Avoid Exchanger Replacement Using Advanced Analysis and Fit for Service Approach

Objective/Scope (25 - 75 word) Shell & Tube Heat exchangers are critical for incessant operation of processing plant. These exchangers may face integrity threats due to reduction in shell thicknesses at Nozzle to Shell Junction below design code requirements. This paper presents the Cost Effective fit for purpose approach utilizing advance Finite Element analysis to explore and recommend the solutions for existing numerous exchangers that are to be safely used even after reported low thickness on account of manufacturing imperfection. Methods, Procedures, Process (75 - 100 word) Reduction in Shell thickness below design value can affect its ability to sustain design pressure & vacuum including nozzle integrity for associated piping loads and service life reduction for exclusion of corrosion allowance. As short-term Mitigation methodology, weld overlay was adopted to restore the areas with lower thickness. For long term solution, fit for purpose review approach was adopted for continued usage of exchangers which involves nozzle load analysis using WRC & FEA based on PAUT thickness data and utilizing actual piping loads, derating of design pressure, comparison of thickness data to establish corrosion rate and service life of exchanger. Results, Observations & Conclusions (100 - 200 words) Thorough Integrity review based on design Code (ASME BPVC Section VIII) and WRC analysis have confirmed that majority of the exchangers have thickness higher than that required to sustain design pressure, vacuum conditions when considered with piping loads acting on nozzles. Thickness data comparison between three (03) year old manual UT and latest Phase array UT confirmed that majority of the exchangers are in clean non-corrosive service thus allowance for corrosion is not required. Where in the nature of exchanger service require corrosion allowance, it is considered in analysis and usage of stiffeners at nozzle to shell intersection and/or on full circumference of shell is recommended to prevent overstress due to piping loads / buckling distortion due to vacuum conditions respectively, based on detailed Finite element analysis (FEA). In order to establish more reliable long-term corrosion rate, next inspection after four (04) years is recommended and impact on integrity can be further evaluated based on the latest data. Change in exchanger nameplate is recommended to consider for design pressure as MAWP and accordingly adjust hydro test pressure followed by R-stamp requirements for rerating and repair. Shell side hydro test is restricted until recommendations are implemented Novel/Additive Information (25 - 75 words) Although conventional approach of replacing complete Shells to meet code requirement would have ensured process safety, performance and structural integrity. However, alternative fit for purpose approach utilizing advanced FEA has not only ensured all these but also led to potential cost saving of multimillion US$. Associated risks of thickness reduction due to corrosion may still be observed, however analysis confirmed structural integrity and safety of heat exchangers with low thicknesses. Accordingly, potential risk is mitigated.

Evaluation of the Explosion Pressure Parameters in Flameproof Enclosures under the Pressure Piling Condition

Explosion resistance is one of the most important performances for all flameproof enclosures. Pressure piling requires the flameproof enclosures to withstand explosion pressure higher than the design pressure. In order to study the explosion parameters in a flameproof enclosure under pressure piling, two experimental setups were prepared based on the theoretical analysis of the mechanism of pressure piling. One setup simulated the condition that the interior of a flameproof box is isolated by a baffle with a small hole. Another setup simulated the condition that a large number of electrical components were installed inside an explosion-proof box. The experimental result showed that the explosion pressure increased significantly in a very short time under pressure piling. When an explosion occurred in a cavity, the pressure wave of the explosion propagated faster than the flame propagation, and the pressure wave was transmitted to another cavity through a gas channel between the two cavities. This resulted in the pre-pressurization of the combustible gas in another cavity. It was observed that the ignition time in the cavity with an ignition source, is the key factor for pressure piling.

Analysis on the Leakage of the Flange Connection of the Water-Containing Hydrofluoric Acid Pipeline

Leakages of bolted pipe flange connections of water-containing hydrofluoric acid pipelines were frequently reported by the extraction section in the fluorine chemical industry. Water-containing hydrofluoric acid can cause severe injuries to human beings due to its strong causticity. The water-containing hydrofluoric acid pipe was a short lined pipe, so a lot of flange connections and supports were adopted in the pipeline. In this paper, the finite element models of the pipeline were established to analyze the internal force of the pipeline under conditions including internal pressure, temperature, self-weight, and so on. Based on this, the equivalent design pressure of the flange connections was determined. The results of the stress analyses of the pipeline showed that leakages were mainly caused by a large bending moment, due to the unreasonable layout of the piping supports under self-weight. When the pipeline was supported on the beam of the pipe gallery, which is not necessarily beneficial to reduce the bending moment of the pipeline, and the flange connection was close to the supporting beam at the same time, leakages frequently occurred in this flange connection. To support the pipeline reasonably, the flange connection should be placed at zero bending moment positions. Therefore, the positions with zero bending moments of the pipeline with equal and unequal spacing supports were obtained under gravity load, to provide a basis for the rational support of lining piping.

Failure Mode Determination of API 12F Shop-Welded Tanks with a New Roof-to-Shell Junction Detail

The API 12F is the specification for vertical, aboveground shop-welded storage tanks published by the American Petroleum Institute (API). The nominal capacity for the twelve tank designs given in the current 13th edition of API 12F ranges from 90 bbl. (14.3 m3) to 1000 bbl. (159 m3). The minimum required component thickness and design pressure levels are also provided in the latest edition. This study is a part of a series research project sponsored by API that dedicates to ensure the safe operation of API 12 series storage tanks. In this study, the twelve API 12F tank designs presented in the latest edition are studied. The elastic stress analysis was conducted following the procedures presented in the ASME Boiler and Pressure Vessel Code 2019, Section VIII, Division 2 (ASME VIII-2). The stress levels at the top, bottom, and cleanout junctions subject to the design pressures are determined through finite element analysis (FEA). The bottom uplift subjected to design pressures are obtained, and the yielding pressure at the roof-shell and shell-bottom junctions are also determined. The specific gravity of the stored liquid is raised from 1.0 to 1.2 in this study. A new roof-shell attachment detail is proposed, and a 0.01 in. (0.254 mm) gap between the bottom shell course and the bottom plate is modeled to simulate the actual construction details. In addition, the flat-top rectangular cleanout presented in the current edition of API 12F is modeled.

