1. LINGKUP
Prosedur ini menguraikan sistematis kerangka penilaian risiko pipeline dan menyediakan cara untuk meningkatkan keamanan sistem pipeline. Program manajemen integritas menyediakan informasi bagi operator untuk secara efektif mengalokasikan sumber daya yang tepat untuk pencegahan, deteksi, dan kegiatan mitigasi yang menghasilkan peningkatan keselamatan dan pengurangan kecelakaan.
Penilaian risiko mencakup sistem pipa darat, seperti flowline, jalur transmisi, jalur layanan, dan jalur distribusi, baik untuk jaringan pipa minyak dan gas. Pada transportasi gas menggunakan ASME B31.8 meliputi desain, fabrikasi, instalasi, inspeksi, dan pengujian fasilitas pipa Sedangkan ASME B31.4 meliputi desain, bahan, konstruksi, perakitan, inspeksi, dan pengujian pada pipa transportasi cairan seperti minyak mentah, kondensat, natural
gasoline, natural gas liquids, liquefied petroleum gas, carbon dioxide, liquid alcohol, liquid anhydrous ammonia , dan produk petroleum cair.
2. TUJUAN
Penilaian risiko pipeline memiliki tujuan sebagai berikut:
- Prioritas pipeline / segmen untuk penjadwalan penilaian integritas dan tindakan mitigasi
- Penilaian terhadap manfaat yang diperoleh dari tindakan mitigasi
- Penentuan langkah-langkah mitigasi yang paling efektif untuk mengidentifikasi ancaman.
- Penilaian pada dampak integritas dari perubahan interval inspeksi.
- Penilaian terhadap penggunaan atau kebutuhan metodologi pemeriksaan alternative.
- Alokasi sumber daya yang lebih efektif
Penilaian risiko memberikan ukuran terhadap evaluasi baik dampak potensial dari jenis kejadian yang berbeda dan kemungkinan terhadap peristiwa yang dapat terjadi.
1. SCOPE
This procedure outline a systematic pipeline risk assessment framework and provide the means to improve the safety of pipeline systems. The integrity management program provide information for operator to effectively allocate resources for appropriate prevention, detection, and mitigation activities that results in improved safety and reduction of accidents.
The risk assessment cover onshore pipeline systems, such as flowlines, transmission lines, service lines, and distribution lines, for both oil and gas pipelines.
ASME B31.8 covers the design, fabrication, installation, inspection, and testing of pipeline facilities used for the transportation of gas. While ASME B31.4 covers the design, materials, construction, assembly, inspection, and testing of piping transporting liquids such as crude oil, condensate, natural gasoline, natural gas liquids, liquefied petroleum gas, carbon dioxide, liquid alcohol, liquid anhydrous ammonia, and liquid petroleum products.
2. PURPOSE
Pipeline risk assessment has the following objectives:
- Prioritization of pipelines/segments for scheduling integrity assessments and mitigating action
- Assessment of the benefits derived from mitigating action
- Determination of the most effective mitigation measures for the identified threats
- Assessment of the integrity impact from modified inspection intervals
- Assessment of the use of or need for alternative inspection methodologies
- More effective resource allocation
Risk assessment provides a measure that evaluates both the potential impact of different incident types and the likelihood that such events may occur..
3. TANGGUNG JAWAB
- Engineer Pipa Penyalur bertanggung jawab atas pekerjaan penilaian risiko pipa penyalur.
- Senior engineer bertanggung jawab atas kualitas dan kesesuaian pekerjaan dengan Order yang diberikan.
4. DEFINISI
Pipa penyalur darat adalah pipa minyak atau gas bumi yang meliputi pipa alir sumur, pipa transmisi, pipa induk dan pipa servis yang dioperasikan didarat
5. INSTRUKSI
5.1 Pengumpulan dan Peninjauan Data
Langkah pertama dalam pengumpulan data adalah mengidentifikasi sumber-sumber data yang diperlukan untuk penilaian risiko pipeline. Sumber-sumber dapat dibagi menjadi lima kelas yang berbeda.
Desain, Material, dan Data Konstruksi - Segmen Pipa
- Rute Pipeline - Diameter pipa - Ketebalan pipa - Material pipa
- Tekanan disain dan operasi - Tanggal konstruksi atau umur - Tipe dan kondisi coating
- Tipe dan kondisi katodik proteksi - Lokasi valve - Relief devices - Tipe tanah Right-of-Way Data - Lebar right-of-ways - Kedalaman penguburan - Kondisi hak-cara-
- Frekuensi dan jenis patroli - Perambahan cek dan mitigasi - Pipa spidol dan signage
- Deskripsi penggunaan lahan: pedesaan, perkotaan, pertanian, industri
- Highway dan perlintasan kereta api: casing,
3. RESPONSIBILITES
- Pipeline Engineer responsible to perform the pipeline risk assessment
- Senior engineer responsible for quality of work and complian to work orders.
4. DEFINITION
Onshore pipeline is an oil or gas pipelines including flowline, transmission pipelines, mainline and service lines
5. INSTRUCTIONS
5.1 Data Collection and Review
The first step in gathering data is to identify the sources of data needed for pipeline risk assessment. These sources can be divided into five different classes.
Design, Material, and Construction Data - Pipeline segment
- Pipeline route - Pipe diameter - Pipe wall thickness - Pipe material, grade
- Design and operating pressures - Construction date or age
- Coating type and condition
- Cathodic Protection type and condition - Valve locations - Relief devices - Soil type Right-of-Way Data - Width of right-of-ways - Depth of burial - Condition of right-of-way
- Frequency and type of patrolling - Encroachment check and mitigation - Pipeline markers and signage
- Description of land use: rural, urban, farm, industrial
uncased
- Sungai danau dan penyeberangan
- Pipa dan penyeberangan utilitas lain, berbagi kanan dari arah koridor
- Publik kesadaran pipa - Pipa paparan laporan
Data Operasi, Inspeksi Perawatan dan Perbaikan - Hasil inspeksi in-line (ILI)
- Hasil penilaian anomali ILI
- Data tekanan pengujian hidrostatis - SCADA dan deteksi kebocoran
- Rencana tanggap darurat, bor dan pelatihan - Tumpahan rencana pengelolaan
- Kualifikasi operator dan rencana pelatihan - Tekanan isi line atau servise
- Tekanan siklus dan profil tekanan - Suhu operasi
- Pembacaan pipe to soil - Close interval survey - Inspeksi Coating
- Pemeriksaan katodik proteksi - Inspeksi kedalaman pemakaman - Re-route, pergantian section
- Cara perlindungan pipeline di sungai, sungai, danau dan air
- Perlindungan dan pemantauan pipeline di tanah yang tidak stabil
Bagian-bagian pipeline di area sensitive: - Dekat dengan air minum: dalam 100m - Dekat dengan daerah berpenduduk - Dekat dengan peternakan
- Dekat dengan taman dan hutan - Dekat dengan tambak
Sejarah insiden kebocoran - Lokasi
- Penyebab dan akar penyebab kegagalan - Konsekuensi
- Tindakan perbaikan - Sejarah perbaikan - Encroachment history
- River, creek and lake crossings
- Pipeline and other utility crossings, sharing right-of-way corridor
- Public awareness of pipeline - Pipeline exposure reports
Operation, Maintenance Inspection and Repair Data - In-line inspection (ILI) results
- Results of ILI anomaly assessment - Hydrostatic pressure testing data - SCADA and leak detection
- Emergency response plan, drill and training - Spill management plan
- Operators qualification and training plan - Line pressure content or service
- Pressure cycles and pressure profile - Operating temperature
- Pipe to soil readings - Close interval survey - Coating inspection
- Cathodic protection inspection - Depth of burial inspection - Re-route, replace sections
- Pipeline protection in river, creek, lakes and water ways
- Pipeline protection and monitoring in unstable ground
Portions of Pipeline at Sensitive Areas: - Proximity to drinking water: within 100m - Proximity to populated areas
- Proximity to farms
- Proximity to parks and forests
- Proximity to commercial fishing waters
Past history of incidents, leaks - Location
- Failure causes and root causes - Consequences
- Remedial action - Repair history
5.2 Pemeriksaan Lapangan
Pemeriksaan lapangan dilakukan apabila diperlukan, pemeriksaan tersebut meliputi:
- Pembacaan Kathodik Proteksi (Instruksi Kerja I-302)
- Pengukuran Ketebalan (Instruksi Kerja I-303) - Survey ROW (Instruksi Kerja I-304)
5.3 Segmentasi
Pipeline tidak memiliki potensi bahaya yang konstan sepanjang pipeline. Kondisi di sepanjang rute pipeline berubah, demikian juga gambar risiko. Karena gambar risiko tidak konstan, lebih efisien menilai pipeline pada bagian yang lebih pendek. Setiap bagian akan memiliki hasil penilaian risiko sendiri. Memutus garis menjadi beberapa bagian pendek meningkatkan akurasi penilaian untuk setiap bagian
5.4 Penilaian Resiko 5.4.1 Gambaran Umum
Risiko paling sering didefinisikan sebagai probabilitas dari suatu peristiwa yang menyebabkan kerugian dan besarnya potensi kerugian itu. Dengan definisi ini, risiko meningkat ketika salah satu kemungkinan meningkat atau ketika potensi kerugian (konsekuensi) meningkat. Transportasi produk-produk dengan menggunakan pipa berisiko karena ada beberapa kemungkinan pipa gagal, melepaskan isinya (bocor), dan menyebabkan kerusakan (di samping potensi kerugian dari produk itu sendiri).
