Convoluted stainless steel flexible hose
Convoluted stainless steel flexible hose
(OP)
Hi
I have a component on my turbine plant that has many high (80 bar) and low (1 bar) pressure oil hoses manufactured out of convoluted stainless steel flexible hose (304L and/or 316L). The wall thickness of the hose is about 0,4mm and it is contained within a braided stainless steel sleeve. The OEM recommends replacement every 6 years. Seems strange to recommend periodic replacement of stainless flexible hose. Rubber products Yes, but stainless steel? Can you suggest reasons why it should be replaced? Have you had any experience with failure in such hoses?
I have a component on my turbine plant that has many high (80 bar) and low (1 bar) pressure oil hoses manufactured out of convoluted stainless steel flexible hose (304L and/or 316L). The wall thickness of the hose is about 0,4mm and it is contained within a braided stainless steel sleeve. The OEM recommends replacement every 6 years. Seems strange to recommend periodic replacement of stainless flexible hose. Rubber products Yes, but stainless steel? Can you suggest reasons why it should be replaced? Have you had any experience with failure in such hoses?
RE: Convoluted stainless steel flexible hose
RE: Convoluted stainless steel flexible hose
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RE: Convoluted stainless steel flexible hose
Many manufacturers have Their quality control systems certified to the ISO standard number 9001. It is a stringent system that among other things requires a designer to document how his product could conceivably fail in service and what testing he has done to make sure it won't. The standard further stipulates that customers must be given access to these records. No more caveat emptor.
RE: Convoluted stainless steel flexible hose
RE: Convoluted stainless steel flexible hose
I know of a failure of flexible fuel lines on a ship that resulted in a disatrous fire in 1998. The cause was fatigue from pressure pulses from the fuel pump.
Do you want more info?
John.
Cheers,
John.
RE: Convoluted stainless steel flexible hose
RE: Convoluted stainless steel flexible hose
28 June 1999
D07/99
RUPTURED FLEXIBLE FUEL HOSE DISABLES RESEARCH SHIP
A worn flexible fuel hose caused a fire aboard the Australian supply ship Aurora Australis en route to the Antarctic, according to a report released today.
more...
http://www.atsb.gov.au/marine/incident/incident_detail.cfm?ID=143
The other important incident was the Westralia fire in 1998. This is an Australian Navy supply ship. The engines had 56 short s/s flexible fuel lines installed. After less than 50 hours engine time, one of these failed due to fatigue and two others showed signs of failure. There was a fire and four sailors died.
There is a picture of the failed hose - I'll try to grab it.
In both incidents, the vibration from positive displacement fuel pumps was thought to be the cause of cyclic stresses.
Cheers,
John.
RE: Convoluted stainless steel flexible hose
I was involved in analyzing an incident in which hose reinforced with stainless steel braid failed at the connector. It was learned that the connectors were mounted onto the hose by peeling the outer cover back to reveal the braiding, lubricating the end with common hand soap (!), and sliding the connection on, which was secured by swaging. Well, the soap was found to contain 2000 ppm chlorides, and the braiding was highly strain hardened, so guess what? Chloride stress corrosion failure! No surprise.
Moral of story - avoid mechanical engineers making decisions that affect material performance. No offense intended to mechanical engineers, as I would consult them for assistance in their area, but I would request that they reciprocate.
RE: Convoluted stainless steel flexible hose
Apart from the soap, is that the normal procedure for fitting the connectors?
Cheers,
John.
RE: Convoluted stainless steel flexible hose
It depends on the design of both the fitting and the hose, but for some of the high strength hose-fitting applications, you want the connector to be tied to the strengthening braiding of the hose. But here I go, straying into the mechanical engineer's realm! I forgot to mention that the joint was recovered with a polymeric shield after swaging the fitting on, but the chloride in the soap was captured in the area of the braiding.
RE: Convoluted stainless steel flexible hose
And all the experts collectively Said: "AHHHHH"