Judul Penilaian Ergonomi TerhadapBeban Kerja Manual MaterialHandling di DepartemenMaintenance Support Service(Studi Kasus : PT. ChevronPacific Indonesia

Jumlah Halaman 4 halamanTahun 2012Penulis Ike Muharmi dan Herto Dwi

ArlesyadyReviewer Muhammad Gandi WiratamaTanggal 4 November 2014

Abstrak PT. Chevron Pacific Indonesia(PT.CPI) merupakan produsenminyak terkemuka di Indonesia.Salah satu tim yang ada diPT.CPI ini adalah DepartemenMaintenance Support Service (MSS),yang merupakan pusat perbaikandan fabrikasi untuk berbagaiperalatan produksi dankonstruksi milik PT. CPI.Kegiatan di MSS masih bersifatmanual (Manual Material Handling),sehingga berpotensi menimbulkanrisiko bagi pekerja. Risikodapat berupa kelelahan dantimbulnya keluhan berupa nyeriotot yang dikenal denganMusculoskeletal Disorders (MSDs).

Tujuan Penelitian Tujuan penelitian ini adalahmengidentifikasi dan mengetahuipengaruh sarana, sikap, posturdan posisi kerja pekerja MMHyang berisiko menimbulkan MSDsdengan menggunakan metode RapidUpper Limb Assessment (RULA) dan

Rapid Entire Body Assessment (REBA)serta mengetahui tingkatkelelahan pekerja secaraobjektif dan subjektif. Secaraobjektif dilihat dari perubahandenyut nadi, tekanan darah, dantemperatur tubuh sebelumbekerja (07.00 WIB) dan sesudahbekerja (16.00 WIB), sedangkansecara subjektif dilihat dariKuesioner Alat Ukur PerasaanKelelahan Kerja (KAUPK2)

Metode Penelitian Penelitian dilaksanakan diempat shop yaitushop Tubing Pump Repair (TP), shopMotor Generator Repair and Services(MGR), shop Machining Services (MS),dan shop Valve & MiscellaneousEquipment Repair and Service Valve) diDepartemen Maintenance SupportService (MMS) PT. Chevron PacificIndonesia yang bertempat di Duri, Riau.Jumlah sampel yang diambil adalah 69orang termasuk didalamnya 11 orangkontrol. Kontrol berasal dari bagianadministrasi yang ada di tiap- tiap shop.Pengumpulan data yang dilakukanmeliputi data primer dan sekunder. Dataprimer yang dilakukan meliputipengukuran iklim lingkungan kerja,pengukuran kelelahan secara subjektifdan objektif, mengetahui keluhan MSDs,dan mengevaluasi faktor risikoergonomi. Data sekunder yangdiperlukan adalah profil perusahaan,layout pekerjaan dan proses kerja diDepartemen MSS PT.CPI.Pengukuran iklim kerjayang dilakukan

meliputi pengukuran kebisingan,pencahayaan, kelembaban dansuhu lingkungan menggunakan 4 in1 Multi Function Environment Meter.Tingkat kelelahan pekerja,secara subjektif dapatdiketahui dari Kuisioner AlatUkur Perasaan Kelelahan Kerja(KAUPK2) (Santoso, 2004).Sedangkan secara objektif,pengukuran kelelahan didapatdengan cara mengukur temperaturtubuh, tekanan darah, sertadenyut nadi (Chang et al.,2009) sebelum bekerja (07.00WIB) dan sesudah bekerja (16.00WIB).Keluhan MSDs pekerjadapat dilakukan denganwawancara, dimana pertanyaannyadisesuaikan dengan pertanyaanNordic Body Map (diadaptasidari Dutch MusculoskeletalQuestionnaire dan NCBI).Evaluasi faktor risiko ergonomidilakukan dengan mengggunakanmetode RULA dan REBA (Abbe etal., 2011). Kedua metode inimerupakan suatu tool yangberbentuk survei untukmengidentifikasi pekerjaan yangmenyebabkan risiko cederakumulatif (Cummulative TraumaDisorders/CTD) melalui analisispostur, gaya, danpenggunaan otot.

Subjek Penelitian Pekerja di Departemen MaintenanceSupport Service (MSS), yangmerupakan pusat perbaikan dan

fabrikasi untuk berbagaiperalatan produksi dankonstruksi milik PT. CPI.Kegiatan di MSS masih bersifatmanual (Manual Material Handling),sehingga berpotensi menimbulkanrisiko bagi pekerja. Risikodapat berupa kelelahan dantimbulnya keluhan berupa nyeriotot yang dikenal denganMusculoskeletal Disorders (MSDs).

Objek Penelitian Tingkat kelelahan pekerjasecara subjektif dan objektifdan juga keluhan MusculoskeletalDisorders (MSDs).