Definisi yang paling umum dari risiko sering dinyatakan sebagai hubungan matematis:
Risk = (Peluang) x (Konsekuensi) Risiko sering dinyatakan dalam jumlah yang terukur seperti frekuensi kematian, cedera, atau kerugian ekonomi.
5.4.2 Model Risiko
Penyajian risiko dalam bentuk matriks adalah cara yang efektif menunjukkan pembagian risiko dengan komponen yang berbeda tanpa nilai numerik. Pada
5.2 Field Inspections
Field inspection carried out if necessary, these can include:
- Cathodoc Protection Reading (Work Instruction I-302)
- Thickness Measurement (Work Instruction I-303) - ROW Survey (Work Instruction I-304)
5.3 Segmentation
Pipeline does not have a constant hazard potential over its entire length. As conditions along the line’s route change, so does the risk picture. Because the risk picture is not constant, it is efficient to assess pipeline in shorter sections. Each section will have its own risk assessment results. Breaking the line into many short sections increases the accuracy of the assessment for each section.
5.4 Risk Assessment 5.4.1 Overview
Risk is most commonly defined as the probability of an event that causes a loss and the potential magnitude of that loss. By this definition, risk is increased when either the probability of the event increases or when the magnitude of the potential loss (the consequences of the event) increases. Transportation of products by pipeline is a risk because there is some probability of the pipeline failing, releasing its contents, and causing damage (in addition to the potential loss of the product itself).
The most commonly accepted definition of risk is often expressed as a mathematical relationship:
Risk = likelihood x consequence
A risk is often expressed in measurable quantities such as the expected frequency of fatalities, injuries, or economic loss.
5.4.2 Risk Model
Presenting the results in a risk matrix is an effective way of showing the distribution of risks for different
Figure 5.1 Risk Matrix matriks risiko, katagori konsekuensi dan probabilitas
tersebut diatur sedemikian sehingga komponen risiko tertinggi berada di pojok kanan atas. Kategori risiko (Tinggi, Sedang dan Rendah) dapat dilihat pada kotak-kotak dalam matriks risiko.
Gambar 5.1 menunjukkan matriks risiko yang digunakan untuk menentukan risiko pipeline.
components in a process unit without numerical values. In the risk matrix, the consequence and probability categories are arranged such that the highest risk components are toward the upper right-hand corner. Risk categories (i.e. High, Medium, and Low) are assigned to the boxes on the risk matrix. Figure 5.1 shows Risk matrix which is used for determining and plotting pipeline related risk .
L IK E L IH O O D Likely 5 10 15 20 25 Unlikely 4 8 12 16 20 Very Unlikely 3 6 9 12 15 Rare 2 4 6 8 10 Remote 1 2 3 4 5
Low Minor Medium Significant Catastrophic CONSEQUENCE
Low Medium Risk High
5.4.3 Probability Of Failure a. Kerusakan Pihak Ketiga Kedalaman dari Penutup
Kedalaman minimum penutup adalah jarak tanah, atau penutup setara pipa yang berfungsi untuk melindungi pipa dari pihak ketiga kegiatan. Poin harus dinilai berdasarkan lokasi dangkal dalam bagian yang dievaluasi. Evaluator harus merasa yakin bahwa kedalaman data tutupan adalah lancar dan akurat, jika tidak, titik penilaian harus mencerminkan ketidakpastian.
Penguburan pita-peringatan dari bahan yang sangat terlihat dengan peringatan jelas tercetak di atasnya-dapat membantu untuk mencegah kerusakan pada pipa
5.4.3 Probability Of Failure a. Third Party Damage Depth of Cover
The minimum depth of cover is the amount of earth, or equivalent cover, over the pipeline that serves to protect the pipe from third-party activities. Points should be assessed based on the shallowest location within the section being evaluated. The evaluator should feel confident that the depth of cover data are current and accurate; otherwise, the point assessments should reflect the uncertainty. Burial of a warning tape-a highly visible strip of material with warnings clearly printed on it-may help to avert damage to a pipeline
Criteria Score None: remote area, no chance of any digging, or other harmful thirdparty activities
near the line 1
Low: location class 1, rural, low population density, less digigng or construction
activities 2
Medium: location class 2, medium population density, few digging or construction
activities 3
High: location class 3, residential/industrial areas, high digging or construction
activities 4
Very High: location class 4, multistorey buildings with underground utilities, heavy and
dense traffics 5
Criteria Score
Above 1 m, with additional concrete slab 1
Above 1 m, with additional warning tape 2
1 m and above 3
Less than 1 m, or unknown 4
Not buried 5
Activity Level
Dalam analisis potensi kerusakan oleh pihak ketiga, sangat dipengaruhi oleh tingkat aktivitas area dekat pipeline. Halini secara jelas bahwa aktivitas menggali meningkatkan kesempatan untuk terkena pipa. Penggalian sering terjadi dalam instalasi sistem utilitas seperti kabel listrik, kabel telepon, pipa air bersih, pipa gas.
Adanya utilitas penguburan secara logis mengarah ke aktivitas penggalian lebih sering sebagai sistem perbaikan, pemeliharaan dan pemeriksaan.
Activity Level
In analysis of third-party damage potential, the area of opportunity is strongly affected by the level of activity near the pipeline. It is intuitively apparent that more digging activity near the line increases the opportunity for a line strike. Excavation occurs frequently in installation of utilities systems such as electricity cables, telephone cables, fresh water pipe, gas pipelines.
The presence of other buried utilities logically leads to more frequent digging activity as these systems are repaired maintained and inspected.
Fasilitas diatas tanah
Fasilitas diatas tanah sangat rentan terhadap gangguan oleh pihak ketiga. Komponen pipa ditas tanah memiliki tipe yang berbeda dari kerusakan oleh pihak ketiga yang terexpose dibandingkan dengan bagian dikubur. Termasuk dalam jenis ancaman benturan kendaraan dan pengrusakan
Aboveground Facilities
This is a measure of the susceptibility of aboveground facilities to third-party disturbance. Aboveground pipeline components have a different type of third-party damage exposure compared to the buried sections. Included in this type of exposure are the threats of vehicular collision and vandalism
Criteria Score
No aboveground facilities 1
Aboveground facilities inside fences / plant area, with warning signs (i.e. hazards,
no trespassing) 2
Aboveground facilties > 15 m from roads, and separated by structures 3 Aboveground facilties, near roads, separated by tress, wall, other structures, or
ditch 4
Aboveground facilties near roads and/or easy to reach by public. 5
Line Locating
Program dan prosedur proses identifikasi lokasi pipeline yang tepat pada pipa yang terkubur agar pihak ketiga menggali dengan aman untuk menghindari pihak ketiga kerusakan.
