tugas menper fmea

8/9/2019 Tugas Menper Fmea

1/18

1 Maintenance

1.1 General

Maintenance recommendations are based on industry standards and experience in Reclamation

facilities. However, equipment and situations vary greatly, and sound engineering andmanagement judgment must be exercised when applying these recommendations. Other sources

of information must be consulted e.g., manufacturer!s recommendations, unusual operating

conditions, personal experience with the equipment, etc." in conjunction with these maintenance

recommendations.

1.2 Preventive Maintenance

#reventive maintenance #M" is the practice of maintaining equipment on a regular schedule

based on elapsed time or meter readings. $he intent of #M is to %prevent& maintenance problems

or failures before they ta'e place by following routine and comprehensive maintenance

procedures. $he goal is to achieve fewer, shorter, and more predictable outages.

(ome advantages of #M are)

* +t is predictable, ma'ing budgeting, planning, and resource leveling possible.

* hen properly practiced, it generally prevents most major problems, thus reducing forced

outages, %reactive maintenance,& and maintenance costs in general.

* +t assures managers that equipment is being maintained.

* +t is easily understood and justified.

#M does have some drawbac's)

* +t is time consuming and resource intensive.

* +t does not consider actual equipment condition when scheduling or performing the

maintenance.

* +t can cause problems in equipment in addition to solving them e.g., damaging seals, stripping

threads".

-espite these drawbac's, #M has proven generally reliable in the past and is still the core of

most maintenance programs.

#M traditionally has been the standard maintenance practice in Reclamation. $he maintenancerecommendations in this document are based on a #M philosophy and should be considered as

%baseline& practices to be used when managing a maintenance program. However, care should be

ta'en in applying #M recommendations. holesale implementation of #M recommendations

without considering equipment criticality or equipment condition may result in a wor'load that is

too large to achieve. $his could result in important equipment not receiving needed

1 | M a n a j e m e n P e r a w a t a n & K e h a n d a l a n


2/18

maintenance, which defeats the purpose of #M management. $o mitigate this problem,

maintenance managers may choose to apply a consciously chosen, effectively implemented, and

properly documentedreliabilitycentered maintenance R/M" program. hether utili0ing a #M,

R/M, or conditionbased maintenance /1M" program, or a combination of these, scheduled

maintenance should be the primary focus of the inhouse maintenance staff.2 $his will reduce

reactive emergency and corrective" maintenance. (cheduled maintenance should have a higher

priority than special projects and should be the number one priority.

1.3 Reliability-Centered Maintenance

R/M programs are gaining in popularity and have been piloted in a few Reclamation power

facilities with good results. $he goal of these programs is to provide the appropriate amount of

maintenance at the right time to prevent forced outages while at the same time eliminating

unnecessary maintenance. +mplemented properly, R/M can eliminate some of the drawbac's of

#M and may result in a more streamlined, efficient maintenance program. R/M seems very

attractive in times of diminishing funding, scarcity of s'illed maintenance staff, and the pressure

to %stay online& due to electric utility industry deregulation.

(ome features of R/M are)

* +t may be labor intensive and time consuming to set up initially.

* +t may require additional monitoring of quantities, li'e temperature and vibration, to be

effective. $his may mean new monitoring equipment with its own #M or more human

monitoring with multiple inspections.

* +t may result in a %runtofailure& or deferred maintenance philosophy for some equipment

which may cause concern for some staff and managers.

* +t may require initial and later revisions to the maintenance schedule in a %trialanderror&

fashion depending on the success of the initial maintenance schedule and equipment condition.

* +t should result in a more manageable maintenance wor'load focused on the most important

equipment.

R/M is not an excuse to move to a %brea'down maintenance& philosophy or to eliminate critical

#M in the name of reducing maintenance staff3 funding. However, to mitigate problems

associated with a #M program, maintenance managers may choose to apply a consciously

chosen, effectively implemented,and properly documented R/M program.

4or a viable R/M program at Reclamation facilities, it must)

* 1e chosen as the local maintenance philosophy by management.

* 1e implemented according to generally accepted R/M practices.

* 1e documented so that maintenance decisions are defensible.



3/18

1.4 Condition-Based Maintenance

$his program relies on 'nowing the condition of individual pieces of equipment.

(ome features of /1M include)

* Monitoring equipment parameters such as temperatures, pressures, vibrations, lea'age current,

dissolved gas analysis, etc.

* $esting on a periodic basis and3or when problems are suspected such as -oble testing, vibration

testing, and infrared scanning.

