Archive | Motors & Drives

119

3:56 pm
February 8, 2017
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How to Start a Predictive Maintenance Program

IIoT motorsDevice and equipment advances, on display in our MT IIoT web section, is past the early adoption stage, but operations and maintenance (O&M) teams are still wrapping their arms around predictive maintenance programs. A recent interview with ARC Advisory’s Ralph Rio via SAP’s Enterprise Asset Management discusses this very issue and more.

Excerpt below:

Q: So how do people begin moving toward predictive maintenance – how do they get there?

Ralph Rio: The first thing people need to do is to educate themselves to understand what is available from a technology standpoint. People just entering this area are no longer “early adopters” so there is plenty of information out there. Get comfortable with the platforms and the business processes.

Sometimes technology education is coming from your machine builder (OEM) with improved data acquisition capabilities. From this post, “Are Smaller IIoT Applications The Next Wave for End Users?” and discussion with Erl Campbell at Aventics, MT found out how this is working:

“By actually monitoring the spool position, the machine can track exactly how each valve performed during a motion cycle: where that valve started, whether it fully shifted or only partially shifted, and its final position. These data points help machine builders and end-user operators correct issues that may affect overall packaging quality and integrity,” the white paper states (written by Erl Campbell.

Campbell added in a recent interview that the company is working on whether the (valve) reliability data should communicate with the factory floor or maintenance. Is it going to be some kind of wireless communication or will techs plug into the manifold and download that data?

>> For more on how to create a predictive maintenance program with Ralph Rio

1601Iot_logoFor more IIoT coverage in maintenance and operations, click here! 

207

9:40 pm
January 13, 2017
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Properly Align Variable-, Fixed-Pitch Sheaves

Aligning sheaves on equipment with multiple V-belts is more complex than aligning them on machines designed with single belts.

Aligning sheaves on equipment with multiple V-belts is more complex than aligning them on machines designed with single belts.

Variable-pitch sheaves are frequently used in air handlers. According to a blog post by Stan Riddle of VibrAlign (Richmond, VA, vibralign.com), they allow design engineers to increase or decrease the speed of the driven machine and, thus, provide:

• changes in motor amp draw to maximize efficiency

• increased or decreased static pressure and air flow.

Normally, a design engineer will specify the use of a variable-pitch sheave on the driver and a fixed-pitch sheave on the driven machine.

Performed on a single-belt machine, proper sheave alignment is simple, if a good sheave-alignment tool is used. When multiple belts are used, as they often are, proper sheave alignment can become more complex. A variable-pitch sheave can be adjusted to increase/decrease the sheave diameter. However, doing so also changes the sheave width, depending on the adjustment.

In his post, Riddle referred to a customer who was attempting to perform a sheave alignment on an air handler. The unit’s motor had a variable-pitch sheave, but the fan sheave was fixed. The customer stated that he could align one belt, but not the other.

As Riddle described it, the customer was struggling because the width of the fixed-diameter sheave was 1 5/8 in., but the width of the variable-pitch sheave was 2 3/8 in. Consequently, only one set of grooves could be aligned, meaning the other was out of alignment.

The key to properly aligning a variable-pitch sheave to a fixed-pitch sheave on equipment with multiple V-belts is to split the difference between the diameter widths of the two sheaves. In this example, splitting the difference between sheave-diameter widths of 2 3/8 in. and 1 5/8 in. would result in a 3/8-in. offset at each groove.

The key to properly aligning a variable-pitch sheave to a fixed-pitch sheave on equipment with multiple V-belts is to split the difference between the diameter widths of the two sheaves. In this example, splitting the difference between sheave-diameter widths of 2 3/8 in. and 1 5/8 in. would result in a 3/8-in. offset at each groove.

The solution

Riddle wrote that the solution to the customer’s problem was simply to split the difference between the width of the two sheave diameters, as shown in the following equation:

2 3/8 in. – 1 5/8 in. = 3/4 in. ÷ 2 = 3/8 in. offset on each groove

randmRiddle also noted that it’s important to keep in mind this approach will probably not align the components sufficiently to eliminate sheave and belt wear. In fact, such wear can’t be eliminated. Still, when it comes to aligning multiple V-belts on an equipment system, splitting the difference between the diameter width of a variable-pitch sheave and that of a fixed-pitch sheave to which it is aligned will make the belts wear evenly.

Variable-pitch sheaves are normally used to balance a system and achieve proper static pressure and speed. When that’s determined, according to Riddle, the variable-pitch sheave should be replaced with a fixed-pitch sheave of the proper diameter to match the desired speed and pressure. Once both sheaves are fixed-pitch, proper alignment can be achieved. MT

—Jane Alexander, Managing Editor

Stan Riddle, a technical trainer for VibraAlign, has spent more than 36 years aligning industrial machinery. For more information from him and other technical experts with the company, visit vibralign.com.

341

8:05 pm
January 13, 2017
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What’s Three Minutes of Motor Testing Worth?