Beberapa metode yang umum digunakan untuk mendeteksi lokasi pipa yang terkubur sebagai berikut.
Line Locating
A line locating program or procedure-the process of identifying the exact location of a buried pipeline in order for third parties to safely excavate nearby-is central to avoiding third-party damages.
Some methods common used for detecting buried pipeline locations were as follow.
Kondisi Right-of-Way
Pengukuran item ini kemampuan mengenali dan memeriksa pada koridor pipeline. Sebuah ROW, ditandai dengan jelas mudah dikenali mengurangi kerentanan gangguan pihak ketiga dan membantu dalam deteksi kebocoran (kemudahan spotting uap atau tumbuhan mati pada tanah atau patroli udara). Pilih skor nilai yang sesuai dengan deskripsi terdekat dari kondisi ROW yang diamati sebenarnya di bagian bawah.
Right-of-Way Conditions
This item is a measure of the recognizability and inspectability of the pipeline corridor. A clearly marked, easily recognized ROW reduces the susceptibility of third-party intrusions and aids in leak detection (ease of spotting vapors or dead vegetations from ground or air patrols).
Select the score values corresponding to the closest description of the actual ROW conditions observed in the section below.
Criteria Score
Excellent: clear ROW, signs and markers visible at road, railroads, ditches, water
crossings, all changes of direction are marked. 1
Good: clear ROW, well marked, no overgrown vegetations. 2
Average: ROW not uniformly clear, more markers are needed for better identification. 3 Below average: ROW are overgrown by vegetation at some area, poorly marked. 4 Poor: No or indistinguishable pipeline ROW, no markers present. 5
Patroli
Patroli pipeline adalah metode yang terbukti efektif mengurangi gangguan pihak ketiga. Frekuensi dan efektivitas patroli harus dipertimbangkan dalam penilaian jumlah patroli.
Pengamatan dilaporkan harus mencakup sebagai berikut:
- Gerakan tanah: tanah longsor, ambles, erosi
- Kegiatan konstruksi, baik di dekatnya dan cenderung bergerak
- Gangguan-gangguan: bangunan, perubahan lansekap, taman
- Penggandaan kegiatan ROW: kendaraan off-road, sepeda motor
- Marker hilang,
- Penanaman pohon, taman
- Perubahan pihak ketiga pada lereng atau drainase.
Patrol
Patrolling the pipeline is a proven effective method of reducing third-party intrusions. The frequency and effectiveness of the patrol should be considered in assessing the patrol value.
Reportable observations should include the following:
- Land movements: landslides, subsidence, bank erosion
- Construction activity, both nearby and likely to move
- Encroachments: buildings, landscaping changes, gardens
- Unauthorized activities on ROW: off-road vehicles, motorcycles
- Missing markers, signs - Plantings of trees, gardens
Criteria Score Daily patrol. 1 Weekly patrol. 2 Monthly patrol. 3 Quarterly patrol. 4 Annual patrol. 5 Criteria Score
Regular education programs for community nearby, officials,
contractors / excavators 1
Regular education programs for community nearby. 2 Door to door contact with adjacent residences. 3 Reading materials (i.e pipeline safety brochures) for community
nearby. 4
None 5
Penyuluhan Masyarakat
Program penyuluhan masyarakat adalah peranan penting dalam mengurangi kerusakan pipeline oleh pihak ketiga. Kebanyakan kerusakan oleh pihak ketiga dikarenakan oleh ketidak sengajaan dan ketidak tahuan. Ketidak tahuan ini tidak hanya pada lokasi pipeline yang terkubur, tetapi juga ketidak tahuan indikasi adanya pipa diatas tanah dan pipa secara umum.
Perusahaan pemilik pipeline berkomitmen untuk melakukan penyuluhan pada masyarakat mengenai masalah pipeline, yang akan secara pasti mengurangi dampak kerusakan oleh pihak ketiga.
Public Education
Public education programs are thought to play a significant role in reducing third-party damage to pipelines. Most third-party damage is unintentional and due to ignorance. This is ignorance not only of the buried pipeline's exact location, but also ignorance of the aboveground indications of the pipeline's presence and of pipelines in general. A pipeline company committed to educating the community on pipeline matters will almost assuredly reduce its exposure to third-party damage.
b. Korosi
Potensi kegagalan pada pipeline disebabkan oleh korosi merupkan bahaya ya ng paling familiar yang berhubungan dengan pipeline baja. Korosi, seperti yang digunakan dalam prosedur ini, fokus utama pada berkurangnya logam pipa. Korosi merupakan perhatian lebih karena kehilangan ketebalan dinding pipa selalu berarti pengurangan integritas struktural dan meningkatnya risiko kegagalan.
Korosi Atmosfir
Korosi Atmosfer pada dasarnya adalah perubahan
b. Corrosion
The potential for pipeline failure caused by corrosion is perhaps the most familiar hazard associated with steel pipelines. Corrosion, as it is used in this procedure, focuses mainly on a loss of metal from pipe. Corrosion is of concern because any loss of pipe wall thickness invariably means a reduction of structural integrity and hence an increase in risk of failure.
Atmospheric Corrosion
Atmospheric Exposure
Criteria Score
Not applicable. 1
Air, low humidity area. 2
Marine, swamp, coastal, high humidity area. 3
Air to water / soil interface, insulation. 4
Chemical, corrosive environment. 5
Coating conditions
kimia pada material pipa yang dihasilkan dari interaksi materi dengan atmosfer. Paling umum interaksi ini disebabkan oksidasi logam. Untuk menilai potensi korosi di sini, evaluator harus melihat item seperti fasilitas yang rentan, jenis atmosfer, dan pengecatan / kondisi lapisan.
Evaluator harus menentukan risiko terbesar dari korosi atmosferik dengan terlebih dahulu mengetahui lokasi bagian dari kondisi pipa terekspose atmosfer yang paling parah.
Udara / air interface - juga dikenal sebagai zona splash, dimana pipa bergantian terkena air dan udara, mekanisme bekerja di sini biasanya konsentrasi oksigen sel. Perbedaan konsentrasi oksigen mengatur daerah anodik dan katodik pada logam. Dalam skenario ini, mekanisme korosi ditingkatkan sebagai oksigen baru yang terus dibawa ke daerah korosi dan karat yang terbawa.
Ground/udara interface - tanah ke interface udara dapat menjadi berat dari sudut pandang korosi. Ini adalah titik di mana pipa masuk dan keluar dari tanah (atau berbaring di tanah). Kekerasan ini disebabkan sebagian oleh potensi kelembaban perangkap terhadap pipa (menciptakan interface air / udara). Gerakan tanah karena adanya perubahan kadar air, pembekuan, dll, juga dapat merusak lapisan pipa, mengekspos logam telanjang untuk elektrolit.
Isolasi - pipa atas tanah untuk menangkap air yang menerpa dinding pipa, yang memungkinkan korosi untuk melanjutkan terdeteksi. Jika kelembaban secara berkala diganti dengan air tawar, pasokan oksigen segar dan mendukung korosi.
change in the pipe material resulting from the material's interaction with the atmosphere. Most commonly this interaction causes the oxidation of metal. To assess the potential for corrosion here, the evaluator must look at items such as susceptible facilities, atmospheric type, and painting/coating conditions.
The evaluator must determine the greatest risk from atmospheric corrosion by first locating the portions of the pipeline that are exposed to the most severe atmospheric conditions.
Air/water interface - also known as a splash zone, where the pipe is alternately exposed to water and air, the mechanism at work here is usually oxygen concentration cells. Differences in oxygen concentration set up anodic and cathodic regions on the metal. Under this scenario, the corrosion mechanism is enhanced as fresh oxygen is continuously brought to the corroding area and rust is carried away.
Ground/air interface - the ground to air interface can be harsh from a corrosion standpoint. This is the point at which the pipe enters and leaves the ground (or is lying on the ground). The harshness is caused in part by the potential for trapping moisture against the pipe (creating a water/air interface). Soil movements due to changing moisture content, freezing, etc., can also damage pipe coating, exposing bare metal to the electrolyte.
