"Introduction
Muglad Oilfield in Sudan is a large oilfield jointly invested and developed by China, Malaysia, Canada and Sudan. It is composed of eight satellite oilfields with an annual output of 15 million tons. The control system of the treatment plant of the oil field surface production facility center adopts the FF Foundation Fieldbus fieldbus control system (FCS fieldbusc controlsy stem) of abb. Fieldbus is an industrial data bus, which is the lowest cost network of computer communication system in the field of automation. According to the definition of IEC 61158 standard: Fieldbus refers to the digital, serial and multipoint communication data bus between the field device installed in the manufacturing or process area and the automatic device in the control room. It has the characteristics of full digitization, full distribution, two-way transmission, self diagnosis, low cost, openness, interoperability and intelligence, It has been successfully applied in petroleum and petrochemical fields. According to the experience of organizing the installation, configuration and commissioning of the control system of the project, the architecture, installation points, configuration and commissioning methods of the fieldbus control system of the device are introduced for reference.
1. Architecture of control system for oilfield surface production facilities
The equipment selected for the control system of the central processing plant is as follows: Fieldbus instruments: 2600t - series, 600t - en, tf202ex, tzid - C 120, etc; Integrated safety barrier: M204; Link equipment: ld800hse; Central controller: ac800fr; Ethernet card: e1803; Fieldbus network card: f1840; Hub: RS2 FX / FX; Cable and multimode optical cable: utp-5, multi-body mode.
2. System installation
The installation of bus system mainly includes the installation of bus cables and the selection and integration of relevant components.
Fieldbus is both a power line and a signal line. In order to ensure the coverage distance of cables, the number of fieldbus devices hung, and the stability and reliability of the system, in addition to selecting low-power field devices and cable models recommended by iec61158-2, adopting repeaters and improving power supply voltage, noise prevention and anti-noise measures are also adopted during installation. It mainly includes: shielded twisted pair cable shall be used, and the shielding layer shall cover at least 90% of the total length of the cable. During cable wiring, the unshielded part of the cable or the part that does not become twisted pair shall be less than 2% of the total length or less than 8m, whichever is shorter; The shielding layer can only be grounded at one point; The shielding layer of branch line and trunk line shall be connected; Capacitor grounding shall be adopted in case of high-frequency interference; The signal cable shall be isolated from the noise source, and the fieldbus signal and non fieldbus signal cannot be stored in the same multi-core cable; The cable laying shall not be crossed as far as possible. When it is unavoidable, the correct crossing angle shall be ensured.
The terminator is a very simple device that does not communicate itself. The first function is to prevent communication errors caused by signal reflection; The second is to convert the current change generated by the transmitting signal equipment into the voltage change across the whole network, so that all equipment on the network can obtain this signal. The network consists of one or more network segments. The terminator shall be installed at both ends of the network segment, one at one end, otherwise the network cannot work.
Repeater is a bidirectional electrical isolation device, which is used to connect several network segments to form a large network. Its function is to synchronously refresh the input signal and amplify its level to overcome the attenuation of the signal along the signal line. There can be no more than 4 repeaters between two devices on the network. Intrinsic safety refers to the method of preventing explosion caused by electrical failure by limiting the energy in the hazardous area. The safety barrier used must comply with the provisions of IEC61158 and pass the intrinsic safety certification of statutory authorities. Only one safety barrier can be installed in the network segment of each hazardous area, and redundancy is not allowed. Only one safety barrier can be connected to a communication port. In order to make full use of the communication port, the safety barrier with built-in repeater can be used. Only one safety zone network segment needs to be led from the communication port to the safety barrier, and each safety barrier can lead to a dangerous zone network segment, which constitutes a large network. Regulated power supply according to the provisions of iec61158-2 International Electrotechnical Commission, the power supply must have output impedance, otherwise it will short circuit the communication signal. The traditional power supply can not be used directly in the system because the output impedance is almost zero. The project does not use the above split components, but integrates the terminator, repeater and power supply into the safety barrier.
The link equipment is directly connected with the master station through the high-speed master station level network. The link equipment is used as the information buffer to take into account the different transmission speeds between the two level networks. It becomes the gateway between the field equipment of H1 section and the high-speed master station of HSE section. The link equipment used in the project is ld800hse, and each link equipment can connect four H1 network segments at the same time. In order to improve the effectiveness of the system, the redundancy scheme is adopted in the whole architecture.
