Abstract Pipeline ruptures have the potential to cause significant economic and environmental impact in a short period of time, and therefore it is critical for a pipeline operator to be able to timely detect ruptures and respond rapidly. Public stakeholder expectations are high and an evolving expectation is that the response to such an event be automated to the greatest extent possible, potentially initiating an automatic pipeline shutdown upon receipt of a system-based rupture alarm. These types of performance expectation are challenging to achieve with conventional, model-based, leak-detection systems (i.e. CPM-RTTMs) as the reliability measured in terms of the false alarm rate is typically too high to initiate automatic pipeline shutdowns. Enbridge Pipelines Inc. (EPI) has been actively participating on an industry task force chaired by the API Cybernetics Committee, focused on the development of best practices in the area of Rupture Recognition and Response. After an industry release of the first version of a Rupture Recognition and Response guidance document, EPI has initiated development of its own internal Rupture Recognition Program (RRP) program. The RRP considers several rupture recognition approaches simultaneously, ranging from improvements to existing CPM leak detection to the development of new SCADA based rupture detection algorithms. This paper will provide an overview of the different rupture detection approaches, present some high level results and share learnings from work completed to date. Introduction Most major liquid pipeline operators have a method of automatic leak detection monitoring and system alarming. Although those leak detection systems are able to detect ruptures the general low reliability of these systems in terms of their high frequency of false alarms (e.g. 1 or 2 false alarm a day for complicated long lines) may have played a role in some past rupture incidents. Those alarms may have caused controller desensitization and thereafter ignored or not given the appropriate attention. Some pipeline industry experts are of the opinion that in the pursuit of detecting the smallest leaks, we may have become more exposed to the ruptures.

ABSTRACT Centrifugal compressors are subject to transient events, such as emergency shutdowns, which can cause energetic surge events during rapid shutdown transients. Many modeling tools are used to predict the behavior of compressor systems during fast transient events. Even more, centrifugal compressor dynamic modeling is a valuable assessment tool that can help improve the design of the compressor anti-surge system to prevent harsh conditions while the unit is coasting down. Modeling of centrifugal compressor transient events requires a detailed evaluation of many system variables to obtain accurate results. Additionally, many parameters should be included and analyzed to adjust the model and obtain acceptable predictions. Those parameters can include recycle valve characteristics, the controller and actuator, suction and discharge piping volumes, aftercoolers, and operating conditions. Other parameters, such as machine coast speed and inertia and different control response times will determine if the compressor will reach its surge limit at a detrimental high head condition, avoid it or go through it at low acceptable energy conditions. Many designs use general guidelines to select and plan the compressor anti-surge system and its main components. For example, the recycle valve type, size and actuation time are key parameters during the shutdown of the compressor unit since they directly affect the amount of flow through the compressor and its reaction time. Other factors are also relevant and should be assessed in detail to assure a proper design to avoid such transient events as a sudden shutdown of a compressor from a full load or high head operating conditions resulting in damaging surge events. In order to refine the simulation approach of the transients in centrifugal compressors, SwRI has conducted an extensive assessment of the main parameters that will affect the modeling predictions. Parameters such as recycle valve size, type, actuation time, after-cooler volume, friction factors, unit speed coast down predictions, compressor map, isolation valve control, acting time, as well as placement of the discharge check valve influence the modeling predictions considerably. Therefore, parametric studies of some of those variables have helped to refine and adjust the modeling technique while improving the accuracy of the results. Moreover, computational predictions have been compared against high fidelity - high accuracy data collected in a full scale compressor system. Initial comparisons indicated reasonable results while adjustments in the technique and main assumptions improved the modeling predictions considerably. A generic methodology to improve modeling predictions and main considerations are part of the analysis. In addition, comparison of the modeling results and experimental data are presented and complemented with parametric studies of different variables. In general, this work should provide guidelines for advancing the modeling of centrifugal compressor transients as well as showing the application of a valuable tool for designing surge control systems for centrifugal compressors.