Insulation - aboveground pipe is notorious for trapping moisture against the pipe wall, allowing corrosion to proceed undetected. If the moisture is periodically replaced with freshwater, the oxygen supply is refreshed and corrosion is promoted.
Criteria Score Excellent: high quality coating suitable for its environment, new
condition or recently repair; or not required. 1 Good: high quality coating, in good condition, less than 10% damage. 2 Fair: adequate coating, fair condition, less than 30% damage. 3
Poor: coating in-place, more than 30% damage 4
Absent: no coating 5
Internal Corrosion
Internal korosi adalah pengurangan dinding pipa atau kerusakan yang disebabkan oleh reaksi antara dinding pipa dalam dan produk yang diangkut. Aktivitas korosif seperti itu tidak hasil dari produk yang diangkut melainkan hasil dari pengotor dalam aliran produk.
Gas alam (metana) tidak akan membahayakan baja, tapi air asin dan kotoran lainnya pasti bisa mendukung korosi. Zat pendukung korosi kadang-kadang ditemukan dalam gas alam termasuk CO, klorida, H2S, asam organik, oksigen, air gratis, padatan atau presipitat, atau belerang-bantalan senyawa.
Mikroorganisme secara tidak langsung dapat mendukung korosi juga harus dipertimbangkan di sini. Sulfat-mengurangi bakteri anaerobik dan bakteri penghasil asam kadang-kadang ditemukan dalam minyak dan pipa gas. Mereka masing-masing menghasilkan H2S dan asam asetat, yang keduanya dapat medukung korosi.
Beberapa langkah yang sama digunakan untuk mencegah korosi internal, seperti lapisan internal, digunakan tidak hanya untuk melindungi pipa, tetapi juga untuk melindungi produk dari kotoran yang dihasilkan oleh korosi. Jet bahan bakar dan tinggi kemurnian bahan kimia adalah contoh dari produk pipa yang hati-hati dilindungi dari kontaminan tersebut.
Product Corrosivity
Penilaian ini terhadap relatif agresivitas dari isi pipa yang kontak langsung dengan dinding pipa. Ancaman terbesar ada dalam sistem di mana produk tersebut tetap bertentangan dengan material pipa. Ancaman lain muncul ketika kotoran korosif secara rutin bisa masuk ke produk.
Internal Corrosion
Internal corrosion is pipe wall loss or damage caused by a reaction between the inside pipe wall and the product being transported. Such corrosive activity may not be the result of the product intended to be transported but rather a result of an impurity in the product stream.
The natural gas (methane) will not harm steel, but saltwater and other impurities can certainly promote corrosion. Other corrosion-promoting substances sometimes found in natural gas include CO, chlorides, H2S, organic acids, oxygen, free water, solids or precipitates, or sulfur-bearing compounds. Microorganisms that can indirectly promote corrosion should also be considered here. Sulfate-reducing bacteria and anaerobic acid-producing bacteria are sometimes found in oil and gas pipelines. They produce H2S and acetic acid, respectively, both of which can promote corrosion.
Some of the same measures used to prevent internal corrosion, such as internal coating, are used not only to protect the pipe, but also to protect the product from impurities that may be produced by corrosion. Jet fuels and high-purity chemicals are examples of pipeline products that are often carefully protected from such contaminants.
Product Corrosivity
This is an assessment of the relative aggressiveness of the pipeline contents that are in immediate contact with the pipe wall. The greatest threat exists in systems where the product is inherently incompatible with the pipe material. Another threat arises when corrosive impurities can routinely get into the
Criteria Score Low corrosion: reasonable material selected for tranport products,
normally product is not corrosive, low corrosion rate. 1 Medium corrosion: damage of pipeline is possible but in slower rate, low percentage of acidic products, medium corrosion rate. 3 High corrosion: rapid corrosion is possible, material selected incompatible with products, high percentage of H2S, CO2 and other acidic products, high corrosion rate.
5 Karakteristik aliran normal harus mewakili ukuran dari
korosivitas produk diangkut dalam pipa. Langkah ini menilai potensi korosi dari kontak normal antara produk mengalir dan dinding pipa, berdasarkan spesifikasi produk dan / atau karakteristik analisis produk. Karakteristik aliran dapat dibagi menjadi dua kategori utama: air terkait dan padatan terkait - untuk tujuan mengevaluasi korosivitas.
Kontaminasi air terkait, seperti: kadar air, oksigen, PH, H2S, suhu, klorida. Kontaminasi padatan terkait, seperti MIC, padatan tersuspensi (potensi erosi), sulfat, karbonat.
product.
The normal flow stream characteristics should represent a measure of the corrosivity of the products transported in the pipeline. This measure assesses corrosion potential from normal contact between flowing product and the pipe wall, based on product specifications and/or product analyses.The flow stream characteristics can be divided into two main categories: water related and solids related - for purposes of evaluating corrosivity.
Water-related contaminations, such as: water content, oxygen, PH, H2S, temperature, chlorides. Solids related contaminations, such as MIC, suspended solids (erosion potential), sulfates, carbonates.
Internal Corrosion Prevention Internal monitoring
Biasanya, hal ini dilakukan salah satu dari dua cara: 1) oleh penyelidikan elektronik yang terus menerus dapat mengirimkan pengukuran yang menunjukkan potensi korosi atau 2) dengan kupon yang benar-benar berkarat dengan adanya produk mengalir dan dikeluarkan dan diukur secara berkala.
Inhibitor injection
Ketika mekanisme korosi dipahami sepenuhnya, bahan kimia tertentu dapat disuntikkan ke dalam aliran produk yang mengalir untuk mengurangi atau menghambat reaksi. Karena oksigen merupakan bahan korosi utama dari baja, sebuah "oksigen scavenging" kimia dapat menggabungkan dengan oksigen dalam produk tersebut untuk mencegah oksigen bereaksi dengan dinding pipa. Sejenis yang
Internal Corrosion Prevention Internal monitoring
Normally, this is done in either of two ways: 1) by an electronic probe that can continuously transmit measurements that indicate a corrosion potential or 2) by a coupon that actually corrodes in the presence of the flowing product and is removed and measured periodically.
Inhibitor injection
When the corrosion mechanism is fully understood, certain chemicals can be injected into the flowing product stream to reduce or inhibit the reaction. Because oxygen is a chief corroding agent of steel, an “oxygen-scavenging” chemical can combine with the oxygen in the product to prevent this oxygen from reacting with the pipe wall. A more common kind of chemical inhibitor forms a protective barrier between
lebih umum dari inhibitor kimia membentuk penghalang pelindung antara baja dan produk - lapisan, berlaku.
Inhibitor ini diterapkan kembali secara berkala atau terus-menerus disuntikkan untuk menggantikan inhibitor yang diserap atau tergeser oleh aliran produk. Dalam kasus di mana aktivitas mikroorganisme adalah masalah, biocides dapat ditambahkan ke inhibitor.
Sebuah program pigging mungkin diperlukan untuk melengkapi injeksi inhibitor. Pigging akan dirancang untuk menghapus cairan bebas atau penutup koloni bakteri pelindung, yang dapat saja mengganggu inhibitor atau kinerja biosida.
Internal coating
Lapisan internal dapat mengambil beberapa bentuk termasuk aplikasi semprot dari plastik, mortir, atau beton serta penyisipan liners untuk jaringan pipa yang ada. Teknologi material baru memungkinkan untuk pembuatan pipa "berlapis". Ini biasanya sebuah pipa baja luar yang diisolasi dari produk berpotensi merusak dengan bahan yang kompatibel dengan produk yang diangkut. Plastik, karet, atau keramik adalah bahan pengisolasi umum. Mereka dapat diinstal selama fabrikasi pipa awal, selama konstruksi pipa atau kadang-kadang material dapat ditambahkan ke pipa yang ada.
the steel and the product - a coating, in effect.
Inhibitor is reapplied periodically or continuously injected to replace the inhibitor that is absorbed or displaced by the product stream. In cases where microorganism activity is a problem, biocides can be added to the inhibitor.
