Vent from condensate receiver tank to atmosphere

[Takket3]

We recently discovered, when a huge mess was made, that the vent off our condensate receiver tank does not extend to outdoors. I want to extend the vent to outside but is there anything special about the termination of the pipe I need to do? Does it need to be a certain distance above grade? Should it terminate (or not terminate) with a gooseneck fitting?

 

[pennpiper]

Takket,
You did not give us anything to work with.
Your Condensate Receiver tank is indoor, Okay,
- What kind of building is this?
- Does it have a built in Drain System for Spills?
- How far is it to the nearest Wall?
- What is just outside that wall?
- What does your Safety Department say about piping hot water out side?
- Why wasn't this addressed when the steam system was originally built?
- I could go on and on, do your home work.

Sometimes its possible to do all the right things and still get bad results

 

[LittleInch]

Why a "huge mess"? Did you get fluid out of the vent?

Do you mean steam or gas condensate?

Vent design varies depending on what is coming out, what velocity, size of vent, location etc etc.

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

 

[racookpe1978]

Steam condensate, or some other liquid?
What environment hazards in the liquid?
What safety hazards (heat, hot liquid dropping or spraying on people or equipment?)

 

[georgeverghese]

In the first place, why the level overflow from this tank? - what happened to the high level trip transmitter / switch or the trip loop ? Is it installed and configured correctly? When was the last time this trip loop was checked by your instrument maintenance team?

 

[mk3223]

IMO, if required to extend the vent pipe outdoor, it should be pointed to a location away from any people or structure as a minimum safety concern. A gooseneck with a bird screen can prevent rain water from getting into the tank.

 

[Takket3]

@pennpiper
- What kind of building is this?

Why does that matter?

- Does it have a built in Drain System for Spills?

Yes, the tank can be drained, but the issue is a vent line, not the drain.

- How far is it to the nearest Wall?

About 20 feet

- What is just outside that wall?

An areaway with some other piping in it that serves an outdoors chiller. Plan was to take the piping into the areaway and up the outside wall maybe 10 feet above grade and terminate. There are no sidewalks/doors/roads/etc anywhere within about 50 feet.

- What does your Safety Department say about piping hot water out side?

It is a vent line. As long as it is away from sidewalks they have no issue.

- Why wasn't this addressed when the steam system was originally built?

Got me. I was in middle school when it was built.

- I could go on and on, do your home work.

 

[Takket3]

@Littleinch

Why a "huge mess"? Did you get fluid out of the vent?

The vent terminates into a pit that is normally exhausted by a fan. The fan was turned off, and the pit filled with steam/water vapor which backed up into the rooms above the pit. Everything in those rooms got the sauna treatment (soaked)

Do you mean steam or gas condensate?

Yeah to be clear we have high pressure steam here but it wasn't direct steam. It was basically the hot saturated water vapor venting off the condensate tank that looks like steam once it hits the cooler, room temperature, areas. We are NOT leaking any steam past traps into the tank.

Vent design varies depending on what is coming out, what velocity, size of vent, location etc etc.

The vent is a 4". I have to extend it about 20 feet to the outside wall and up about 15 feet. So figure I'm adding 40 feet of pipe and let's conservatively say four 90 degree elbows. Existing vent has 15 feet of pipe and five 90 degree elbows

The condensate tank holds 250 gallons and a 15GPM pump turns on and off with a level switch to drain the tank. Condensate temperature runs around 180F max.

 

[Takket3]

@racookpe1978

Steam condensate, or some other liquid?

Steam condensate

What environment hazards in the liquid?

The steam is chemically treated which is all the more reason to be venting it outdoors and not inside the building!!!

What safety hazards (heat, hot liquid dropping or spraying on people or equipment?)

Where I plan to terminate the vent.... none. I have a large clear area I can terminate away from people and equipment.

 

[Takket3]

@georgeverghese
In the first place, why the level overflow from this tank? - what happened to the high level trip transmitter / switch or the trip loop ? Is it installed and configured correctly? When was the last time this trip loop was checked by your instrument maintenance team?

The tank didn't overflow, the vent line just terminated inside the building. Steam traps are fine and the pumps are functioning properly.

