Pipeline control

Using the elaborated theoretical and computing approaches a most effective pipeline management system has been conceptually elaborated with control modes at local level, station level and pipeline level. Local control is manually implemented from the device itself. The automatic or manual control of an installation is affected from its local micro-SCADA system. The supervisory pipeline control is effected from the active pipeline control centre. 

The pipeline is assumed to be highly reliable. In certain intervals, however, the pipeline control system reports failures which are partly caused by misestimations of pressure but sometimes also due to micro-leakages. In any case, an inspection of the identified pipeline segment is necessary which forces an interruption of pipeline operations. It is assumed that the time span between two alarms (given in days) is Weibull distributed with... 

Instructions in the EP/3 flow in a circular pipeline controlled by a ISOMHz clock. New instructions flow from the ly (Instruction Highway) into the Inst, where they are decoded and issued onto the My (Memory Highway). All instructions consist of a command field which specifies the operation and operands, and a destination field which specifies the target instructions to which the result will be sent An instroc-tion is accompanied by a word of data which forms one of the operands. The other operand can specify a location in the main memory which is read from or written to. 

Task-based filter for operator s focus and pipeline controller attention... 

Typical pipeline controls and safety. SCADA, supervisory control and data acquisition. 

Functional divisions in typical pipeline controls and safety are depicted in Fig. XII/4.2.1-3. This is self-explanatory. One thing to note is that in pipeline controls, the SCADA system plays a major role. Also it is used in terminal automation. 

Nlth the increasing speed of computer systems coupled with their decreasing cost computer aided systems are penetrating ever deeper into application areas that go beyond the scope of these examples. Pipeline control systems are mentioned here. 

The purpose of the pipeline control system is to control and monitor the transportation of crude oil through two pipelines. For safety and availability reasons a redundant process controlling computer system is used. An important component of the pipeline control system is a microprocessor controlled remote action system which transmits all measured values and commands ... 

The examination of the pipeline control system was done in two parts a purely computer specific examination and a systems engineering examination. The computer exaoaination aimed to show that the hardware and particular parts of the software fulfilled the requirements that were made not only for safety, but also for ergonomic reasons. All these examinations were practical tests performed directly on the computer system (black box tests). 

Figure 10. The event graph and resulting circuit for a self-timed pipeline control module. The functionality is that of two interlocked four-cycle handshakes. The templates could not be further optimized.

By using the above-mentioned functions, SFL can describe parallel control architecture (i.e., leave-behind control, parallel control, and pipeline control), as shown in Fig. 3.3. 

The gas processing options described in the previous section were designed primarily to meet on-site usage or evacuation specifications. Before delivery to the customer further processing would normally be carried out at dedicated gas processing plants, which may receive gas from many different gas and oil fields. Gas piped to such plants is normally treated to prevent liquid drop out under pipeline conditions (dew point control) but may still contain considerable volumes of natural gas liquids (NGL) and also contaminants. 

The most basic subsea satellite is a single Subsea Wellhead with Subsea Tree, connected to a production facility by a series of pipelines and umbilicals. A control module, usually situated on the subsea tree, allows the production platform to remotely operate the subsea facility (i.e. valves, chokes). 

Pipelines are cleaned and inspected using pigs . Pigs usually have a steel body fitted with rubber cups and brushes or scrapers to remove wax and rust deposits on the pipe wall, as the pig is pumped along the pipe. Sometimes spherical pigs are used for product separation or controlling liquid hold up. In field lines handling untreated crude may have to be insulated to prevent wax formation. 

Practical applications [2] of a GammaMat M model using the new Selenium crawler camera loaded with approx. 1 TBq (30Ci) on a pipeline of diameter 12 and wall thickness of 0.25 showed 6-7 m axial distance to the exposed source as limit of the radiation controlled area (40pSv/h) and 22m perpendicular to the pipeline. Other authors [3] have reported about a comparison for Ir-192 and Selenium source on a 4.5 diameter pipe and 0,125 steel thickness they have found for 0.7 Tbq (18Ci) Selenium a value of 1 Om behind the film (in the unshielded beam) comparing under same conditions to approx. 40m for Iridium. 