A pigging program may be necessary to supplement inhibitor injection. The pigging would be designed to remove free liquids or bacteria colony protective coverings, which might otherwise interfere with inhibitor or biocide performance.
Internal coating
Internal coating can take several forms including spray-on applications of plastics, mortar, or concrete as well as insertion liners for existing pipelines. New materials technology allows for the creation of “lined” pipe. This is usually a steel outer pipe that is isolated from a potentially damaging product by a material that is compatible with the product being transported. Plastics, rubbers, or ceramics are common isolating materials. They can be installed during initial pipe fabrication, during pipeline construction or
sometimes the material can be added to an existing pipeline.
Criteria Score
Not needed 1
Internal coating 2
Inhibitor injection 3
Internal corrosion monitoring 4
Subsurface Corrosion Soil Corrosivity
Karena sistem pelapisan selalu dianggap penghalang yang tidak sempurna, tanah selalu diasumsikan bersentuhan dengan dinding pipa di beberapa titik. Korosivitas tanah sering sebagai ukuran kualitatif seberapa baik tanah dapat bertindak sebagai elektrolit untuk mendorong korosi galvanik pada pipa.
Resistivitas tanah atau konduktivitas adalah fungsi dari variabel yang saling tergantung seperti kadar air, porositas. temperatur, konsentrasi ion, dan jenis tanah.
Subsurface Corrosion Soil Corrosivity
Because a coating system is always considered to he an imperfect barrier, the soil is always assumed to he in contact with the pipe wall at some points. Soil corrosivity is often a qualitative measure of how well the soil can act as an electrolyte to promote galvanic corrosion on the pipe.
Soil resistivity or conductivity is a function of interdependent variables such as moisture content, porosity. temperature, ion concentrations, and soil type.
Criteria Score
Relatively less corrosive (≥25000) 1
Mildly corrosive (10000 - 25000) 2
Moderately corrosive (10000 - 5000) 3
Corrosive (2000 - 5000) 4
Very corrosive (0 - 2000) 5
Stress Corrosion Cracking
Setiap segmen harus dinilai untuk kemungkinan ancaman risiko SCC jika termasuk semua kriteria berikut:
(a) Operating stress level > 60% SMYS (b) Umur dari pipa> 10 tahun
(c) Semua sistem pelapisan korosi selain plant applied or field applied fusion bonded epoxy (FBE) or liquid epoxy
Setiap segmen harus dinilai untuk kemungkinan ancaman risiko SCC pH tinggi jika memenuhi kriteria di atas dan semua kriteria berikut:
(a) suhu operasi> 100 °F (38 °C)
(b) jarak dari stasiun kompresor ≤ 20 mil (32 km) Jika kondisi untuk SCC ada (yaitu, memenuhi kriteria di atas), pemeriksaan tertulis, pengujian, dan rencana evaluasi harus disiapkan.
Jika pipa mengalami kebocoran di-service atau pecah
Stress Corrosion Cracking
Each segment should be assessed for risk for the possible threat of SCC if all of the following criteria are present:
(a) Operating stress level > 60% SMYS (b) Age of pipe >10 yr
(c) All corrosion coating systems other than plant
applied or field applied fusion bonded epoxy (FBE) or liquid epoxy
Each segment should be assessed for risk for the possible threat of high pH SCC if the above criteria are present and all of the following criteria are present:
(a) operating temperature >100°F (38°C)
(b) distance from compressor station ≤20 miles (32
km)
If conditions for SCC are present (i.e., meet the criteria above), a written inspection, examination,
Criteria Score SCC not possible, or SCC with severity category 0 1 SCC very unlikely, or SCC with severity category 1 2 SCC unlikely, or SCC with severity category 2 3 SCC likely, or SCC with severity category 3 4 SCC very likely, or SCC with severity category 4 5 yang dikaitkan dengan SCC, segmen tertentu harus
dikenakan tes hidrostatik dalam 12 bulan.
Metode yang direkomendasikan untuk pemeriksaan SCC adalah bell hole inspection, in-line inspection (intelligent pigging) dan hydrotest.
Indikasi terjadinya SCC ditemukan selama inspeksi, harus ditangani dengan menggunakan pedoman dalam tabel berikut yang menunjukkan kriteria keparahan dari SCC.
and evaluation plan shall be prepared.
If the pipeline experiences an in-service leak or rupture that is attributed to SCC, the particular segment shall be subjected to a hydrostatic test within 12 months.
Recommended methods for SCC inspection are bell hole inspection, in-line inspection (intelligent pigging) and hydrotest.
Any indications of SCC found during inspection, shall be addressed using guidance in the following table shows the severity criteria of SCC.
Cathodic Protection
Kehadiran arus pelindung yang memadai biasanya ditentukan oleh pengukuran perbedaan (potensi) tegangan antara logam pipa dan elektrolit. Dengan beberapa praktek umum dan persyaratan standar, potensi pipa-ke-tanah minimal -0.85 volt (-850 milivolt), yang diukur dengan elektroda referensi tembaga-tembaga sulfat, adalah kriteria umum yang menunjukkan perlindungan yang memadai dari korosi.
Cathodic Protection
The presence of adequate protective currents is normally determined by measurement of the voltage (potential) difference between the pipe metal and the electrolyte. By some common practices and standard requirements, a pipe-to-soil potential of at least -0.85 volts (-850 millivolts), as measured by a copper-copper sulfate reference electrode, is the general criterion indicating adequate protection from corrosion.
Criteria Score
Aerial, or no CP required 1
CP installed, providing very good protection (lower than -1,000 mv) 2 CP installed, providing adequate protection (lower than -850 mv) 3 CP installed, but underprotection (higher than -850 mv) 4
No CP installed, broken or missing 5
CP Potential Interference
Korosi adalah proses elektro-kimia dan metode pencegahan korosi dirancang untuk mengganggu proses itu, seringkali dengan metode listrik seperti proteksi katodik. Namun, metode pencegahan itu sendiri rentan untuk mengalahkan dari efek listrik lainnya. Istilah umum untuk efek ini adalah
interference.
Pipa dekat fasilitas transmisi listrik AC terkena ancaman. Baik melalui kesalahan tanah atau proses induksi, pipa dapat menjadi bermuatan listrik. Tidak hanya perubahan potensi bahaya untuk orang yang datang kontak dengan pipa, juga berpotensi berbahaya untuk pipa itu sendiri.
CP Potential Interference
Corrosion is an electro-chemical process and corrosion prevention methods are designed to interrupt that process, often with electrical methods like cathodic protection. However, the prevention methods themselves are susceptible to defeat from other electrical effects. The common term for these effects is interference.
Pipelines near AC power transmission facilities are exposed to a unique threat. Through either a ground fault or an induction process, the pipeline may become electrically charged. Not only is this charge potentially dangerous to people coming into contact with the pipeline, it is also potentially dangerous to the pipeline itself.
Criteria Score
No AC power within 300 m, or very low AC power 1 AC power nearby but preventive measures are taken, or survey
confirm no induction occuring 3
Sub-surface coating conditions
Coating harus dapat menahan sejumlah tekanan mekanis dari konstruksi awal, tanah, kerikil, gerakan akar, dan dari perubahan suhu, pipa bergerak melawan tanah disekelilingnya. Lapisan ini akan terus terkena kelembaban tanah dan merusak zat-zat yang terkandung dalam tanah. Selain itu, lapisan memadai harus melayani tujuan utamanya: mengisolasi baja dari elektrolit.
Sistem pelapisan yang umum termasuk: - Cold-applied asphalt mastics
- Layered extruded polyethylene - Fusion-bonded epoxy
- Coal tar enamel and wrap - Tapes (hot or cold applied).
Faktor yang mempengaruhi kegagalan meliputi:
- Kerusakan mekanik dari gerakan tanah, batu, akar, kegiatan konstruksi
- Disbondment disebabkan oleh generasi hidrogen dari berlebihan arus proteksi katodik
- Jenis lapisan yang tidak benar atau aplikasi untuk kondisi operasi pipa dan lingkungan
- Air
Sub-surface coating conditions
Coating must be able to withstand a certain amount of mechanical stress from initial construction, from subsequent soil, rock, root movements, and from temperature changes as the pipe moves against the adjacent soil. The coating will be continuously exposed to ground moisture and any damaging substances contained in the soil. Additionally, the coating must adequately serve its main purpose: isolating the steel from the electrolyte.
