Transmitter Nitrogen Issue

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jbarth200
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Transmitter Nitrogen Issue

Post by jbarth200 » Thu Mar 22, 2018 9:37 am

Hi,

I am somewhat new to using a nitrogen solution on my RF line. I have a system where the nitrogen is pumped into my wave guide for my transmission line that goes my to antenna for OTA. My nitrogen tanks are empty within 2 days of connecting them to my system, I'm trying to determine if I have a leak somewhere. The biggest thing that is confusing me is, if I remove my nitrogen line from my wave guide...pressurized air is coming back out of the wave guide, this doesn't seem like it should be the case but I don't have much experience with this system. Any info regarding proper use if the nitrogen system and if I should feel any pressurized air coming out of my wave guide would be much appreciated.

Thanks

grich
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Re: Transmitter Nitrogen Issue

Post by grich » Thu Mar 22, 2018 9:42 am

What pressure is your regulator set to?

Have you tested for leaks at the tank?

jbarth200
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Re: Transmitter Nitrogen Issue

Post by jbarth200 » Thu Mar 22, 2018 9:51 am

Im on my 3rd nitrogen tank, I recently purchased a new regulator for the tank, from that regulator I goes through a 4 output manifold kit, all are closed except the gauge connected to my wave guide. I have been setting the regulator to show around 4 PSI on the manifold kit gauge that is connected to my wave guide. I initially thought I had a bad regulator as when I connected to a new tank and turned it in you can somewhat hear the air flow which made me tjink maybe i have a loose connection, but I have felt all around the regulator and do not feel any air escaping. And as stated which is the most confusing to me (it may not be as confusing to someone with more experience) is the fact that pressurized air is pushing back out from the waveguide to my regulator.

grich
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Re: Transmitter Nitrogen Issue

Post by grich » Thu Mar 22, 2018 10:37 am

Get some leak detector fluid or soapy water. Spray the fittings on the waveguide, manifold and N tank. Look for bubbles.

If you can't find a leak on the ground, you'll have to have a tower crew check the line.

jbarth200
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Re: Transmitter Nitrogen Issue

Post by jbarth200 » Thu Mar 22, 2018 11:14 am

Thanks, I will do that. Although if that were the case wouldn't you think when I remove my nitrogen cable from the waveguide I shouldn't feel pressurized air coming back out?

grich
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Re: Transmitter Nitrogen Issue

Post by grich » Thu Mar 22, 2018 11:41 am

Depends on the leak location. If the leak is where the nitrogen bottle connects to the regulator, the line MIGHT still hold some pressure.

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RGORJANCE
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Re: Transmitter Nitrogen Issue

Post by RGORJANCE » Thu Mar 22, 2018 11:58 am

I find that using a kids bubble liquid works really good as it is fairly viscous, and really makes good bubbles. Saw yesterday KMART had a basket full going for a buck each.

Get an empty spray jug like an old Windex bottle and put the bubble solution in that.

Fossil

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RGORJANCE
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Re: Transmitter Nitrogen Issue

Post by RGORJANCE » Thu Mar 22, 2018 12:02 pm

Whoops! Just remembered another issue. We had a site where the tanks were going empty pretty fast and found the leak was caused by a bad fitting that attached the regulator to the nitrogen tank. Check that fitting to see if it is grooved, or deformed. Don't over tighten as the nitro tank is steel, and the regulator fitting is brass.

If the fitting is bad, you will probably have to replace the whole regulator.

Fossil.

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PID_Stop
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Re: Transmitter Nitrogen Issue

Post by PID_Stop » Thu Mar 22, 2018 12:25 pm

jbarth200 wrote:
Thu Mar 22, 2018 9:51 am
And as stated which is the most confusing to me (it may not be as confusing to someone with more experience) is the fact that pressurized air is pushing back out from the waveguide to my regulator.
Let's suppose you're pressurizing 1,000 feet of 3-1/8" transmission line... that line has a volume on the order of 50 cubic feet, or about thirty times the volume of a size-300 bottle of nitrogen tank. When you pressurize the line, you're essentially filling a very large tank (albeit at a fairly low pressure). No surprise, then, that when you disconnect the fitting you will get the gas you put in, coming back out.

It's not so much that the transmission line is elastic (like a balloon)... it's that nitrogen gas is easily compressible.