Hasil Penelitian Dengan menggunakan metodestatistik faktor yang palingdominan mempengaruhi tekanandarah sistolik dan denyut nadiadalah risiko ergonomi atauposisi tubuh saat bekerja.Semakin besar risiko ergonomimaka akan semakin mudahmengalami kelelahan. Faktoryang dominan untuk temperaturtubuh adalah suhu lingkungan.Sedangkan untuk tekanan darahdiastolik faktor yang dominanadalah Indeks Massa Tubuh(IMT).

Kesimpulan Berdasarkan hasil penelitiandapat diambil beberapakesimpulan, diantaranyaadalah :

Hasil analisis mengenaipengaruh sarana, sikap,postur dan posisi tubuhsaat bekerja menggunakan

metode RULA,mengindikasikan bahwarisiko di shop MGR, TP danMS termasuk kategorisedang dan di shopValve termasuk kategoriberat. Sedangkan denganmenggunakan metode REBAsemua shop termasuk risikosedang.

Bagian tubuh yang banyakmengalami keluhan MSDsadalah leher dan punggungbagian atas, pinggang danpunggung bagian bawah,serta jari dan pergelangantangan kanan.

Hasil pengukuran kelelahansecara subjektifmenunjukkan sekitar 34,48%pekerja lapangan(terpapar) tingkatkelelahannya adalahrendah, dan 65,52%mengalami tingkatkelelahan yang sedang.Jika dibandingkandengan pekerja office(tidak terpapar),sebagian besar yaitu63,64% tingkatkelelahannya rendah, danhanya 36,36% yang tingkatkelelahannya sedang. Halini mengindikasikan bahwaterdapat perbedaan bebandan tingkat pekerjaanantara pekerja lapangandan office. Sedangkan

pengukuran kelelahansecara objektif,menunjukkan bahwaterdapat perbedaan yangsignifikan fisiologistubuh pekerja baik tekanandarah, denyut nadi, dantemperatur tubuh sebelumdan sesudah bekerja.

Faktor yang palingmempengaruhi tekanandarah sistolik dan denyutnadi adalah risikoergonomi atau posisi tubuhsaat bekerja. Semakinbesar risiko ergonomi makaakan semakin mudahmengalami kelelahan.Faktor yang dominan untuktemperatur tubuh adalahsuhu lingkungan. Sedangkanfaktor yang dominan untuktekanan darah diastolikadalah IMT.

Biomechanical Bases of Ergonomics

5.1 INTRODUCTION

Biomechanics combine engineering physics (mechanics),anthropometry and basic medical science (biology andphysiology), through mathematical relationships. Itutilizes the laws of physics to describe biologicalphenomena in the human body. Biomechanics principles areused to study the responses of human body to loads andstresses placed on the body in the workplace.Biomechanics models are often utilized to analyze theforces and torques on segments of the body and to comparethose forces to muscle strengthlimitations of people, topredict stressful work postures and conditions.

5.2 DEFINITIONS AND BASICS MECHANICS

The branch of physics that deals with the action offorces on matter is referred to as mechanics. Allconsiderations of motion are addressed by mechanics, aswell as the transmission of forces through the use ofsimple machines. In our class, the goal is a mechanicalgoal (placing blocks into a bin) and electronics are usedto control the mechanics.

While it is not necessary to sit down and draw free bodydiagrams or figure out the static coefficient of frictionbetween the LEGO tires and the game board, it is helpfulto keep certain mechanical concepts in mind whenconstructing a robot. If a robot's tires are spinningbecause they do not grip the floor, then something mustbe done to increase the friction between the tires andthe floor. One solution is to glue a rubber band aroundthe circumference of the tire. That problem/solution did

not require an in-depth study of physics. Simplyconsidering the different possibilities can lead to moremechanically creative robots.

Describing motion involves more than just saying that anobject moved three feet to the right. The magnitude anddirection of the displacement are important, but so arethe characteristics of the object's velocity andacceleration. To understand these concepts, we mustexamine the nature of force. Changes in the motion of anobject are created by forces

5.3 NEWTON’S LAWS OF MOTION A body will maintain its state of rest or of

uniform motion (at a constant speed) along astraight line unless compelled by some unbalancedforce to change that state. In other words, a bodyaccelerates only if any unbalanced force acts uponit.

An unbalanced force (F) acting on a body producesin it an acceleration (a), which is in thedirection of the force and directly proportionalto the force, and inversely proportional to themass (m) of the body.

Newton’s laws of motion will be utilized in biomechanicalmodel development. However, before discussingbiomechanical models, it is appropriate to examine theunits of mechanics.