Personnel at the motor-distributor’s service center used an AT5 to perform a de-energized, non-destructive motor-circuit-analysis test on the hospital’s failed motor. This type of analysis evaluates the condition of electric-motor connections, stator, and rotor.

Personnel at the motor-distributor’s service center used an AT5 to perform a de-energized, non-destructive motor-circuit-analysis test on the hospital’s failed motor. This type of analysis evaluates the condition of electric-motor connections, stator, and rotor.

A non-destructive technique offered payback by determining the root cause of a critical, repeatedly failing hospital motor.

A motor distributor in The Netherlands provided a 17-kW, 400-V motor to a local hospital in 2015. The hospital rented a portable crane to install the motor on the roof, where it was used to operate a fan. In the spring of 2016, the motor suddenly failed.

Challenge

When the motor first stopped running, the hospital’s maintenance technician had reset the unit’s variable-frequency drive (VFD). Although the motor restarted, the VFD shut it down once again.

The technician then performed an insulation-to-ground test and determined the motor winding wasn’t shorted to ground. Using a digital multimeter, he measured phase resistance and learned the phases weren’t open. Since the motor testing tools indicated a “good” motor, a decision was made to replace the VFD.

After the new VFD was installed, the motor started, but, much to the technician’s chagrin, didn’t continue running. It was at this point that the hospital reached out to the motor distributor, which promptly dispatched a technician from its service center to test the motor.

The service-center technician used a meg-ohm meter and DMM to determine that the motor wasn’t grounded and the phases weren’t open—the same as the previous findings by the hospital’s maintenance technician. Given these results, the decision was made to replace the motor. The new unit started and operated normally, confirming the new VFD was working as intended. The “suspect” motor was sent to the distributor’s service center for a more thorough inspection.

This figure shows the stator and rotor signatures from the motor-circuit analysis report, with phases listed at the top of the image.

Fig. 1. This figure shows the stator and rotor signatures from the motor-circuit analysis report, with phases listed at the top of the image.

Solution

At the service center, personnel used an All-Test Pro 5 (AT5) to perform a de-energized, non-destructive motor-circuit analysis (MCA) test on the failed unit. This type of test evaluates the condition of motor connections, stator, and rotor.

Using the AT5, connections were made to the three phases of the motor and a static test was performed. Next, the motor shaft was manually moved during the dynamic portion of the three-phase test. At the end of the test the instrument indicated the results shown in Fig. 1. This testing made it clear phase 2-1 (shown as “21” in the figure) had the problem.

Lessons learned

Owners/operators can reduce maintenance costs. A 17-kW, 400-V motor is not expensive, but when it is mounted on a roof and the owner has to rent a crane to lift that motor for installation and removal, the owner’s maintenance cost can become quite high. Had the hospital’s maintenance team used an effective motor-circuit-analysis device, they would have discovered that the motor was the bad actor, not the VFD. Many hours and dollars were wasted by ordering and installing a new VFD that had not been the true cause of the problem.

Distributors and suppliers can improve quality assurance. Motor distributors and suppliers should implement an additional quality-control measure prior to delivering new or off-the-shelf motors to their customers. Spending a few minutes to check the condition of motors will help distributors and suppliers avoid warranty issues and increase customer satisfaction. MT

To learn more about motor-testing tools and techniques from All-Test Pro (Old Saybrook, CT), visit alltestpro.com.

351

6:02 pm
December 22, 2016
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Understand How Temperatures Affect Gearboxes

Environmental factors can significantly affect gear-drive service life and maintenance costs. Temperature and temperature variations are at the top of the list.

Environmental factors can significantly affect gear-drive service life and maintenance costs. Temperature and temperature variations are at the top of the list.

Understanding the impact that the environment can have on the long-term well being of gearboxes is key to keeping them healthy. According to experts at Philadelphia Gear (philagear.com, King of Prussia, PA), environmental factors can significantly influence gear-drive service life and associated maintenance costs. A white paper from the company offers tips on how to deal with several of those factors, including temperature and temperature variations.

When choosing lubricating and cooling oil for a particular gear-drive application, consider viscosity under normal and “cold iron” conditions. The viscosity must be capable of providing adequate oil film to support gear-tooth and bearing loads under all operating conditions. When a gear drive is in the “cold iron” state, viscosity must be low enough so that during the unit’s operation, the splash-lubrication or force-feed lubrication system is capable of distributing the proper amount of oil to where it’s needed. If oil is too thick (due to the cold), there may be no splash, or the pump in a force-feed-lubrication system might stall, thus failing to supply oil to critical surfaces.

Several oil characteristics must be taken into account when selecting products for specific applications and temperature differentials. Some formulations have a flatter temperature index than others, meaning that, as oil temperature increases, viscosity will decrease at a lesser rate than comparable fluids. For example, synthetics have a flatter temperature index than mineral-based oils and, at a low temperature, will be less viscous than similar-viscosity mineral-based products.