ABSTRACT A multiple-stage compressor train which is part of an off-shore booster installation was facing process and mechanical related problems. The frequency of these problems has increased lately leading to frequent trips and shut downs. These interruptions affect the operation of the plant and resulted in a loss in production and and a subsequent loss of revenue to the company. The platform contains two similar compressor trains consisting of a four-stage compressor with a gas turbine driver. Each train is fitted with an integrated turbine compressor control panel. Thus, a detailed dynamic pipeline system simulation of the subject compressor trains was performed in order to provide a series of recommendations that would improve the safe operation and increase the reliability of the compression systems. A detailed dynamic model of the multi-stage compression system was built for each train. These models included compressor performance maps, gas compositions for each stage and train, piping yard, recycle, isolation, check and blowdown valves, scrubbers, separators, and coolers. Several simulation cases were conducted for both the platform systems. These cases evaluated the effect of the delay and travel times of the existing anti-surge valves, delay of the coast down action, failure of the non-return valves (NRVs), action of a blowdown valve on the emergency shutdown (ESD) sequences, recycle valve bypasses, check valve arrays, and process upset conditions. The results of this analysis provide recommendations in solving some of the existing issues and creating more understanding of the dynamics of the system. It was found that any proposed recommendations or changes in the sequence or timing of one stage would affect the surrounding stages, since they are not only connected through the piping but also driven by the same gas turbine shaft. Therefore, a very comprehensive analysis was conducted for each train to provide recommendations that would be feasible for implementation while reducing the constant risk of mechanical failure and surge events. Thus, results of the analysis and some of the recommendations obtained are presented in this paper.

ABSTRACT: An existing 20″ pipeline system is being modified to operate in a batching mode to integrate the production of a new field. Two dismissible crude oils will be pumped in a specific batching scheduled to minimize the mixing volume and avoid further contamination of the highest quality oil. The fluids to be carried by the pipelines are primarily crude oils with density differences of approximately 15% and dynamic viscosity ratios up to 12.5. Both the transient response and steady-state analysis are being performed for each of the two pipelines and the entire system to determine its operating constraints and estimate the batch volume to be received at the end facility. The conducted analysis estimates the contaminated interface volume in this pipeline segment for various pipeline operating conditions. Determination of blending interface was calculated by using a pipeline simulation approach. From the pipeline modeling, it was observed that the mixing interface is slightly larger when the lighter oil batch is followed by the heavy oil. In addition, results indicated a similar mixing trending of the two fluids when the batching cycle is modified. One of the critical parameters in the calculations is the dispersion coefficient that is linear dependent of the molecular diffusion coefficient. Thus, a parametric analysis was included in the estimation of the volumes for both cases, since an exact diffusion coefficient value was not available for these types of crude oils. The pipeline modeling results provided a good estimate of the volume interface. The mixing volumes calculated by this approach are not only relevant for the operational stand point of view of the pipeline, but they are good indicators for the economic feasibility of the pipeline operation and project expansion. Thus, this study presents results from the pipeline modeling and covers the basic parameters that will affect a batching operation of two different fluids. INTRODUCTION: The oil transport system under consideration is composed of an existing 84 miles of 20″ diameter pipeline connecting Oil Center "A" (OCA) to a refinery facility. In addition, a 20″ diameter pipeline that runs from another Oil Center "B" (OCB) ties into the OCA pipeline at a node junction. Therefore, from the node junction to the refinery facility, both systems share a common 20″ pipeline that travels approximately 73 miles through a relatively downhill terrain. The two oil centers are managed by different operators, and they provide oil with different characteristics. Therefore, the operation of the system is based on a batch transport philosophy. The design batch transport system has been performed by flow rate control at oil centers and pressure control at the refinery receiving facility. However, a production increase is anticipated from OCA. Thus, the transport philosophy has been modified to adjust this increment of capacity. The proposed operating method is based on pressure control at the oil center. The targeted production will vary from 4,300 GPM to 3,700 GPM at the light crude oil center, OCA, while OCB was scheduled to maintain a constant rate of approximately 1,500 GPM.