 

[Latexman]

Sounds like the vent should always slope downward and not pocket/trap any condensate. Pick a termination point that can handle steam/vapor and liquid. or invest in a small condenser and collect the water.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[pennpiper]

Takket3,
Please accept my apologies; it is obvious I did not give proper thought to my questions.
Let me try again.
- My question: What kind of building is this? Your answer: Why does that matter? Well I was actually thinking of all the different types and styles of “Buildings, including totally open (no wall) structures, partial walled (Curtain Wall to Stub-wall) structures that would not require venting of steam vapor. Then there are totally enclosed structures that would require venting. Some building may have only one level and others may have multiple floors. Each different type of building presents its own opportunities and challenges of which would influence what can and cannot be done to solve your problem.
- My question: Does it have a built in Drain System for Spills? Your answer: Yes, the tank can be drained, but the issue is a vent line, not the drain. My line of thought here was to have a proper Vent to the outside of the building but slope the line so it slopes up slightly to allow for the Steam to vent, but allow the condensate to drain back to a point near the vessel then drain down to the floor drain system. The last vertical drop of the Drain line would have a “Goose Neck” seal to prevent the Steam Vapor from traveling down the vertical drop.
- My question: How far is it to the nearest Wall? Your answer: About 20 feet. This is good; there should be no problem with supporting this slopping line to the outside of the building.
- My question: What is just outside that wall? Your answer: An area-way with some other piping in it that serves an outdoors chiller. Plan was to take the piping into the area-way and up the outside wall maybe 10 feet above grade and terminate. There is no sidewalks/doors/roads/etc anywhere within about 50 feet. This is also good; it means there should be no problems with the Steam release.
- My question: What does your Safety Department say about piping hot water out side? Your answer: It is a vent line. As long as it is away from sidewalks they have no issue. Then I also see no problem.
- My question: Why wasn't this addressed when the steam system was originally built? Your answer: Got me. I was in middle school when it was built. Good one!!


Sometimes its possible to do all the right things and still get bad results

 

[georgeverghese]

Lokks like this condensate drum should be fitted with at least one LSHH to effect a plant shutdown now that you plan to route this vapor line away from this internal pit. The risk of level overflow in the reconfiguration would be the scalding of personnel with hot water. In most cases, drums like these which are the last line of defense against level overflow should be fitted with 1oo2 voting high level trip switches. Currently this pit in the room is your last line of defense. The level switch you've got now is used for level control purposes and should not be used for this safety trip function also.

The ground level area beneath the remote vent line should also be designated as a sterile zone and cordoned off.

 

[LittleInch]

Ok, lets see what we have here.

We have a fairly small tank 250 gals, ~ 0.9 m3 which fills with hot water at about 180F ~ 80C. Filling rate unknown as is the number of times it fills per hour, but given pump out rate is low (15GPM) assume it's not more than once an hour? The tank is assumed to be "atmospheric", i.e. no specified design pressure.

Your current vent is a 4" pipe about 15 feet long which ends in a pit for some reason.

You want now to extend this to an approx. 40 ft and higher outside the building.

A few things still unknown that you need to know or fill in. Be aware that any change to this vent by you will now take on responsibility for the system and anything that goes wrong with it will be YOUR FAULT...

I can't work out how a vent from a small tank with 80C water would create such an atmosphere as you describe. Despite your assertion that you're not leaking steam how are you sure? A small steam leak would be capable of creating "sauna".

More importantly for the vent design what is the assumption about steam quantity that the vent needs to cope with? This is needed for vent sizing.

George makes a good point about overfill. If your current design is all down from the tank then the vent would start to act like an overflow into this mysterious pit. Your new design with a constant slope up if filled with water crates a pressure of 7-10 psi on the tank which may not be suitable for it.

At the end of the day I would simply point this vent up on the basis that if you get a steam blow by you want it going up. Add a bird cage to stop it getting blocked and think about what might happen if your pump stops working or your high level switch jams.

Some pictures or a diagram would help....


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

 

[georgeverghese]

Agreed, check for any gas blowby / control valve failure scenarios for each of the feeds into this tank, and set up this vent pipe line size and length to keep backpressures on the drum within process design limits.

Must say the area around this new vent may turn out to be a swamp in a few years...