Unloading tanker truck hose and pipe when loading point is lower then A/G tank nozzle

[curtis2004]

Hello colleagues,

I am reviewing a design of Light Oil system with a Light Oil storage tank. The system is used to store and distribute diesel fuel to emergency generators and auxiliary heating boilers.
My storage tank is about 80,000 liters with horizontal construction and have 6" loading nozzle on top (12 o'clock) position. I have three 3" unloading quick connect ports with isolation valves connected to a single 6" header (with check valve) which then goes up and connected to top nozzle of horizontal tank.
I have one issue: How do I empty my 6" loading line and unloading hose before decoupling it? I have heard that you need blow this line with low pressure air in order to push diesel into storage tank and empty hose and loading line. However, I have concerns if this safe procedure. Does standard tanker trucks have this feature (blowing air into their loading hose) or do I need to design this low pressure air system?
Does anyone have previous experience with this type of problems? Did we had any discussion before here? I do not think this is unique situation.

Thanks in advance for your time,

Curtis

 

[bimr]

Don't believe the hoses are blown out. You need to determine what type of couplers that the terminal company or trucking company is using so that the installation matches.

There are various drip-less bottom loading couplers that are available. There are also Kamvalok fittings. Review the catalog at the link:

http://www.opwglobal.com/docs/libra...systems/loading-systems-catalog.pdf?sfvrsn=12

 

[LittleInch]

It would be good if you could provide a sketch of this operation as it sounds like you're asking fluid to flow uphill? How are you getting the fluid from the tanker into the tank if it needs to go up into the top of the tank? Most tanker trucks I know don't have pumps, but maybe you've missed that bit out?

otherwise this is commonly don by having a small drain tank suitably sized for the hose volume and then a small pump (could be a hand pump) to pump out the drain tank into the main tank.

Blowing fuel lines put with air is introducing a significant safety risk, both in the production of large amounts of vapour and the potential to overpressure the tank or tanker and the velocity of air needed to blow out a pipe or hose is quite high needing a significant amount of air. All rather impractical.

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

 

[curtis2004]

LittleInch,

See attached a hand sketch simplified isometric drawing.
You are correct! We are pumping fluid uphill, because A/G storage tank elevation is about 12' high then quick connect unloading point. We can't lower it because of size of the storage tank and we do not want go U/G. There are three (3) unloading points (3" size each), but only one tanker truck will be unloading during the same time. Main header is 6" size.
Are you sure that tanker trucks do not have pumping capacity? I'm not familiar with this at all and do not want to build something which will not work.

Regarding emptying of the filled lines I have two concerns:
1. How we will empty truck's hose, up to Ball Valves BV-01/02/03 before decoupling quick connect;
2. How we will empty unloading 6" header from Ball Valve BV-01/02/03 to top elbow going into Light Oil Tank (or it will be always filled with diesel?).
If 6" loading header always filled with diesel, I probably need heat trace it, because I have to design to -45C design temperature.

Your thoughts are appreciated.

Thank you,

Curtis

 

[LittleInch]

Curtis,

Maybe I'm missing something here, but not sure where your pump is? tankers don't normally carry them.

Not sure why you can't just put yur drain point shown on the header between the BV and the QC couplings?

Either that or connect this to a small stripper pump (some sort of run dry PD pump - screw, diaphragm...) and ump into your header. Could even be a manual pump if you've got no power.

I hope your tank has a vent and you just haven't shown it... Assuming this then you could do the same thing to the header, but use a smaller line.

Often these sorts of lines do remain full. I also hope your pipe inside the tank goes down to the floor. Normally these have small holes at the top in the tank so that you don't syphon the product back out. Apologies if this is obvious to you....

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

 

[bimr]

If you have only occasional deliveries, you may be able to have the supplier pump it off the truck at additional cost to you. Normally, tankers do not have pumps.

The connection QC-01 will be a drip less fitting. Look at the catalog link above. You need to talk to the fuel supplier so that your fittings match what is on the tanker truck.