Typical coating systems include: - Cold-applied asphalt mastics - Layered extruded polyethylene - Fusion-bonded epoxy
- Coal tar enamel and wrap - Tapes (hot or cold applied).
Factors contributing to failure include:
- Mechanical damages from soil movements, rocks, roots, construction activities
- Disbondment caused by hydrogen generation from excessive cathodic protection currents
- Incorrect coating type or application for the pipeline operating condition and environment - Water penetration
Criteria Score
Excellent: high quality coating suitable for its environment, new
condition or recently repair 1
Good: high quality coating, in good condition, less than 10% damage. 2 Fair: adequate coating, fair condition, less than 30% damage. 3
Poor: coating in-place, more than 30% damage 4
Absent: no coating 5
Sub-surface Coating Surveys
Evaluator harus memuaskan dirinya bahwa operator memahami teknik ini dan dapat menunjukkan beberapa keberhasilan dalam penggunaannya untuk inspeksi coating.
Kesalahan lapisan umum termasuk retak, lubang kecil, dampak (benda tajam). tekan beban (susunan coating pipa), disbondment, pelunakan atau mengalir, dan penurunan umum (misalnya degradasi ultraviolet).
Sub-surface Coating Surveys
The evaluator should satisfy himself that the operator understands the technique and can demonstrate some success in its use for coating inspection.
Typical coating faults include cracking, pinholes,impacts (sharp objects). compressive loadings (stacking of coated pipes), disbondment, softening or flowing, and general deterioration (ultraviolet degradation, for example).
Criteria Score Excellent: A formal, thorough inspection is performed. Inspections performed by qualified and
experienced personel at appropriate intervals. One or more indirect assesment techniques were used and followed by direct assesment.
1
Good: A formal, thorough inspection is performed. Inspections performed by qualified and experienced personel at appropriate intervals. One or more indirect assesment techniques were used.
2
Fair: Inspections are informal, but performed routinely by qualified personel, using indirect
technique. 3
Poor: Little inspection is done; reliance is on chance sighting of problem areas by using visual
inspection. 4
Absent: No inspection done. 5
Criteria Score
Design to MOP ratio > 2.0 1 Design to MOP ratio: 1.5 - 2.0 2 Design to MOP ratio: 1.25 - 1.5 3 Design to MOP ratio: 1.0 - 1.25 4 Design to MOP ratio < 1.0 5
Kelelahan
Kelelahan adalah melemahnya material akibat siklus stress yang berulang-ulang. Besar melemahnya tergantung pada jumlah dan magnitude dari siklus. Tekanan yang lebih tinggi terjadi lebih sering, dapat menyebabkan kerusakan material lebih banyak. Faktor-faktor seperti kondisi permukaan, geometri, fracture toughness, jenis tegangan, dan proses pengelasan rentan terhadap pengaruh fatigue failure.
Fatigue
Fatigue is the weakening of material due to repeated cycles of stress. The amount of weakening depend on the number and magnitude of the cycles. Higher stresses, occurring more often, can cause more damage to materials. Factors such as surface conditions, geometry, fracture toughness, type of stress applied, and welding process influence susceptibility to fatigue failure.
5.2.3 Disain Safety Factor
Dalam sistem pipa, 'Perbandingan Desain Tekanan dengan MOP' dapat digunakan untuk mengetahui perbedaan antara system komponen yang dapat dilakukan dan apa yang saat ini sedang diminta untuk melakukan. Bila rasio ini sama dengan 1.0, saat ini tidak ada faktor keamanan, ini berarti sistem sedang dioperasikan pada batasnya. Jika rasio kurang dari 1.0 secara teoritis sistem dapat setiap saat gagal. Jika rasio lebih besar dari 1.0 berarti saat ini ada faktor keamanan, dan sistem beroperasi di bawah batasnya.
5.2.3 Design Safety Factor
In the pipeline system, ‘Design Pressure to MOP Ratio’ can be used show difference between what a system component can do and what it is presently being asked to do. When this ratio is equal to 1.0 there is no safety factor present, this means the system is being operated at its limit. If the ratio less than 1.0 the system theoretically can fail at any time. A ratio greater than 1.0 means that there is a safety factor present, and the system is being operated below its limit.
Criteria Score Fatigue is not expected to lead to failure within the given time frame. 1 Fatigue could possibly lead to failure within the given time frame. 3 Fatigue is expected to lead to failure in the given time frame. 5
Struktur penahan Support
Criteria Score
Pipeline support properly 1
Support damage recorded, assessed and no remediation required. 2 Support damage recorded, not assessed and remediation. 3 Support damage recorded, minor pipe deformation found. 4 Support damage recorded, major pipe deformation found. 5
Criteria Score
Not possible: means fluid property can not produces a pressure surge
greater than 10% MOP. 1
Low probability: surge can happen, but pipeline completed with mechanical devices such as surge tank, relief valves, and slow valve closures.
3
High probability, exist where closure devices, equipment and fluid velocity support the possibility of pressure surge. No mechanical preventers in-place. Operating procedures may not be in-place.
5 Surge Potential
Potensi efek pressure surge atau water hammer, adalah konversi tiba-tiba energi kinetik menjadi energi potensial. Sebuah massa fluida yang mengalir dalam pipa mempunyai sejumlah energi kinetik, jika massa cairan tiba-tiba yang dibawa ke berhenti, energi kinetik diubah menjadi energi potensial dalam bentuk tekanan. Sebuah penutupan valve mendadak, menjalankan dan menghentikan pompa adalah kemungkinan inisiator.
Surge Potential
The potential for pressure surge or water hammer effects, is the sudden conversion of kinetic energy to potential energy. A mass of flowing fluid in pipeline has certain amount of kinetic energy, if this mass of fluid is suddenly brought to a halt, the kinetic energy is converted to potential energy in form of pressure. A sudden valve closure, starting and stopping pumps are the possible initiator.
Integrity Verification
Integritas pipa dipastikan dengan dua usaha utama: (1) deteksi dan penghapusan anomali yang mengancam integritas dan (2) menghindari ancaman masa depan bagi integritas (melindungi aset).
Upaya pertama melibatkan pemeriksaan dan pengujian merupakan dasar untuk memastikan integritas pipa. Tujuan dari inspeksi dan pengujian adalah untuk memvalidasi integritas struktural dari pipa dan kemampuannya untuk mempertahankan tekanan operasi dan beban lainnya. Tujuannya adalah menguji dan memeriksa sistem pipa pada interval cukup sering untuk memastikan integritas pipa dan menjaga margin of safety.
Cacat yang dianggap akan ada anomali pipa tidak diinginkan, seperti crack. gouge, dent atau metal loss, yang kemudian dapat menyebabkan kebocoran atau tumpahan. Tidak semua anomali cacat. Beberapa gouge, dent, metal loss, dan bahkan crack tidak akan mempengaruhi pelayanan saluran pipa.
Asumsi konservatif yang mendasari verifikasi integritas adalah bahwa cacat yang hadir di dalam pipa dan tumbuh pada tingkat tertentu. Dengan memeriksa atau menguji pipa pada interval tertentu, pertumbuhan ini dapat terganggu sebelum cacat mencapai ukuran kegagalan.
Metode penilaian integritas yang dapat digunakan adalah inspeksi inline, pengujian tekanan, penilaian langsung, atau metode NDT lainnya. Metode penilaian integritas didasarkan pada ancaman segmen yang rentan. Lebih dari satu metode dan / atau alat mungkin diperlukan untuk mengatasi semua ancaman dalam segmen pipa.