Leak Testing

While the exercise of pressurizing a piping system and checking for leaks is sometimes called pressure testing, the Code refers to it as leak testing. The main purpose of the test is to demonstrate that the piping can confine fluid without leaking. When the piping is leak tested at pressures above the design pressure, the test also demonstrates that the piping is strong enough to withstand the pressure. For large bore piping where the pipe wall thickness is close to the minimum required by the Code, being strong enough to withstand the pressure is an important test. For small bore piping that typically has a significant amount of extra pipe wall thickness, being strong enough is not in question. Making sure that the piping is leak free is important for all piping systems.

Design Conditions and Criteria

Design conditions in ASME B31.3 are specifically intended for pressure design. The design pressure and temperature are the most severe coincident conditions, defined as the conditions that result in the greatest pipe wall thickness or highest required pressure class or other component rating. Design conditions are not intended to be a combination of the highest potential pressure and the highest potential temperature, unless such conditions occur at the same time.

ASESMEN KOROSI & ANALISIS RISIKO KUALITATIF PADA VERTIKAL BEJANA TEKAN

Keselamatan dan keamanan dalam penggunaan bejana tekan sangat penting dan hal utama dalam penggunaan bejana tekan, terlebih lagi jika bejana tekan tersebut sudah melewati umur desain nya. Penelitian ini bertujuan untuk menilai kelayakan kondisi terkini dari suatu bejana tekan vertikal (vertical pressure vessel) yang telah beroperasi sejak tahun 1970 tetapi berhenti beroperasi pada tahun 2011. Pendekatan penilaian pada bejana tekan vertikal ini berbasis pada metode penilaian korosi dan risiko secara kualitatif. Selain itu juga dipergunakan metode-metode lain dalam aspek penilaian nya seperti visual inspeksi, laju korosi (corrosion rate), Non-Destructive Examination (NDE), software calculation dan analisa risiko kualitatif (qualitative risk analysis). Dari hasil observasi dan inspeksi di dapat tekanan desain (design pressure) adalah 7 kg/cm2, Temperatur desain (design temperature) adalah 61°C dengan material konstruksi adalah SA-283 Gr. C dan standard & code yang dipergunakan adalah ASME Sect. VIII Div. 1 dan API 510 serta beberapa standard & code lainnya. Dari hasil kajian dan kalkulasi di lapangan, maka didapat faktor penyebab kerusakan yang kemungkinan terjadi adalah atmospheric corrosion & uniform corrosion dengan nilai laju korosi adalah sebesar 0,127mm/yr dan tingkat risiko dari bejana tekan vertikal ini masuk dalam kategori 2D yang artinya adalah medium-high dengan maksimal umur pakai sampai usia 27 tahun untuk top head dan 24 tahun dan bottom head serta 23 tahun untuk shell. Sehingga dapat disimpulkan bahwa bejana tekan ini masih aman dan layak dipergunakan dengan batasan-batasan di atas.

A Case for New Low Pressure Vessel (LPV) Codes for Design Pressures Below 15 psi (100 kPA)

Today the ASME Boiler and Pressure Vessel Code Section VIII (ASME Code) covers pressure vessels for design pressure above 15 psi (100 kPa) but not for design pressures below 15 psi. Manufacturers of pressure vessels under 10ft (3048mm) and with design pressure under 15 psi (100 kPa) design to the ASME Code but do not stamp them. The ASME Code is explicit in not allowing this. Manufacturers of low pressure vessels over 10 ft (3048 mm) in diameter, design and built to “good engineering practice” using Finite Element Analysis, the ASME Code, API and the AISC Manual of Steel Construction. This paper provides an overview of these existing codes, standards with their methods for design, fabrication and testing then provides an outline of a Code with two classes of low pressure vessels (LPV). The audience for the smaller pressure vessels would be small batch chemical, pharmaceutical, food, and beverage processing facilities who require small near atmospheric pressure vessels. The audience for the larger pressure vessels would be power plants, refineries, chemical plant, steel mills and concrete plants flue gas treatment and CO2 sequestration of exhaust products.

Considering Hydrotest Pressure Loading in the Calculation of MAWP of a Pressure Vessel

As defined in UG-98 of the Code, the Maximum Allowable Working Pressure (MAWP), is the maximum pressure permissible at the top of the vessel in its normal operating position. It is the least of the values calculated for each of the vessel part adjusted for the static head and by including the effect of any combination of loadings listed in UG-22 of the Code. Conventional method of calculating the MAWP is to consider only the main pressure parts viz., the shells and the heads and the significant UG-22 loading viz., the wind and the seismic. Once the MAWP is determined, the rest of the vessel design is completed considering this value of MAWP as design pressure combined with any other applicable UG-22 loading. At the end, the vessel is verified for its adequacy to the test condition. It is noted that, the MAWP obtained through this method is often higher than the design pressure thus leading to the overdesign of the vessel. Moreover, higher MAWP results in higher test pressure, which might have a considerable impact of its own on the design of the vessel. The objective of this paper is to propose a design approach in which the test pressure itself is included as one of the governing loads in the determination of the MAWP so that the impact on vessel design, as explained above, is minimized.