On the design of a new machine which is to be run with a hydraulic motor, a determination of required speed and horsepower must be made so a model with suitable ratings can be selected. This article describes several methods of making such a determination.
Hydraulic vs. Electric Motor Characteristics
Designers who are experienced only in selecting electric motor drives need to be careful in designing hydraulic drives because of important differences between these two motors.
Normally, an electric motor is selected on the basis of horsepower. It is selected to match an existing power source which provides constant voltage and frequency. If it happens to be a little oversize for the job, no harm is done, although it may cost a little too much. Continue reading
by Terry Taylor, Senior Consultant, IDCON INC
Brush grades are usually classified according to the manufacturing processes and the types of carbons, graphites and other ingredients used. The 4 main brush grade families are –
Carbon-Graphite Brushes made their entrance early in the brush industry. These are generally limited to lower current densities (45 amps/sq.in.) and are used in older, slower speed motors with a maximum surface speed of 4000 ft./min. These are high friction brushes that make them very unattractive for present day use on commutators.
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Hydraulic Oil Flow through Orifices
The chart shows approximate pressure drops which may be expected at various flows rates through sharp edge orifices for petroleum type hydraulic oil. It may be used for designing limiting flow orifices in hydraulic systems. Chart values must be considered as approximate because a number of factors such as specific gravity, orifice efficiency, plumbing ahead of and behind the orifice may cause variations from the values shown.
By making the orifice with a knife edge, it becomes insensitive to temperature, and the flow and pressure drop will remain the same over a reasonable range of oil temperatures (and viscosity changes).
by Ashley Halligan
Property Management Analyst, Software Advice
A couple months ago, I wrote an article about the top five careers in facility management. I interviewed a broad range of professionals for that story. But it was during an interview with Joel Leonard, President of SkillTV, that I started to ponder what he referred to as “the maintenance crisis”–a depletion of skilled workers in the maintenance management workforce caused by baby boomers retiring and too few young professionals entering the field.
by Henri Azibert
Fluid Sealing Association
The use of variable speed drives (VSD) has become increasingly more prevalent in an effort to improve the energy efficiency of pumping systems. Efficiency is improved through the ability of the VSD to adjust the rotational speed of a rotodynamic pump and match its hydraulic characteristics to those of the system in which it operates.
Whether the mismatch was due to the variation in required pump output or incorrect sizing of the pump, there is no question that the ability to easily vary pump speed has been a major advance in the overall performance of a pumping system. This has increased the energy efficiency, as well as the reliability of the equipment. Problems—such as
cavitation or shaft deflection—can be alleviated by running the pump at optimal system speed. But how do VSDs affect mechanical seals?
by Michael Lippig
Bolts and screws are not something that occupies a lot of our reliability thoughts. After, the life of an appropriate bolt in a non-aggressive environment has been extrapolated to something like 11,000 years. Yet if you use the wrong fastener, it is bound to be very aggravating. It may not even survive its own virgin installation!
Luckily, there are some visual cues to help guide against using the wrong fastener. The following table shows grading of common US and Metric fasteners.
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by Ned Callahan
Apollo RCA Facilitator and Trainer, ARMS Reliability
“How long should an RCA take?”
This question is similar to how long is a piece of string?
I have heard one manager in a plant that has stipulated a maximum of two hours for an RCA to be conducted in his organisation. Another expects at least “brainstormed” solutions before the conclusion of day one – within 6 or 7 hours. It is not uncommon for a draft report to be required within 48 hours of the RCA. Continue reading
Continuous monitoring of the filter elements in a hydraulic system can provide valuable clues to the performance of the filter and the condition of the system. Before I discuss this, let’s consider some of the advantages and disadvantages of common filter locations in a hydraulic system. Continue reading
from Eaton / Vickers
It would be a virtually impossible task to try to document the cause and remedy of every possible fault that occur on even the simplest hydraulic system. For this reason it is necessary to adopt a logical approach to troubleshooting, in order to locate a fault as quickly and accurately as possible. Click here for pdf file.