Advanced motor protective relays provide superior protection for motors and pumps.
For years, motor overload relays have been used to protect pumping systems. Traditionally, they monitored current to protect the motor and relied on separate electromechanical sensors, such as flow meters or pressure gauges to protect the pump.
Today, advanced motor protective relays are able to provide superior protection for not only the motor but the pump as well by monitoring under-power conditions, which are a direct linear interpretation of pump performance.
The increasing intelligence of electrical controls is shifting knowledge from mechanical systems to electrical controls, essentially following the flow of data.
In pumping applications, today's advanced motor protective relays provide a spectrum of real-time performance data and diagnostics, helping facilities save energy, optimize maintenance and extend equipment life.
Further, they have such a degree of flexibility that the user is able to customize the level and type of protection depending on how critical the equipment is to the process.
Every motor of any value needs an overload relay. Today's overload relays have evolved significantly from traditional overload protection. Advanced overload relays provide continuous data on motors and pumps.
Since they reside in the motor control center or in pump houses, they are able to communicate on standard industrial protocols and tie into SCADA, PLC and DCS systems.
Using the data provided by the relay, maintenance teams can be scheduled when changes are detected and before downtime occurs, enabling optimized use of personnel time.
With real-time, remote, continuous information, end users are able to identify a potential issue before it causes downtime or wasted energy, and maintenance can be targeted at real or detected variations.
Extend Life & Avoid Deadhead
Advanced overload relays provide remote data monitoring of a host of parameters. The goal of this information is to prevent the failure of a motor or pump asset. Overload relays can act on their down data with a host of flexible protection settings.
Specifically, the low-power protection configuration is designed to protect the load or (centrifugal and submersible) pumps from starved and deadhead conditions, which are common causes of pump and pump seal failure. In such a situation, overload relays, performing as pump-off relays, can shut down the pump, extending equipment life and reducing downtime and maintenance expenditures.
This low-power condition occurs when real power provided to the motor or pump falls below the normal operating conditions, which is caused by a deadhead or starved pump.
A dead-head situation occurs when a pump continues to run against a mostly closed valve.
A starved condition occurs when a blockage occurs upstream of the pump or if a submersible pump runs dry. These situations can cause mechanical failure by excessively heat aging expensive pump seals, which in-turn fail and cause leakage.
Without an advanced overload relay with low-power detection, the pump would continue to run, because a float limit switch would not drop because the water level would not decrease. A second pump would likely be turned on to compensate. In other words, two pumps would be running and performing the work of a single pump. Meanwhile, the seal of the first pump would be heat aging, shortening its life.
Today, this situation can be monitored, detected and avoided. Wasted run-time hours can be prevented, with the protective fault, under-power feature. The overload relay would take the first motor offline, and the second pump would come online and complete the pumping activity.
Additionally, the wear and tear on components would be reduced, as the overload relay would have taken the first pump offline, avoiding the heat aging of the seal. Maintenance and energy consumption would also be reduced by avoiding a total failure of the first pump and running two pumps to do the work of one.
Optimize Maintenance
Tapping the monitoring capabilities of today's overload relays, maintenance can be optimized. This means scheduled downtime, unnecessary inspections eliminated, labor skill sets optimized, reduced service time.With a remote view of the performance of a motor or pump, maintenance can be optimized and costs can be reduced.
Advanced overload relays enable personnel to check motor or pump operation from any computer in a plant or facility and even from home. Trending data collection allows for the detection or prediction of potential failure conditions. Further, when conditions indicate an imminent failure, operators can switch to spare or secondary motors or pumps to avoid downtime.
Intelligent pump, motor and line quality monitoring arms operators with the information that they need to only send personnel when data indicates an issue, which eliminates unnecessary inspections. With an understanding of the fault type or pending fault type, individuals are sent who have the appropriate experience and expertise to address the defined issues. Additionally, an understanding of fault type enables personnel to come equipped with the appropriate tools, which can reduce service time.
Improve Energy Efficiency
Overload relays that monitor power factor and energy can help:
- Avoid peak demand charges
- Shed non-vital loads
- Identify and rectify increased consumption over time
- Identify a discrepancy between equal loads
- Identify power factor line items
Today's advanced overload relays allow for the staggered and deliberate starting of motors and pumps after power loss.
This prevents numerous loads from coming on simultaneously, facilitates successful startup and avoids peak demand charges. Overload relays with advanced power monitoring and flexible communications capabilities allow for the observation of abnormal and inefficient operation in real time.
For across-the-line loads, they are able to do more than protect the motor. They let end users see consumption at the specific load—something that used to be reserved to expensive meters on groups of motors.
With an individual look into each motor, operators can catch increased consumption in real time, control it and prevent it.
Using a power-monitoring-equip-ped overload relay, system inefficiencies can be monitored with side-by-side comparisons of similarly-sized assets as well as comparisons on a single asset made over time.
Such situations prior to the use of a power monitoring overload relay would often go unnoticed and result in higher utility bills. Further, commands over numerous fieldbus networks allow remote or programmed shutdown of non-vital assets.
Many facilities must run continuously, and all operations want to run efficiently. So, being able to prevent equipment failure and schedule downtime to address detected problems is critical.
Continuously monitoring key failure indicators with remote monitoring solutions helps maintenance and operation teams respond to equipment problems sooner. The early detection of system degradation is crucial to productivity and the bottom line.
Overload relays with advanced remote monitoring and power capabilities can yield significant energy and cost savings while improving system reliability and reducing maintenance.
Pumps & Systems, May 2011
