Above ground tank dispenser problems...
Above ground tank dispenser problems...
(OP)
I’ll try to be thorough as to not leave many questions, hopefully someone is familiar with our above ground tank set up. I am not an engineer but rather a mechanical tech, trying to resolve a problem with our above ground tank diesel dispensing set up. Our company engineers are clueless... We have two 9,900 gal. diesel tanks, arctic climate (-40 to 70 deg F year round) supply for the dispenser (gasboy 9153K) comes off the bottom of the tank to a manual gate valve, then to a butterfly valve with a solenoid that is dispenser controlled(actuates when dispenser pump is turned on/off) then to a Tokheim Model 52 pressure regulating valve, then the sheer valve and dispenser. Total length of piping is not long, maybe 30', 2" dia. i believe. The problems we are having are leakage from every gasketed surface of the pump and nozzle. Nozzles fail regularly, and most recently we had a spill from the dispenser pump air separator vent. After some research, i found that the Model 52 pressure regulating valve we have installed still has the blue shipping plug installed on the atmospheric vent (no vent line installed higher than tank level) This could definitely be the cause of the spill from the air separator vent line. My understanding of the air separator on the pump is incomplete at best. Initially i thought that the leakage problem was being caused by thermal expansion downstream of the PRV (dispenser side) which does contain an internal thermal relief for any pressure that builds UP stream of it, and is supposed to bleed through the pumps air separator vent line. In the trouble shooting section of the Model 52 PRV it clearly states that failure of the valves diaphragm or specifically not removing the blue shipping plug can cause release of fuel through the pumps air separator line, no mystery there. After researching this further though the mystery for me is why are we having so many leaks that initially I attributed to thermal expansion within the pump, not understanding that the pressure could vent itself downstream of the Model 52 PRV out the pumps air separator vent. Ambient temp for the past two months during this problem have been around -20 to 20 above F. Fuel from the tanks is at ambient, and the dispenser is enclosed and sometimes heated to around 80 deg. F. (some think that will fix our problem and I keep telling them it is making it worse!!) Any input would be greatly appreciated. I contacted the local vendor and their “expert” is out of state for a week. Thanks.





RE: Above ground tank dispenser problems...
You could try hoses instead of piping, but at -70 might find it difficult to get any.
I don't understand how the air separator can act aa RV. If it did you would be getting fuel out of the vent.
The only other issue is potentially surge preassure when you stop dispensing. What pressure relief system is built into the pump? If you're able to fit a pressure guages on the piping you can then see what happens during operation and static condition. This willgive you the data you really needs to see what is actually going on.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Above ground tank dispenser problems...
RE: Above ground tank dispenser problems...
RE: Above ground tank dispenser problems...
If there are no pressure relief valves on the system then this is not good practice. You need to add some pressure gauges to check what's happening, but thermal relief valves would appear to be required.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Above ground tank dispenser problems...
Again, my lack of knowledge of how the suction pumps are separator functions is my hang up here... and your description would stand to reason that it would not function as a thermal expansion pressure relief as described through the air separator vent.
It seems that after the model 52 PRV it is pretty standard to have a shear valve, and then the dispenser intake piping... there is no space to plumb in a pressure relief, that would have to return the expanded fuel upstream of the solenoid operated tank valve.
At any rate after talking with our station engineer this morning, I am going to simply replace the Model 52 diaphragm, and install the vent for the diaphram that is supposed to be there anyway, instead of a 90 with the blue shipping plug in it. I will see what that solves if anything, I know for sure that will cure the spilling through the air separator vent, but not sure if it will have any effect on the thermal expansion leak problems. Thanks for your input littleinch.
www.google.com/patents/US5143258
RE: Above ground tank dispenser problems...
RE: Above ground tank dispenser problems...
Chicopee has a very valid point. Elastomers don't like low temps and the type 52 sheet quotes -13 to + 130F as its normal range.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Above ground tank dispenser problems...
Leakage through your air separator is either because the model 52 or some other componnet is letting in air which is them being forced out with some liquid through the air separator or your air separator seal is not functioning properly, posisbly due to the extreme low temp.
IMO you should fix the model 52 and its vent, install a thermal relief on the incoming line u/s the model 52 and check the temperature range of your elastomers in the system.
good luck
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way