5.4 BIOMECHANICAL ANALYSIS AND MODELS5.4.1 STATIC ANALYSIS AND MODELS

In many cases, the ergonomist can examine a “worst-case” scenario and determine the forces and stressesplaces on the body as a result of the load on the bodyand the required body posture. Usually the activitycan be represented as a two-dimensional task (e.g.,twisting is not recommended for manual materialshandling activities).One of the decision has been madeto conduct a two-dimensional static analysis thefollowing information must be obtained: externalforces acting on the body and their directions, bodyposture, and the body segment parameters (segmentmasses and locations of centers of mass) of the personbeing analyzed.

5.4.2 STATIC ANALYSIS AND MODELSTime-diplacedment data are often obtained for jointcenter movement and/or center of segment massmovement. Through a process of inverse dynamics(velocity is obtained by taking the derivative ofdisplacement and acceleration is found by taking thederivative of velocity) the kinematics of a body inmotion can be determined. Techniques exist (e.g.,video-based systems, and a variety of sensor-basedsystems) to collect time-displacement dataautomatically. Many of these systems also incorporatecomputer software to smooth the data and calculate thevelocity and acceleration profile of the motion.

5.5 MUSCULAR STRENGTHBoth static and dynamic biomechanical analyses canprovide information about the forces and momentsgenerated doing various activities. As previously

illustrated, we can estimate muscle forces necessary toperform an activity or to maintain static equilibrium. Inorder to know if that activity can be safely performed byvariety of people, we would like to know the strength ofthose people in the muscle group being used for theactivity. The existing knowledge of muscle mechanics wasgained from experiments performed on whole muscles,single-fiber preparations, and isolated myofibrilpreparations. Experiments on whole muscles were conductedin vivo (within a living body), in situ (in the originalplace but with partial isolation), or in vitro (isolatedfrom a living body). To perform experiments on excisedmuscles or muscle fibers, the investigator must keep themalive. The muscles (fibers, myofibrils) should be bathedin physiological solution with osmotic pressure and ioniccomposition similar to those in the tissue fluids in theanimal’s body. Usually muscles contain plenty of sourcesof energy, mostly glycogen, that allow them to work forlong periods without additional supply of foodsubstances. The crucial issue is adequate oxygen supply.Mammalian muscles have a high metabolic rate. To supplythem with oxygen, intact blood circulation has to bepreserved. Due to this requirement, experiments onmammalian muscles in vitroare not performed.In experiments, muscles are typically activated byelectric stimuli applied to muscle surface or to thenerve innervating the muscle. If the strength of a singlestimulus exceeds a certain threshold, the muscle respondsby a brief period of contraction followed by relaxation(twitch). If the stimuli are repeated at a sufficientlyhigh frequency, summation occurs and a smooth tetanus isobserved. Smooth tetanus is characterized by force levelshigher than the maximal twitch force. When single fibers(i.e., muscle cells) of mammalian skeletal muscles are

stimulated, the fibers follow the all-or-nothing law: theresponse to any suprathreshold stimulus is maximal andcannot be increased by increasing the strength of thestimulus. In contrast, when the whole muscle isstimulated, the response is graded; with an increasingstrength of the stimulus, the muscle force increasesbecause of the increased number of activated fibers. Toobtain reproducible results, investigators usually usesupramaximal stimuli, which are expected to inducecontraction of all the fibers at each presentation.

5.6 APPLICATIONS AND DISCUSSION

During last couple of years there has been an increasingrecognition that problems arising in biology or relatedto medicine really need a multidisciplinary approach. Forthis reason some special branches of both appliedtheoretical physics and mathematics have recently emergedsuch as biomechanics, mechanobiology, mathematicalbiology, biothermodynamics. The Biomechanics inApplication is focusing on experimental praxis andclinical findings. The first section is devoted to Injuryand clinical biomechanics including overview of thebiomechanics of musculoskeletal injury, distractionosteogenesis in mandible, or consequences of drilling.The next section is on Spine biomechanics withbiomechanical models for upper limb after spinal cordinjury and an animal model looking at changes occurringas a consequence of spinal cord injury. SectionMusculoskeletal Biomechanics includes the chapter whichis devoted to dynamical stability of lumbo-pelvi-femoralcomplex which involves analysis of relationship amongappropriate anatomical structures in this region. Thefourth section is on Human and Animal Biomechanics with

contributions from foot biomechanics and chewing rhythmsin mammals, or adaptations of bats. The last section,Sport Biomechanics, is discussing various measurementtechniques for assessment and analysis of movement andtwo applications in swimming.

TUGAS TAMBAHAN

FISIOLOGI DAN PENGUKURAN KERJA

(BIOMEKANIKA dan FISOLOGI 1)

Muhammad Gandi Wiratama (13522127)

Kelompok: C-3

Asisten Pembimbing:

Julius Sidhatama (E-89)

TEKNIK INDUSTRI

FAKULTAS TEKNOLOGI INDUSTRI

UNIVERSITAS ISLAM INDONESIA

2014