Steam and static discharge.

[v8landy]

Hi

We regularly use Nitrogen from trasfer of material from one vessel to another via pressurisation of the vessel to trasfer along the pipe.

A project I am working on has highlighted that the opperators always combine the 5bar Nitrogen with the 9bar steam to speed things up!!!

I have read many instances where steam /condesate has been linked to static discharge leading to explosions in flamable atms.

But would the same be true of what my operators are doing with 5 bar Nitrogen and 9 bar steam?

Safe solution open to me is just incease nitrogen to 10Bar.

 

[gr2vessels]

The static generated by the steam is usually grounded immediately via metallic piping;- it could be an issue with plastic piping, with no grounding facility to the metallic braid of the hose ( you still could insert metallic connectors between lengths of piping, grounded to the plant grid). If you discharge Nitrogen / steam in an explosive mixture, then to be on a safe side, prevent the build-up of static with continuous metallic piping, grounded to the plant grid. Make sure to use bridges accross flanges to ensure electrical continuity, also no screwed connections!
If money is no object, look at the high tech static dissipative plastic materials to solve your concerns. However, if you can pressurize the Nitrogen to 10 bar, that's the best solution.
cheers,
gr2vessels

 

[itdepends]

They can't actually be pressurising up to 9bar- or they wouldn't be using any nitrogen at all. Increasing the nitrogen pressure won't necessarily fix the problem either.

You need to understand what pressure they are actually doing the transfer at- and what the volume limitation is on the nitrogen system at that pressure. I'd suspect they're using the steam to provide additional volume rather than pressure.

 

[v8landy]

Hi Itdepends.

Yes you are correct, they are not pressurising upto 9 bar.

Pressure is genarally about 2 bar and trasfer takes about 10 mins when both steam and nitrogen are being used.

When only either steam (@9 bar) or Nitrogen (@5 Bar) are used it can take upto 20 mins.

 

[itdepends]

When they use only nitrogen or only steam- do they also get to ~2bar? i.e. does it just take them longer to generate the required pressure when using (only) steam or nitrogen?

 

[v8landy]

Hi Itdepends

Yes it just takes them longer when they one only one of either steam or Nitrogen. 20 mins vers about 5/10 min

 

[itdepends]

In that cuase I'd suggest investigating the flow limiting components of the nitrogen system rather than increasing the pressure.

Chers

 

[v8landy]

I see what you are saying. If our nitrogen system can not keep up with the required demand that could be the cause rather than lack of pressure. And increasing pressure might not have any effect.

 

[mbt22]

As an aside, I assume from the fact that this question is being asked that the system was not designed to use steam for this. Is there an additional issue around management of change that needs to be looked at?

 

[v8landy]

Managment of change is also been looked at. This notification that both steam and nitrogen are being used only came about when operators where asked to record trasfer data, I happened to include tick boxes for, one for Nitrogen, and one for steam.

We recived the complted sheet back, and all times, both nitrogen and steam had been ticked.

Operators being operators! we asked them to confirm their actions, and yes they do both because "it is faster"