Purging #6 FO line with #2 Fuel Oil

[dtharris]

We have several #6 FO tanks with common barge unloading. We are converting one tank to stoe #2 oil, but we want ot use the same barge unloading line. The thought is to purge the line with #2 oil to a waste tank, until the supply is all #2 and then send it to the #2 tank.

I'm being asked what volume of #2 will be needed to purge the line.

Two questions - the first is will this work , the second it what volume of #2 is needed to purge the line.

 

[LittleInch]

IM not familiar with the terms #6 and #2, but assume you mean non waxy heavy fuel oils. In this instance, yes it will work. Providing you can pump at a velocity of at least 1m/sec continuously then the volume of the piping and pumps plus 10% should do it. Look for any dead legs or duplicate equipment (filters, pumps etc) which c can harbour large volumes.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[racookpe1978]

Rather than go a waste tank, can't the lighter-weight (more expensive, more highly-refined) oil be directed to the heavier oil tank as a "diluted but serviceable" flush liquid? That is, you could never put heavy oil into the light tank, but not the reverse?

So, if you know that the next cargo to arrive will be light oil, and the current load in the pipe is heavy oil; you set up your flush sequence after the current heavy oil load so that the light oil flushes out the line, but discharges the flushing mix into the heavy oil tank. Then you are set up to receive the light oil.

If the next load is to be heavy oil, and the current is light oil, then you can just leave the light oil in the line with no flush, only the usual drain and close.

 

[LittleInch]

I missed the regular offloading bit. If the volume is relatively small then the difference in cost is probably small. Whilst it is nice to schedule deliveries, it doesn't always go as planned and if the no 2 is infrequent, won't work.

If the pipework volume is large then you could look at interface mgt, by flushing no 6 into the no 6 tank before switching. For flushing the no 2 out of the line, a bit of caution is required, but you will minimise the amount of no 2 dumped into the no 6 tank.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way