how long should it take for main-line air vents to close? drip-leg and strainer maintenance ..

bkc

Hi,

Our church has a 2 pipe system on a 22HP Weil-Mclain LGB-8 boiler, with 3 remote condensate pumps and one boiler-room condensate tank/pump.

As near as I can tell there has been no maintenance on this system in more than 10 years, perhaps 20.

I am working through the system to develop a summer to-do list.

One thing I've noticed is 4 or 5 main-line air vents that continue to vent more than 2 hours after the boiler has begun making steam. Some of these vents are post-automatic valve. When the valves open and stay open for over an hour, the vents are still venting (e.g. during building warm-up after the boiler has been off for a few days..)

Can vents be repaired/rebuilt or is it better to replace them if we can afford it? I recall seeing an article about actual vent performance on this forum or somewhere else. If I have to replace the vents I'll check that out.




The one below appears to have been failed for a long time, the paint has been steamed off the old metal ceiling panels



video of same vent https://photos.app.goo.gl/wxSv3qycmtrSPkuE8



How often should strainers be cleaned? Do I only need to drain the strainer (inner-most plug), or should I remove the strainer and inspect it (outer-most plug?)

Should the cap on the drip-leg be removed and drained?



Finally, are these main-line plugs intended to be removed, perhaps for inspection or are they for potential future connections?



Thanks,
-B

JUGHNE

Are the vents passing air or steam? An inspection mirror would fog up if steam.
You may not see the steam.
If passing steam then replacement is usually the option. Gorton #2 steam main vents are a good buy for the high capacity.
Actually 2 pipe systems usually vent thru the condensate pump, you may have an unusual sit up though.
More pictures showing all the piping at the boiler, floor to ceiling and around the air vents may help.

IIWM, I would remove the small plug on the strainers and install a ball valve in it.
Then you can check the strainers by blowing down with the ball valve, while in operation.....careful very hot....also cap the ball valve for safety.
Removing the large nut (if possible) will let you remove the strainer screen, there may be a gasket. What is downstream of the strainer?

The drip pipes just about never get checked.
I have seen some completely full of sludge and backing up into the tee headed for the strainer. It usually takes a few years to accumulate much.

Jamie Hall

Those vents are cute. They are also woefully inadequate to be main vents. As @JUGHNE said, are they venting steam or air? The mirror test works, but you can also check to see if the pipe leading to them is steam hot. They could also be failed closed -- or, given that at least some of them seem to be on uninsulated pipe, the steam just may never get there at all.

As a further check, however -- are they all really on steam mains and not on the dry returns? If they are on dry returns, and your traps are working, they never will see steam at all.

bkc

Hi,

All of the vents are on main supply lines that are carrying steam and are super hot (checked by burning myself and/or IR camera). All of the radiators on these legs were plenty hot, having raised the temp of the rooms from 55 to 70F over the course of 2 hours.

There are no vents in the boiler room.

all condensate receivers do have an open air-vent, but that's on the return side. These vents are on the supply side.

downstream of the strainer pictured above is an F/T trap.

I'll try the mirror trick, but given the 2 hour runtime and temperature I'm quite sure its steam. Thanks

dopey27177

Here is the dilemma!
In two pipe steam systems vent valves do not belong.
In two pipe steam systems only stem traps are to be used, F&T traps are the choice.
Strainers should be cleaned before each heating season.
Remove the plugs and install nipples and ball valves.
Restore your two pipe system and get rid of the air vents.

Jake

Jamie Hall

With all due respect to your expertise, @dopey27177 , I beg to differ. While it is quite true that in some types of two pipe steam systems vent valves do not belong, and F&T traps may be the choice, on many, if not most, systems, main line vents or dry return air vents not only belong, but are in fact required, and F&T traps do not belong, and are to be avoided if possible.

If you meant that vents should not be on radiators in two pipe systems, this is true (except in rare cases).

dopey27177

Dear JAMIE HALL

When Steam Traps are used in two pipe steam systems with condensate pumps the steam systems must be
equipped with F&T traps or a float trap with a vent valve at the top outlet small plug of the float trap.

