Modernise and maintain: implementing wireless to monitor beyond the P&ID
Many operational and maintenance problems around a plant can be solved by deploying WirelessHART transmitters beyond the P&ID together with an asset management system and other software to obtain asset health information and other additional plant data. However, plant procedures must be written so as to make full use of this new information.
Plant-wide modernisation can be achieved through installing wireless transmitters beyond the piping and instrumentation diagram (P&ID) and feeding raw data into essential asset monitoring (EAM) software and other applications. The basic deployment phases are illustrated in Figure 1. But with the hardware, software and updated operating procedures in place, central maintenance planning, energy conservation measures, HS&E (health, safety and environment) improvement and remote operations can become a reality. That is, the new plant information must be institutionalised in daily work processes to be effective.
There will be minor differences depending on whether the project is the modernisation of an existing plant or a greenfield installation.
The initial step is to get buy-in from the plant management that will approve the project. For an existing plant, there is a need to justify modernisation with wireless, and with a new plant, expanding the scope beyond P&ID to include EAM, ECM (energy conservation measures) and HS&E packages as part of the project must also be justified.
The opportunity to improve maintenance, energy consumption and HS&E by modernising should be explained to the plant management, maintenance manager, reliability engineer, HS&E officer and project/turnaround manager. Investment in wireless transmitters and centralised EAM software can be justified on the basis of reduced downtime, lower maintenance cost, lower energy consumption and improved HS&E, provided the new information is institutionalised in the daily work processes and the plant culture.
Typically, critical plant assets such as expensive compressors and large pumps are already monitored, but due to the high cost of traditional machine protection and monitoring systems, the balance of assets may not have previously been monitored. These ‘second-tier’ assets, although essential to the process, are typically only spot-checked manually on a periodic basis (see the breakout for examples). Improving the monitoring of these assets can have a direct positive impact on maintenance and energy costs.
The modernisation has to be accompanied by a culture shift, especially for EAM. Maintenance technicians will be able to tell if assets need to be maintained urgently, if they can wait until the next turnaround or if they need no maintenance at all. This not only enables turnarounds to be shortened, but reduces the crane and crane operator costs, and the need for hoist, scaffolding, fitters, riggers, instrument technicians, electricians, pipe fitters as well as insulation and other material. Incorporation of EAM in daily maintenance practices must be a management directive, with follow-up to ensure new work processes and EAM tools get adopted, and continue to be used to derive value from the asset health information. Deployment will have associated engineering hours and cost.
Audit existing plant
For an existing plant to deploy EAM, ECM and HS&E packages as part of a brownfield modernisation project, it is necessary to audit the entire plant’s assets, processing equipment, machinery and valves to identify shortcomings in measurements beyond the P&ID which need to be filled before work practices based on asset health and automatic data collection can be adopted. The audit is an opportunity to rate the plant’s asset management readiness. The assessment should also include a look at the current work processes and procedures for operation and maintenance, as well as the maintenance regime, culture and the skills of the plant staff. That which is missing in the existing plant architecture to support essential asset monitoring, energy conservation measures and HS&E becomes the input for the front-end engineering design (FEED) stage of the project.
The asset management system for the EAM, ECM and HS&E packages can be a standalone or can be integrated with the DCS. The plant-wide asset health information will mostly be used by the maintenance department for daily maintenance scheduling and turnaround planning, but operations can also benefit from being aware of assets which have failed or are degraded, as the plant can be operated differently to work around the limitations. Conversely, the EAM diagnostic algorithms in the EAM software often use process measurements already available by connecting to the DCS.
WirelessHART and OPC are the enabling technologies that permit easy deployment of automation beyond the P&ID in an existing plant. An OPC server should be added to the DCS in the event that OPC is not already available.
The scope has to be defined early on in the modernisation project and should involve the project/turnaround team, the DCS team, instrumentation team, modernisation solution supplier and the maintenance group. It should be documented in the form of a basis of design, a functional design specification including system architecture, network protocols to be used for DCS integration, hardware and software as well as associated services. For an existing plant, the system architecture requirements will be based on the plant audit and gap analysis.
No essential asset should be left stranded without EAM.
A remote site may not have personnel with the necessary skills required for analysis of asset health information. For such locations, remote access infrastructure such as a wired or wireless backhaul network between the site and a centralised location should be considered.
Assign roles and responsibilities
A number of persons are involved in the initial deployment of the EAM, ECM and HS&E package, the instrumentation and in sustaining the EAM software and associated work processes for the long term. The person that is responsible for the rollout of new practices for maintenance should be on the modernisation team and is best suited as a lead for the team. The plant management is also instrumental in leading the cultural change required to institutionalise EAM, ECM and HS&E packages in daily plant activities, so a senior member of the management should be the executive sponsor to drive the change. This includes providing required resources for the deployment of the EAM software and the continued running of the system for the long term.
The turnaround manager or project manager also needs to be on the modernisation team to manage the work and resources required to deploy the EAM software. It is also necessary to identify the persons responsible for work processes associated with the EAM software and to establish a cross-functional modernisation team of instrumentation, control system and maintenance specialists. These will be the experts on essential asset monitoring, energy conservation measures and HS&E to continue the modernisation for the long term.
It is a good idea to develop an organisation chart for the team with roles and responsibilities - defining who is responsible for delivering what.
The modernisation team leader should develop and document a plant-wide and site-specific modernisation plan for how the EAM software, OPC server and underlying wireless infrastructure and transmitters will be deployed at the specific site. This should include a schedule for when each phase of the modernisation project will take place and the resources required, when people will take on their new roles as well as detailed plans for the training of people in different roles.
Based on the short-listed assets and the types of asset health diagnostics required for each asset, the number of WirelessHART transmitters can be determined. Next, the number of gateways and supporting networking equipment can be determined. Lastly, assets need to be ranked and their health alarms prioritised in a rationalisation process to ensure effective plant-wide alarm management.