* Monitoring carefully operatorgathered data.

* (ecuring results in 'nowledgeable maintenance decisions which would reduce overall costs by

focusing only on equipment that really needs attention.

-rawbac's to /1M include it being very difficult and expensive to monitor some quantities. +t

requires 'nowledgeable and consistent analysis to be effective5 and also condition monitoring

equipment and systems themselves require maintenance. 1ecause of these drawbac's, it is nearly

impossible to have an entirely /1M program.

1.5 Combination of Condition-Based and Preventive Maintenance

6 combination of /1M and #M is perhaps the most practical approach. Monitoring, testing, and

using historical data and #M schedules may provide the best information on when equipment

should be maintained. 1y 'eeping accurate records of the %as found& condition of equipment

when it is torn down for maintenance, one can determine what maintenance was really necessary.

+n this manner, maintenance schedules can be lengthened or perhaps shortened, based on

experience and monitoring.



4/18

2. Nomenclatre

!N"# 6merican 7ational (tandards +nstitute

!P# 6merican #etroleum +nstitute

!"M$ 6merican (ociety of Mechanical 8ngineers

C!%&'"(! /alifornia Occupational (afety and Health Regulations

CBM conditionbased maintenance

C)R /ode of 4ederal Regulations

CMM" computeri0ed maintenance management system

$P"" emergency power supply systems

)#"* 4acilities +nstructions, (tandards, and $echniques

(.P high pressure

+,&cm2 'ilogram per square centimeter

%.P low pressure

M megawatt

mm(, millimeter of mercury

'M operation and maintenance

'"(! Occupational (afety and Health 6dministration

P$B #ower 8quipment 1ulletins

P'Mpower operation and maintenance

PMpreventive maintenance

RCM reliabilitycentered maintenance

Reclamation 1ureau of Reclamation

r/m rotations per minute

""*singlestate steam turbine

Celcius



5/18

3. Content

9. Maintenance ::::::::::::::::::::::::::::::: 9

9.9 ;eneral ::::::::::::::::::::::::::::::::: 9

9.2 #reventive Maintenance ::::::::::::::::::::::::::.. 99.< Reliability/entered Maintenance ::::::::::::::::::::::.. 2

9.= /ondition1ased Maintenance :::::::::::::::::::::::.... /ombination of /ondition1ased and #reventive Maintenance.............................................. (team $urbine @ $ypes::::::::::::::::::::::::::... 9A=.? (team $urbine @ (tandard Operational and Maintenance:::::::::::::. 9A

=.A (team $urbine @ 4M86::::::::::::::::::::::::::. 9A

>. +ndex:::::::::::::::::::::::::::::::::.. 9B



6/18


7/18

$he shape and finish of the no00le should be designed so that the conversion of thermal

energy into 'inetic energy should ta'e place with greatest possible efficiency.

+n order to reduce friction, specially when the steam velocity is high, the valve surface

should be as smooth as possible.

Constrction of conver,ent nole

)irst "ta,e Conver,ent Nole

6 segment of convergent no00le suitable for the first stage of an impulse turbine of medium

power is shown in figure)

$his segment consists of ? no00les and comprises a casting IaI into which the no00le guide

vanes IbI are embedded by Icasting inI. 4or casting of the guide vanes, they are first made from

sheet metal of uniform thic'ness which is cut to save and then curved in press. ith the correct

shape and correct curvature at inlet, these are embedded in a sand core to form the steam

passage. $hen molten metal is poured into the mould which the projecting edges of the guide

vanes are surrounded, on free0ing of the metal, the vanes become firmly held and casting is

ta'en out.

4or this type of no00le, rolled copper guide blades cast in gun metal no00le segments are used

for saturated steel. 1ut for superheated steam steel or alloy steel must be used. +n steel or alloy

steel group materials such as low carbon, steel, G 7ic'el, stainless steel, +ron and hadfleldIs

hecla 6.$.J. steel may be used.

Bilt-/ Nole

1uiltup construction is shown in figure.



8/18


9/18

$he no00le is fitted with a valve arrangement IcI which opens or closes it to a steam chest IaI. +t

is mostly used in experimental type of impulse turbine.

Cast -in *y/e

/astin type is shown in figure.

+t is largely used in marine impulse turbine. ;uide blades are rolled to the section shown by

dotted lines in the upper part of figure, and then cut to shape and cast into the no00le segment

in the usual manner.

Bilt-/ Nole

1uiltup no00le is shown in figure.



