This Friday's case

RayWohlfarth

On this Friday's case, I withheld the name of the case because that would let you know the answer. A brewer contacted me and said, he was getting steam to the kettle when the boiler first started. After about twenty minutes, the steam stopped going to the kettle. It seemed that when the boiler first started and the pipes were cool, he would get steam. As the pressure built, the steam flow to the kettle would stop, which didnt make sense to the brewer or me. The brewer operated the boiler between 11 and 13 psi. I will let you know the name of the case and video on Friday at 6am EST. Until then, have fun. I wont respond to any questions or comments till then.

EdTheHeaterMan

Since I know very little about brewing with steam, and I am only looking that this diagram you provided, I can only think of what might stop the flow of steam after a prescribed amount of time. The air vent will allow the steam to get to the Kettle in short order, the kettle will absorb the latent steam and cause the condensate to drain out at the trap, Any air in the steam side of the kettle should vent thru the trap. then at some point the trap will close for the proper reason. Perhaps temperature. At some point the trap gets stuck closed (I don't know why because the condensation should open it to drain the liquid, Perhaps the pressure being over 5PSI is preventing the trap from opening). But as the steam condenses in the kettle condensation builds up and eventually the stuck trap will not allow the liquid out, leaving no room for new steam to enter the kettle. Eventually the operator notices the problem and shuts down the boiler, the pressure drops and the trap opens. Ready for a new cycle.

I'm going with a trap problem. Maybe the wrong one, maybe defective

The Case of the Faulty Trap

mattmia2

Steam trap on the kettle is failed closed. The vent allows steam in the main to that point then the pressure of the steam compresses the air in the jacket of the kettle enough so some steam gets to the kettle which condenses and brings more steam in. Eventually the jacket is full of air and condensate and no more steam is pulled in. The trap is clogged but not completely so when the boiler is off the condensate eventually drains out of the jacket.

Sylvain

I suppose

• there is condensation in the kettle and that
• the boiler doesn't stop on low water.

1. The trap of the kettle is partially clogged. "partially" because it would have let the kettle slowly drain between two cycles.
2. or, the common return of the two traps is partially clogged;
3. or, the trap at the end of the horizontal pipe is partially clogged and the pipe becomes filled with water and block steam access to the kettle.
4. the feed/condensate tank vent is partially clogged;
5. …

EBEBRATT-Ed

Others have mentioned trap failure which is what I also think.

So I am going with vacuum on the kettle not allowing it to drain.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1800058#Comment_1800058

but the air vent or the steam from the boiler should take care of that depending on the current operating conditions

mattmia2

Unless there is a valve that is not shown.

retiredguy

I am late to the party with my answer but I would have to agree with the others that the problem is a bad trap or possibly a restriction in the return line, not allowing the condensate to drain properly.

RayWohlfarth

Ok I messed up and posted the wrong picture. I am sorry for that. It led you down a false trail. In this case, the condensate pipe rose after the kettle. The case is the Case of the intermittent steam vent. Everything worked great for several years until the steam vent (Why does Hoffman call it a steam vent when it vents air?) failed and the owner/brewer replaced it with one he found on Ebay that looked just like the one he had. This vent was different. He replaced a 75H vent with a 75 vent. The difference between the two was the drop away pressure. The drop away pressure is the pressure for a 75 h is 10 psi and for a 75 is 3 psi. In other words, the 75 H dropped and open when steam pressure dropped to 10 psi. This allowed air to be vented.When he installed the 75 vent, it stayed closed until the steam pressure dropped below 3 psi, kinda tough to do when he was operating between 11-13 psi Again I apologize, here is the link to the story.

https://www.youtube.com/watch?v=ukd-SrOHqqA

Steamhead

They could probably run less pressure by getting rid of the condensate line rise after the trap. This would save energy and maybe lead to a reduction in the price of the beer.

RayWohlfarth

@Steamhead Its been such a battle with the brewers. The equipment manufacturers want 15 psi to their equipment. I try telling them the boiler cannot provide 15 psi at the kettle. I try explaining the pop safety will open and the manual reset limit will trip but still they do it

Steamhead

We worked in a plating plant once where they were running about 10 PSI or so IIRC, to force condensate from their tank coils up to an overhead return. We installed a transfer pump and reduced the pressure, and it ran much more efficiently.

RayWohlfarth

@Steamhead they need the temperature of the steam to cook

EdTheHeaterMan

I had a feeling it had to do with drop away pressure. I just assumed it was a trap drop away pressure. but it makes sense now. (dont know of any trap that has a drop away pressure issue based on the float design)

EBEBRATT-Ed

@RayWohlfarth

I have run into that as well. People can't understand that a 15psi steam boiler can't operate at 15 psi.

retiredguy

I know just what @RayWohlfarth is talking about when he says that the customers want higher steam pressures. I had customers that said that since the steam boiler was rated at 15PSI that is the pressure that they wanted. I always told them that the maximum they would get was 12 psi and if they actually needed more pressure then they bought the wrong boiler. As soon as they got the price of a high pressure boiler that would satisfy their need, they all of a sudden got quiet.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1800214#Comment_1800214

Not that much temp difference. 35 degrees or so, max, between 1 PSI and 15 PSI:

https://www.engineeringtoolbox.com/saturated-steam-properties-d_273.html

As long as the kettle gets up to temp, they should run at whatever minimum pressure will get them there.

RayWohlfarth

@Steamhead I get it. Enclosed is a required steam pressure spec for a brewery

Steamhead

Ahhhh, the dreaded "Recommended".

My next two questions would be:

1- what temperatures are required to successfully and safely process the various ingredients, and

2- do these units have internal thermometers so we can see when we've reached those temperatures? If not, we need to add them.

Obviously this won't be a situation where we can run at the ounce pressures we use in steam heating, but if I had money I'd still bet we don't need to get to 15 PSI.

RPK

Can someone please help me out here, I’m having a hard time understanding how the lower drop away pressure was causing the issue, must be missing something.

1. Operation of the Hoffman vent
a. Vent starts out open during off cycle

b. Vent is thermostatically actuated in presence of steam and closes

c. Once vent cools down, it will open as soon as pressure goes below drop out pressure

2. How I imagine vent working in the scenario described

a. Vent is open during off cycle

b. Boiler fires and steam forces air from piping until it reaches the kettle

c. Vent closes

d. Kettle is heated (but wondering how air that is downstream of vent in piping and inside the kettle is released if there is a water seal in the piping downstream of the F&T)

e. Assuming all air is out of the way and steam is condensing in the kettle, condensate is drained via the F&T, there is enough steam pressure to lift the condensate where the piping rise

f. No need at this point to vent anymore air, kettle will heat until the boiler cycles off

3.Question

a. In the scenario described in the solution, it sounds like additional air is getting into the piping somehow. Where does it come from?

BTW, thank you Ray for this “Friday’s Case” series. Please keep them coming.

RPK

Bump…. Hoping someone can help me understand what I’m missing. Why does the it matter if the vent doesn’t open until pressure drops to 3psi? Doesn’t the system drop to zero on every off cycle? The vent is just open until it sees steam and then closed for the rest of the cycle, isn’t it?

RayWohlfarth

@RPK On a call for steam, the boiler operates between 11 and 13 psi. It shuts off at 13 psi and restarts at 11 during the call. It has a 2 psi differential. When the steam condenses in the kettle, air rushes in from the condensate side. The vent will not open because the pressure is between 11 psi and 13. The 75 vent does not open until the steam pressure drops to 3 psi. When brewing, the boiler may operate continuously for a few hours cycling between 11 and 13. Hope this helped