- July 19, 2017
- Emerson Automation Solutions
By Tom Bass, Emerson Automation Solutions Pumps in remote locations can be monitored with wireless transmitters in a cost-effective manner to improve uptime, avoid incidents and increase reliability.
By Tom Bass, Emerson Automation Solutions
Pumps in chemical, petrochemical, refining and other industrial plants need to be monitored, even if they are in remote locations, such as a lift station or pipeline. When a pump fails, it can cause catastrophic failures that can lead to expensive repairs, fires and plant downtime. A pump or seal failure can start a fire or shut down a complete process, requiring expensive unplanned emergency maintenance.
In many facilities, automated monitoring is used for only 10%of the most critical pumps, or not at all. That leaves nearly 90% of pumps in a typical facility to rely on manual rounds, unnecessary maintenance or running to failure.
Many pumps are located in hazardous areas, in locations difficult to reach, or in locations where power for instrumentation is limited (Figure 1). In many of these cases, using wired transmitters for monitoring may be too expensive. In these situations, wireless instrumentation makes it feasible for plants to perform remote pump monitoring.
Figure 1: Some pumps in remote locations are difficult to monitor with standard wired transmitters.
Wireless for Remote Monitoring
Early detection with remote monitoring is the key to preventing pump failures. But in many facilities, installing wired 4-20mA or fieldbus flow, pressure, level, temperature, vibration and other transmitters is expensive and time consuming, especially in remote areas.
Wired transmitters require a supporting wired infrastructure, which can include a power supply, cabling, conduit and cable trays to bring the signal to a field junction box or marshalling cabinet, along with I/O devices at the control and monitoring system to accept the transmitter’s 4-20 mA or fieldbus signal. This can make wired transmitter installation a very expensive and difficult undertaking. If the installation is in a hazardous area, then appropriate rules, regulations and procedures must be followed for the installation and maintenance.
The chief advantage of wireless systems is they can be installed virtually anywhere in a cost-effective manner. Wireless transmitters have power modules and require no wired infrastructure or local power supply, so they can be installed in locations far away from a process unit’s wired infrastructure. They can also be installed in locations where supplying power and cabling would be too expensive or hazardous.
Installation, therefore, is simple: The transmitter merely has to be mounted to the application, and no wiring is required. A typical wireless transmitter can be installed, configured, and commissioned in a matter of a few hours, as opposed to days or even weeks for its wired equivalent.
Wireless technology has changed the landscape of remote pump monitoring. At a fraction of the installed cost of wired transmitters, plants can enhance preventive maintenance and support manual rounds with on-line condition monitoring. This not only gives early indication of failure, but also avoids unnecessary maintenance on pumps that are healthy.
Cost Competitive Wireless
For almost the same cost as hard-wiring additional process transmitters from a remote pump to a control system, a complete wireless pump monitoring system with diagnostic software can be installed. And it costs even less if the plant already has a WirelessHART® infrastructure installed (Figure 2), because the new transmitters simply “join” and strengthen the existing infrastructure.
Figure 2: If a plant already has a WirelessHART infrastructure installed, adding a wireless pump monitoring system is simple because new transmitters simply “join” and strengthen the network.
WirelessHART is an industry standard available from multiple vendors, and more than 30,000 networks have been installed all over the world over the past 10 years. There is an excellent chance your plant already has such a system.
WirelessHART infrastructure consists of wireless transmitters, a wireless mesh network, and a gateway. The gateway receives data from the transmitters and transfers it to a control or monitoring system via Ethernet, Modbus or other hardwired methods. If a plant does not already have a WirelessHART system, then a gateway must be installed.
If the pump is remotely located on an offshore platform or pipeline, the gateway can send data from the transmitters via a wired network, RF, cell phone or satellite link to a remote control room.
The estimated cost of a complete remote wireless pump monitoring system in a typical plant is about $10,000, including process transmitters, a gateway, and software (Figure 3) to analyze pump health. Once the first system is installed, additional pumps can be added for about $2,000 to $5,000 each.
Figure 3: Pump health software, such as Emerson’s Plantweb Insight Pump APP, takes data from WirelessHART transmitters, analyzes it and displays results on a PC, tablet or smartphone.
Pump analytics software is now available as an inexpensive “app” that runs on a PC, tablet or smartphone, completely separate from the plant’s control or monitoring system. The app takes data from the gateway, runs analytics to verify overall pump health, and provides results on the screen.
Pumps in critical processes need automated remote monitoring to prevent failures and process shutdowns, but non-critical pumps may also need automated monitoring.