10/18

+t is made of steel to 1.(.8n >B1 and is readily replaceable at any time. +t consists of two parts

lower and upper forming rectangular crosssection. +t is machined from a bar by employing jigs

and fixtures to the required shape. +t is used in many impulse turbines and another form of built

up no00les is also shown in figure.

+t consists of < parts segment strips IaI in which the no00le passages are machined, a covering

segment IbI and a wedge piece IcI. $he loc'ing screws IdI on the ring IcI causes the strips IaI and

IbI to be forced against the steam chest. $he cap nut IeI covers the set screw IdI so that there

should not be any lea'age. +t is used in so many turbines.

2. Contrction of *rbine Blades

Production of Blades

1lades may be considered to be heart of turbine, and all other members exist for the sa'e of

blades. ithout blading, there would be no power and the slightest fault in blading would mean

a reduction in efficiency or lengthy and costly repairs.

$he following are some of the methods adopted for the production of blades)

9. Rollin, (ections are rolled to the finished si0e and used in conjunction with pac'ing

pieces. 1lades manufactured by this method do not fail under combined bending and

centrifugal force.

2. Macinin, - 1lades are also machined from rectangular bars. $his method has more or

less same advantage as that of rolling. +mpulse bladings are manufactured by this

technique.


11/18

fletting and polishing. $he machining of the firtree root is often done by broaching, and

electrochemical machining may be used in some parts to avoid the conventional cutting

processes. +n advance method, computers are used to determine the blade shape required

by aerodynamic and stress criteria. $he computer may then instruct a numerically

controlled milling machine to prepare the dies.

=. $trsion 1lades are sometimes extruded and the roots are left on for subsequent

machining. $his method is not as reliable as rolled section, because of narrow limits

imposed on the composition of the blade material.

>. Cold 0ra6in, 1lades are also cold drawn.

3. Rotor Constrction

*y/es of Rotors

$here are > types of steam turbine rotors)

9. $he builtup rotor

2. $he integral rotor

. $he welded disc rotor

1. *e Bilt-/ Rotor

+t consists of forged steel shaft on which separate forged steel discs are shrun' and 'eyed. +t is

cheaper since the disc and shaft are relatively easy to forge and inspect for flaws andmachining of these components can be carried out concurrently. +ts shaft is machined with a

series of stepped diameters ending with central collar. 8ach disc is heated and assembled on the

shaft in turn, each being held in position by a form of circlip. Relative rotation is prevented

either by 'eys, or by hub dowels 'nown as buttons, which locate the hubs one to another to the

central collar. $he number of discs depend upon the number of stages which in turn depends

upon the turbine output.

11 | M a n a j e m e n P e r a w a t a n & Ke h a n d a l a n


12/18

2. *e #nte,ral Rotor

$he shaft and wheels of this type of rotors are formed from one solid forging. +ntegral rotors

are expensive and difficult to forge, and there is a high incidence of rejects. Over and above, a

large amount of machining time and waste material are involved.

7evertheless, the advantages are such that the are invariably used for the H.#. high pressure"

rotors on modern reheat turbines, and sometimes for the +.#. and K.#. rotors as well. 4ollowing

are the advantages of integral rotors)

$here is no chance of disc to become loose, particularly at high temperature end where at

times the wheels may be hot and the shaft pull as found in the builtup rotor.

$his rotor is also free from the effect of creep which may cause the shrin' fit of builtup

rotor to disappear after a large number of running hours.

$he hoop stress is of lower magnitude as it contains a small hole meant for inspecting the

forging.

$here is saving in axial length and reduction in spindle diameter over the builtup type.

3. (ollo6 0rm Rotor

$his type of rotor promotes even temperature distribution because it is designed with the same

thic'ness of material as the casing.

4. "olid 0rm Rotor

12 | M a n a j e m e n P e r a w a t a n & Ke h a n d a l a n


13/18

$his type of rotors are suitable for cylinders where there are lower temperatures but large

diameters, as in +.#. cylinders without reheat.

5. elded 0isc Rotor

$he last stage disc is the most heavily stressed part of the turbine and this is one of the main

problem of K.#. rotor. $he centrifugal load of the large rotating blades set up a tensile stress in

the rim of disc, and this stress increases with decreasing radius, its maximum value being at the

bore of the hub. +f the bore is exceedingly small, the hoop stress becomes very less but of there

is no hole, the hoop stresses throughout the disc are theoretically halved. (ince there is no

central hole in welded disc rotor, it suitable for K.#. rotors. +t has two main advantages) +t is

less stressed and no need for large shaft forgings which are expensive and difficult to

manufacture. $he welding process and subsequent heat treatment should be performed with

great attention.

