Case Study: Wireless Solution & Process Automation Scales Plant Operations

 

A leading pulp and paper company in the Pacific Northwest needed to monitor effluent water flow as it drains into a remote pond at their facility. Because of a new government regulation, personnel had to drive a truck to the remote location three times a day, log the height of the water along with the date and time, and return to the office. 

• The company realized that this was not an efficient use of time and wanted to automate this process. 

• They wanted to be able to display the data on a particular interface in an exact location on site.

• They needed to maintain accurate historical records and archiving for report production and regulatory compliance.  

The team first suggested implementing a system at the pond site that utilized a HART radar level transmitter with precise measurement capabilities and a Moore Industries HCS HART® Concentrator System (Figure 2). 

The HCS is a HART to MODBUS RTU converter that serves as a HART master and polls the HART radar level transmitter to obtain its Primary Variable (PV) data – in this case water flow level. Additionally, the HCS receives and converts to MODBUS RTU the level transmitter’s Secondary Variable (SV), Tertiary Variable (TV) and Fourth Variable (FV) along with any diagnostic data.

Why Was the HCS the Proposed Solution? 

1. First, the HCS accurately gathers the digital level data from the transmitter along with giving the pulp and paper managers access to additional process variable data and critical diagnostic data about the transmitter’s health and performance. 
2. Second, the HCS converts this HART data directly to an industry standard MODBUS RTU format, a serial communication standard that almost all industrial radios support.

Features of the HART Radar Level Transmitter

• Houses a front panel display for local viewing
• Connects to the HCS’s input via a 2-wire twisted pair cable. 
• Radar gauge sensor measures the water height in the weir
• Data is published (along with other process variable and diagnostic data) to its internal HART memory location
• HART data is then polled by the HCS 2-3 times per second. 
• The data is then mapped to a MODBUS memory map that resides in the HCS. 

This constant polling process ensures that data is continually updated on both the HART and MODBUS side of the HCS, allowing for real-time updates without the extra manual process or employee manpower.

PROBLEM: Measuring the water level

SOLUTION: The HART radar transmitter was connected to the HCS.

PROBLEM: Transmitting data to site operators via Ethernet-based host HMI panel and historical collection system with no available Ethernet networks or land lines in place from the pond site to the control room

SOLUTION: Installation of a local wireless network was chosen as the best method for acquiring these signals.

PROBLEM: No direct path for clear transmission of wireless signals (tree growth and snow accumulation)

SOLUTION: The following wireless components were suggested:

• Moore Industries WNM Wireless Network Module radios. 900MHz FHSS (Frequency Hopping Spread Spectrum) radios were used instead of 2.4GHz models as its longer signal wave length tends to better penetrate foliage.

• Ethernet versions of WNM radios were installed to meet the customer’s existing preference to utilize Ethernet communications throughout the facility. While the remote pond site previously had no communications links, using Ethernet communications at the pond site is a desirable forward step in extending the ability to add future assets with minimum added investment.

• 900MHz Yagi antennas were installed at both the boiler site and at the pond site with the narrow RF beams directed toward each other. After this was proven to be successful, the boiler site antenna was changed to an omnidirectional antenna to enable expansion of the boiler site to communicate via wireless Ethernet with all locations of the facility.
• Low-loss coax antenna cables with lightning arrestors were used.

PROBLEM: Meet all of the plant and regulatory requirements for delivery of transmitter’s signals to the host system in both digital and analog.

SOLUTION: Addition of a small Moore Industries NCS NET Concentrator System® to the host site. 

See Features of the NCS NET Concentrator System

• The NCS is a dynamic I/O system that can act as an expandable I/O system, MODBUS RTU master, MODBUS RTU slave or MODBUS/TCP slave. The NCS also provides a myriad of math and logic solutions through its ISaGRAF embedded control and logic program.
• The heart of the NCS system is the Ethernet/MODBUS Module (EMM), which is essentially the NCS’ CPU and communications center. 
• The EMM acts as the MODBUS RTU master and polls the HCS at the pond site through the serial port of the WNM radio. 
• The MODBUS RTU data collected from the HCS contains the HART data from the level transmitter and is then placed into the EMM’s local memory map. 
• The data is stored here as MODBUS RTU and MODBUS/TCP compliant registers.
  

  Figure 4. The wireless receiving panel  1Figure 4. The wireless receiving panel installed at the boiler room of the pulp and paper mill. An EMM Ethernet/MODBUS Interface Module of the NCS NET Concentrator System served as a MODBUS Master to retrieve HART data from the HCS at the pond site.

  Custom Solutions to Processes and Automated Systems 

  The EMM is polled as a MODBUS/TCP slave by the Ethernet-based HMI at the boiler room so that site operations can view the level and diagnostic data. The EMM is then programmed with ISaGRAF logic to assign process variables to the NCS’s AOM Analog Output Module. The AOM provides up to four 4-20mA or voltage signals (ranges from 0-10V) that can be taken to any analog receiving device, such as a historical data collection system.

  Ensuring a full-time communication link with the pond site was also a latent request by site operations. Therefore, a simple communication watchdog routine residing in the EMM was written in ISaGRAF to monitor the wireless connection and instruct the MODBUS RTU, MODBUS/ TCP and 4-20mA values from the AOM module to go to predefined limits if there is a wireless link failure to the EMM.

  This allows site operations at the boiler room to immediately tell when the wireless communication link has failed. Once the link is re-established the system automatically picks up where it left off, transmitting and making real-time process variable and diagnostic data from the level transmitter available. 

  The Results

  • Moore Industries application engineers pre-configured the electronics and bench tested the solution using a similar radar level transmitter kept at Moore Industries’ headquarters for such customer applications. 
  • Pre-configuration made installation quick, efficient, and fully operational with just minimal adjustments.

  The fully-automated, configured and modernized system application solution is now enabling the pulp and paper company to efficiently get accurate and required readings on the levels in their effluent water system.

  

  Figure 5. HART flow level measurements at the pond site were converted to MODBUS RTU by a HCS HART Concentrator System and sent from a WNM Wireless Network Module at the pond to a receiver radio at the boiler control room. The information was relayed from the wireless radio to an HMI display and DCS/Historian by the NCS NET Concentrator System.

RELATED: Learn More About Remote I/O Solutions with TechStar

RELATED: Read More Industry-Specific Solutions by Moore Industries

Moore Industries is a world leader in the design and manufacture of interface instruments for industrial process control, system integration, and factory automation. 

• Provides products and services to fortune 500 companies worldwide
• Serves the following industries: 
• Chemical and Petrochemical 
• Power Generation and Transmission 
• Petroleum Extraction, Refining and Transport
• Pulp and paper
• Food and Beverage 
• Metal Refining
• Mining
• Pharmaceuticals and Biotechnology
• Industrial Machinery and Equipment
• Water and Wastewater
• Environmental and Pollution Monitoring

Need more help with choosing your industrial solutions application or provider? Drop us a line and let us know what application you are looking to measure, and we’ll help you figure out the best choice. 

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