Automating & Educating the World’s Leading Companies

The Challenge 

A leading fuel company needed a reliable process to safely convert large quantities of natural gas products into a liquid,  utilizing a liquefaction process. A reliable, automated, small-scale prototype solution was necessary for evaluation prior to  deployment in the country of Qatar. This solution had to control elaborate compressor/expander (compander) units and  incorporate a multi-screen application that is flexible enough to allow the user to change tests and export data when  demanded. It involved very complicated mathematical algorithms for process characterization and verification. Data Science  Automation was selected to develop, install, and test the entire system in just three weeks!  

Figure 1. Software System Architecture

The Solution 

Working under such a tight deadline, National Instruments LabVIEW 7.1 was selected as the rapid application development  environment. An NI-GPIB interface was used for controlling an existing Keithley 2700 DMM system to acquire data during  the testing process. The solution that was created is based on three-module software architecture to isolate the main user  interface from the other critical acquisition and data management functions. Figure 1 illustrates the architectural approach.  Utilizing queue technology native to LabVIEW, an elaborate system was designed to send messages/requests back and forth to control the three independently-operating modules. The main application will request data from the data manager. The data  manager will execute complex equations, and condition the raw data that is being acquired by the acquisition manager. The  data manager will also service all requests by the main application such as logging to files and controlling the actions of the  acquisition manager. The acquisition manager strictly acquires data and publishes the data to the data manager. This three  module architecture is flexible enough to account for any issues in the acquisition process and without affecting the main  application. Shown in Figure 2, the main application, called Scribe, allows the user to define, save, and load  file configurations, including all output paths for  the raw data files, result data files, hardware  configurations, and the calibration files. 

Figure 2. System Configuration Screen 

When the user initially wants to configure this application they must either use a previous configuration or create a new  configuration. The first step in setting up the new configuration is configuring the high channel count Keithley DMM for  native settings such as Temp Scale, Polarity, Auto Zero, etc. The second part to the hardware configuration is to setup each  data acquisition channel and their associated transducer inputs. During this configuration the user must specify the type of  measurement, scaling, filtering, tag names, and a serial number. This information is stored in the hardware configuration files  for future use. This configuration is shown below in Figure 3. 

The next step in the configuration process is to setup the measurement names for everything from simple temperature and  voltage readings, to outputs from complex equations. These measurement names are aliases for the actual hardware channels or calculations resulting from one or multiple channel inputs. Multiple aliases can be given to a channel for use in multiple  calculations. Each of these measurement names are used in calculations during the running stage of the application. Due to  the complexity of the liquefaction process multiple calculations must be done to verify the process was successful. The  measurement configuration screen is shown in Figure 4. 

 Figure 3. Hardware  

Configuration

Figure 4. Measurement Configuration

Once all measurement names and variables have been created, the user can configure the proprietary equations based on the  measurement names. Each of these equations will be evaluated each iteration of the acquisition process. This will allow the  user to view all calculated data without having to post process results. This real-time approach significantly increased the  throughput of the combined research and analysis procedures.  

Before starting the test and controlling the compander units, the application initializes queues to start the Keithley Manager  and the Data Manager based on configuration and setup information saved in files. Once all parameters and hardware  configuration information has been sent, the user will have the ability to calibrate the RTD and non-RTD devices before  logging data. 

After all calibration has been completed, the test will begin. During the test execution the user will have the ability to view  real-time results from the Keithley device and from the sophisticated equation calculations. These results can be exported to  file during run time or can be viewed on charts, or tables shown in Figure 5. Data can be saved at automatic intervals or upon  user activation.  

 

Figure 5. Test Results 

Summary 

Data Science Automation’s prototype solution created to automate the liquefaction process using commercial compander  units. The advanced data acquisition and data analysis techniques were successfully used to simulate the future deployment  of large scale natural gas liquefaction processes. This solution leveraged National Instruments LabVIEW 7.1 software, and  the GPIB interface to the Keithley DMM. It has saved countless hours of planning, and eliminated costly field testing by  simulating the real world deployment on a smaller scale.