Analisis Karakteristik Aliran Turbulen dan Laju Erosi pada Berbagai Tipe Valve di Wellpad Geothermal

Ilham Abdul Aziz, Dr. Nyayu Aisyah, SST, M.T.

2026 | Tugas Akhir | D4 TEKNOLOGI REKAYASA MESIN

Erosi yang disebabkan oleh partikel padat yang terbawa dalam fluida geotermal dua fase bersuhu tinggi merupakan penyebab utama penipisan dinding pipa, waktu henti (downtime) yang tidak terencana, dan peningkatan biaya perawatan pada sistem perpipaan wellpad geotermal. Penelitian ini menyelidiki secara numerik karakteristik aliran turbulen dan laju erosi dari empat tipe valve yaitu gate, ball, butterfly, dan globe yang terpasang pada jalur pipa wellpad geotermal menggunakan Computational Fluid Dynamics (CFD). Simulasi steady state dilakukan menggunakan model turbulensi k-w SST yang dikombinasikan dengan model multifase Mixture untuk aliran uap brine dan Discrete Phase Model (DPM) two-way coupled untuk pelacakan partikel pasir, dengan erosi yang diprediksi melalui model Finnie. Kondisi batas didasarkan pada data operasional lapangan: laju aliran massa sebesar 148,65 ton/jam, tekanan outlet 25 bar, temperatur 250,36 Celcius, kualitas uap (steam quality) sebesar 0,2408, dan laju aliran massa partikel sebesar 0,001 kg/s. Seluruh simulasi telah mencapai konvergensi penuh. Ball valve menghasilkan kecepatan maksimum tertinggi (94,2 m/s) dan turbulensi paling ekstrem (intensitas turbulen sebesar 1.240% TKE sebesar 9,23 m2/s2) akibat efek vena contracta yang kuat, diikuti oleh butterfly valve (85,4 m/s) dan gate valve (23,4 m/s), sedangkan globe valve mencatat kecepatan maksimum terendah (8,76 m/s). Titik kritis (hotspot) erosi teridentifikasi pada piringan gate (tegangan geser dinding maksimum sebesar 8,507 Pa), lubang orifice serta dinding hilir ball, piringan butterfly, dan zona resirkulasi kiri bawah pada penyumbat (plug) globe. Laju erosi maksimum diurutkan dari yang tertinggi hingga terendah adalah: gate (2.75×10*-4 kg/m2·s), ball (2.02×10*-6 kg/m2·s), globe (4.07×10*-9 kg/m2·s), dan butterfly (7.03×10*-20 kg/m2·s). Hasil penelitian menunjukkan bahwa gate valve merupakan komponen yang paling rawan terhadap erosi, sedangkan butterfly valve menawarkan ketahanan erosi terbaik sehingga direkomendasikan untuk layanan wellpad geotermal dua fase uap.

Erosion caused by solid particles entrained in high-temperature two-phase geothermal fluid is a major cause of pipe wall thinning, unplanned downtime, and increased maintenance costs at geothermal wellpad piping systems. This study numerically investigated the turbulent flow characteristics and erosion rates of four valve types (gate, ball, butterfly, and globe) installed in a geothermal wellpad pipeline using Computational Fluid Dynamics (CFD). A steady-state simulation was performed using the k-w SST turbulence model combined with a Mixture multiphase model for the steam-brine flow and a two-way coupled Discrete Phase Model (DPM) for sand particle tracking, with erosion predicted by the Finnie model. Boundary conditions were based on field operating data: a mass flow rate of 148.65 t/h, outlet pressure of 25 bar, temperature of 250.36 Celcius, steam quality of 0.2408, and a particle mass flow rate of 0.001 kg/s. All simulations reached full convergence. The ball valve produced the highest maximum velocity (94.2 m/s) and the most extreme turbulence (turbulent intensity of 1,240% and TKE of 9.23 m2/s2) due to a strong vena contracta effect, followed by the butterfly (85.4 m/s) and gate valves (23.4 m/s), while the globe valve recorded the lowest maximum velocity (8.76 m/s). Erosion hotspots were identified on the gate disc (maximum wall shear stress of 8.507 Pa), the ball orifice and downstream wall, the butterfly disc, and the lower-left recirculation zone of the globe plug. The maximum erosion rates ranked from highest to lowest were: gate (2.75×10*-4 kg/m2·s), ball (2.02×10*-6 kg/m2·s), globe (4.07×10*-9 kg/m2·s), and butterfly (7.03×10*-20 kg/m2·s). The results indicate that the gate valve is the most erosion-prone component, whereas the butterfly valve offers the best erosion resistance and is recommended for two-phase steam-brine geothermal wellpad service.

Kata Kunci : CFD, valve, two-phase flow, erosion rate.