In the field of radiation methods of control, development work was performed in order to create the X-ray detectors with a low content of silver. X-ray TV systems with improved performance for automatic interpretation of the X-ray TV images, portable radiometers and dosimeters, creation of portable equipment for radioscopy of the welded joints of pipelines, etc. 

In order to control the tightness of welded joints on various products and structures, a range of units and complexes for control of pipes, pipelines, tanks, protective casings were developed, in particular, a set of put-on vacuum chambers for sheet structures. 

The Institute has many-year experience of investigations and developments in the field of NDT. These are, mainly, developments which allowed creation of a series of eddy current flaw detectors for various applications. The Institute has traditionally studied the physico-mechanical properties of materials, their stressed-strained state, fracture mechanics and developed on this basis the procedures and instruments which measure the properties and predict the behaviour of materials. Quite important are also developments of technologies and equipment for control of thickness and adhesion of thin protective coatings on various bases, corrosion control of underground pipelines by indirect method, acoustic emission control of hydrogen and corrosion cracking in structural materials, etc. 

Absorber oil units offer the advantage that Hquids can be removed at the expense of only a small (34—69 kPa (4.9—10.0 psi)) pressure loss in the absorption column. If the feed gas is available at pipeline pressure, then Httle if any recompression is required to introduce the processed natural gas into the transmission system. However, the absorption and subsequent absorber-oil regeneration process tends to be complex, favoring the simpler, more efficient expander plants. Separations using soHd desiccants are energy-intensive because of the bed regeneration requirements. This process option is generally considered only in special situations such as hydrocarbon dew point control in remote locations. 

Polyethylene. This is essentially a closed-ceU insulation manufactured at 448 2 K by an extmsion process. A blowing agent and nucleating agent are employed to control the ceU size, and primary use is in insulating pipelines for hot and chilled water lines, air conditioning, and processing systems. 

Instmmentation and control guidelines for processes utilizing magnesium hydroxide and other slurries have been outlined (82). An experimental deterrnination of the accuracy of magnetic dow meters for magnesium hydroxide slurries d owing in pipelines (qv) has been reported (83). 

A CIP system includes pipelines, interconnected with valves to direct fluid to appropriate locations, and the control circuit, which consists of interlines to control the valves that direct the cleaning solutions and water through the lines, and air lines which control and move the valves. A programmer controls the timing and the air flow to the valves on a set schedule. The 3A Standards for CIP components, equipment, and installation have been developed. A simple CIP system circuit is shown in Figure 11. 

Vegetation Control rights-of-way along fence rows, roads, highways, railroads, utility lines, pipelines... 

Coal Slurry Pipelines. The only operating U.S. coal slurry pipeline is the 439-km Black Mesa Pipeline that has provided the 1500-MW Mohave power plant of Southern California Edison with coal from the Kayenta Mine in northern Arizona since 1970. It is a 457-mm dia system that aimuaHy deHvers - 4.5 x 10 t of coal, the plant s only fuel source, as a 48.5—50% slurry. Remote control of slurry and pipeline operations is achieved with a SCADA computer system. In 1992 coal deHvery cost from mine to power plant was calculated to be 0.010/tkm ( 0.015/t-mi) (28). 

When constmction is complete, the pipeline must be tested for leaks and strength before being put into service industry code specifies the test procedures. Water is the test fluid of choice for natural gas pipelines, and hydrostatic testing is often carried out beyond the yield strength in order to reHeve secondary stresses added during constmction or to ensure that all defects are found. Industry code limits on the hoop stress control the test pressures, which are also limited by location classification based on population. Hoop stress is calculated from the formula, S = PD/2t, where S is the hoop stress in kPa (psig) P is the internal pressure in kPa (psig), and D and T are the outside pipe diameter and nominal wall thickness, respectively, in mm (in.). 

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