ABSTRACT This paper focuses on improving PL safety by providing a methodology for detecting, locating rupture and reducing emergency response time. Pipeline rupture can be due to many factors such as such as corrosion, third party damage or over pressure in the system. In the oil & gas Industries, there are several rupture prevention measures to monitor and ensure safe pipeline operation. These include regular inspection, corrosion program and ongoing maintenance program. However, in few cases where we have rupture, the consequences can be serious. Over the last few years, major oil and gas industries experienced several major incidents related to pipeline ruptures. In all of these incidents, a common contributing factor to the problem is the time required to report and isolate rupture location. Therefore, to mitigate rupture consequences, the proposed solution is to help Pipelines Operations to reduce the response time to isolate rupture either through Manual or Automatic intervention. This paper considers current pipeline operation emergency response plan individual steps and look for area of improvements to reduce response time. In this paper, a comprehensive pipeline hydraulics transient analysis was performed for liquid and gas services addressing single and network pipeline systems to improve pipeline operating companies' emergency response plan during pipeline ruptures. The pipeline protection break set points for gas, liquid, single and network example cases are also presented in detail in the report. Implementation of study findings and recommendations will mitigate the harmful Consequences of a pipeline Rupture by MINIMIZING TIME to ISOLATE Ruptured Pipeline. INTRODUCTION To meet corporate management objective of protecting environment and improving safety, the study was conducted to mitigate the harmful consequences of a rupture by minimizing time to isolate ruptured pipeline. Rupture consequences could be: Losing lives due to Toxic release, explosion or fire. Oil spill or gas released can damage the environment. Rupture impacts on other facilities including adjacent pipelines. In addition to loosing production and interrupting business. In order to minimize the pipeline rupture losses, one needs go over the critical components of pipeline rupture, Figure 1. In the event of rupture, at any point along the pipeline system, the magnitude of losses to people, environment, assets is a function of the time to isolate rupture. So the longer it takes to report and isolate rupture, the more damages. It is also a function of operational parameters such as pipeline capacity, operating pressure & temperature and fluid composition. At the second part of the equation, we have little control over pipeline flow rate, pressure or toxicity. Therefore, to minimize the losses, it is essential to isolate the damaged section as quickly as possible. To reduce the response time to isolate rupture location, Operation current emergency response plan should be considered to look for areas of improvement. The emergency plan is shown in Figure 2.

ABSTRACT Being a planning centre for any activities involving suppliers and customers, PETRONAS Gas Control Center (PGCC) involves in challenging tasks of coordinating various type of operation and maintenance activities like offshore, compressor and plant shutdown, curtailment planning and customers' low demand planning during holiday period. Planning simply based on operators' experience and rule of thumb will give room for errors and inconsistent results. Hydraulic simulation was given a bigger role since 2006 in shutdown coordination and maintenance planning. Various scenarios for various types of activities were simulated and the results were presented in operational and planners meeting. Important decisions were made based on simulation trending. This paper will highlight some of the most important activities that were planned based on the hydraulic simulation, the comparison between simulated and actual profile and the challenges that still lie ahead. ABOUT PETRONAS GAS BHD (PGB) PETRONAS Gas was incorporated in Malaysia on 23 May 1983 under the Companies Act, 1965, as a private limited company and commenced business on 1 April 1984. It was initially a wholly own subsidiary of PETRONAS and known as PETRONAS Gas Sdn Bhd. The Company was converted into a public limited company and changed its name to PETRONAS Gas Bhd (PGB) on 28 March 1995. PGB was formed to serve as the platform to implement the Peninsular Gas Utilisation (PGU) project. The principal activities of the Company consist of the processing of natural gas produced from the gas fields offshore the East Coast of Peninsular Malaysia and the transmission of the processed gas to end-users throughout Peninsular Malaysia and to Singapore. Apart from the PGU system in Peninsular Malaysia, PGB also owns and operates two gas distribution systems in East Malaysia. In this regard, PGB operates as a throughput service company providing the service of processing and transmission of gas to the various customers on behalf of PETRONAS for a fee as set out in a the Gas Processing and Transmission Agreement(GPTA). In expanding the business, PGB had also diversified into Centralised Utility Facilities (CUF) business that involves marketing, manufacturing and supplying of industrial utility products such as electricity, steam, industrial gases and also waste water treatment services to manufacturing plants in the Integrated Petrochemical Complexes in Terengganu and Pahang. The commercial operations of CUF commenced in January 2000. With regards to its CUF business, PGB operates as a commercial provider of industrial utilities products and services to its own customers, with whom it has concluded individual Sale and Purchase Agreements. The various processed products are transmitted via pipelines to PETRONAS customers in the power, industrial and commercial sectors. Processed gas is also supplied to Senoko and Keppel Energy in Singapore through the PGU network.

