The rapid induction of Fiber Reinforced Plastics (FRP) into process industry due to high corrosion resistance and cost effectiveness made End Users to overlook FRP's specific design, fabrication and quality control aspects. This also affected various Utility and firewater networks in ADNOC Gas Processing plants. It is addressed by enhancing Vendor pre-qualification, relevant specifications and construction procedures. This paper presents measures adopted to ensure reliable design, supply and installation of FRP piping systems.
FRP piping systems have unique design/construction requirements that was not followed in totality in AGP past installations. Also, international standards do not offer adequate guidance on design, resins selection, fabrication methods and joint systems. Vendors were trusted upon for complete design. A campaign is initiated to engage FRP pipe manufacturer having binding single point responsibility from beginning of project for particular FRP system design to ensure desired performance of FRP piping system with extended warranty. Measures have been taken to improve quality material supply through enhanced vendor pre-qualification, ADNOC Gas Processing specifications and CONTRACTORS pre-qualification having certified site crew.
Studies revealed that material quality, velocity/surge pressure were the main contributing factors for failures which were not adequately addressed in design of FRP piping systems. Gaps noticed in previous projects were use of inadequate Codes, Composite's mechanical properties, design approach, inadequate joint preparation and QA/QC in construction phase. During manufacturing using wrong resin can be a cause for premature failure. Absence of certified personnel for project execution and
Non-compliance of manufacturer's instructions were also key lapses noted in construction phase. The gaps in design process, necessitated improvement and consolidation of ADNOC Gas Processing existing design specifications/criteria and analysis requirements which now mandate that the required hydraulic / surge / static analysis shall be carried out by pre-qualified FRP manufacturer. Material property issues were addressed by clearly specifying the material composition & properties requirements and procedural requirements for storage are incorporated into the manufacturing process, along with mandating minimum prior experience for the manufacturers for material supply and design. Certification of contractor's personnel and presence of FRP manufacturer's representative at site during construction and pre-commissioning has been emphasized as mandatory requirement. In addition Specialist 3rd party inspection/supervision must be deployed to ensure quality control during every step of construction and commissioning
Design specifications, procedures, manufacturing process, QA/QC and installation methods for FRP piping systems are available, but lacked activity interface between consultant, vendor and contractor. ADNOC Gas Processing enhanced the FRP specification ensuring single point responsibility with Vendor and procedures to ensure consistency from the design phase coherent with manufacturing process and appropriate implementation during the execution phase, in order to ensure the safety and integrity of FRP Piping systems.
Rafiq, Shahid (ADNOC Gas Processing) | Locharla, Haribabu (ADNOC Gas Processing) | Al Awadhi, Ibrahim (ADNOC Gas Processing) | Al Ahmad, Alya (ADNOC Gas Processing) | Miranda, Robert (ADNOC Gas Processing) | Al Braiki, Ahmed (ADNOC Gas Processing) | Al Qaydi, Alya (ADNOC Gas Processing)
Piping systems having service temperatures lower than ambient present a challenge for the pipe support design. Pipe supports for these cold piping systems are different from normal type of supports on pipes with service temperatures above ambient. Normally hot insulated piping systems have shoe type of supports directly welded to the pipe. In this case there is no relative movement between pipe support i.e. shoe and pipe while the pipe displaces due to changes in fluid service temperature inside the pipe. As the pipe expands when temperatures rise inside pipe, it displaces from its mean position of structural support. The shoe having been welded to pipe moves along with the pipe.
On the other hand, shoe type supports on cold service pipes are not directly and permanently connected to pipe. This is due to the fact that the pipe insulation on cold service piping is designed to be seal tight so that outside air cannot get inside the insulation and reach pipe surface where it starts condensation. The condensation in turn causes corrosion issues. To avoid this moist air ingress inside the insulation, the shoes are made of clamp types and are placed outside the insulation cladding. This causes problem of clamp type shoe slippage on cladding and total displacement of pipe shoe from its structural support. This paper presents an engineering study of a piping system with cold fluid service (propane) where multiple supports had fallen from the structural supports or had dislocated considerably. At few support locations, cladding was found to be damaged and ice formation was noticed. In addition, many clamped shoes had rotated as shown in
A comprehensive study was conducted to identify the root cause of piping supports dislocation, displacement and rotation. The static/dynamic stress analysis of the piping system was carried out. The results revealed that the displacements in the piping system were not so high to cause the supports dislocation or high displacements of shoes. In addition, the stresses on the piping system due to the contraction of pipe upon cooling were within allowable limits. Rotated and dislocated Clamp support on Cold Service Pipes
Rotated and dislocated Clamp support on Cold Service Pipes
As a part of study process, operation was enquired if any upset had happened which might have caused the dislocation and abnormal movement of pipe and hence transferred to its supports. Operations informed that there was no such incident and the line had been operating normally without any trouble.
