SWAGELOCK in Hydrocarbon/Hydrogen Service
SWAGELOCK in Hydrocarbon/Hydrogen Service
(OP)
Greetings,
Does anyone have any experience using Swagelock tubing/hoses in a hydrogen or hydrocarbon service. The operating pressure is around 45 bar and this is a pilot plant application. My concern is regarding leaking at the connections.
Has anyone had any similar problems using Swagelock?
any experience on this would be greatly appreciated.
Thanks,
Does anyone have any experience using Swagelock tubing/hoses in a hydrogen or hydrocarbon service. The operating pressure is around 45 bar and this is a pilot plant application. My concern is regarding leaking at the connections.
Has anyone had any similar problems using Swagelock?
any experience on this would be greatly appreciated.
Thanks,





RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
It is the only fitting we have found that can be used repeatedly in a make and break service. This feature is especially good for benchscale and pilot plants.
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
For hot hydrogen and hydrocarbon services, the issue is more one of thermal cycling and vibration than of simple pressure service. If the lines do not cycle from cold to hot daily, and are properly supported so there is minimal vibration transmission from compressors, PD pumps etc. to the tubing runs, Swagelok is still acceptable. However, if vibration, extreme temperatures (beyond 1000 F) and/or frequent thermal cycling are expected, there are other fitting systems which are arguably superior (Autoclave Engineers SpeedBite, Parker CPI single-ferrule) or abjectly superior but significantly more expensive to buy and fabricate (i.e. cone and thread). Cone and thread is not only more expensive and labour-intensive to build, but this technique also significantly more limited in function relative to ordinary compression fittings.
As to hoses, use extreme caution. The teflon hoses with stainless steel overbraid have a temperature dependence on pressure which is not well understood (even by Swagelok), and permeation of hydrogen out and oxygen in are also of concern. The corrugated metal hoses with overbraid are a different story, and there the same concerns about thermal cycling and vibration apply to the Swagelok ends.
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
Don't be afraid to use a thread lock or dope the ferral of the tubed fitting. Although not necessary, the thread dope literally helps with thread pickup and galling of the soft stainless steel, the grease in the ferral assists with lubricity in torsion of the metal-to-metal seat.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
The big unknown (for me anyway) is the hydrogen service. I know that hydrogen is tough to contain, and even when there is not leak path, it can "migrate" (not the correct word, but hopefully, the correct meaning) through the material itself (something related to electron/ion displacement?).
Someone more versed in hydrogen with metal, please help.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
Mike
90% of a project takes 90% of the time...the last 10% of a project takes the other 90% of the time!
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
Swagelok Compression Fittings
Swagelok and Parker compression fittings are engineered commodities. Swagelok fittings are not like the stuff they sell at Home Depot.
To assure proper makeup with Swagelok and tubing fittings by other manufacturers use a fitting gap inspection gauge. A problem occures when fitters tighten fittings excessively. Swagelok recommends finger tight plus 1.25 turns. This should be the same for the knockoffs but may not be the same for all fittings because of the different ferrule interactions. However I think that a little practice permits one to feel the tubing give as the ferrules compress the wall of the tubing. I am a fan of Swagelok with two-ferrule fittings. Single ferrule fittings are also common in hydrocarbon service. The Swagelok fittings can be madeup and disconnected several times without leakage.
Tubing
Tubing is a generic commodity. I do not know of any advantage of Swagelok tubing over other tubing. Swagelok sells tubing because they sell fittings. There are interactions to consider. The fittings must be harder than the tubing. Do not use brass fittings and stainless tubing. If the tubing and fitting material is the same the tubing should be annealed.
I think that ASTM A 269 covers most SSt process tubing. Other tubing standards include A 213, A 249 and A 632 for small bore tubing.
You need to watch the wall thickness requirements for various tubing diameters. ASME B31.3 applies. At 45 bar consider 0.035" wall thickness minimum for 1/4 increasing to 0.049" at 1/2". You need to refer to tubing pressure rating charts to select the tubing. Consider the next heavier tubing than required to accommodate corrosion, etc.
Use a catalog and careful study for hoses. I rarely apply hoses to process applications but they exist.
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
We also ran periodic hydrogen leak checks of the lab pipings using sniffers in addition to having permanently installed monitors.
Good luck.
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
And I've experienced the leaks from fittings where components were mixed from different vendors (like Chris 1982 mentions).
Compression fittings are great when installed properly.
Dan
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
The only exception was using Monel for HCl delivery.
TTFN
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
Can you expand it abit more?
"the primary cause of failed joint is in failing to butt the tube flush into the fitting before tightening the 1.25 turns".
RE: SWAGELOCK in Hydrocarbon/Hydrogen Service
Put the nut then ferrules on the tubing. Notice the direction of the ferrules when you take the connector appart. With the nut on the tubing, put the ferrules on then bottom the tubing onto the connector. Bring the nut to the threads and tighten finger tight. Hold some pressure on the tubing against the connector so that the ferrules tighten and compress the tubing. This will move the ferrules forward a bit driving a ferrule onto the tubing as the tubing is deformed.