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A joint industry project (JIP) comprising ABB, Equinor, Total, and Chevron, is developing technologies for subsea power transmission, distribution, and conversion. The output will form a critical part of future advanced subsea-field developments. Begun in 2013, the project reached a major milestone in late 2017 when the first full-scale prototype of the variable-speed drive (VSD) passed a shallow-water test (Figure 1). Final preparations are now underway for a 3,000-hour test of the complete subsea power system with two VSDs in a parallel configuration combined with subsea switchgears and controls. The complete paper highlights elements of the technical development and an overview of the primary building blocks of the system, and presents in detail some of the challenges in developing, designing, and testing the control system.
Buntoengpesuchsakul, Chanwith (PTTEP) | Limsakul, Chanapol (PTTEP) | Prakitrittanon, Chatchai (PTTEP) | Phongchaisrikul, Nannawat (PTTEP) | Kijkla, Pruch (PTTEP) | -, Zin Phyo Thet (PTTEP) | -, Zay Yar Tun (PTTEP) | Khetdee, Chanawan (PTTEP) | Viriyasomboon, Napas (PTTEP) | -, Thant Zin (PTTEP) | -, Yan Naing (PTTEP) | Vattanajaroen, Nattapong (PTTEP) | Burik, Surin (PTTEP) | Pengsri, Jumnongwit (PTTEP) | Sapchaophraya, Worrawut (PTTEP) | Promlert, Paradorn (PTTEP) | Eadkaew, Monchai (PTTEP)
The square exhaust duct and the improper insulation design of the Gas Turbine Compressors in Zawtika field initiated the premature failure on the duct, expansion joint and heat insulation. The exhaust duct's temperature over the limitation is considered as a severe consequence in the hazardous gas area. The valuable lesson learnt from the deviation on the safety issues that we had struggled during operation phase and the final safe condition shall be shared with other oil and gas operating asset.
The high temperature on the GTC exhaust duct was firstly assumed from the degraded external insulation. After the insulation rectification for a while, the over limit temperature was appeared again. The exhaust insulation was removed and inspected the internal duct and expansion joint. The severe crack at each duct's corner were found.
The crack on the duct's corner and expansion joint's metal frame were rectified by welding and the expansion joint's flexible parts were replaced. However, the problems continued to happen again. Maintenance team had engaged with the specialists to redesign the expansion joint's corner and facilitating the external convection.
The external exhaust duct's surface temperature was reduced significantly after the new solution implementation, but it could not be reduced to be lower than the limitation of Zone 2, T3, IIA which the maximum limit temperature is 200 degC in some area. The risk assessment had been carefully reviewed to ensure the actual risks were in the "ALARP" level and the mitigation investment was well optimized. After revisiting the ZPQ hazardous area classification, most of the locations on the ZPQ could be considered safe to be deviated to Zone 2, T1, IIA which the maximum limit temperature can be extended to 450 degC.
However, the T3 limitation was still maintain in some locations which the condensate can be accidentally leaked. The possibility of heat accumulation area under the T3 Zone had to be solved with the optimized solutions which are composed of 3 main items as follows: Install internal duct insulation Replace the sharp edge corner to curvature in order to reduce the heat stress over the material strength Install external fin on the heat conducted area of the expansion joint to facilitate heat convection over the high temperature zone
Install internal duct insulation
Replace the sharp edge corner to curvature in order to reduce the heat stress over the material strength
Install external fin on the heat conducted area of the expansion joint to facilitate heat convection over the high temperature zone
Three years of struggling journey would be valuable to share with the other operating assets. Previously, the risk of high temperature on the surface of exhaust duct in the hazardous area was unknown. Then it was addressed and recommended to monitor the hot surface temperature. Some other operating assets had also requested to share the optimized solution to mitigate their own problem from the similar exhaust rectangular duct design. This struggling journey can help not only Zawtika but also help the other operating assets in the industry to live safely in the hazardous area.
The prime mover (PM) rotates the gear-reducer gears through a V-belt drive. The two most common PMs are electric motors and internal combustion (IC) engines. These considerations, as well as other factors, have been discussed in numerous publications. The characteristics of these engines are summarized here, and the detailed comparisons and field experiences have been published elsewhere. These test data should be requested and furnished to the purchaser from the manufacturer. The data should include the manufacturer's curves showing the torque, maximum brake HP, and the rated-brake HP vs. engine speed. These are important to know the speed range in which the engine would be able to operate. A general guide for installation and maintenance of gas engines is API RP 7C-11F,  which covers all three types of engines and includes a troubleshooting section. This practice should be used as a starting point for engines unless the specific manufacturer's operating manual details otherwise.