Integrity Verification
Pipeline integrity is ensured by two main efforts: (1) the detection and removal of any integrity-threatening anomalies and (2) the avoidance of future threats to the integrity (protecting the asset). The former effort involves inspection and testing and is fundamental to ensuring pipeline integrity. The purpose of inspection and testing is to validate the structural integrity of the pipeline and its ability to sustain the operating pressures and other anticipated loads. The goal is to test and inspect the pipeline system at frequent enough intervals to ensure pipeline integrity and maintain the margin of safety. A defect is considered to be any undesirable pipe anomaly, such as a crack. gouge, dent. or metal loss, that could later lead to a leak or spill. Note that not all anomalies are defects. Some dents, gouges, metal loss, and even cracks will not affect the service life of a pipeline.
A conservative assumption underlying integrity verification is that defects are present in the pipeline and are growing at some rate. By inspecting or testing the pipeline at certain intervals, this growth can be interrupted before any defect reaches a failure size.
The integrity assessment methods that can be used are inline inspection, pressure testing, direct assessment, or other NDT methods. The integrity assessment method is based on the threats to which the segment is susceptible. More than one method and/or tool may be required to address all the threats in a pipeline segment.
Criteria Score
Very good, where inspection and testing have a high probability of detecting the damage mechanisms under consideration and is able to accurately measure the extent of this damage; and with comprehensive coverage of expected damage locations. i.e combination of ILI and direct assement.
1
Good, where the inspection and testing are generally effective in detecting and measuring the damage under consideration, and with good coverage of expected damage. i.e. UT scan, CIPS, DCVG.
2
Average, where the inspection and testing are insensitive at low damage levels, with adequate coverage of expected damage locations, i.e. spot UT and CP readings. 3
Below average, where the inspection and testing are insensitive to the suspected damage mechanism or with inadequate coverage of expected damage locations, i.e visual inspection, random UT spot.
4
Poor, where no inspection program established or inspection activity is inappropriate for the damage concerned and does not cover expected damage locations. 5
Ground Movement
Pipa dapat mengalami tegangan akibat gerakan tanah dan / atau peristiwa geoteknik dari berbagai macam. Gerakan-gerakan ini bisa mendadak dan sebagai bencana atau mungkin deformasi yang menyebabkan tekanan pada pipa selama jangka waktu tahunan.
Ini dapat menyebabkan kegagalan atau menambahkan tekanan yang cukup besar untuk pipa dan harus dipertimbangkan dalam analisis risiko.
Tanah Longsor
Banyak skenario gerakan lahan berpotensi berbahaya yang memiliki kemiringan (lihat Gambar di bawah). Kehadiran lereng menambahkan gaya gravitasi. Tanah longsor dapat terjadi dari hujan lebat, terutama di lereng atau bukit dengan pemotongan berat tanaman atau beban dari konstruksi atau kegiatan lain yang mengganggu tanah. Slide juga dapat disebabkan oleh aktivitas seismik. Longsor perpindahan pipa dapat menyebabkan kerusakan struktur dan kebocoran oleh kekuatan eksternal meningkat jika pipa yang terkubur di bawah tanah pengungsi.
Ground Movement
A pipeline may be subjected to stresses due to land movements and/or geotechnical events of various kinds. These movements may be sudden and catastrophic or they may be long-term deformations that induce stresses on the pipeline over a period of years.
These can cause immediate failures or add considerable stresses to the pipeline and should be considered in a risk analysis.
Landslide
Many of the potentially dangerous land movement scenarios have a slope involved (see Figure below). The presence of a slope adds the force of gravity. Landslides can occur from heavy rain, especially on slopes or hillsides with heavy cutting of vegetation or loadings from construction or other activities that disturb the land. Slides can also be caused by seismic activity. Landslide displacement of pipe can cause structural damage and leaks by increased external force loading if the pipeline is buried under displaced soil.
Criteria Score Very stable: no evidence of threatening instability events occurring
from the presence of soil, earth or water characteristics. 1 Infrequent movement: ground movements are possible but rare, or
unlikely to affect the pipeline integrity. 3
Frequent movement: where damaging ground movements are common or severe, or where movements are likely to affect the pipeline integrity. Or unknown.
5
Persilangan pipa Pipeline Crossings
Criteria Score
No pipeline crossings with roads, railway or rivers, etc 1
Design of Pipeline Crossing is CORRECT 2
Design of Pipeline Crossing is ADEQUATE 3
Design of Pipeline Crossing is INADEQUATE 4
Design of Pipeline Crossing UNKNOWN 5
Gempa bumi
Ancaman dari peristiwa gempa bumi menyebabkan pipa bergetar karena penjalaran gelombang seismik. Pipa dipasang di daerah gempa harus memiliki desain teknik yang tepat, untuk menahan kekuatan gempa, mempertimbangkan jenis gempa dan parameter frekuensi.
Scour dan erosi
Erosi adalah ancaman umum untuk pipa dangkal atau di atas, terutama ketika dekat sungai atau daerah yang biasa banjir kecepatan arus tinggi. Bahkan pipa terkubur terkena ancaman dari gerusan dalam situasi tertentu. Potensi kedalaman penutup yang mengikis selama arus banjir, memperlihatkan pipeline tersebut. Jika gaya lateral yang cukup besar, pipa bisa menjadi tertekan.
Seismic
Threats from seismic events cause pipeline seismic shaking due to the propagation of seismic waves. Pipeline installed in seismic area shall have proper engineering design, to withstand seismic forces, considering earthquake type and frequency parameters.
Scour and erosion
Erosion is a common threat for shallow or above-grade pipelines, especially when near stream banks or areas subject to high velocity flood flows. Even buried pipelines are exposed to threats from scour in certain situations. A potential is for the depth of cover to erode during flood flows, exposing the ipeline. If a lateral force were sufficiently large, the pipeline could become overstressed.
c. Operasi
Indeks ini menilai potensi kegagalan pipa disebabkan oleh kesalahan yang dilakukan oleh personil pipa dalam perancangan, konstruksi, operasi, atau memelihara saluran pipa. Human error secara logis dapat berdampak salah satu probabilitas-kegagalan sebelum indeks-aktif korosi, misalnya, dapat menunjukkan kesalahan dalam kegiatan pengendalian korosi. Scoring potensi kesalahan dalam indeks yang terpisah memiliki keuntungan untuk menghindari penilaian ganda untuk banyak variabel risiko yang bersangkutan. Misalnya, penilaian program pelatihan dan penggunaan prosedur tertulis umumnya akan berlaku untuk semua mode kegagalan. Menangkap penilaian seperti di lokasi pusat adalah kenyamanan pemodelan dan lebih mempermudah identifikasi peluang mitigasi risiko dalam tahap manajemen risiko. Jika evaluator merasa bahwa ada perbedaan dalam potensi kesalahan manusia untuk setiap mode kegagalan, dia dapat mendasarkan skornya pada kasus terburuk atau mengevaluasi variabel kesalahan manusia secara terpisah untuk setiap mode kegagalan.
HAZID / Penilaian Risiko
Di sini, evaluator memeriksa untuk melihat bahwa upaya yang dilakukan untuk mengidentifikasi semua bahaya yang kredibel terkait dengan pipa dan operasi. Bahaya harus dipahami dengan jelas sebelum langkah-langkah pengurangan risiko digunakan. Hal ini termasuk semua mode kegagalan yang mungkin dalam penilaian risiko pipa.
Poin diberikan berdasarkan ketelitian dari studi bahaya, dengan proses identifikasi bahaya yang terdokumentasi, arus, dan formal mendapatkan nilai tertinggi.
c. Operation
This index assesses the potential for pipeline failure caused by errors committed by the pipeline personnel in designing, construction, operating, or maintaining a pipeline. Human error can logically impact any of the previous probability-of-failure indexes-active corrosion, for example, could indicate an error in corrosion control activities. Scoring error potential in a separate index has the advantage of avoiding duplicate assessments for many of the pertinent risk variables. For instance, assessments of training programs and use of written procedures will generally apply to all failure modes. Capturing such assessments in a central location is a modeling convenience and further facilitates identification of risk mitigation opportunities in the risk management phase. If the evaluator feels that there are differences in human error potential for each failure mode, he can base his score on the worst case or evaluate human error variables separately for each failure mode.
