Interesting problem.
I can’t give you a gospel answer, just some thoughts about how I’d tackle it and what factors I’d consider.
You will need to get the ideas from the other forum mebmers and some comment on my thoughts.
Questions:
[ul][li]how do you measure the quantity delivered?[/li]
[li]how do you check the quality?[/li]
[li]6.5 miles total pipeline will contain how much stranded fuel?[/li]
[li]what type of pump or pumps are you using?[/li]
[li]will they have to blow out the lines at the mooring anyway or are these self sealing or otherwise sealed connections when separated?[/li]
[li] what is the nature of the terrain under which the pipe will be run?[/li][/ul]
I’d say you have several different aspects to consider:
Environmental, commercial and security plus capital costs.
If you are within reach of the EPA and I’d guess this is a power station, take note of what happened to PREPA (Puerto Rico) who settled out of court on a range of pollution offences. I’d hate to think what they would have paid if they had gone to trial. If not, then you must still have some serious environmental concerns to consider. One would be how to prevent some leakage from a 6.5 mil pipe full of heavy fuel oil that is unused and untended for long periods. How do you know it won’t leak under ground? If it is only used for unloading then the scope for harm is less.
Secondly, however much fuel the pipeline will hold, if you leave the fuel in the pipe it becomes stranded asset and at $386 a ton for 380cst (Houston price) work out just how much extra cost is invested in this pipeline. Now you might be paying that sort of price but you might be getting it from Hugo Chavez at whatever knock down price it is today, but if someone can tap into your pipeline, it is the market price that controls what they can sell it for. Now this has had some disastrous consequences in some parts of the world but don’t think it just happens in Africa. I know of a paper mill in the UK where they piped high pressure steam to the next mill a couple of miles away. People in “gypsy camps” would regularly tap into the line and pirate the steam. They’d also tap into the electric lines.
Now consider quality and quantity. Both can be suspect when delivered and any opportunity for the issue to become clouded will be exploited in a dispute.
There isn’t much argument about fault when you find dry cleaning solvents in your fuel but there are a great many other problems for which plausible “accidents” can be claimed. These include entrained air (cappuccino effect which messes up tank dipping) and air bowing (at the end of batch which messes up flow meters and can also disturb tank dipping to an extent) plus air will cause false density and viscosity readings if you do an offline test. Now air just affects the quantity invoiced.
Water is the other most common problem, fresh or salt. I’ve visited power stations where the fuel delivered was so full of water it couldn’t be used but they didn’t find out till too late. Was it an accident or deliberate? If you provide water or air to the pipeline, you may create an opportunity for them to be introduced into your fuel rather than just into the pipe.
OK, you can see that I lean toward leaving the pipe line empty after unloading but how to do it? That depends on how you are pumping the fuel? One big PD pump at the mooring pushing it all the way on its own? Or a sequence of pumps sharing the load along the pipeline?
If a sequence then are you using centrifugal pumps? Fuel barges prefer centrifugal pumps to bunker vessels because they are cheaper and all that happens is that if the fuel gets too cold the delivery rate drops.
If centrifugals then I’d think about once the unloading is complete just keep pumping and as the air reaches each pump, shut it down. When starting up, just switch them on as the fuel reaches each pump.
If these are PD pumps then you’ll need to vent air into the lines at each pump discharge when finished unloading so that as you shut down each pump you don’t close the suction to the next, and conversely, when starting up you’ll need to vent the pump inlets to purge the air out of the line ahead of the fuel. Alternatively, just shutdown and bypass each pump until you need it. That way you jiust shunt the air and fuel around dormant pumps.
JMW