The overall system implementation is normally done by the modernisation solution supplier. This will involve building the EAM database, including the graphics, tags, historian, alarm management and reports based on the detail design, and also the ECM database with steam trap information.
Automatic pressure, temperature, flow, level, pH and conductivity measurements as well as safety shower and eye wash stations, valve position feedback, along with automatic vibration, temperature and leak testing data can be routed to the existing DCS or a separate HMI for HS&E purposes.
The factory acceptance test (FAT) is done at the modernisation solution supplier’s staging area, witnessed by the buyer. A FAT test plan shall be agreed on and forms the basis for the FAT test procedures to verify the graphics, asset health alarm management and reports etc.
For the IDM software, verify all versions of all device types from all manufacturers are integrated, that is, their EDDL files are loaded. This involves the IDM supplier, plant instrument specialist and plant system engineer.
In an existing plant, a local contractor installs the wireless transmitters as well as the wireless gateways with network infrastructure and power. In a new plant, the EPC does this work.
The modernisation package vendor can help supervise the installation of wireless transmitters and gateways.
If the correct make and model of manual valves, relief valves, safety showers and eye wash stations etc have been identified in the design phase and the correct mounting kits have been specified, the wireless transmitter installation will be smooth.
The wireless transmitters and the software have to be commissioned. Normally a local contractor would commission the transmitters and gateways, including setting the network ID and join key, as well as the device tag and update period if this was not configured in the factory. The site instrument technicians should also take part in the commissioning so they become familiar with the WirelessHART technology.
Wireless commissioning should at least involve checking all instruments join the network and meet the requirements for number of neighbours, signal strength and reliability, and that they are transmitting correct measurement values.
The EAM system would normally be commissioned (and the baselines and weightings tuned) by the EAM system supplier.
The modernisation solution supplier works with the DCS supplier to establish communication between the two systems: for operators to receive asset health information and alarms, and for the EAM diagnostic algorithm to receive process variables already measured by wired transmitters. Site integration starts by establishing the bidirectional OPC link between the plant DCS and the EAM software.
Having a list of parameters to be linked between the systems developed in the detail design phase speeds up the integration work in the two systems.
Note that for EAM, only computed information like one overall asset health index for each asset is passed to the DCS, not all of the dozens of raw data points like vibration and temperature for every asset. This way the DCS tag count is kept low and the integration is simple.
Process variables already measured by wired transmitters connected to the DCS come from the DCS through OPC into the EAM software. At sites where the EAM software gets process variables like heat exchanger flows or variable pump speed from the DCS through OPC, the site integration and commissioning may happen in parallel.
Procedures and work processes should be written making use of the new plant-wide information. Development of these procedures can start early in the project and does not need to wait for the detail design to be completed. A consultant can help in the development of the procedures and work processes for maintenance, energy conservation and HS&E. These services should be included as part of the project budget.
Training for competency
Use of EAM software and other applications requires new skills, therefore training is required for all those involved to get the necessary competency in asset management. With asset management, work is centred around computers, so computer skills are a prerequisite for maintenance work in a modern plant.
Asset management training has to be specific to the competencies required for the tasks which each role has to carry out. Training has to be conducted not at the end of the modernisation project, but throughout the duration of the project before the next phase of the project starts. Once the plant is operational, new employee training and refresher courses should be conducted periodically.
EAM for second-tier assets
Three common examples of second-tier assets that are prime candidates for wireless EAM are heat exchangers, pumps and steam traps.
Plants typically do not know the rate of fouling of heat exchangers, because the manual measurement of the hot fluid involved is difficult and time-consuming. Since cleaning heat exchangers usually requires a process shutdown, cleaning them too often is costly. But if they become severely fouled, they may need to be removed completely to be cleaned - an even far more costly exercise.
Finding the optimum cleaning time for heat exchangers requires performance data at least daily to calculate the rate of fouling. This can be achieved by measuring hot and cold fluid inlet and outlet temperatures and flow using wireless transmitters. The raw data is transmitted back to EAM software and the plant historian, to allow the automatic computation of all the factors necessary to trend the rate of transfer degradation, making it possible to predict the optimum time for cleaning.
A pump can be affected by many different problems, with one type of problem often leading to another. Cavitation, for example, can be caused by a plugged suction strainer before the pump creating a pressure drop, or a downstream flow restriction causing internal recirculation across the impeller - leading to impeller damage and vibration. Vibration can also be caused by poor mounting or misalignment, poor lubrication or worn bearings. The list goes on …
Most pump problems can be detected by vibration testing, but in many cases, manual checking may not occur frequently enough to capture impending failures. Early detection of problems can be achieved by wirelessly monitoring various factors, depending on the pump, and processing the data in the EAM system. Wireless instruments that can be used to do this include vibration transmitters, DP transmitters (detecting pressure drop caused by strainers and seals), level switches (for sealing fluid), temperature transmitters (for bearings and motor windings) and hydrocarbon sensors to detect leakage. Not all pumps will need all these factors monitored, but EAM applications can be customised to suit the individual pump applications.
Typically a steam trap has a life expectancy of four years, so if they are only inspected yearly, then on average, 25% of them may be found to have failed or be ready for replacement - and a typical plant may have thousands of them. Manually checking them is therefore difficult, because of the quantity, and the fact that many of them are difficult to access. They also require a high level of technical experience to diagnose.
Using a wireless acoustic transmitter on the outside of the steam trap inlet, with a built-in temperature transmitter, allows the detection of the ultrasonic noise and temperature change caused by steam or condensate that results from steam trap failure. The status of all steam traps can therefore be displayed in the EAM software for easy review by technicians.
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