Until recently, when engineers wanted to monitor plant equipment, such as steam traps, pumps or heat exchangers, they were often faced with difficult, complex and expensive projects. First, they had to install and wire new instruments at the equipment. They then had to wire the new instruments to the existing 4-20mA or fieldbus I/O system. If the existing system was full, this required new cabling, conduit, junction boxes, marshalling cabinets and/or input cards. In some cases, adding a single wired instrument could cost $15,000 or more in labour, materials, new wiring, additional input cards, etc.
Next, they had to analyse the data provided by the new instruments. In existing measurement and control systems, this typically meant that the data had to be acquired by the control system and sent to the plant historian or SCADA system, where it became part of the system’s enterprise-level database.
Software to diagnose data provided by these instruments had to be purchased, installed and configured. In some cases, such software was non-existent, so engineers had to write programmes, manually perform calculations, or figure out how to use the plant’s existing asset management, maintenance management or historian software to perform the required data analysis.
In the worst case, the plant had to buy additional computer hardware, such as servers and dedicated computers; purchase the necessary software or pay to have it written; hire outside consultants to implement the equipment monitoring system and conduct training to acquaint plant personnel with the new system. Such an installation could cost well into six figures and take many months to deploy.
Today, however, wireless instrumentation and low-cost apps make it possible to monitor pumps, steam traps and other equipment for a fraction of the previous cost and in much less time.
WirelessHART has been one of the industry standards for wireless communications for the past 10 years. It is supported by dozens of vendors and administered by the independent FieldComm Group organisation and Emerson alone has nearly 30,000 wireless networks installed with more than 8 billion hours of operation. Though wireless networks do not require a wired infrastructure, a wireless instrument can be installed for one-third to one-fifth of the cost of a wired 4-20mA or fieldbus instrument.
Non-intrusive instruments including process temperature transmitters further reduce the overall cost of the installation by eliminating the need for pipe cutting, drilling or welding and eliminate leak points. Other sensors such as acoustic (for steam trap and pressure relief device monitoring), corrosion, vibration, valve position, DP flow and hydrocarbon leak detection are available in various clamp-on, bolt-on, magnetic and slip-in forms.
Advantages of wireless system
A wireless system is easy to install, particularly for wireless instruments with their own power modules. These instruments do not require power wiring so they can be installed virtually anywhere to monitor just about anything. All a wireless system needs is a combination of one or more wireless instruments, a gateway to communicate with the instruments and a wired connection from the gateway to the control or monitoring system. This wired connection is typically Ethernet or Modbus.
Once a wireless infrastructure is set up to monitor one or more pieces of equipment, additional wireless instruments can be added for very little marginal cost, with each one joining the existing network. Multiple wireless instruments form a mesh network so that data can be passed from one instrument to another, thus, avoiding obstacles, increasing transmission distance and providing reliability of the network in case one instrument fails.
For example, adding a steam trap monitoring system is simple and inexpensive. When Rosemount 708 wireless acoustic transmitters are installed on steam traps, they automatically join the plant’s WirelessHART mesh network, are recognised by the wireless gateway, and begin transmitting data. The instrument clamps on to existing piping, eliminating the need for process penetrations or welding and further simplifying installation.
Software applications or apps collect the raw data from these monitoring points and perform analytics to determine the condition of plant equipment and assets. This allows users greater visibility into operations, enabling improved reliability and energy efficiency.
As with apps for smartphones and tablets, these types of industrial apps are becoming a common way for vendors to supply software to end users, supplanting more traditional software products. Like smartphone and tablet apps, these industrial apps are lightweight and low-cost software applications requiring very little in the way of corporate IT support. The examples below use Emerson Plantweb™ Insight apps as an example, referred to generically as apps.
These software apps utilise pre-built analytics with embedded domain expertise to diagnose the health of plant assets. The resulting information and insights can be accessed and visualised on a web-user interface running on PCs, laptops, tablets or smartphones. Dashboards and charts make navigation and interpretation of information simple, so minimal training is required. The apps include features to ensure security, including role-based access.
For example, each app addresses specific assets, such as steam traps, pumps, heat exchangers and other items with simple and inexpensive plug-in solutions. These apps run independently of a plant’s control system. The app package is provided as a virtual machine, making it simple to install, easy to manage and available to multiple users simultaneously. No specific hardware is needed—only the virtualisation environment.
Each of these apps is purpose-built for a specific asset, making them quick, easy and inexpensive to implement. This contrasts with general purpose data analytic solutions, which often require extensive configuration or programming by the end-user to yield meaningful results.
These apps access the wireless gateways, which funnel data from the wireless instruments to the apps. Once the gateways are installed, additional wireless instruments and apps can be added at minimal cost. The additional instrumentation will use the same gateways in most cases depending on how many instruments are connected and the apps can connect to hundreds of gateways.
