Install drain for buried pipe 1

[mangocanh]

Hi everybody.
I need to pump Gasoline from my plant across 30 meter road to a Tank

The pipe will be buried and my problem is how to install a drain for that pipe in case of maintenance when the gasoline need to be removed completely for inspection, cleaning...
Somebody advised me that to build a pit for the drain (3.5 - 4 meter depth) with lower elevation to the buried pipe but there are some other problems arise. Could anybody help me with this? Do i need that drain and where can i install it?
Thanks a lot.

 

[robyengIT]

why not to use compressed air/nitrogen to push the ramaining gasoline (part of pipe under level 0) ??

 

[LittleInch]

I'm struggling to see why you need to drain this other than in very rare cases of leakage, but assuming you do then your options are:

1) make the pipe pigable by using at least 1.5D elbows and the same pipe size and allowing potential to gain access to the pipe. - seems very expensive for 30m of pipe.
2) Make one of your top elbows a tee with a flange which you can then drain down the AG sections, remove the flange then insert a hose or tube and pump out the contents
3) Make the below ground section at a small slope and at the lowest point make the elbow a vertical tee or attach a drain point and then pipe a drain with flange and maybe valve to the surface ( prefereably) or small pit and again just pump out the contents.

A lift of 3m should be ok for gasoline.

Avoid pits whenever you can - nothing but a nightmare long term.

Or accept that you don't need to install a drain which has its own risks of corrosion (it's a water trap) and historically causes more leaks than its worth for the once in 20 years you might need to drain it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mangocanh]

Thanks Robyeng and LittleInch for your advice.
Per your ideas, i understand that making a drain on the ground section of the pipe is the simplest way. However, my concern is how to remove completely all hydrocarbon in the whole pipe, especially the buried section. That must be sure for safety reason. When using compressed air, N2 or pump out, i dont think that it could empty the pipe perfectly. I am thinking about using water to push out the trace of hydrocarbon, however how to remove the remained water after that or even after hydrotest when doing pre-commissioning at the beginning, or when doing steam-out for cleaning...

 

[LittleInch]

I kind of forgot option 4
Flush with water until no more product, then drain out as required.
you seem to be very concerned about this, but I can't see why.

So long as you pump at a velocity of > 1m/sec you should flush out either water or gasoline very quickly.

I think you're seeing problems which don't really exist.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

Soem thoughst:
1. Is the road elevated up from the surrounding area with a slope? A drain can be installed where the pipe is daylight after the slope.
2. Depending on the O&M requirement, the pipe may need to be potable, and the connections of the purge and drain.
3. How about the pipe run inside the trench with the grating.