain until water is clean
5
n case of cleanliness doubts sample B!$ from T% upstream drains and check for iron presence
n case of maintenance of the header itself, it is better to wash the sstem with utilit water, 'through temporar connections( from BL to the end of the header 'removing !T orifice plate and the blind flange at the end( to minimi#e B!$ losses and safet problems 'B!$ is hot, at high pressure and more expensive than D$(.
P /!ler Feed 0ater
=) B!$ header is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as followsAct!n
5.2.)
Turn open BL spectacle blind
+lose user valves 'line block valve upstream of 11"T%"15 assembl(
1
nform B!$ Dnit responsible about water withdrawal
2
Slowl open BL valve and pressuri#e the sstem
4
&rain until water is clean
5
n case of cleanliness doubts sample B!$ from T% upstream drains and check for iron presence
"eminerali*e( !ater &eminerali#ed water header is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as followsAct!n
Turn open BL spectacle blind
+lose all user valves
1
nform &emi $ater Dnit responsible about water withdrawal
2
Slowl open BL valve and pressuri#e the sstem
4
&rain until water is clean
5
n case of cleanliness doubts, sample &= and check for iron presence
n case of maintenance of the header itself, it is better to wash the sstem using Dtilit $ater 'through temporar connections( from BL to the end of the header 'removing the !T orifice plate and blind flange at the end( in order to save &emi $ater wastage.
5.2.+
,o# Pressure -team L) Steam sstem is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as follows.
Act!n
Turn open BL spectacle blind
+lose all user valves
1
2
4
Slowl open BL valve and graduall warm up the sstem b draining condensate from low points such as drains and hose connections
5
$hen condensate is clean and hot enough, close drain valves and check header steam traps performance
6
!ull open BL valve and pressuri#e the sstem 'check pressure via 11")@"2A2(
7
+ommission steam tracing sstem
n case of maintenance of the header itself, it is better to wash the sstem using Dtilit $ater, 'through temporar connections( from BL to the end of the header 'removing !T orifice plate and the blind flange at the end( and then blow the sstem with steam until everthing is clean.
5.2.1
,o# Pressure -team Con(ensate L) Steam +ondensate sstem is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as followsAct!n
5.2.11
Turn open BL spectacle blind
+lose all valves from users
1
2
+rack open isolation valve at BL and pressuri#e the sstem 'check pressure via 11")@"2A1(
4
+lose drain valves
5
!ull open BL valve after pressuri#ation
Me(ium Pressure -team =) Steam sstem is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as followsAct!n
Turn open BL spectacle blind
+lose all user valves 'line block valve upstream of each control valve(
1
2
4
Slowl open BL valve and graduall warm up the sstem b draining condensate
5
$hen condensate is clean and hot enough, close drain valves and check header steam traps performance
6
!ull open BL valve and pressuri#e the sstem 'check pressure via )@"2A(
7
+lose the warm"up bpass valve
n case of maintenance of the header itself it is better to wash the sstem with utilit water, 'through temporar connections( from BL to the end of the header 'removing the !T orifice plate and blind flange at the end( and then blow the sstem with steam until everthing is clean.
5.2.12
/igh Pressure -team 3) Steam sstem is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as follows. 3) Steam sstem is normall put out of service >ust b closing isolation valve at BL and, if necessar, b turning closed the BL spectacle blind. To put the sstem in service act as followsAct!n
Turn open BL spectacle blind
+lose produced steam valve 'downstream Steam &esuperheater(
1
2
4
Slowl open BL valve and graduall warm up the sstem b draining condensate
5
$hen condensate is clean and hot enough, close drain valves and check header steam traps performance
6
!ull open BL valve and pressuri#e the sstem 'check pressure via )@"2A(
7
+lose the warm"up bpass valve
n case of maintenance of the header itself it is better to wash the sstem with utilit water, 'through temporar connections( from BL to the end of the header 'removing the !T orifice plate and blind flange at the end( and then blow the sstem with steam until everthing is clean.
5.2.13
Amine "rain -stem :mine &rain Sstem is not normall put out of service. n case of check for mechanical completion of :& network after specific maintenance, the header can be disconnected at drum '11"%"A( inlet and washed with Dtilit $ater. The :mine +losed &rain Sump should be steamed out separatel and blanketed with 9itrogen.
5.2.14
,ight /C Close( "rain -stem Light 3+ +losed &rain Sstem is not normall put out of service. n case of check for mechanical completion of +& network after specific maintenance, the header can be disconnected at drum '11"%"A( inlet and washed with Dtilit $ater. The 3+ +losed &rain &rum should be steamed out separatel and blanketed with !uel @as.