Each app can acquire data via a wired connection to the plant’s gateway or from a wireless I/O card. Each app can also access data from historians, databases or other sources via industry-standard interfaces such as OPC UA and Modbus TCP/IP.
In short, these apps complement a plant’s existing control and monitoring system and do not interfere with the existing operations. This means equipment diagnostics can be done parallel to any legacy control and monitoring system. This is significant because most chemical plants have very stringent, expensive and time-consuming procedures for adding an input point to an existing control system. Since these are monitoring points in most cases and are not used for control, they can be installed and commissioned much more quickly and inexpensively than input points used for control.
Typical examples of equipment lending itself to wireless monitoring and app-based solutions include:
Pipes and vessels subject to corrosion
Safety shower and eye wash stations
The following sections will detail just how this is done for various items of equipment.
Steam trap monitoring
Steam traps are not often automatically monitored in chemical plants because of the expense of adding wired instrumentation and accompanying analysis software. Instead, many plants rely on manual rounds where maintenance technicians test traps once or twice a year and look for signs of leaking. With manual rounds, much of the analysis is done based on the judgment of the person making the measurements and observations, introducing inconsistencies and the possibility of errors.
Manual rounds are often ineffective and many problems can go undetected between rounds. Estimates are that 18% of the steam traps in a large petrochemical plant fail every year, each causing about $16,000 in extra fuel and steam costs.
By installing wireless acoustic sensors and a steam trap app, plants can quickly identify steam traps that fail open or closed, are leaking or are working improperly. Maintenance or replacement can take place when problems are found instead of waiting for the next manual round.
Acoustic steam trap monitors simply clamp on to the steam line, so there is no need to shut down the process during installation. Once installed, a technician enters Join Key information and the monitor automatically joins the wireless network and starts transmitting information to the gateway. Installation takes only a few minutes, depending mostly on how difficult it is to access the mounting location.
The acoustic monitor ‘listens’ to the steam line and transmits data to the gateway. Information from the gateway is then sent to a steam trap app, which uses an algorithm to identify failure modes (good, blow through, cold, inactive). The app also automatically performs an analysis of economic and environmental impact, displayed in terms of excess energy costs and emissions loss.
Heat exchanger monitoring
Data from wireless temperature, pressure and other instruments installed on heat exchangers can be analysed to identify abnormal situations such as early detection of accelerated fouling in a transfer line exchanger used to rapidly cool cracked ethylene. Analysis also determines the optimum time to clean the exchanger, based on heat transfer degradation and economic calculations.
A heat exchanger app provides in-depth monitoring of shell and tube heat exchangers. It can determine real-time heat exchanger status and alerts, heat duty, fouling factor and rates, heat transfer coefficient and process variable thresholds based on baseline capture. This and other information is provided in realtime via the user interface.
Many pumps in the chemical industry are not monitored, often because of the high cost to wire instrumentation back to the control system, especially in hazardous areas. Historically, only those pumps deemed critical to process operations have been monitored. Wireless instruments can monitor pumps no matter where they are located in a chemical plant without the expense of adding new wiring. Pump diagnostic apps can be used to monitor pump operation.
A complete pump monitoring system requires the installation of wireless pressure instruments to measure pressure at the inlet and outlet; a wireless vibration instrument; wireless temperature instruments on the pump and motor; and a wireless flow instrument. Additional instruments may be needed to monitor pump seal, strainer and other systems. Less critical pumps can be instrumented accordingly to monitor fewer points of measurement.
The pump app monitors strainer differential pressure, vibration analysis, cavitation and process variable thresholds based on baseline capture. The app provides warnings of pump cavitation, plugged strainers, dead-headed pumps and early bearing and gear wear as well as imminent seal leaks.
Corrosion and erosion can negatively impact the safe and reliable operation of industrial companies’ infrastructure, often with dire consequences. Wireless non-intrusive corrosion monitoring allows users immediate visibility into pipe thickness— the best indicator of corrosion.
A corrosion monitoring app provides further visibility into pipe integrity and corrosion/erosion rates. Taking in data from numerous point sensors, the app provides deeper understanding and immediate notification of problem areas and degrading equipment before leaks or spills occur, optimising operations and improving safety.
Wireless instrumentation and accompanying apps simplify the installation, configuration and maintenance of equipment monitoring systems. These systems can be brought online in hours or days rather than months, and often at a fraction of the cost of traditional wired instrumentation coupled with large and complex analysis software. In many cases, payback is achieved in a matter of months, and an initial system can be installed at minimal cost to prove viability.
This article was first published in Automation.com in July 2017