PEMBUATAN JIG PROSES PRE DRILL MODEL B74 GUNA MENURUNKAN REJECT CONCENTRIC PADA LINI PRODUKSI PENGECORAN OUTER TUBE DI PT KAYABA INDONESIA

Salah satu produk PT Kayaba Indonesia adalah front fork assy yang mana didalamnya terdapat part yaitu outer tube. Proses awal pembuatan outer tube adalah proses pengecoran. Ada 2 macam mesin pengecoran gravitasi yang digunakan oleh PT Kayaba Indonesia yaitu mesin pengecoran gravitasi existing tipe core dan mesin pengecoran gravitasi tilting tipe solid. Model B74 salah satu produk yang menggunakan mesin pengecoran gravitasi tilting sehingga model B74 termasuk ke dalam tipe solid. Sebelum masuk ke proses machining, outer tube model B74 harus melewati proses Pre drill untuk membuat diameter dalam agar memudahkan proses selanjutnya pada lini pemesinan. Saat ini proses Pre drill model B74 memiliki masalah reject concentric yang cukup tinggi, yaitu 7%. Proses penurunkan reject concentric proses Pre-drill model B74 telah dilakukan Penulis bersama tim mekanik proses pengecoran meliputi upaya memindahkan proses Pre-drill model B74 ke mesin macod dan pembuatan jig untuk mendukung proses tersebut. Perbaikan yang dilakukan berhasil menurunkan reject yang terjadi, dari 7% dari 8.812 set menjadi 1,4% dari 3.360 set. Selain itu perbaikan ini juga menaikan kuantitas produksi sehingga yang awalnya membutuhkan 2 shift untuk mencapai target menjadi cukup hanya 1 shift dengan hari kerja normal.

Movement of gas slug in annular channels with different diameter ratios

The motion of gas slugs in annular channels was studied experimentally. The outer tube diameter was 32 mm. The inner tube diameter varied from 4 to 25 mm. The gas slugs were produced by injecting air through a capillary tube. The shapes of gas slugs were studied by high-speed videos. The paper presents data on the rise velocity of gas slugs in the channels, and wall shear stress measurements, performed by electrodiffusional technique. The probes were mounted on both walls of the channel. The evolution of wall shear stress during slug passage was recorded.

Free Vibration and Frequency Calculation in Tall Buildings with Stepped Tube-in-Tube Systems

This study investigates the free vibration and frequency analysis of tall buildings with stepped cross-sections for stepped tube-in-tube structures. Dynamic equations were presented in accordance with the stepped structural system for free vibration and the differential equations were solved according to the application of boundary conditions and flexural and shear stiffness and stepped cross-section of different steps. The answer was converted to an 8x8 matrix and was obtained using the determinants of matrix and mathematical calculations of frequency. Nine mathematical computational models were designed for stepped tube-in-tube structures for a 50-story tube-in-tube building by increasing the height of the outer tube by 15 meters. Finally, the heights of the inner and outer tubes were equalized by increasing the height of the outer tube and then compared with the results of free vibration in the articles with the tube-in-tube structural system with equal height and characteristics. Using this method, the frequency of structures was calculated correctly and the obtained results from finite element analysis showed that this mathematical method accurately calculated the frequency. It was found that this method was accurate enough and the obtained computational error was very small. The results showed that the frequency decreases by adding to the outer tube and increasing its height.

Investigation of Effect of Aluminium Oxide Nanoparticles on the Thermal Properties of Water-Based Fluids in a Double Tube Heat Exchanger

The thermal behavior of aluminium oxide-water nanofluid in a double pipe carbon steel heat exchanger was investigated in the present study. The overall heat transfer coefficient, Nusselt, and heat transfer coefficient of nanofluid were compared with the base fluid. The volume fraction of the nanoparticles was 1%. By adding nanoparticles to the fluid, the thermal properties of the base fluid improved significantly. The hot and cold fluid flow was considered counter-current, and the nanofluid was pumped into the inner tube and once into the outer tube, and the flow rate of each fluid was 0.05 kg/s. The convective heat transfer and the overall heat transfer coefficient enhanced 94% and 253% for the hot fluid flow in the outer tube and 308 % and 144% for the hot fluid flow in the inner tube, respectively. The pressure drop calculations also showed that the pressure drop would not change significantly when using nanofluid.

Compact Steam Bottoming Cycles: Minimum Weight Design Optimization and Transient Response of Once-Through Steam Generators

Compactness and weight minimization are key aspects for successful and widespread implementation of waste heat recovery steam cycles in off-shore oil and gas platforms due to the site weight and volume footprint constraints. The power plant off-shore must be designed for flexibility in its operations to provide varying power demands across multiple time scales. Reliability of the heat and power production units is crucial. Within a case study in an off-shore platform in the Norwegian Continental Shelf, this article conducts design optimization of compact and low-weight steam cycles for power production from gas turbine exhaust and transient analysis of the core of heat recovery steam generators (HRSGs) via dynamic modeling and simulation, considering once-through steam generators (OTSGs) for the HRSGs. A method for simultaneous thermodynamic and heat exchanger geometry optimization design for bottoming cycles is applied, with the main objective being weight minimization and compactness of the cycle heat exchangers. Ten different optimal minimum weight bottoming cycle designs are provided by selecting ten different manufacturable tubes. The resulting bottoming cycle designs are compared in terms of weight, OTSG core weight distribution, heat transfer area, and footprint. The resulting bottoming cycle weight varies from 48.4 to ca. 87.10 ton for designs sensible for off-shore applications, and from 95.8 to 178.9 ton when selecting outer tube diameters typical of onshore applications. Smaller outer tube diameter selection in OTSG bundles is a key driver for low-weight and compact steam cycle designs. Three different designs representing light, normal, and heavy OTSG designs are compared by dynamic trajectory and response time analysis under transient scenarios by means of dynamic modeling and simulation. More compact and lighter designs respond faster to changes in the gas turbine (GT) operation upstream the OTSG. The results in this analysis indicate the need for feedforward control. Feedback control alone is probably not a good option due to the high OTSG open loop stabilization time and large sensitivity to GT exhaust gas variations. More compact and low-weight designs based on the OTSG can reduce potential challenges in controlling and stabilizing bottoming cycles for power production.

Static bearing capacity investigation of grouted square hollow section sleeve connection

As a pilot research for an aimed beam-column joint of steel prefabricated prefinished volumetric construction (PPVC) buildings, this study investigates the axial static bearing capacity of grouted square hollow section (SHS) sleeve connections via carrying out experimental tests. Ten specimens with different dimensions were tested to failure under monotonic axial compressive loading and their loading-displacement curves were measured and recorded. The effect of the grouted length, the shear-key spacing, and the grout strength to the bearing capacity of the grouted SHS sleeve connections are investigated in this study. It is found that the axial static bearing capacity of the specimens tested increases approximately in a linear manner with the grouted length increases and can reach the bearing capacity of the outer tube’s cross-section when the grouted length is sufficient. Besides, the benefits brought by the increment of the grout strength to the axial bearing capacity of the grouted SHS sleeve connection may depend on other parameters such as the shear-key size and spacing, the gap between two tubes, and the thickness of the outer tube. Therefore, more experimental tests are required to understand the effect of the grout strength comprehensively.