Motors are designed with certain speed-torque characteristics to match speed-torque requirements of various loads. A motor must be able to develop enough torque to start, accelerate, and operate a load at rated speed. The National Electrical Manufacturers Association (NEMA) has established class designations for motors on the basis of motors' starting-torque and accelerating loads. The four standard NEMA designs are NEMA A, NEMA B, NEMA C, and NEMA D. NEMA A motors usually are used for applications that require extremely high efficiency and extremely high full-load speed. NEMA A-design motors are special and are not used very often.
The electrical system of a typical oil field consists of power generation, power distribution, electric motors, system protection, and electrical grounding. The power is either generated on site or purchased from a local utility company. To ensure continuous production from an oil field, it is of utmost importance that the associated electrical systems be designed adequately. This chapter covers essential topics in the design and operation of the electrical system and discusses the construction and specification of electric motors. The required power for the oil field is either generated on site by engine- or turbine-driven generator sets or purchased from a local utility company. The engines or turbines may use diesel or natural gas as a fuel. Some units are dual-fueled, using natural gas and diesel. Natural-gas-fueled prime movers are most practical for normal power generation for most applications. Diesel is used where natural gas is unavailable and for units that provide black-start and emergency power. Some remote oil fields lack access to utility power lines and require on-site power generation. In such cases, in addition to normal generators, a standby generator might be needed to provide emergency power and black-start capability. Sometimes, a standby generator is designed to handle the total facility electrical load, but usually it is designed only for essential loads. When commercial power is purchased from a utility company, an electrical substation generally is installed near the oilfield facility. Most local utility companies bring their power into their main substation(s) through high-voltage overhead transmission lines from a large generating plant in a remote area.
Abstract Understanding why incidents re-occur from similar causes despite the previous experiences, lessons and available tools to ensure that they do not happen again has been a cause of concern for company management for years and different reasons have been attributed to this issue. In recent past, below are few examples of incidents from similar causes. On 25 January 2012, during the pre-mob inspection of a pile load tester pump by a DIL pile rig operator (Mechanical-24yrs old) with his Supervisor, the unit was put under pressure three times successfully but there was no movement of the pump piston. The pump was put under pressure the fourth time with a declared pressure of 500 bars, the pile load tester flange suddenly gave way and caused several severe injuries to the operator. He was confirmed dead at around 18h30. The unit was brand new with test certificate; IP was trained for it and note that the design pressure of the pile load tester was 690bars. In addition, when the unit failed, the 25 out of 26 bolts of the flange cut off while the last one had its nut pulled out. On 15 May 2017, a fatal accident occurred when an analyzer engineer removed the cover on an explosion-proof enclosure as part of the routine task for the day. The ~5.5kg weighing threaded cover and with a 14 inches in diameter was propelled forcefully from the enclosure as the Engineer unscrewed it inflicting a fatal head injury. The pressure inside the enclosure from leaking sample gas or instrument air components caused the forceful propulsion of the enclosure cover. There was no gauge or indicator on the enclosure to monitor the internal pressure inside the enclosure and there was no means to relieve internal pressure ().