From what I have gleaned from bkc is because of costs some uninformed church members decided to take the cheap path to maintain their two pipe steam systems and used a company or companies to upgrade or maintain the steam system. ( Unfortunately many houses of worship or small schools take the cheap path for maintenance forgetting that steam systems are a long term investment).

The only treason I can see to use 3 remote condensate pumps is the possibility of zoning three locations or operating them at lower zone temperatures with possibly using an automatic valve controlled by a thermostat or torque clock when the zones need heat.

We are not talking about a two pipe vapor system where crossover traps are needed to vent air to the dry return.

Condensate pumps must have steam traps installed to prevent steam from exiting the vent on the condensate pump or in rare instances the the vent from the condensate pump is tied into the dry return to vent air and steam vapors to the dry return where in some rare instances the system will work on an induced vacuum. Those systems are very rare in use.

This is my view based on what was shown in the pictures.

The best move for long term economical results is to restore the system to a true 2 pipe steqm system.

Jake

Jamie Hall

Yes. In the case of condensate pumps (or boiler feed pumps) and receivers -- F&Ts are required. That's one of the exceptions!

Steamhead

However, with regard to steam mains, F&T traps may not have enough air throughput to vent them adequately. In that case, you either need large main vents such as Gorton #2, or a huge crossover trap like this one:

https://forum.heatinghelp.com/discussion/142217/the-king-of-all-crossover-traps

dopey27177

Steam head said big vent valve or large cross over trap'

I don"t think so!

As stated there are 4 condensate pumps, that means at least 4 F&T traps.
If a 3/4 or 1" trap is used the orifice is .313"" diameter, A 1 1/4" steam trap has a .344 orifice.

These orifice sizes compared to a vent valve orifice are huge. so the problem with getting rid of air is not venting with F&T Traps.

There is a possibility that some of the end of steam main traps are thermostatic traps and they may be defective or there are crossover traps in the building that are defective or were removed.

Looking again at the plugs in the steam side of the system and the placement of the vent valves I believe that the original F&T traps were removed and vent valves were installed in their place.

The only proper way to fix this system is to restore it to original installation design.

If money is a problem run a raffle for a nice TV set and use the that income to repair the system.

Jake

Steamhead

@dopey27177 , I based that on the throughput values in @gerry gill 's and @StevePajek 's chart, here:

https://heatinghelp.com/assets/documents/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-1.pdf

According to the chart, at 1 ounce pressure, the usual Sarco or Hoffman six-bolt F&T trap will vent 0.5 cubic feet per minute (CFM). Barnes & Jones six-bolts do a bit better, 0.75. Note that B&J six-bolt trap kits will fit Sarco and Hoffman bodies, so that's one way to upgrade these traps.

Sterling F&T traps have even better vent throughputs- 1.3 CFM at 1 ounce, but I don't think they make six-bolt trap kits.

At one ounce pressure, a Gorton #2 vent is good for 1.1 CFM. The B&J Big Mouth doesn't appear on the chart. Neither does the monster Nicholson C73HC in the thread I linked to.

So it looks like the easiest way to add venting capacity is to add main vents. This is much easier than repiping F&T traps.

Jamie Hall

Furthermore, vents don't upset the pressure balances in a steam system. F&T traps do, and that must be taken into account in the design of the system.

bkc

@Jamie Hall @dopey27177

These vents are venting steam, here's a video https://photos.app.goo.gl/bKznomAEhbnTZN979

All but one of the vents are placed just before end-of-main F/T traps, and all the vents are located on main lines that are gated by automatic valves.

While the church is low on funds now, I would say that was not always so. I doubt church trustees have removed any components, nor advised a qualified contractor to "take short-cuts".

@Steamhead thanks for reposting the vent capacity chart, I knew I'd seen that somewhere.

-Brad

Steamhead

@bkc , how long is each steam main, and what pipe size?

Jamie Hall

If these vents are venting steam, and if they are on steam mains, they're busted. They're busted in any case come to think of it, and need to be replaced.

That said... First check your gauge pressure. Anything over 3 psi is damaging to vents, anything over 5 or so -- other than a one shot -- will kill them.

Second, if they are on a dry return -- a true dry return, not a steam main coming back to the boiler -- they should not have steam at them, and you need to find out what other traps are leaking or busted.