Tube & hose failures
Tube & hose failures
(OP)
Our plant has several places where plastic tubing (typically Tygon) has been used to temporarily connect 2 lenghts of pipe. This has been done when piping mods were required and the pipe fitters couldn't weld or thread the pipe (due to many reasons). These are low pressure situations (<15 psi). The fitter just pushes a lenght of tubing over the pipe that will fit and uses a hose clamp at either end. We haven't had any failures yet. Neither the tubing or hose clamp manufacturer recommend doing this without using a hose barb type fitting.
I'm looking for some experience based information where someone else has done something like this and has had a failure. Tubing size and pressure type info would be very helpful. Maintenance argues that since we havn't ever popped off a hose, that it's not a problem.
Suggestions?
I'm looking for some experience based information where someone else has done something like this and has had a failure. Tubing size and pressure type info would be very helpful. Maintenance argues that since we havn't ever popped off a hose, that it's not a problem.
Suggestions?





RE: Tube & hose failures
RE: Tube & hose failures
My primary concern was putting the tubing on the pipe without using barbed fittings. The folks at Saint-Gobain don't recommend using ever using it without barbed fittings. It's obviously easier just to slide it over the pipe and clamp. One of these days, I'm going to try to find the time to see at what pressure a single clamp starts to be a problem.
RE: Tube & hose failures
The only real solution is to hold the maintenance/piping crews to the piping/tubing/hose specifications religously. The only proper place for hose usage is at the supplied utility stations using the proper hook-up connections for the service supplied at the utility station.
RE: Tube & hose failures
Through much table pounding and chest thumping, I have been able to require double clamps on any line that is not a gravity drain or vent type situation, and currently limit tubing use to 15 psig or less, or in cases on attended temporary transfers. That's the best I could do. So until we burn the plant down due to a failure, I'm afraid we will always have some tubing to contend with.
Fortunately, we haven't had any failures. The problem with this is that it is difficult to be ridgid about establishing limits, when you don't have any failures to point to. If you know of any, whether at 2am or just after the morning coffee break, I would appreciate any info you could provide (without giving away trade secrets or embarrassing details like plant manager's names).
RE: Tube & hose failures
The failure mode to expect is the hose sliding off the pipe. A pressure surge, slamming a valve shut downstream, or some other event, will eventually make it fail. It only took once for me to learn my lesson, I'll never do it again.
RE: Tube & hose failures
The boys back in the shop learned a hard lesson on this one. Luckily the plant was down for only a couple of hours, but more importantly, no one got hurt.
saxon
RE: Tube & hose failures
Saxon - You indicate max wp of hose was 200 psi. Any idea what pressure the hose was actually exposed to at failure?
graybeard
RE: Tube & hose failures
You wrote:
"Maintenance argues that since we havn't ever popped off a hose, that it's not a problem."
I suppose that counts for something, but "it's never happenned before" must be a frequent statement after the catastrophe occurs. Like "But my dog's never bitten anyone before."
Have you thought about testing a hose & clamp to determine the pressure at which it will fail? Can you ask a State or industry body to perform such tests?
John.
Cheers,
John.
RE: Tube & hose failures
How tight are the clamps? Are they torqued? Any Quality Assurance around that? What if a fitter leaves in place a loose clamp?
Incidentally, can you mention the fluids involved?
Cheers,
John.
RE: Tube & hose failures
Saxon
RE: Tube & hose failures
In my experience flex piping/tubing (that is how is referred in technicalese) made out of plastic, PTFE, rubber etc... can only be used in water and air/nitrogen service up to 75psig.
Any other service flex piping/tubing can be applied if terminated with proper tube-fittings or flanges and has an external sleeve of braided stainless steel.
Swagelok is an example of a supplier that offer all these goods.
HTH
Saludos.
a.