The hoses will typically have fuel in them between deliveries.
What is the point of the 6-Inch header if you only have one truck?
Why multiple spots if one delivery happens at a time?
What is the purpose of the vent in the piping?
The tank should have a conservation vent.
The tank needs to have automatic overflow protection.
This should be a dedicated truck spot.
You will need some type of spill containment and a spill containment plan.
The tank should have containment around it.
The whole area should be electrically classified.

http://www.pumpschool.com/applications/Fuel_Oil.pdf

 

[curtis2004]

Hi Everyone,

1. Yes, my storage tank has vent pipe with fire arrestor.
2. Yes, my tank have level instrumentation with level control, gauges, and horns to whistle when 95% capacity is full.
3. Yes, my storage tank has a concrete secondary containment around it with 110% tank capacity. And unloading area also has spill containment area which is drained to oily water system U/G lines.
4. Yes, we have a dedicated truck spot near unloading point.
5. Yes, we have appropriate hazardous area classification around the tank.
6. I think three unloading points are for redundancies, although I would install two points for redundancy though.

I have spoke with a guy who supplies tank truck and according to him modern tank trucks have their own pumping system which can pump up to 18' and also have compressed air system to blow the lines nowadays.
He has suggested to install "sight glass" after BV-01/02/03 in order to make sure that line is clear before closing BV-01/02/03. Driver will make sure that fill line is emptied before closing ball valves and decoupling his hose.

I will check tank drawings if intake nozzle goes to the tank bottom and have holes in them.

I have another question: I have installed only one check valve in main 6" header. I have seen designs with check valve installed at unloading point between ball valve and quick connector. Is there any preference one design against the other?

Thanks,
Curtis

 

[curtis2004]

LittleInch,

The tank doesn't have intake nozzle doesn't go to the bottom. Is this a big concern? I guess we don't want' diesel splashing, agitating and increasing vapour inside the tank.
Although the tank is atmospheric, it was specified to be built to ASME Section VIII Div. 1. I would personally buy UL listed fuel storage tank instead.

Thanks,
Curtis

 

[bimr]

You can have a drop pipe fabricated and mount it on the flange.

It really does not matter too much where the check valve is located. Put it in a convenient location.

 

[curtis2004]

Bimr,

Vent is needed for hydro test.
Another thing I found out is the tank will be painted inside and out, insulated, and have electrical submerged heaters on it. This may be a bit overkill, however, it is designed for outside temperature of -46C.
Is there any concern about under insulation corrosion? It will be painted though.

Thanks to everyone,
Curtis

 

[curtis2004]

Bimr,

Is drop pipe really necessary? What are risks not having one?
Can it be fabricated from perforated sheet smaller then 6" OD and having flat flange with 6"x150# holes pattern?

Thanks,
Curtis

 

[bimr]

The insulation should be something that can not absorb oil such as cellular glass.

Since the tank is heated, you should not have to worry about corrosion. Water trapped in the insulation will evaporate off with the heat.

The fill nozzle should be flanged. If so mount the drop pipe into it. The drop pipe would have a weld neck flange with another flange on the end for connection to the inlet pipe.

 

[curtis2004]

Bimr,

Electric heaters will be energized only below -10C to keep diesel above -15C. We have winter diesel. It will heat, but not a lot that would vaporize water. So this might have a different consequence to moisture accumulating underneath insulation.
Yes, fill nozzle of the tank 6"x150#. Can you provide a link to drop pipe? Can't imagine what is the best construction I have to chose.

Thanks,
Curtis

 

[bimr]

The use of protective coatings on insulated steel is recognized as being an effective method of combating corosion. However it is essential that the coating has been specifically approved for use beneath insulation and is suitable for the expected service temperature.

If you tank is 10 feet deep, have a 6-Inch weld neck flange welded 9 feet 6 inches from the end of a 11 feet long section of 4-Inch pipe. Weld a 4-Inch flange on the other end. That is the drop pipe.

 

[LittleInch]

Hmmm,

Good set of answers.

What happens when a tanker turns up which is not a "modern tank truck". I'm with bimr here - unless you specifically order one, many tankers are simply vessels with which to transport liquid and nothing else as this is weight which can be used to transport liquid.