HAZID / Risk Assesment
Here, the evaluator checks to see that efforts were made to identify all credible hazards associated with the pipeline and its operation. A hazard must be clearly understood before appropriate risk reduction measures can be employed. This would include all possible failure modes in a pipeline risk assessment. Points are awarded based on the thoroughness of the hazard studies, with a documented, current, and formal hazard identification process getting the highest score.
Criteria Score
Formal hazard identification / risk assessment performed, documentation is available, recommendations are fully implemented 1 Formal hazard identification/ risk assessment performed, documentation is available, recommendations are partially implemented
2 Informal hazard identification / risk assessment performed, documentation is available, recommendations are either fully or partially implemented
Informal hazard identification / risk assessment performed, documentation is not available, recommendations are either fully or partially implemented
4
No hazard identification / risk assessment performed. 5
Potensi MOP
Kemungkinan melebihi tekanan di mana sistem tersebut dirancang dari elemen gambar risiko. Sebuah sistem di mana tidak mungkin secara fisik melebihi tekanan desain, kemungkinan secara inheren lebih aman. Hal ini sering terjadi ketika sistem pipa dioperasikan pada tingkat jauh di bawah desain aslinya.
Mustahil: operasi normal dapat memungkinkan sistem untuk mencapai MOP. Overpressure akan terjadi cukup cepat akibat incompressible fluid or rapid introduction dari volume cairan kompresibel yang relatif tinggi.
Sangat Tidak mungkin: overpressure dapat terjadi melalui kombinasi kesalahan prosedural atau kelalaian, atau kegagalan perangkat pengaman.
Tidak mungkin: overpressure mungkin (tekanan sumber cukup), dapat terjadi melalui kombinasi kesalahan prosedural atau kelalaian, dan kegagalan alat pengaman
Kemungkinan: overpressure mungkin (tekanan sumber cukup), tetapi hanya melalui sebuah rangkaian kesalahan, kelalaian, dan kegagalan perangkat keamanan yang tidak mungkin.
Rutin: tidak ada sumber tekanan, di bawah setiap kejadian yang mungkin, overpressure pipa.
MOP Potential
The possibility of exceeding the pressure for which the system was designed is an element of the risk picture. A system where it is not physically possible to exceed the design pressure is inherently safer than one where the possibility exists. This often occurs when a pipeline system is operated at levels well below its original design intent.
Impossible : Normal operations could allow the system to reach MOP. Overpressure would occur fairly rapid due to incompressible fluid or rapid introduction of relatively high volumes of compressible fluids.
Very Unlikely : Overpressure can occur through a combination of procedural errors or omissions, OR failure of safety devices.
Unlikely : Overpressure is possible (sufficient source pressure), can occur through a combination of procedural errors or omissions, AND failure of safety device
Likely : Overpressure is possible (sufficient source pressure), but only through an very unlikely chain of events including errors, omissions, and safety device failures.
Routine : The pressure source cannot, under any conceivable chain of events, overpressure the pipeline Criteria Score Impossible 1 Very Unlikely 2 Unlikely 3 Likely 4 Routine 5
Sistem Pengaman
Sistem Pengaman sebagai cadangan situasi di mana kesalahan manusia menyebabkan atau memungkinkan terjadi MOP. Evaluator harus berhati-hati mempertimbangkan semua sistem keamanan di tempat. Sebuah sistem Pengaman atau perangkat adalah perangkat, mekanik listrik, pneumatik, atau dikendalikan komputer yang mencegah pipa overpressured.
Pencegahan dapat berupa mematikan sumber tekanan atau mengurangi isi pipa bertekanan. Perangkat Pengaman umumnya meliputi valve pelepas, disk pecah, dan switch yang dapat menutup valve, shut down equipment, dll, berdasarkan kondisi.
Sistem pengaman tidak diperlukan: Dalam item
sebelumnya, potensial MOP, poin terbanyak diberikan untuk situasi di mana tidak mungkin pipa mencapai MOP. Dalam skenario ini, tingkat tertinggi poin juga diberikan untuk variabel ini karena tidak ada sistem keamanan yang diperlukan.
Onsite, satu tingkat sistem pengaman. Untuk kondisi
ini single device, terletak di lokasi, melindungi dari overpressure. lokasi ini bisa menjadi sumber tekanan pipa. Saklar tekanan yang menutup valve adalah contoh mengisolasi segmen pipa. Contoh lain adalah relief valve dengan ukuran pada pipa itu sendiri.
Onsite, dua atau lebih tingkat Sistem Keamanan: Di
sini, lebih dari satu perangkat keamanan dipasang di lokasi. Setiap perangkat harus independen dan didukung oleh sumber daya yang berbeda dari yang lain. Ini berarti bahwa setiap perangkat memberikan tingkat independen dari keselamatan. Poin lebih harus diberikan untuk situasi ini karena redundansi perangkat keselamatan jelas mengurangi risiko.
Safety Systems
Safety systems exist as backup situations in which human error causes or allows MOP to be reached. The risk evaluator should carefully consider any and all safety systems in place. A safety system or device is a mechanical, electrical, pneumatic, or computer-controlled device that prevents the pipeline from being overpressured.
Prevention may take the form of shutting down a pressure source or relieving pressurized pipeline contents. Common safety devices include relief valves, rupture disks, and switches that may close valves, shut down equipment, etc., based on conditions.
Safety systems not needed: In the previous item,
MOP potential, the most points were awarded for the situation in which it is impossible for the pipeline to reach MOP. Under this scenario, the highest level of points is also awarded for this variable because no safety systems are needed.
Onsite, one level safety system. For this condition a
single device, located at the site, offers protection from overpressure. The site can be the pipeline or the pressure source. A pressure switch that closes a valve to isolate the pipeline segment is an example. A properly sized relief valve on the pipeline itself is another example.
Onsite, two or more levels Safety Systems: Here,
more than one safety device is installed at the site. Each device must be independent of all others and be powered by a power source different from the others. This means that each device provides an independent level of safety. More points should be awarded for this situation because redundancy of safety devices obviously reduces risk.
Criteria Score
Safety systems not needed 1
Onsite, two or more levels Safety Systems 2
Onsite, one level safety system 3
Remote, observation and control 4
Remote, observation only, or no safety system 5
Remote, observation only. Dalam hal ini, tekanan
dimonitor dari lokasi remote. Remote control tidak mungkin dan otomatis perlindungan overpressure tidak ada. Meskipun tidak ada pengganti untuk sistem pengaman otomatis, observasi remote seperti menyediakan beberapa cadangan tambahan personil pemantauan setidaknya bisa memberitahu personil lapangan untuk mengambil tindakan.
Remote, observasi dan kontrol. Ini adalah situasi yang sama seperti sebelumnya dengan fitur tambahan kemampuan remote control. Pemberitahuan tingkat tekanan meningkat, pengamat mampu untuk jarak jauh mengambil tindakan untuk mencegah tekanan berlebih. Berarti menghentikan pompa atau kompresor dan membuka atau menutup valve. Remote control umumnya dengan membuka atau menutup valve dan menghentikan pompa atau kompresor.
Remote, observation only. In this case, the pressure
is monitored from a remote location. Remote control is not possible and automatic overpressure protection is not present. While not a replacement for an automatic safety system, such remote observation provides some additional backup the monitoring personnel can at least notify field personnel to take action.
Remote, observation and control. This is the same
situation as the previous one with the added feature of remote control capabilities. On notification of rising pressure levels, the observer is able to remotely take action to prevent overpressure. This may mean stopping a pump or compressor and opening or closing valves. Remote control generally takes the form of opening or closing valves and stopping pumps or compressors.
Specifikasi Material
Evaluator harus mencari bukti bahwa bahan-bahan yang diidentifikasi dan ditentukan tepat. Hal ini termasuk pipa, fitting, flensa, pelapis beton, pelapis internal dan eksternal, mur dan baut, support, dan (load-bearing) anggota struktural dari sistem.
Material Specifications
The evaluator should look for evidence that proper materials were identified and specified. This would include pipes, fittings, flanges, concrete coatings, internal and external coatings, nuts and bolts, supports, and the structural (load-bearing) members of the system.