3. System configuration
System configuration includes network configuration, equipment configuration and control strategy configuration. The engineering tool used is CBF 7.1. The tool supports two configuration modes: offline and online, and can be permanently connected with all field instruments. Network configuration is mainly used to allocate network and set communication parameters for link equipment and communication ports. These tasks are basically completed automatically by the configuration tool. On line configuration needs to consider the influence of parameter modification on the production process, and the method is exactly the same as off-line configuration. The following describes the equipment configuration and policy configuration under offline mode.
3.1 equipment configuration
Equipment configuration is mainly to select fieldbus level equipment and master station level equipment, configure the resource block and conversion block of the selected equipment, and set the parameters of resource block and conversion block. Each device must be configured with one resource block, one or more conversion blocks and several function blocks. When the device is the network, the first mock exam must be assigned to the device module. The location of the same module is composed of 32 characters. The key to assign the bit number is that the P&I D will make the bit number of the resource block identical to the physical device. Make the tag number of the conversion block consistent with the tag number of the function block, and add a suffix. The selected equipment should preferably support dynamic instantiation of function blocks, so that both standard function blocks and extended function blocks with enhanced features are used in the system to improve system interoperability. Each device must be configured with a resource block. The resource block contains the overall information of the equipment, such as diagnosis, calibration, equipment archives and other information, and is responsible for the interface between physical sensors and actuators. There are no input and output parameters in the resource block, that is, the parameters in the resource block are embedded parameters and cannot be linked. They can only be used for module setting, operation and diagnosis. These parameter values can be set by the user or by the module itself. For most devices, only a few parameters need to be set for resource block configuration, such as module mode parameters, sometimes feature selection parameters, fail safe parameters and clear fail safe parameters. Usually, the target mode of the resource block is set to automatic. Each device must be configured with one or more conversion blocks, which are the interface between physical 1 / 0 hardware and function blocks. Therefore, the installation related to 1 / 0 hardware, such as selection and verification of sensor and actuator types, wiring, etc., can be completed by setting the conversion block parameters corresponding to each input and output, Input and output conversion blocks are associated with input and output function blocks, respectively. By setting the parameters of I / 0 hardware channel of I / O function block, the function block and conversion block in the same device are associated. There are three types of conversion blocks: input, output and display. All parameters in the conversion block are embedded parameters and cannot be linked. They can only be set by the user or automatically configured by the device. Just like the resource block configuration, the conversion block configuration requires few parameters, generally only module mode parameters.
3.2 control strategy configuration
Control strategy configuration refers to the process of selecting appropriate functional modules according to the process control and process monitoring scheme in the process and instrument flow diagram (P & ID), setting the parameters of the selected functional blocks according to the requirements of the control and monitoring scheme, and linking the selected functional blocks after considering the macro cycle of the functional blocks. The control strategy is organized according to the operating devices it controls, not according to the instruments connected together during wiring.
Selection of function blocks: the types of function blocks available for selection in this project include input class, control class, calculation class and output class.
Concept of link: function blocks are linked to each other from output parameters to input parameters. The link includes both parameter values and parameter states. The link of function blocks between different devices is called external link. The link of function blocks on the same device through network communication is called internal link. The link does not need to communicate through the bus, will be completed immediately and does not occupy the network bandwidth. Therefore, when allocating function blocks to devices, arrange the function blocks in one device as much as possible to make the link exist inside the device, so as to reduce the link communication time. There are three types of links: non cascade forward, cascade forward and cascade backward. The module at the source of the forward link is called the high-end or upstream module, and the module receiving the forward link is called the low-end or downstream module. Cascade in the foundation refers to any type of function block that receives setpoint signals from other function blocks. It is associated with the cascade forward that transmits the output of the upstream module to the cascade setpoint of the downstream module. It is a backward feedback link that feeds back from the downstream module to the setpoint source. The feedback link starts from the recalculation output and stops at the recalculation input. Forward and backward cascade links are commonly referred to as cascade structures.