Many locales, of course, experience severe temperature swings from summer to winter that can dramatically affect oil viscosity. Sites in such regions should change to different-viscosity products as seasons change. Oils that aren’t changed out seasonally could thin to a kerosene-like consistency in severe summer heat, and thicken to a molasses-like substance in frigid winter cold. Either scenario puts gear drives at risk. (NOTE: To help overcome environmental extremes, oil heaters are often employed to maintain a minimum oil temperature of 40 F to 50 F during colder months, and air-to-oil or water/glycol-to-oil coolers are used to control oil operating temperatures during extreme heat.) MT

randmMore Points to Ponder

When gear operation generates higher-than-normal operating temperatures, mineral-based oil can break down and lose some of its lubricating capability. Over time, this deterioration can cause the fluid to separate into its constituent organic parts, i.e., carbon, hydrogen, and oxygen in various chemical combinations. In such cases, the carbon manifests as fine grit that can be introduced into the oil. If this condition persists and the sludge approaches the thickness of the oil film between gear and bearing components, a loss of film can be expected. This situation, in turn, could result in metal-to-metal contact between gears and bearing components, eventually leading to gearbox failure.

Extreme Pressure (EP) mineral oils, in particular, contain additives such as phosphorous and sulfur, that enhance the products’ ability to support load, but, when broken down, introduce additional, potentially corrosive and abrasive, materials into the mix. Thus, when using EP oils, it is extremely important to monitor the oil through periodic sampling.

While the additives in EP products increase load-carrying capacity, they can be depleted over time. In that event, such oils no longer exhibit their original load-carrying capabilities. How can you tell if this is happening/has happened? Extended gearbox operation with EP oil that has lost its load-carrying capabilities can result in gear-tooth overload symptoms such as pitting.

— Jane Alexander, Managing Editor

For more information from Philadelphia Gear’s experts, and/or to request a copy of  “The Impact of Environmental Conditions on Gearbox Lifecycle,” (the white paper on which this article is based), visit philagear.com.

186

5:55 pm
December 22, 2016
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Gaps in Your Motor Reliability Program?

Quality control, trending, and troubleshooting are three keys to a successful motor-reliability program.

Quality control, trending, and troubleshooting are three keys to a successful motor-reliability program.

Businesses invest millions of dollars in what they believe will be a fail-safe maintenance program for their electric motors, according to Noah Bethel, vice president, Product Development for PdMA Corp., Tampa, FL. Regular tests are scheduled for each motor; engineers dutifully record the data, when required, and then move on to the next motor.

Collected data is meaningless unless it is analyzed. But, frequently, analysis is nonexistent. When your motor reliability is in question, there could be many reasons including safety issues, quality control, and storage. Motor experts Bethel and Wayne Pilliner, CMRP, The Mosaic Co., Plymouth, MN, say there are three keys to motor reliability:

Quality control. Spend time in the motor-repair shop monitoring the activity.

Trending. Collect data, take advantage of new technology, and remember that trending is your friend.

Troubleshooting. There is an end of life for everything. Get ahead of that. Have a casualty procedure and follow it. Alleviate time delays.

randmDuring the 24th Annual SMRP Conference, held Nov. 2016 in Jacksonville, FL, Bethel and Pilliner presented more tips on avoiding gaps in your motor-reliability program. The first question to ask, they advised, is “Where is your motor-maintenance program?”

Bethel emphasized that it is also important to develop a good business case. This is critical to get buy-in from management for equipment-improvement initiatives, he said.

More questions to answer

• What is the problem?

• What is the gap?

• What is the financial impact?

• What are the goals and objectives?

• What are the roles and responsibilities of the motor-maintenance team? Ensure that these are clearly defined.

• What is the return on investment? Make calculations and predictions for an expanded time period.

The strategy is also something that should be clearly defined. Consider these proven motor-maintenance-strategy process steps:

• Maintain an accurate list of the motors you have in stock and the ones you need to order.

• Identify the criticality of every motor.

• Determine motor-failure modes based on past history.

• Assign corrective actions to prevent established failure modes.

• Develop a sustainable program to ensure compliance.

• Set testing standards and tailor them for your site.

Bethel and Pilliner described several case studies in which this approach helped companies determine the gaps in their motor-reliability program. Look at the gaps as opportunities to learn and improve, they said. Once gaps are identified and a strategic plan is in place, motor reliability at your facility will improve.

Key tips

• Success is dependent on buy-in from stakeholders.

• Motor-testing compliance is greatly improved with M-tap installation, compliant with the 70E standard.

• Put a fundamental maintenance program in place to complement the motor-testing protocol.

• Ensure motor-testing technicians are trained in the technology.

• Knowing the condition of your motors enhances your workflow process. This can result in significant savings from an efficiency and cost-of-failure point of view.

“Productive and long-lasting operation of motors in today’s business environment is the reason for the development of advanced technology and site procedures to increase reliability and assure a quick return to productivity in the event of troubleshooting and repairs,” Bethel said. “The transition of data to usable information becomes more efficient when the analyst has help to make the right decisions.” MT

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