Matching a Hydraulic Motor to the Load

from Womack

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

Carbon Brushes for DC Motors and Generators

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-graphitesCarbon graphite brushes
  • Electrographitics
  • Graphites
  • Metal-graphites

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.

Continue reading →

Flow through Orifices

from womackmachine.com

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).

Continue reading

The ‘Maintenance Crisis’ & Innovations that are Changing it

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.

Continue reading

How Do Variable Speed Drives Impact Mechanical Seals?

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?

Continue reading

Blessed Bolts or Freaking Fasteners or Bolt Basics!

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.

Continue reading →

Planning and Scheduling in the Process Industry

by Josef Kallrath

Abstract
Since there has been tremendous progress in planning and scheduling in the process industry during the last 20 years,it might be worthwhile to give an overview of the current state-of-the-art of planning and scheduling problems in the chemical process industry. This is the purpose of the current review which has the following structure: we start with some conceptional thoughts and some comments on special features of planning and scheduling problems in the process industry. In Section 2 the focus is on planning problems while in Section 3 different types of scheduling problems are discussed. Section 4 presents some solution approaches especially those applied to a benchmark problem which has received considerable interest during the last years. Section 5 allows a short view into the future of planning and scheduling. In the appendix we describe the Westenberger-Kallrath problem which has already been used extensively as a benchmark problem for planning and scheduling in the process industry.    Continue reading →

 

Three Simple RCA (Root Cause Analysis) Facilitation Tips

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

Hydraulic Filter Condition Monitoring

from www.hydraulicsupermarket.com

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