$hese > types of rotors are also used in gas turbines.

4.3 "team *rbine - '/eration

$he following are the sequences of turbine operation)

!. "tartin, "eence

9. 6pplication of controlled power illuminates all of the malfunction lights. $his provides a

chec' of the malfunction lights before starting the turbines.

2. Reset malfunction circuit by operating a reset switch. Malfunction lights go off and all

control devices assume the condition for starting.


14/18

=. Open the boiler stop valve to permit heating of the line and avoid condensation in the

line.

>. Open header, separator, throttle and turbine casing drills.

?. (tart auxiliary oil pump. $his has to be stopped when the main oil pump starts deliveringoil at normal pressure.

A. 6djust middle valve to secure required oil pressure for the bearing.

B. (tart the circulating water pumps and dry vacuum pumps of the condenser. Operate the

condensate extraction pumps as found necessary to remove water during the warming up

period.

E. $urn on the turbine steam or water seal.

9F. $urn on the water to the generator oil cooler and other water requiring parts.

99. Leep open all the drains ahead of the throttle valve untill all water of condensation has

been removed.

92. Open the throttle or governor valve quic'ly to set the rotor in motion.

9


15/18

9E. Once the machine comes under the control of governor, test the emergency governor by

opening the valve in the oil line to it. (ee that all valves controlled by this tripping

mechanism close promptly. Reset open throttle valve and restore speed to normal.

2F. /lose all drains.

29. Open lea' off from H.#. side gland in order to flow any excess steam to the filled water

heater or to one of the lower stage of the turbine.

22. (ynchroni0e the generator and tie it in the line.

2. (top the supply of cooling water to the condenser.

?. (hut down the condensing equipment and open drains on turbine pipings and casings.

A. /ontinue auxiliary oil pumps in operation untill the turbine rotor has stopped.

B. Operate turning gear to rotate rotor at about


16/18


17/18

=. Remove the thrust bearings and then the turbine rotors to have a detailed examination of

fixed and moving blades and diaphragms gland segments, casings, bearings, bolts,etc.

concerning any type irregularities and damages.

>. Reform all gland and baffle segment 'nifeedge and restore all radial clearances.

8xamine the bedding of all bearings to journals and measure oil clearances. /hec' theadhesion of wright metal of journal bearings.

?. 6fter cleaning the blade deposits by water washing, chemical washing or blasting

process, refit the rotors and measure clearances on the bottom points of glands and blades

with lead or plastic strip. Measure similar clearances on the hori0ontal joint and compare

for eccentricity of the shaft in the casing.

A. 6fter cleaning the bearings, chec' the wear down of bearings with the help of appropriate

bridge gauge and filler gauges and compare the figures with those ta'en on the irection of

previous overhaul

B. /hec' the alignment of shaft by ta'ing readings on all couplings and also record the level

of all journals.

E. Refit top half cylinders and before bolting up ta'e a further set of top blade and gland

clearances to confirm the concentricity of the rotor within the cylinder.

9F. Remar' the hori0ontal casing joints and refit all heavy parts. 6fter this, ta'e the readings

for final coupling alignment and adjust it if necessary.

99. 6fter refitting the coupling bolts, refit the thrust bearings and all other bearing covers.

92. +nspect turbine governor gear with stop, throttle and intercept valves.

9. +nspect all the measuring instruments installed on the turbine and replace if necessary.

4.5 "team *rbine 7 *y/es

$ype 5 6$2, 6$?=, 6$A?, 6$E2, 6$9FF

#ower 5 F.2


18/18

4.8 "team *rbine 7 "tandard '/erational and Maintenance

$he 6#+ ?99 and 6#+ ?92compliant singlestage steam turbine (($" is a versatile, rugged

steam turbine typically specified by the refining, petrochemical, food processing, steel, and other

industries as an economical and reliable mechanical drive for lube oil pumps, process pumps,

feed water pumps, fans, compressors, and generators. (($ >FF3AFF"

4.9 "team *rbine 7 )M$!

attached

5. #nde

http)33www.usbr.gov3power3data3fist3fist=N9a3=96.pdf

http)33mechanicalengineeringnoteboo'.blogspot.com

http)33en.wi'ipedia.org3wi'i3(teamNturbine

http)33www.mhi.co.jp3en3products3pdf3atNturbine.pdf

http)33www.dresserrand.com3literature3steam329>

tugas menper fmea

Documents