I'm not going to say it's a thing specific to just excavators, but the majority of them I've worked on, of all brands and sizes, have port reiefs on them. That said there is also a main system relief on them also that protects things like the pumps, etc from over pressurization. Even then some of the main reliefs are designed in such a way that pilot pressure is directed to the top of them to increase their setting when a function that requires a higher than normal pressure is activated. I've seen this happen on the travel function on the ones that have it. The main relief on a system is located within the valve body and is prior to te valve spools for the individual functions. Like I said it's main purpose is to protect the pump. With the port reliefs they are located on the downstream/function side of the valve spool. This is done in order to protect the cylinders and structure of the function. For instance the port relefs on an excavator would allow a pressure spike from something like a rock falling into the bucket or onto the end of the dipper to dissipate back to the tank instead of bending the rod on a cylinder or breaking a weld on the boom.
Like I said, in the most basic terms, the main relief is designed mainly to protect the pump and supply side of the system. The port reliefs are designed to protect the individual functions.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - Third Brush Generators - by Chris Pratt. While I love straightening sheet metal, cleaning, and painting old tractors, I use every excuse to avoid working on the on the electrics. I find the whole process sheer mystery. I have picked up and attempted to read every auto and farm electrics book with no improvement in the situation. They all seem to start with a chapter entitled "Theory of Electricity". After a few paragraphs I usually close the book and go back to banging out dents. A good friend and I were recently discussing our tractor electrical systems when he stated "I figure it all comes back to applying Ohms Law". At this point
... [Read Article]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