The process study including review of hydraulics, verification of line size and surge was performed to identify the root cause of piping abnormal movement. The process study concluded that line size was adequate and no surge scenario was identified for the line's concerned portion.
So following reasons which could cause abnormal pipe movements and dislocation of supports were ruled out based on above study: Operation upset in the piping system (such as sudden opening or closing of a valve or sudden starting/stopping of a pump), Line sizing or surge flow, Contraction of line due to cooling of piping system or piping configuration.
Operation upset in the piping system (such as sudden opening or closing of a valve or sudden starting/stopping of a pump),
Line sizing or surge flow,
Contraction of line due to cooling of piping system or piping configuration.
The next step in the study was to review the support configuration in detail. Study found basic design problem with the support configuration that was the cause of supports dislocation, excessive movement and rotation of clamped supports.
The considerations and standards guiding pipeline design insures stability and integrity in the industry. The fluid flow equations and formulas presented thus far enable the engineer to initiate the design of a piping or pipeline system, where the pressure drop available governs the selection of pipe size. This is discussed below in the section on velocity considerations for pipelines. Once the inner diameter (ID) of the piping segment has been determined, the pipe wall thickness must be calculated. If there are no codes or standards that specifically apply to the oil and gas production facilities, the design engineer may select one of the industry codes or standards as the basis of design. The design and operation of gathering, transmission, and distribution pipeline systems are usually governed by codes, standards, and regulations. The design engineer must verify whether the particular country in which the project is located has regulations, codes, and standards that apply to facilities and/or pipelines. In the U.S, piping on offshore facilities is mandated by regulation to be done in accordance with ANSI/ASME Standard B31.3. Some companies use the more stringent ANSI/ASME Standard B31.3 for onshore facilities. In other countries, similar standards apply with minor variations.
Assuming steady-state flow, there are a number of equations, which are based upon the general energy equation, that can be employed to design the piping system. The variables associated with the fluid (i.e., liquid, gas, or multiphase) affect the flow. This leads to the derivation and development of equations that are applicable to a particular fluid. Although piping systems and pipeline design can get complex, the vast majority of the design problems encountered by the engineer can be solved by the standard flow equations. The basic equation developed to represent steady-state fluid flow is the Bernoulli equation which assumes that total mechanical energy is conserved for steady, incompressible, inviscid, isothermal flow with no heat transfer or work done.
A pilot of cryogenic distillation technology is designed and installed for separation of the high CO2 concentration of feed up to 80 mol % from natural gas. However, the main concern was the dry ice formation during depressurization or blowdown might cause the pipeline and equipment blockage and consequently resulting in safety issues.
A dynamics simulation and modeling were conducted using commercialize software to determine the settle out temperature during the blowdown especially emergency condition. The investigations were focused on the high operating pressure and low operating temperature with a high CO2 composition which is closer to transient condition and solid region. Then, more comprehensive modeling was conducted by incorporating the equipment and piping design data including the sizing of relieve valves (RVs) and blowdown valves (BDVs). The accuracy of information is very crucial to obtain more reliable results.
It was observed that at high operating pressure, (50 to 75 barg) and low operating temperature,(-58 to 15 °C) the settle out temperature due Joule-Thomson (JT) effect were −58 °C and −92 °C for 60% and 80% CO2 concentration, respectively. Based on the phase diagram, in this condition, the CO2 will be under a solid region. As a result, the Minimum Design Metal Temperature (MDMT) of −100 °C was selected for equipment and pipelines design to avoid material brittle-fracture. Few mitigations measure were designed and installed to avoid the CO2 solidification. The BDVs were installed at the warmer area to minimize the JT effect leading to lower operating temperature than CO2 solidification temperature resulting to potential equipment blockage. The electrical heat tracings were installed at the outlet flange and outlet line of RVs and BDVs to maintain fluid temperature above CO2 solidification limit. This is to prevent CO2 solid from attaching to the pipe wall and build up in the piping in the event of relief. Another mitigation was by installing the outlet line with sloped toward vent header and free from instrument probe or sensor to prevent CO2 solid from build up at piping dead leg section. As a result, no sign of CO2 solid found in the sections that equipped with mitigations measure during experiments.
An inherently safer design of equipment and pipelines are very crucial especially for high CO2 concentration, high operating pressure and low operating temperature with the appropriate mitigations to avoid catastrophic failure.
