Flow Control of Hot Oil System

Hi,

I do not know about oil system design.

Regarding valve selection , I suggest to use dual plate check valve or nozzle valve to protect pump.

Thanks /VInay

The secondary containment for a tank (sometimes described as a "skirted tank" or "diapered tank") does not necessarily have a much larger footprint than the tank itself.

In the case of power failure, all of the oil above the tank may drain into the tank, either backwards through the pump or by gravity drainage from the piping. This is regardless of whatever valves are furnished, because they could leak back.

Even if the tank is mounted high, leaks in the piping could result in oil spillage that would fall on the ground rather than into the tank. If the tank is mounted low, and is large enough to contain all the oil; then in the event of power failure or leakage, the shutting off of the pump would allow all or most of the oil to drain to the tank.

I would revisit the given design assumptions.

I agree with KJK, You do not have enough knowledge to design this system. Get professional help.

The oil must not be able to flow out of the pipework when a pump fails. If it does, the bitumen will go solid in the pipes and take days to reheat to a liquid state. When refilling the system you will get air locks just like in a domestic central heating system. The only way to find these is to go round the system looking for cold spots and if the system is as well lagged as it should be, that means removing lagging.

Have your professionals design the system with two tall legs so the pump has to lift oil over the first leg to feed the system and lift oil over the second leg to return to the header tank. This creates a U tube and on failure most of the oil just sits there keeping the product warm while you fix the problem. Put enough manual valves into the oil loop to be able to drain parts of it so that when you get problems you are only working on a manageable segment. Install drain cocks to the lowest part of each segment and feed them directly back to the header tank mounted at the lowest point on the system.

Make your tank large enough to contain all the oil. There will be times when you need to drain the oil and it is false economy to have nowhere to store it. Putting it back into drums means you have to store empty drums on site, maintain them to keep them from leaking, move them to your drain cocks, drain the oil into them, make sure that you don't overflow a drum, move them back to the header tank and get the oil from the drum back into the system. The first time you have a big problem you will spend more than installing a larger tank.

I am with KJK on this STOP!!!!!!

I have worked on the design of several of these systems over the years and we have ALWAYS had the expansion tank as the highest point in the system. You made a comment about deadheading the pump if the valve fails with the pump running but the main issue you have is the expansion / contraction of the oil in use as loads change.

As the loads change the temperatures of the return fluids change and so they expand / contract - if the valve in line ot the expansion tank is closed there is nowhere for this expnsion to go or fluid to pull in for the contraction. With expansion you overpressure your piping at probably causing a leak at a flange gasket; if the fluid is contracting you will again cause a containment failure (flange gasket or valve packing perhaps). Remember fluids are incompressible so a tiny expansion causes a massive pressure increase. Loads change all the time causing tiny changes in average temp and volume of fluid so the level in the expansion vessel will move continuously even if by small amounts.

We installed a locked open valve in the line to the expansion vessel on my last project and there was intense debate during the HAZOP as to if this should be removed. We installed it so that the operators had local isolation for maintenance but the operations team were more concerned at the problems if the valve was inadvertently closed.

You could engineer a solution but all the extra detection safety options etc needed to make the solution work (and teh regular maintenance and testing of these devices) means that its cheaper to put the vessel at the high point and have the intrinsic safety of doing it right.

As a general comment....

I agree the best and safest solution is to have the tank at the highest point in the system. Not one of you asked why I am looking for alternatives.

If the tank were mounted above the heater as the manufacturer does with nearly all is systems, the tank has to be large enough to accomodate al the oil in the system that can flow back in the tank. That means a very large tank the manufacturer is resisting offering. A 2000 galon tank is much larger than the 280 gallon tank included with the sytem, and much harder to support on his skid.

Mounting the smaller tank at the high point in the system is a solution that now falls in my company's area of responsibility rather than the manufacturer's. Of course we would like to avoid this if possible. It also will cost our client money for additional structural steel. He simply wants to know if there is an alternative.

The simple fact is I have been asked for those alternatives and I asked if controlling gravity backflow with valving was a good (and safe) solution. The simple answer is: no. It is not necessary to question my expertise to say this. I already thought it wasn't good idea but I asked just in case.

I appreciate the time everyone took to respond, yet the righteousness and questioning of my ability I got was uncalled for. I realize this sounds like I am ungrateful but I am not. I simply wish to be treated with respect and I didn't get that.

Further response is not necessary....I will not read them.