Hydraulic, pneumatic or lubrication systems should be efficient and leak free. Sometimes, they are not, because of improper tube line routing—the result of either lack of knowledge, or corners cut on planning time, or both. What can go wrong if routing is not done properly? All kinds of things! From not being able to access fittings for efficient maintenance all the way to leaking connections, inefficient or poor tube routing can create unintended issues that need to be addressed. An ounce of planning is worth a pound of troubleshooting.
Case-in-point: A connection in a million-dollar test stand used to test transmission systems was “leaking like a sieve” according to a puzzled plant engineer. This involved two ports directly across from each other—a very short distance between them—connected by a straight routing using a large (2-inch) OD line. Everything was tightened properly, but the connections kept leaking. It turns out, vibration along the line caused the joints to loosen over time. So while the existing straight line seemed like the most logical design because it was the most direct path, actually the appropriate design necessitated adding a U-bend in the tubing and incorporating elbow fittings—providing “give” to the line. With this fix, the system no longer leaked.
Yes, planning tube line routing is a time investment, but it can have a big ROI—especially for complex systems. During system design, routing should be developed as the next step after sizing the tube lines and selecting the appropriate fittings.
Usually, when planning tube line routing, you should follow the rule that fewer joints = fewer leaks. (Makes sense, right? Minimize possible points of failure.) By following this rule, your routing design will often be less likely to leak, will take less time to assemble and maintain and will result in reduced pressure drop/turbulence. But, as the story above illustrates, simpler is not always better; the key is appropriate design for the specific application.
Here are guidelines for planning appropriate tube line routing:
So, although generally speaking you want to minimize joints, the the best (most efficient, least likely to leak) path for connecting tubing from one point to another isn’t always the most direct.
And finally, proper line routing isn’t just a matter of optimal function, but also achieving a neat appearance. You can always be proud of good design.
Tube Routing Recommendations Tweet this image
Download a print-friendly PDF version of the visual Tube Routing Recommendations shown above.
For more line routing tips, as well as helpful tips on creating leak-free systems, download Parker’s Dry Technology: The Guide to Leak-Free Connections.
With proper line routing in place, the next step is to assure adequate tube line support (aka clamping). We’ll cover this in a follow-up techConnect post.
Do you have any additional tips or stories from the field about design for tube line routing? If so, please share by commenting using the link above. If you have any questions or comments, please post them and we will respond if warranted. To talk to our techConnect engineer team directly, they can be reached at Parker Tube Fittings Division, 614.279.7070.
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Ted Amling, Sr. Project Engineer at Parker Tube Fittings Division
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