All process plants have control, reliability and energy-use improvement objectives that must be met to remain competitive and keep pace with industry best practices. Health, safety, security, and environmental (HSSE) compliance objectives also must be addressed. Meeting these objectives will often require some level of instrumentation as part of the design, and conventionally this instrumentation tends to be connected back to the automation system with hard wiring or via a fieldbus protocol. But both of these technologies have significant design, cost, and installation implications.
When capital is constrained, budget reprioritization can sometimes result in improvement projects taking a lower priority. When managers see the cost of a wired instrumentation solution, they may postpone implementing it. When wired instrumentation projects do get executed, they tend to be done on a stand-alone basis, offering no opportunity to generate incremental benefits for other projects. The challenge for plant engineers is to develop a common instrumentation framework enabling support for multiple projects, thereby reducing or spreading the cost burden across multiple project budgets.
By consolidating budgets and using funds to install wireless instrumentation (Figure 1) and its accompanying infrastructure, plants can not only meet current objectives but also put in place an infrastructure for future improvements. A wireless sensing infrastructure enabled by a common standard such as WirelessHART can create a framework to support multiple continuous improvement initiatives, with these improvements capable of being implemented very quickly at low cost.
Figure 1. Wireless transmitters can be installed anywhere at minimal cost. Once installed with a supporting infrastructure, additional wireless devices can be added easily.
Wireless sensing infrastructure can be used as an alternative or as a complement to wired instrumentation to reduce cost, efficiently manage projects, and reduce the risk of cost escalation. Here's how.
Organizing for success
The first step is to perform an operational assessment of the plant. Through this assessment, you'll get a better handle on the status of current automation investments and potential problem areas pertaining to reliability, energy, or safety.
The second step is to define an automation roadmap for the site. Implicit within this definition is how technologies such as wireless can achieve a measurable difference in the problem areas defined within the assessment.
Technologies such as WirelessHART are internationally recognized standards that build upon existing HART technology, which is already in common use in process plants. This means the WirelessHART standard is readily accepted and easily integrated into most any automation system, irrespective of the system's age. The user is thus not constrained by the limitations of the site’s existing automation and instrumentation systems.
The monitoring of heat exchangers offers one example of where wireless can be used to quickly implement improvements at low cost with little or no interruption to existing operations.
Heat exchanger monitoring
Heat exchangers can be a major source of downtime, resulting in considerable maintenance expense, significant loss of production, and poor plant performance. A plant's existing monitoring approach may involve manual spot measurements performed on a periodic basis. These types of measurements provide an inconsistent view of failures and are time-consuming, with the accuracy of assessments dependent upon technician expertise.
Automating the collection of heat exchanger operating status using a conventional approach of installing and wiring new instruments to an existing automation system is often prohibitively costly. Tying in new wired signals to an existing system will involve locating spare input cards, marshalling panel space and field junction boxes (Figure 2). Often, required space and system capacity won’t be available, or at best it will be severely limited. This is one of those projects where the cost means the priority is relegated in favor of a more pressing or urgent task or one that costs less.