This article, written by JPT Technology Editor Judy Feder, contains highlights of paper OTC 29550, “ABB Subsea Power JIP—Going the Distance,” by Stian Ingebrigtsen, Svein Vatland, John Pretlove, and Henning Nesheim, ABB, prepared for the 2019 Offshore Technology Conference, Houston, 6–9 May. The paper has not been peer reviewed. Copyright 2019 Offshore Technology Conference. Reproduced by permission. A joint industry project (JIP) comprising ABB, Equinor, Total, and Chevron, is developing technologies for subsea power transmission, distribution, and conversion. The output will form a critical part of future advanced subsea-field developments. Begun in 2013, the project reached a major milestone in late 2017 when the first full-scale prototype of the variable-speed drive (VSD) passed a shallow-water test (Fig.•1). Final preparations are now underway for a 3,000-hour test of the complete subsea power system with two VSDs in a parallel configuration combined with subsea switchgears and controls.•The complete paper highlights elements of the technical development and an overview of the primary building blocks of the system, and presents in detail some of the challenges in developing, designing, and testing the•control system. Introduction A subsea power transmission and distribution system will enable an entire oil or gas production system to be placed directly on the seabed, allowing expansion of development to deeper and more-remote locations while yielding cost and safety benefits from reducing significantly, or even eliminating, the need for topside installation. The JIP is developing three products for the system: Subsea VSD Subsea medium-voltage (MV) switchgear Subsea control and low-voltage (LV) distribution Providing a technical solution that is realistic, possible to engineer, tolerant of extreme environments, and reliable in its performance presents a significant challenge. The equipment—the MV switch-gear, control and LV distribution, and the VSDs—must be able to run without intervention for many years. The equipment is qualified for water depths to 3000 m and will have capacity of up to 100•MW with a transmission distance of up to 600 km. The primary focus thus far has been to qualify the basic building blocks to serve the typical voltage and power ratings for subsea processing. All project-qualification activities follow the recommendations and technology readiness level (TRL) stages defined in DNV Recommended Practice (RP)-A203, applicable for components, equipment, and assemblies in hydrocarbon exploration and exploitation offshore. This RP provides a systematic approach to ensure that the technology will function reliably within specified limits, and it provides a common understanding and terminology of technology status and risk management. Other important aspects of the RP include the ability to identify required design changes at an early stage and to improve confidence in the new technology by close interactions and traceable•documentation. To ensure compact and reliable solutions, oil-filled pressure-compensated tanks are used for enclosure of the VSD and switchgear. All components are tested extensively under the full pressure they will experience at the target water depth. A high-level objective of the project is to design the equipment to minimize production downtime and the number of retrievals.
Electrical grounding can be classified in either system grounding and equipment grounding. Requirements for system grounding are covered in detail in the Natl. System grounding includes grounding of the power supply neutral so that the circuit protective devices will remove a faulty circuit from the system quickly and effectively. To protect personnel from electric shock, all enclosures that house electrical devices that might become energized because of unintentional contact with energized electrical conductors should be effectively grounded. If the enclosures are not grounded properly, unsafe voltages could exist, which could be fatal to the operating personnel.
An enclosure protects a motor from contaminants in the environment in which it is operating. In addition, the type of enclosure affects the cooling of the motor. Enclosures are categorized as either open or totally enclosed, and there are different types of enclosures within each category. Open enclosures permit cooling air to flow through the motor. One type of open enclosure is the ODP enclosure.
Abstract Use of GIS to handle bulk power distribution has now become popular in offshore facilities due to the inherent advantage of a compact design. This paper highlights the challenges faced during GIS (and associated items) design based on experience on recent offshore projects and recommendations are proposed for methodical approach. Handling of bulk power at Extra High Voltages poses numerous risks to both personnel as well as assets. This paper discusses the key design parameters, industry standards, interface requirements with transformers/subsea cables/platform structure and installation challenges. Design engineer must be familiar with industry codes so that all design requirements, including proper selection of GIS configuration, are considered from early stages of the project. Omissions or oversight in this regard can impact the whole project. Duration for design, procurement, installation and commissioning phases must be adequately accounted for. Specialist studies such as insulation coordination, very fast transient and touch potentials shall be carried out in addition to usual power system and arc flash studies. Special consideration must be given in case of ring configuration with regard to logic diagrams and differential protection based on multiple CT locations and interconnections. Requirement of voltage selection scheme requires extensive wiring for synchronization function. Relay & CT selection shall be made considering required protection functions, interface with remote location and communication interface with Electrical Control & Monitoring System. Interfaces with transformers and subsea cables shall be in strict compliance with industry standards such as IEC 62271-209 & 211. Requirement of additional surge arrestors shall be verified. GIS exerts large static and dynamic forces on platform steel structure. These are also sensitive to forces during platform lifting and transportation. Support structure suitably shall be designed to mitigate the same. This paper addresses concerns and interface requirements to be considered during design of GIS which will benefit the design engineers, Client personnel and Structural designers along with Project Management Team for safe and smooth execution. Note: Data / details used in this paper are typical for the GIS handled by our Company that may vary based on the makes, models and ratings of GIS.