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During the operation of a system on a ship, a large number of key parameters need to be monitored in real-time, such as vessel pressure, seawater pressure, water tank pressure, hydraulic oil pressure, etc. These pressures reflect the operation status of the system on the one hand, and the system controls the system by collecting the above pressures as input parameters. Only by accurately collecting the key parameters can the coordinated actions of each subsystem be accurately controlled, thus ensuring the success of the task. As the measuring equipment of key parameters, the accuracy and precision of the pressure transmitter directly relate to the success of the task and the safety of the ship system. In order to ensure the measurement accuracy and stability of the pressure transmitter, especially the long-term stability and the ability to cope with various working environments, the pressure transmitter must be measured regularly.
According to the accuracy requirements of a certain system of the ship, the pressure transmitter of the system needs to be measured every six months. At present, the pressure transmitter of the system is completed manually. First, disconnect the pressure transmitter from the measuring system, and then manually record the pressure of the standard pressure gauge and the field pressure transmitter by pressurizing the field pressure transmitter to determine whether the pressure transmitter meets the metering standard requirements. There are many human operation links in the measurement process, which require high measurement personnel and low work efficiency, so it is easy to introduce human error. In order to improve measurement efficiency and accuracy, it is necessary to develop a set of pressure transmitter online measurement systems.
According to the on-site measurement requirements of the pressure transmitter of a certain system of the ship, the automatic online measurement system of the pressure transmitter shall have the following functions:
The online measurement system of pressure transmitters is mainly composed of the power module, pressure calibrator, reinforced computer, pressure connecting pipeline and connector, special cable, printer, etc. Considering the high reliability, high integration, convenient loading and unloading and other characteristics of the system, the hardware of the system should be selected as mature as possible. The online automatic measurement system of pressure transmitters is mainly used for the online measurement of the pressure transmitter of a certain system of the ship. It has the ability to display, record, and analyze the measurement results, and print the measurement report.
The power module converts 220 V 50 Hz power supply into power supply available for industrial computers and pressure calibrators. Generally, the industrial computer and pressure calibrator can be powered by a built-in battery. When the battery of the industrial control computer and the pressure calibrator is low, the power module can be used to charge them. The power module has overvoltage, under-voltage, and overcurrent protection functions.
The pressure calibrator is mainly composed of an internal pressure controller, a built-in electric pressure pump, and a built-in standard pressure module. As the core part of the pressure calibrator, the internal pressure controller can receive the control information of the reinforced computer through the communication interface, control the built-in electric pressure pump to pressurize according to the specified pressure verification point and provide the pressure source for the built-in standard pressure module and the on-site pressure transmitter. At the same time, the internal pressure controller can collect the pressure value of the internal pressure transmitter and the standard pressure module, and transmit the collected pressure value to the industrial control computer in real-time through the communication interface.
The reinforcement computer automatically selects the verification pressure according to the pressure transmitter information input by the user, transmits the verification pressure to the pressure calibrator, and the pressure calibrator automatically controls the built-in pressure pump to pressurize to the specified pressure, providing a pressure source for the standard pressure module and the on-site pressure transmitter. At the same time, it receives the pressure value of the standard pressure module and the pressure value of the field pressure transmitter collected by the pressure calibrator. The system software calculates various errors of the pressure transmitter according to the set algorithm and gives the measurement results.
The pressure connecting hose and connector are connected with the measuring interface of the pressure calibrator and the on-site pressure transmitter to provide pressure for the on-site pressure transmitter.
The special cables mainly include power supply cables and communication cables. The power module supplies power to the industrial computer and pressure calibrator through the power supply cables. The pressure calibrator communicates with the industrial computer and pressure transmitter through the communication cables.
The software part of the online automatic measurement system of pressure transmitters runs on the reinforced computer, which is mainly used to set, display, process, and save the measurement process data.
Before measuring the pressure transmitter, users need to input the specification, model, measuring range, accuracy, measurement date, installation location, and other information about the pressure transmitter into the online measurement system. The system will record the above information and establish a data file for the pressure transmitter.
The system automatically calculates the pressure point to be measured according to the accuracy, range, and other information of the pressure transmitter input by the user, and transmits the pressure value to the pressure calibrator through the real-time communication module. At the same time, the system receives the standard pressure module collected by the pressure calibrator and the pressure value of the on-site pressure transmitter through the real-time communication module.
The system automatically selects the number of metering points according to the parameters of the pressure transmitter and calculates the theoretical output value. Control the pressure calibrator to increase and decrease the pressure to each measuring point, prepare a data analysis and processing program according to the relevant verification regulations, determine the indication curve of the pressure transmitter, compare the pressure value of the standard module at each measuring point with the measured value of the pressure transmitter, calculate various errors, and judge whether the errors of the pressure transmitter meet the requirements.
The system automatically generates metering results according to various errors calculated by the "Transmitter Metering Module", and stores the metering results in the data file established by the "Transmitter Parameter Setting Module" for the pressure transmitter for future reference. Print and generate measurement reports according to user requirements.
You can view and analyze historical measurement information. When a certain measurement is selected, the system can analyze the out-of-tolerance rate of the pressure transmitter in this measurement. When a pressure transmitter is selected, the system can analyze the historical measurement system of the pressure transmitter, such as the changing trend of previous measurement errors, the long-term measurement stability of the pressure transmitter, etc.
The operation steps of the automatic online measuring system of the pressure transmitter are as follows:
The automatic online measurement system is used for the measurement test of the pressure transmitter of a certain system of the ship. The model of the measured pressure transmitter is Rosemount 3051, the output signal is 4~20 mA standard current, and the accuracy is 0.25%. According to the verification regulation of the pressure transmitter, the selection of verification points shall be evenly distributed according to the range, generally including no less than 5 points including the upper limit value and lower limit value (or within 10% of the input range nearby). Therefore, the selected verification points are 0 kPa, 125 kPa, 250 kPa, 375 kPa, and 500 kPa.
This research analyzes the use demand of online measurement of pressure transmitters in a ship system, designs an automatic online measurement system of pressure transmitters, introduces the functions of each hardware part of the system and each software function module, and then introduces the use method of the system. Finally, the measurement test shows that the online measurement automatic system realizes automatic data collection and calculation, with high measurement accuracy, simple operation, and portability, which is suitable for the measurement of pressure transmitters in industrial sites and can greatly improve the measurement efficiency of pressure transmitters.
