SWAGELOCK in Hydrocarbon/Hydrogen Service 1

[SAeng]

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,

 

[Ashereng]

Many of my clients use "Swagelok" products, from tubing, compression fittings to manifolds and others, in hydrocarbon service. It is very common. Many clients have standardised on Swagelok, "without equivalent".

"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?

 

[unclesyd]

Swagelok is our site standard. Our bench scale labs and pilot plants use "Swagelok" as the standard, in fact the labs will not permit any other fitting except Autoclave Engineers fittings in the labs. In the plant it used for all process materials including H2.

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.

 

[JLSeagull]

Many companies use Swagelok knockoff products for general instrument hookups - and still require Swagelok - no equal for process analyzers.

 

[moltenmetal]

Swagelok compression fittings are fine for cold hydrogen, hydrocarbons and combinations thereof to the limit of the tubing. There is lots of industrial experience out there showing this, from laboratory and pilot units to impulse lines on instrumentation on commercial plants.

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.

 

[Cockroach]

I've never experienced a problem with Swagelok in the oil & gas applications, hydrocarbon liquid or gas as the working fluid, sweet or sour. You will need to follow the manufacturer's recommended procedure for tubing make-up.

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

 

[Ashereng]

In "average" oil and gas, both plants and upstream, Swagelok is very common, and not much problem if you follow the manufacturer's guidelines and ratings and such.

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?

 

[mikeg8]

I have used SwageLok components for over 10 years on hydrogen lines of 1" and smaller and never yet had a problem. Pressures were never more than 6barg admittedly, but fittings are repeatedly made/un-made with no problem. I have never 'doped' a ferrule, indeed the only leaks I've ever seen have been when someone has! Use a silver-bearing grease on stainless nut/fitting threads to avoid galling and don't over-tighten.

Mike

90% of a project takes 90% of the time...the last 10% of a project takes the other 90% of the time!

 

[JLSeagull]

Hydrogen and hydrocarbon applications typically use type 316 stainless steel tubing and fittings. The Swagelok responses have not addressed this point. I think that Shell requires Inconel alloy 825 for process tubing in refineries. Swagelok sells alloys like monel, brass and plastic fittings too.

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.

 

[chris1982]

I ran a test lab, including hydrogen vaporization units, for a fuel cell company. We used swagelok exclusively. Proper joint makeup and avoiding mixed stock (Parker A-lok, etc) are important. The Parker A-lok system is similar to Swagelok and similar in price. Again - the key is not to mix vendor parts.

We also ran periodic hydrogen leak checks of the lab pipings using sniffers in addition to having permanently installed monitors.

Good luck.

 

[danw2]

I can re-iterate from personal experience the point that JLSeagull makes: installation is critical to proper performance. The installers need to be trained (if they haven't already) in the proper assembly and tightening of a compression fitting.

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

 

[DiegoMartinez]

As you see, everybody is supporting Swagelock fittings and tubings. We are using them in the gas plant as well on a line with 24,000KPag service. No worries at all!

 

[IRstuff]

Swagelok 316SS piping is, or at least was, used extensively in the semiconductor industry to pipe O[sub]2[/sub], H[sub]2[/sub], ammonia, methane, etc.

The only exception was using Monel for HCl delivery.



TTFN

 

[KiwiMace]

As a former Instrument Tech with thousands of swagelok joints to my name, I must say that the primary cause of failed joint is in failing to butt the tube flush into the fitting before tightening the 1.25 turns. I've let a few slip, but you usually find them if you make it a habit to completely part the joint before retightening.

 

[DiegoMartinez]

CinciMace,

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".

 

[JLSeagull]

Cut the tubing square. This is automatic with tubing cutters but not if done with a saw. CinciMace is only pointing out that the end of the tubing needs to touch the connector when you begin tightening.

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.