HI, I JUST PURCHASED A USED WALKER TANK FOR MAKING MAPLE SYRUP AND AM NOT SURE ON WHAT SIZE RELIEF VALVE I NEED. I GOT A LOT OF FREE ADVICE ALREADY BUT MANY DIFFERANT IDEA'S.
WHAT I HAVE IS A 800 GALLON WALKER TANK AND THE INFO ON THE STICKER IS AS FOLLOWS:

VESSEL ATM PSIG MAWP AT 250 DEGREE'S F.
JACKET HEAT 15 PSIG MAWP AT 250 DEGREE'S F.
COOL 100 PSIG MAWP AT 100 DEGREE'S F.
I WANT TO KEEP THE TANK AT 160 DEGREE'S F. I HAVE A 100 PSI RELIEF VALVE FOR THIS TANK. SOME SAY IT IS OK, SOME SAY IT ISN'T. WHAT IS YOUR OPINION. I DON'T WANT TO RUPTURE THIS TANK. IT IS LIKE NEW.
THANKS AGAIN, JEFF S.

"Hi,

I just purchased a used Walker tank for making maple syrup and am not sure on what size relief valve I need. I got a lot of free advice already but many different idea's.

What I have is an 800 gallon Walker tank and the info on the sticker is as follows:

vessel: atm psig mawp at 250 degrees F.
jacket: heat 15 psig mawp at 250 degrees F.
cool: 100 psig mawp at 100 degrees F.

I want to keep the tank at 160 degrees F. I have a 100 psi relief valve for this tank. Some say it is OK; some say it isn't.

What is your opinion? I don't want to rupture this tank. It is like new.

Thanks again,
jeff s. "


Jeff:

I’ve taken the liberty of formatting your post – not to pick on your English or composition, but to make sure we all on the Forum interpret correctly what you have written. To some of us old-timers, when we see someone asking about the possibility of using a used tank as a pressure vessel we start to get very nervous, suspicious, and wary of the impending situation. I’m sure that you also feel some apprehension and that is why you have posted your query. The veterans on the Forum will know this and treat this as a very serious and formal subject that deserves everyone’s careful attention and correct understanding.

It is very distracting to read a post in capital letters. And I want to make sure we don’t miss any critical information on this subject. Although we can’t grow sugar maple trees here in Texas, we import our maple syrup because we can’t live without it on our flap jacks. What little I know of maple syrup and how it is produced has to do with an evaporator step where the raw sap juice is subjected to a heating in a vessel in order to evaporate out any water and to concentrate the juice. Please correct us on what I have assumed. Although we are Chemical Engineers and well versed in evaporation and heat transfer, we are poor in maple syrup technology because it is an arcane science and art that is restricted to a small portion of our country in actual, hands-on, know-how. The more we know about the process (including a sketch) the more that we can comment on about the need for a pressure relief device and how it should be sized - if needed. Now, lets start on the basics:

1) What is a “Walker tank”? Please take into consideration that we are all neophytes here on the Forum when it comes to making maple syrup. What is the material of construction? Is it jacketed? Does it have nozzles? A detailed sketch would help out tremendously as well as a specification sheet. If you don’t have these or can’t produce them, then write out the details about the tank and how it is used.
2) Is the tank “stamped” with an ASME mark on its name plate? What is the thickness of the tank?
3) How old is the tank and has it been hydro-tested? What was its prior service?
4) Is the tank jacketed? Or does it have an internal coil?
5) Is the tank insulated? Has it been thoroughly visually inspected for corrosion, defects, wear, and prior repairs? Is it totally welded and enclosed?
6) Is it steam heated? If so, what is the steam pressure used?
7) Is it a vertical or a horizontal vessel?
8) Is it also cooled? How is it cooled?

The information you furnish is very “sketchy” and doesn’t tell us specifically what it represents. You may know it, but we don’t. We need to know what the information represents in order to guide you or comment on the involved safety and operational issues. For example, you state “vessel: atm psig mawp at 250 degrees F”. We can take this to mean that the vessel is designed for atmospheric pressure operation. However, if it contains some water and the temperature is 250 ^oF, then there will be some pressure above atmospheric in the tank. This seems to be contradictory and we don’t want to get a mistaken understanding if we are to discuss the tank intelligently. We need to know EXACTLY and PRECISELY what it is that you are going to do with and in this tank. We don't necessarily want to know the secrets of making maple syrup; we want to make sure that no hazardous, over-pressure scenarios can occur without safe relief.

Please furnish us with SPECIFIC and detailed information – especially a drawing and a specification sheet, if possible.

Await your reply.

Hi Art, I am not to good with a computer so I am not sure if you got my reply so I am trying it again. I will try and give you more detail about my tank. First of all it is going to be used as a preheater for my maple sap to warm it to 160 degree's before it goes into the evaporator, hopefully to speed up the process a little. Walker is the brand of tank. It is stainless steel, round, about 5 feet wide and 4 feet tall inside. Half of the top is open with an agitator mounted in the middle. It has a cover on the other half just to keep foreign mater out. It is not a sealed tank. It does have a jacket construction and is insulated because it stays cool on the outside. The wall of the tank is about 3 inches thick. It has a 2 inch inlet pipe about half way up on the tank and a 2 inch outlet pipe about 6 inches away from the inlet. This tank was being used to melt butter into a liquid form for food processing. I want to hook up a closed loop system with water but need help with the releif sizing.
Once again the plate welded on the tanks says
Vessel ATM PSIG MAWP AT 250 degree's F.
Jacket Heat 15 PSIG MAWP AT 250 degree's F.
Cool 100 PSIG MAWP AT 100 degree's F.
The way I read the plate, the hotter the water gets the smaller relief valve you need.
An example would be if the tank is at 175 degrees you would need about a 60 psi releif valve?
Or 250 degree's you would use a 15psi relief valve?
I am not an engineer or a typist so I would appreciate any advice even if it means don't play with things you know nothing about.
P.S. I am a maintenance mechanic by trade but know its better to ask if not sure.
Thanks, Jeff

Simple sketch tell million story...engineer prefer drawing and facts rather than long winded report...

Hi again. I don't have a clue how to add a picture or draw one so I guess you can't help me.

Thanks anyway, jeff s.

Please don't give up on us!!!!

Just make a simple sketch using whatever software you have available - maybe you have some exotic imaging software? Or maybe you can use the drawing tools in excel and save it as an .xls document. If nothing else, do it in MS Paint (Start...Programs...Accessories...Paint - assuming you're using windows).

Write a reply to this forum - and underneath the message box you should see a frame called 'Attachments' click the browse button...find your file and select it - then click upload. Finally click on 'Add Reply' as you would any other post.

Can I just commend you for your diligence in assessing the relief inteegrity of a used vessel. Many of the companies I have worked for will reuse vessels - if they see if already has a relief device then they will assume this is acceptable - this horrendous approach normally comes back to land on the engineers shoulders too s