Pump efficiencies depend on design, and the highest efficiency a pump can reach is called the Best Efficiency Point (BEP). Maintaining flow rates near this point not only minimizes energy costs, but also reduces pump load and maintenance requirements.For example, pumps suffering repeated failures, and pumps for which there are no spares, can often benefit from remote monitoring. Remote monitoring may discover the cause of repeated failures or find problems that maintenance can repair before the pump fails.
Remote monitoring can help plant operators control the pump nearer its BEP while detecting any problems, such as bearing and seal wear, cavitation and deadheads.
Seal Monitoring—Mechanical seals are typically used in applications that require a better seal than packing can provide. Contaminants can quickly degrade a seal, but with proper flushing seal systems can last thousands of hours. Figure 4 shows a dual pressurized seal flush system commonly used with hazardous products. A wireless pressure measurement is used to indicate a leak either from the process to the barrier fluid, or from the barrier fluid to the environment, while a wireless level transmitter monitors level in the fluid reservoir.
Figure 4: Wireless pressure and level transmitters can be used to monitor pump seal systems and predict problems.
Cavitation—Centrifugal pumps accelerate liquids to higher velocities, creating a drop in static pressure. If the liquid pressure falls below its vapor pressure, bubbles form and implode on impellers and interior surfaces. Although cavitation typically happens when pumps operate to the right of the BEP, it can also be caused by restrictions on pump suction or discharge. Cavitation and pre-cavitation can be detected by measuring pump discharge pressure, suction pressure and differential pressure across the pump strainer. All of these measurements (Figure 5) give greater visibility to the root cause of cavitation, and can often predict problems before they occur.
Figure 5: Wireless pressure sensors can measure suction and discharge pressures on a centrifugal pump to detect cavitation before it occurs.
Bearing Wear—Several factors can accelerate bearing wear. Poor lubrication, excessive motor or pump vibration, and high temperature are common culprits. Bearing temperature is often monitored because of the simplicity of measurement as compared to spectrum analysis with vibration equipment. Multi-input wireless temperature transmitters have made it affordable to bring these measurements online for early detection of increasing bearing temperature.
Vibration—Excessive motor and pump vibration are commonly caused by poor installation, shaft misalignment and bearing wear. These problems often lead to bearing and seal failure. Specialized software uses vibration and temperature data from wireless transmitters to measure frequency impacting faults—such as when metal comes into contact with metal—to give early warning of rolling element bearing faults and cavitation, both of which are a frequent root cause of seal failure.
A wireless vibration transmitter can have two accelerometers, or one accelerometer and one temperature measurement (Figure 6).
Figure 6: Accelerometers mounted on the pump measure vibration to detect early signs of bearing failure.
Detecting Deadheads—A leading cause of pump failures is running dry, or being “deadheaded.” This can be caused by clogged or failed upstream filters, by flow conditioners or by closed upstream valves—or simply by a tank level dropping below the pump pickup point. Wireless flow and level transmitters can be installed at critical locations to detect the loss of fluid to a pump.
Remote Monitoring Results
An oil & gas company’s refinery in Argentina produces 190,000 bpd, supplying 70% of the local market needs. The refinery has 120 critical pumps distributed throughout its process and auxiliary plants. Cavitation problems are its biggest issue, followed by leaking seals.
The refineryinstalled wireless pump health monitoring systems for early failure detection on the 120 pumps. The system helps detect pump problems, thereby reducing pump failures, cutting maintenance costs, and saving the refinery approximately $1 million per year.
A complete wireless pump health monitoring system can pay for itself in a matter of months. At one 250,000 bpd refinery, for example, pump monitoring systems were installed on 80 pumps throughout the complex. The implementation cost was $550,000 and the annual savings were $1,272,500, resulting in a payback period of less than six months. The savings came from decreased maintenance costs of $360,000, and fewer losses from process shutdowns because of failed pumps, valued at $912,000.
Wireless remote pump health monitoring solutions can be customized to a particular process environment and pump design. These solutions are fully scalable—ranging anywhere from one discharge pressure measurement for pre-cavitation alerts—to a complete solution integrated into a preprogrammed software package to indicate overall pump system health, provide actionable alerts and prevent downtime. Online pump health monitoring reduces production losses, cuts maintenance costs, improves safety and mitigates recordable incidents.
About the Author
Tom Bass is the Wireless Business Development Director at Emerson Automation Solutions Rosemount headquarters in Shakopee, MN, USA. Since joining Emerson in 2006, he has served in several industry focused business development roles. In his current capacity, he is responsible for leading business development for Rosemount Wireless and manages the Plantweb pervasive sensing application portfolio.Learn More
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