ABSTRACT Centrifugal compressors are required to rapidly shutdown or trip in the event of a high vibration, a loss of lube oil, or a similar alarm condition and to avoid energetic surge events during these rapid shutdown transients. The recycle valve and its controller and actuator as well as the suction and discharge piping volumes, aftercoolers, operating conditions, other parameters, and various control response times are all characteristics that govern whether a compressor will reach its surge limit at a detrimental high head condition or at a more satisfactory low head condition. Although there are rules of thumb and other general guidelines for designing recycle valves and surge control systems, the only way to assure a proper design such that a sudden shutdown of a compressor from a full load or high head operating condition will not result in a damaging surge event is to simulate the transient events that take place immediately after a trip. In the past, SwRI conducted these transient simulations with large special purpose computer codes written in FORTRAN, which required extensive specific input data and considerable computer execution time. Recently, SwRI has been able to implement use of the Stoner Pipeline Simulation software to model rapid trips of centrifugal compressors in order to avoid energetic, potentially damaging surge events. These simulations account for the actions of recycle valves, their actuators, vent valves, compressor inertia, and control system responses while accounting for upstream and downstream piping, scrubbers, aftercoolers, parallel compressors, and other features of the compressor installation. The simulations require modeling of small pipe sections, very small time steps, and full details in terms of compressor performance curves, recycle, and other valve characteristics. The factors that determine if a damaging surge occurs when a compressor trips includes recycle valve sizes, response and opening times, piping size and arrangements, location of the compressor on its operating map, and many other factors. Detailed simulations that account for all of these factors are necessary to design surge control systems that avoid high energy damaging surge. Centrifugal compressors experience surge whenever they are suddenly tripped, however, controlling the head and total energy of the surge event by reaching a sufficient recycle valve opening and a low enough head before the surge occurs is the objective of transient simulations. It will be shown that this type of transient simulation is a valuable tool for designing surge control systems for centrifugal compressors. INTRODUCTION Centrifugal compressors are used extensively in the pipeline and gas processing industries to move large flows of gas from low pressure pipes or sources to higher pressure pipelines, process vessels, or storage locations. Over a wide range of operating conditions, centrifugal

1. INTRODUCTION The transport of different petroleum products or different grades of a same product through a single pipeline is known as batch transfer and is a very common practice in the pipeline industry. Unless mechanical separators are used such as scrapers, there will be a certain amount of mixing between the products' interface which is called mixing volume. To ensure the quality of the products being transported, the mixing volume should be accurately predicted and/or continuously monitored so that the contaminant can be isolated without harming the products' specifications. The mixing zone which develops at 1 the batches' boundary increases in extension as the batches travels along the pipe. Such a phenomenon is driven by dispersion of matter and is currently evaluated by a number of classical models (Aunicky, 1970; Austin and Palfrey, 1964; Levenspiel, 1958; Ovffadi and Torok, 1977; Sjenitzer, 1958; Smith and Schulze, 1948a; Netchval et al., 1972) which assume, as a basic hypothesis, continuous pumping during the transfer. However, in many practical situations, the pumping must be interrupted either by voluntary or unintentional operational events. In such cases pipeline flow rate experiences significant variations and so does the dispersion coefficient. So, a question arises as to the suitability of the classical models in predicting mixing volumes under these conditions. On the other hand, it has been pointed out by some specialists that the act of stopping the line during a batch transfer could be one of the factors responsible for the increase in the mixing volume. Since the occurrence of mixing zones implies in additional costs associated to shipping the mixture back to refinery for later reprocessing, it becomes evident the reason for investigating the influence of pumping shut-down on the mixing volume. A new model capable to evaluate mixing volumes under pump shut-down and start-up events is presented in this paper. The model is formed by a set of differential equations that describes the momentum conservation and concentration distribution for the fluids, which are considered as incompressible. By assuming that the concentration distribution does not affect substantially the momentum variation, the time-dependent flow rate in the line is firstly computed by solving the momentum equation and then used as an input in the solution of the dispersion equation. Numerical simulations carried out for a specific batch have shown that if the pumping shut-down operation is repeated several times during the transfer it may induce a significant growth in mixing volume. 2. THEORETICAL DEVELOPMENT To manage different products in the line, product pipelines conveying batches are commonly susceptible to pump-shut down operational conditions. In such a event, the hydraulic gradient line is severely reduced causing the fluids to de accelerate and even to stop in the entire pipeline extension. The flow, which is in general highly turbulent in batch transfers, becomes laminar until the fluid comes to rest.