High Pressure/Temperature Hose Testing

[AKBen]

I'm designing a steam heat system that requires a hose. The temperature/pressure of the steam is 345 F/125 psig. The size of the hose is 4". I've located hose (steam pile driver hose) and fittings that are rated for the service described above. However, there is no empirical data on the hose-fitting assembly for the service above. The connections are 150# RF flanges. Does anybody know of a testing agency that could test my hose assembly in the service described above.

 

[jmiles]

I am a little confused, you say they are rated but there is no data? are they not fabricated to any standard?

If they are going to be part of a pressure piping system you could just always hydrotest it witht he rest of the piping, the only caution there would be to make sure you test to the cold pressure not the temperature derated pressure.

 

[AKBen]

The hose is rated, and the fitting is rated, but the hose and fitting assembly is not rated. The distributer who is assembling the fitting and hose will not issue the hose assembly without a disclaimer stating that the hose assembly is not rated for steam service. So, I need to test the hose in the actual service conditions.

 

[jmiles]

I could be wrong ehre, so id really appreciate input from someone who knows better than me, but this is what im getting.

All the parts hose fittigns connections are designed and rated for steam service.

The company selling it to you has basically said that they wont gurantee their assembly of the hose fittigns and connections.

The disclaimer does not actually mean that steam service is wrong for the materials at all.

as far as i can tell you dont actually need to do a service test just ebcause of the disclaimer, all the parts are rated for the service. so your standard hydro test of the system ebfore operation should meet all code requirements.

I think your vendor is just being weird.

Though you might want to double check that all individual parts are rated for the service, i get the feeling ytour vendor is either trying to sneak somethign past you, or is just crazy afraid of selling anythign with disclaimers on it all.

 

[AKBen]

The disclaimer does not mean that steam service is wrong for the materials, but it definately does not mean it is right.

The vendor is concerned that the hose-fitting connection will fail, which will result in a hose whipping around while spraying steam all over the place, possibly killing someone. I am concerned as well. I am not going to put a hose assembly in steam service when the vendor providing the hose assembly has a disclaimer against steam service without testing the hose assembly for steam service.

 

[jmiles]

I follow what your saying, but if the hose, and the fittings are rated for steam service, which you said they were int eh first post, and makes since since they are for use with steam pile drivers.

You are correct it would be a problem if the connection failed and the hose were to whip around spraying steam, but i really dont see what more you can do other than use a hose and fittings rated for the service.

You could secure the hose with clamps, but im assuming your using hose because you need to move it around? or is the hose purely for pipe stress? if it is the latter securing the hose in several places might give you the safety your lookign for, and large radius loops (think a sine wave) could be left int he hose to soak up any movement int he pipe.

 

[moltenmetal]

I've seen hose assemblies that are rated for high pressures at room temperature and given de-rating factors for increasing temperature by the vendor. These de-rating factors are sometimes based on very limited at-temperature tests, or tests of limited duration etc., and are therefore rather suspect. It gives one pause in using such assemblies under continuous hot service conditions, especially when the consequences of a hose failure could be very serious.

However, in this case, the hose assembly IS used in a steam application (steam-driven pile drivers), and there must be service history for this service.

I'd suggest getting the distributor to put you in touch with the hose and fittings manufacturer directly. Sometimes distributors/assemblers get in the way rather than providing useful assistance. There's somebody at that hose manufacturer who knows the answer to this question.

Mechanical safeguarding around the hose might be worthy of consideration regardless- a 4" hose can leak a lot of steam before you get a chance to do anything about it. Your geometry and application will determine what sort of safeguarding will be most practical and effective.