The existing API equation for internal leak predicts the internal pressure to overcome the pin-box contact pressure generated from the makeup interference plus the energizing effect of internal pressure which enhances the seal. For threaded connections, internal and external pressures close the connection and increase the leak resistance, whereas axial loads open the connection and decrease the leak resistance. These competing effects must be included to accurately assess the connection leak resistance under any combination of loads at any point in any string. Following the same approach used by API for internal leak, this paper obtains similar results for external leak. For API connections, the effects of combined axial force and backup pressure are then incorporated into the internal/external leak equations using results from the Mitchell and Goodman (2018) paper presented at the 2018 SPE-IADC Drilling Conference. Sensitivities of leak ratings to combined loads for API connections are presented for both tubing and casing sizes. An example design case shows the importance of considering combined loads.
To mitigate the risk of twistoff during high dogleg-severity (DLS) drilling and to reduce cost of service delivery induced by frequent recuts, an advanced rotary shouldered threaded connection design with significantly enhanced fatigue life over existing API connections has recently been developed and released for field operation. Modeling and simulation techniques had been extensively used to drive the design and qualification processes. In this paper, an overview of the numerical modeling methodology and its experimental validation is presented with an emphasis on the key functional requirements of the design.
The newly developed connection design involves an optimized thread form and an advanced manufacturing process. Finite element analysis (FEA) was heavily used to optimize the design prior to physical prototyping and testing. High-fidelity modeling methods were developed, and comprehensive numerical analyses were performed to digitally evaluate the performance of the new design, including fatigue resistance, galling resistance, combined load capacity, sealability, and so on. The FEA models had very well predicted the performance of the new design, which was later validated through full-scale experimental tests. Several qualification tests, such as torsional yield limit test and tensile capacity test, were carried out completely digitally. As a result of the extensive modeling and simulation work conducted, the connection design met all requirements in one iteration.
The work presented in this paper represents a successful example of model-driven product development, which significantly reduces development time and cost. It is the first time that a high-fidelity modeling methodology, in conjunction with full-scale experimental validation, is introduced for advanced rotary shouldered threaded connections in the oil and gas industry.
This updated NACE International standard practice provides the most current technology and industry practices for material requirements and the use of tape coatings for external mainline coating, coating repair, coating rehabilitation, and coating weld joints on buried metal pipelines. The standard is applicable to underground metal pipelines in the oil and gas gathering, distribution, and transmission industries, as well as water and wastewater pipelines. This standard is intended for use by corrosion control personnel, design engineers, project managers, purchasing personnel, and construction engineers and managers.
This NACE International standard practice provides the most current technology and industry practices for material requirements and the use of tape coatings for external mainline coating, coating repair, coating rehabilitation, and coating weld joints on buried metal pipelines. This standard is intended for use by corrosion control personnel, design engineers, project managers, purchasing personnel, and construction engineers and managers. It is applicable to underground metal pipelines in the oil and gas gathering, distribution, and transmission industries, as well as water and wastewater pipelines.
This standard was prepared in 2009 and revised in 2019 by NACE Task Group (TG) 251, “Coatings, Tape for External Repair, Rehabilitations, and Weld Joints on Pipelines.” This TG is administered by Specific Technology Group (STG) 03, “Coatings and Linings, Protective: Immersion and Buried Service.” It is sponsored by STG 04, “Coatings and Linings, Protective: Surface Preparation,” and STG 35, “Pipelines, Tanks, and Well Casings.” This standard is issued by NACE International under the auspices of STG 03.
In today's challenging work and business environment, swift response to structural integrity concerns is the need of the hour to minimize the damages that will reduce down time, specifically in oil & gas sector. The solution devised to address structural concerns shall prevent further failure of structural members and avert major catastrophic accidents, as they support process equipment and piping. This paper outlines case studies of such structural failures, potential reasons of incidents and approaches followed in restoring structural integrity in a safe and economical way that ensures uninterrupted plant operation.
Key parameters to be studied / considered while arriving solutions to structural damage / incidents include reliability of data, primary cause of incident, inventory of readily available material, execution feasibility under plant operating conditions thereby avoiding plant or unit shutdowns and manpower skillsets. Due to various constraints, the solution arrived may be temporary that averts multiple structural failures or a major accident. Further studies would be required to identify the root cause and to confirm or enhance the implemented solution that will reaffirm long term integrity of structure.
In almost all of the incidents, some of the common steps followed for swift restoration of structural integrity include conducting a site survey to identify and judge the probable cause, reviewing available data, structural assessment and details of material in stock.
After analyzing numerous factors, diverse approaches unique to each incident were considered in arriving a solution that is fit-for-purpose.
Structural integrity issues, if not attended swiftly, can worsen the situation leading to safety concerns and major accidents. Solutions adopted for various incidents ensured restoration of structural integrity with minimal consequences. Suggested improvements and recommendations were implemented and no further issues were reported until this time.