The danger to me is that you have no control over this "pump" or the air used to clear the lines. Unless you really know what this is you won't be able to correctly size your vent and could overpressure your atmospheric tank. Forces from even a small over pressure are large and significant. Be very careful when introducing gas into a tank designed only for liquid.

You can't use ASME VIII for an atmospheric tank - you will need to specify / use a design pressure of at least 15psig and this will cost you a lot more than a simple standard atmospheric tank.

Yes the intake nozzle is important. Especially if you have atmospheric venting, a significant quantity of your fuel oil will come out as vapour if you don't and the fire / explosion risk is significant. see

http://www.healthnsafety.info/elect...-grounding/static-electricity-protection.html

for info. search this site for "fall pipe" or "Dip pipe" design

Corrosion under insulation is a known issue and "painting" is not sufficient to prevent it. You will probably need to allow for a strip down at periodic intervals even with insulation like cellular glass and more frequently if you use rock wool or similar.

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

 

[curtis2004]

LittleInch,

I have spoken with fuel delivery company representative and he told me that horizontal A/G storage tanks with top loading is not unusual. They know before delivering fuel what kind of truck they need to send based on each client site requirements.
He also mentioned that emptying loading hose with low pressure air is the feature they are using for a long time. I asked him what is air pressure and flow they are using for this feature. According him it is 10-15 psig pressure with very low air flow, just enough to lift fuel in the hose and clear a sight glass installed after an isolation valve. Driver-Operator will close the isolation valve and decouple the hose only after seeing that there is no fuel in a hose. This seems kind of neat feature to avoid spill during de-coupling of loading hoses.

I totally agree that ASME VIII is overkill for atmospheric tank and I would ordered horizontal UL listed fuel storage tank. That would saved thousand of dollars (if not hundred thousand). However, this has been ordered before me and I can't cancel it (it will cost even more). So I was left with this MAWP = 85 psig tank. I think we still can use this tank. I have to order dip pipe though, because it has not been specified.

Regards,
Curtis

 

[LittleInch]

Ok, looks like you've covered all the bases. The cost of that tank will be something else [shakes head].

Having buried tanks is more common, but if that's your design and operation then its not unusual. Getting a dip or fill pipe is non negotiable.

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

 

[curtis2004]

Hi Everyone,

I have question regarding insulation of piping for Light Oil system (Oil #2 or diesel). I need to electrically heat trace and insulate lines because of ambient winter temperatures of -40F/-46C. I was told that below 0F diesel turns into wax and will clog filters, strainers, even piping. Now, how am I going to insulate piping? Am I going to insulate valves and flanges also?

My concern is if there is small leak in a flange this may left unnoticed for a long time. My first thought to keep flanges and valves not insulated. On the other hand if temperatures will deep low in winter (installation is in Northern Canada), I am afraid this may lead clogging of lines.

What is your thoughts?

Thanks,
Curtis

 

[bimr]

Valves and flanges are also insulated. Special insulation blankets that are removable are used to insulate the valves so that the valve may be serviced.

If there is a leak, you will be aware of it shortly. FRP insulation is not used on flammable products. Something like cellular glass is normally used as it does not absorb liquids.

 

[Sparky1949]

Curtis2004,

Perhaps I missed something in the drawing and your comments on the installation, but it appears that there is more than one valve in the piping. If two valves are closed with oil between them, a pressure relief system of some sort is needed. If a pressure relief system is not installed, then the long summer sun can heat the oil to the point...oh, sorry the pipe is insulated. Perhaps it will be fine without the pressure relief system(s).

In the USA, we use alarms set to 90% full and positive shut off valves at 95%.

There are systems for monitoring oil and condensation under insulation. They consist of clear bottles mounted in ports at low points in the insulation jacket.

Piping often corrodes at support points because of the normal movement from temperature changes. If there are supports which touch the pipe, provide a method to easily remove the support and inspect the pipe annually. One method is to cut the support (if it is a pipe)at a 45 degree angle and slip a slightly larger tube over the cut. The larger pipe is bolted in place and can be removed for inspection. A union ($$) can also be used.