The 4-20mA current loop is used to transmit analog data representing various process variables like level, pressure, temperature or flow. Although conceptually simple, a 4-20mA current loop can be tricky to troubleshoot. Current flows in a single direction through each device in the loop.
An 1,800 MW power station in the Midwest experienced constant trouble with four of its four-stage boiler feed pumps, which were driven by steam turbines and operated at variable speed to meet the required plant load.
Vertically mounted pumps can resonate as a total structure in a "rocking" mode, as shown in Figures 1 and 2 below. This is one of the toughest unsolved vibration problems at several plants.
Qualified, quality solution providers can resolve many aftermarket problems.
Even though control technology has become an integral part of many pumping systems, over half of our readers have not expressed much interest in pump controls. I think I know why - today's controls are simply not as intuitively understandable as they once were. Who wants to read about the advantages of PID control without a basic understanding of P, I, and D itself?
One electrical equipment specialist is relying on a cleaning system to ensure that a variety of stamped and turned parts are thoroughly degreased at their production facility.
Lindmore Irrigation District uses Ethernet radios to improve SCADA communications system and pumping efficiency.
Last month, we ended our discussion of proportional control by saying there are times when P alone cannot provide the accuracy required by a process. Take, for example, a constant pressure booster system under VFD control. If changes in flow and the resulting change in pressure occurred gradually over a long period of time, the VFD could use proportional control to keep pressure constant.
Frequency analysis is an important method of vibration analysis.
It required only a couple notes of the haunting soundtrack to signal an imminent shark attack in the movie Jaws. As the theme began to swell, it became obvious that someone was going to “get it.” It would be nice to have a sixth sense that allowed us to hear "warning" music in daily situations. Condition monitoring systems provide a means of sensing when sharks are skulking toward your critical machines.
Cavitation is a destructive condition that can destroy the inside of a pump before you even realize it is occurring. Early detection can minimize damage, reduce downtime, and save money. Cavitation involves the creation of bubbles formed when the fluid being pumped vaporizes due to a decrease in pressure as the fluid enters the pump. These bubbles are then acted on by the pump impeller, causing them to implode.
One of the most neglected tools in the vibration analysis toolbox is phase. This neglect is partially due to the extra time and effort often necessary to collect the information. Many analysts are also not properly trained in phase measurement and analysis.
In the past, the nuclear power industry has experienced equipment failures due to improperly set oilers. There was never a precision tool available to help ensure the level was being properly set on a typical oiler . . . until now.
When measuring vibration, one of the most important factors in obtaining accurate information involves selecting the proper vibration transducer. Selecting the wrong vibration transducer can yield results that are misleading or, worse, mask a problem.
PWM inverters introduce motor shaft voltages and bearing currents. The bearing damage in inverter-driven motors is mainly caused by the shaft voltage and bearing currents created by the common-mode voltage and its sharp edges . All inverters generate common-mode voltages relative to the power source ground that cause coupling currents through the parasitic capacitances inside the motor. The main source of bearing currents is the capacitance-coupling currents that return via the motor bearings back to the ground.
When the City of Delaware, Ohio, expanded its wastewater treatment plant, it looked to increase more than just capacity. It also wanted to increase its efficiency and automation capabilities to benefit the plant's operators and taxpayers.
Mechanical pressure gauges, which require no external power, provide an affordable and reliable source of accurate pressure measurement. Using the criteria below can help maximize gauge life.
Sensors and automation passively participate in our everyday lives to improve comfort, add safety and reliability, and increase the efficiency of needed products and services.
Changing traditional industry ways of thinking can help usher in the plant of the future.
In only a couple of years, the focus on energy efficiency has gone from blurred to steely-eyed. Green business practice is now a necessity, and organizations must find the best way to transition to this new reality. There are many opinions and approaches on "how we get there," and each one will have its own merits. A journey of a thousand miles starts with a single step, and making the right steps in the beginning will hasten the achievement of energy efficient goals.
Soft starters and VFDs are useful for extending equipment life in HVAC applications.