Steaming, where?

[shahyar]

In which cases we are thinking about steaming out, and prepare provisions for that in designing pipes and tanks?
I have seen them in oil and oil/water lines. What is criteria for that? do we need them for all oil lines? (even with high API gravity ones?)
Thanks for your replies.

 

[SeanB]

In general practice, any line containing a hydrocarbon should be steamed out. With this in mind, the pipe should be specified for an external pressure of at least 1/2 vacuum. Normally I just specify full vacuum.

 

[roker]

hello,

this demand for steaming out is usually coming from the production people before handing over lines or equipment for maintanance. in the oil industry it is a general practice but can be used also in other fields, vessels and other equipment are designed to full vacuum.

regards,
roker

 

[unclesyd]

In a chemical plant.

We have two areas in our plant where the product has very high freeze points and there is a specific protocol for steam out stations. The steam outs are all block and bleed type. All the lines are slightly sloped to the steam out stations to facilitate drainage. There is caveat in that the steam temperature has to be compatible with the process. In one of the above areas the steam pressure is limited to 25 psig as any high temperature steam can and has caused a deflagration.

In another area where we oxidize Cyclohexane with air there are provisions for very large steam outs due to the formation of a polymer type deposit. Without steam you could never get an acceptable flammability level for maintenance.

All site line and vessels are designed for or capable of FV.

 

[sshep]

shahyar
consider this:
1) hard pipe steam to process- typically a double block and bleed with figure 8. This is typically merited only for towers (facilitated by condenser if practical) or large equipment which must be entered for inspection, or specific filters etc which are required be opened frequently.
2) utility steam stations, hoses, steam out blinds etc- typically sufficient for pipe clean-up such as might be required for modifications, pump clearing, etc. in this case only "provision" is available bleeds and drains. how to dispose of dirty condensate and air pollution may be tricky for some chemicals, and steam out to flare is often the only practical option.
3) no provision- It will not be economical to provide steamin areas where there is no steam supply if no specific need is indicated . Fortunately well designed pipelines are inspected by smart pig, so need to clear with steam is rare-perhaps you need when you decommission and you won't generally design for that up front!

steam cannot evaporate heavy oils, but will render equipment safe to open if there is doubt, or cold cut under some work permit conditions.

not exactly sure want you were looking for but best wishes, sshep

 

[jeyx]

I would just add up here that steaming out is good for removal wax etc from the h-exchangers. The steaming out is more likely to see in downstream. To remove the H/C vapors you can sometimes replace the steaming out with nitrogen purging, especially if you do not do it very often. I also saw some refineries that use it as a primary fire suppression agent, f.e. inside of fired heaters

hope this gives some help as well,
Jeyx