Function block parameters are mainly set for the following function blocks:
(1) Input function block: the input module accesses the field physical equipment, such as pressure, temperature, liquid level or flow transmitter, through a hardware channel in the conversion block, obtains its corresponding basic value, and provides the corresponding value to other function blocks. AI module completes channel configuration, simulation, damping and process variable alarm. According to the signal type and processing requirements, the possible configuration of the input function block is to set the following parameters: channel parameters, module mode parameters, process variable filtering time parameters, linearization type parameters, converter scale parameters, output scale parameters, status option parameters, etc.
(2) Control function block: the control function block receives and processes inputs from other function blocks and generates outputs for other function blocks. This kind of function block has both set point selection and output selection, and supports cascade structure. The module generally has filtering, set point selection and limiting, PID algorithm, output selection and limiting, feedforward, set point tracking, output tracking, process variable and deviation alarm, etc. According to the control strategy, the possible configuration of the control function block is to set the following parameters: module mode parameters, process variable filtering time parameters, back calculation output parameters, process variable scale parameters, output scale parameters, feedforward variable scale parameters, control option parameters, mode migration bypass parameters, etc.
(3) Calculation function block: the calculation function block receives input from other function blocks and processes it to generate output for other function blocks. It supports output selection, but does not support cascade structure. According to different calculated functions, the calculation function block has different parameters and its configuration is also different, but the general module mode is set to automatic.
(4) Output function block: the output function block receives setpoint input from other function blocks, may process the value, and then transmit it to physical output devices such as valve positioner and electrical converter through the hardware channel in the conversion block. The output function block has set point selection. It provides many functions that users want for the positioner, such as amplitude limiting, signal inversion, actual position readback, simulation and fault safety. According to the control strategy and the type of output equipment used, the possible configurations are the settings of the following parameters: module mode parameters, channel parameters, 1 / 0 option parameters, fail safe time parameters, fault state values, process variable scale parameters, converter scale parameters, output scale parameters, mode migration options, etc.
4. System debugging
The link device automatically manages the addresses of all devices on each network. As long as the device connects to the network, the link device automatically detects it. As long as the network connected to the device is correct and working normally, the device will be displayed in the online device list of the network together with other devices of the same network. The fieldbus device configuration database is prepared based on the user-defined device tag number and has nothing to do with specific physical devices. The physical devices connected to the network must be combined with its associated configuration to work normally. The combination method is: each fieldbus device has a unique 32-bit character device identifier, It is the hardware address of the equipment, like the MAC address of Ethernet card, which is set on the circuit board by the manufacturer and is unique and unchangeable. As long as the equipment is connected to the network, the equipment identifier will be taken into the online equipment list, and the tag number of the equipment is also pre configured in the manufacturer. As long as the tag number of the equipment configuration and the tag number of its policy configuration are consistent with the tag number pre configured by the equipment manufacturer, the field equipment will be associated with its configuration. After associating the equipment and its tag number, download the configuration file. After the configuration file is downloaded correctly, check the circuit and verify the field instrument. The verification of Fieldbus equipment is carried out in the control room. Including input verification and output verification.
Input verification: add a known standard signal value to the transmitter and write the value into the high and low calibration point parameters of the input conversion block. The low point value is not necessarily lower than the high point value, such as range migration in liquid level measurement. The measurement range is set in the converter scale parameters of function blocks such as PID or AI. The minimum range of sensor calibration can be queried from the calibration minimum range parameters of the conversion module, and the unit of calibration point value is selected from the calibration point unit parameters of the conversion module.
Output verification: output verification is to force the conversion block output of electric valve positioner, signal converter and other actuators. Select the verification type in the self verification type parameter and start the verification command in the self verification command parameter. Because the bus valve positioner has automatic installation characteristics, the positioner can automatically make the valve do a full stroke full close and full open action. In addition, it is also necessary to verify the fault safety performance of the circuit.
The low-end and high-end verification points, whether input verification or output verification, do not interfere with each other and do not need to be verified repeatedly. In order to keep calibration records, relevant data can be stored and verified in the equipment, including date, place, use method, calibration personnel, etc.
In short, compared with the mature DCS system, the fieldbus control system has more convenient installation, more flexible configuration and simpler debugging.
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