HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Blogs
Guest Blogs

Fluid Power Systems: The Hidden Giant

NO RATINGS
View Comments: Newest First|Oldest First|Threaded View
GlennA
User Rank
Gold
Nomenclature
GlennA   6/20/2012 8:43:31 AM
NO RATINGS
An unloading valve is not the same as a relief valve or a regulating valve.  From my training:  An unloading valve is used to direct all flow from the pump to the tank at low pressure to reduce heating, and to allow the electric motor / pump to start under no-load.  A relief valve is used to control maximum system pressure.  When the maximum pressure is reached, the valve opens to direct flow to the tank without reducing the pressure.  A pressure reducing valve, also called a regulating valve, is used to reduce pressure to a segment of the system.  Not everyone that works in hydraulics agrees with the nomenclature that I learned.

Instead of a variable speed motor, I have seen pressure and flow compensating pumps that have a swash plate that is adjusted to reduce the flow from the pump without affecting the pressure, at a constant electric motor speed.

crob09
User Rank
Iron
Re: hydraulics vs working applications
crob09   6/19/2012 4:44:37 PM
NO RATINGS
No you still need an "unloading valve" or Bypass valve, no different from an electric forklift. The PTO is variable speed and the unloading valve is still necessary when the load is too great, or if the cylinder has reached it's maximum travel. Otherwise you would burn out the PTO or motor.

Rob

http://www.whatisacnc.com

Alex.W
User Rank
Iron
Re: hydraulics vs working applications
Alex.W   6/19/2012 1:51:55 PM
NO RATINGS
I think the variable speed drive would negate the need for an unloading valve, assuming there were no other loads requiring driving while this subset of the machine is in standby.

TJ McDermott
User Rank
Blogger
Each has its place
TJ McDermott   6/18/2012 1:57:58 PM
NO RATINGS
Hydraulic vs. Electric is not a winner-take-all competition.  Each has roles in which it is better suited.  One of my customers offers products that use either one or the other as the prime mover, depending on application.  It means more engineering work for my customer, but their end users are happy with a solution that fits their needs, rather than adjusting their needs to fit a single solution.

 

GlennA
User Rank
Gold
hydraulics vs working applications
GlennA   6/18/2012 9:34:11 AM
NO RATINGS
Hydraulic robots have become few and far between (in my experience).  The rationale that I was told was because of the automotive industry.  Automotive is a big user of robots.  When robots were hydraulic, 3 (sometimes 4) trades were required to work on them.  The electrician for the controller, the millwright for the hardware, or for tooling issues (sometimes a tool-maker also), and a plumber for the hydraulics.  The all-electric robot eliminated one trade from that group.

The manipulator arm on the Space Shuttle was a 'hydraulic' application = high torque and low speed.  Clean-room issues i.e. hydraulic oil leaks would have been a problem.  A broken wire does not 'leak' electricity in the same way a broken hose would leak oil.

One thing that I think is missing from your hydraulic system is the unloading valve.  Many of the machines that I have worked on had an unloading valve to direct flow to the tank at low pressure to reduce heating when the system was in standby.

Partner Zone
More Blogs from Guest Blogs
The age of touch could soon come to an end. From smartphones and smartwatches, to home devices, to in-car infotainment systems, touch is no longer the primary user interface. Technology market leaders are driving a migration from touch to voice as a user interface.
Soft starter technology has become a way to mitigate startup stressors by moderating a motor’s voltage supply during the machine start-up phase, slowly ramping it up and effectively adjusting the machine’s load behavior to protect mechanical components.
Despite the astronomical benefits offered by 3D modeling, it is quite surprising that nearly 75% of the manufacturing industries still perform design operations using 2D CAD systems. What is the reason that keeps companies hesitant from adopting 3D technology?
Energy harvesting in particular seems to be moving at an accelerating pace. We now seem to be at a point where it is possible to run low-power systems primarily from energy harvesting sources. This is a big shift from even just a couple of years ago. Three key trends seem to have accelerated this dramatic shift.
ABI Research, a firm based in the UK that specializes in analyzing global connectivity and other emerging technologies, estimates there will be 40.9 billion active wirelessly interconnected “things” by 2020. The driving force is the usual suspect: the Internet of Things.
Design News Webinar Series
3/31/2015 11:00 a.m. California / 2:00 p.m. New York
2/25/2015 11:00 a.m. California / 2:00 p.m. New York
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
5/7/2015 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
May 4 - 8, Designing Low Power Systems using Battery and Energy Harvesting Energy Sources
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Last Archived Class
Sponsored by Proto Labs
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2015 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service