Jeff

grich
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Re: Transmitter Nitrogen Issue

Post by grich » Thu Mar 22, 2018 1:47 pm

RGORJANCE wrote:
Thu Mar 22, 2018 12:02 pm
Whoops! Just remembered another issue. We had a site where the tanks were going empty pretty fast and found the leak was caused by a bad fitting that attached the regulator to the nitrogen tank. Check that fitting to see if it is grooved, or deformed. Don't over tighten as the nitro tank is steel, and the regulator fitting is brass.

If the fitting is bad, you will probably have to replace the whole regulator.

Fossil.
My boss crafted a washer from some copper strap, and inserts it into the valve. The soft copper seals around the deformity, and holds pressure perfectly.

jbarth200
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Re: Transmitter Nitrogen Issue

Post by jbarth200 » Thu Mar 22, 2018 1:58 pm

RGORJANCE wrote:
Thu Mar 22, 2018 12:02 pm
Whoops! Just remembered another issue. We had a site where the tanks were going empty pretty fast and found the leak was caused by a bad fitting that attached the regulator to the nitrogen tank. Check that fitting to see if it is grooved, or deformed. Don't over tighten as the nitro tank is steel, and the regulator fitting is brass.

If the fitting is bad, you will probably have to replace the whole regulator.

Fossil.

Could this explain why I hear airflow around the regulator and tank? As I would assume when the fittings are correct you shouldn't really hear any airflow? I purchased a new regulator and installed it this week. Although I cannot feel any leaks around the regulator to tank connection is it still possible it's a bad fitting? I did crank on the connection between the regulator and tank pretty hard to ensure it was tight..maybe I went to far?

I appreciate the responses from everyone.

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Re: Transmitter Nitrogen Issue

Post by NECRAT » Thu Mar 22, 2018 7:21 pm

Are you all waveguide to the antenna or do you transition to coax?

You say you have pressure when you disconnect the nitrogen tank, where do you have the pressure? On the line going into your regulator?

What size tanks are you buying for your system as well?

I had to replace a bad regulator about a year ago, as there was a leak somewhere in the controller part. I was loosing a lot of nitrogen, but not the alarming amount you are.

With the amount of Nitrogen you are losing, you have a very serious leak, especially if you're using "300" tanks. If your regulator was leaking air to drain a big tank like that in two days, you'd hear it very clearly.

At WNAC-TV in Providence, on our analog, we had a bad leak in our system. We were draining tanks at an alarming rate. At the base of the antenna was a Coax to Wave Guide adaptor that had a rather large hole in it. Because of the location of the hole, it never showed up as VSWR, and didn't affect the RF envelope at all.
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Re: Transmitter Nitrogen Issue

Post by Ray » Fri Mar 23, 2018 6:45 am

There is a product called Snoop that is similar to the Bubble soap that works well. I think Snoop is more sensitive than bubble soap.
I've used both; I use the Snoop if I have it, otherwise it is a trip to the toy store for bubbles. We also have an electronic air leak detector that works OK (some folks like it, others don't)

I know lots of folks use Nitrogen instead of dry air. I suppose Nitrogen is more inert and protects against corrosion better.
We have never had any issues using dry air dehydrators (no tanks to refill). The only issues occur if we lose pressure for an extended time.
I would be interested in the pros/cons of dry air vs Nitrogen.
I see the dry air dehydrators on ebay all the time for a few hundred dollars. Is the only advantage of Nitrogen corrosion protection?

Ray

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Shane
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Re: Transmitter Nitrogen Issue

Post by Shane » Fri Mar 23, 2018 9:43 am

Well, you don’t have to service a dehydrator if you use nitrogen. You won’t burn up a dehydrator on a leaky line with nitrogen. You won’t soil your underwear when the dehydrator fires up (I just do not ever get used to that!). There are probably better reasons.

I think one thing to try, if you haven’t already, is to pressurize the line to your 4 PSI, assuming it can hold any pressure at all, then turn off the valve from the tank.* See how long it takes for the 4 PSI to start to decrease. Also, if you still hear flow after shutting off the tank and the line pressure holds, you have found your leak.

*There may also be a valve by the manifold that lets you isolate the line upstream from the last gauge.

Hopefully, you’ll find your leak on the ground and not have to bring in the climbers.
Mike Shane, CBRE
---Omaha---

jbarth200
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Re: Transmitter Nitrogen Issue

Post by jbarth200 » Fri Mar 23, 2018 11:27 am

PID_Stop wrote:
Thu Mar 22, 2018 12:25 pm
jbarth200 wrote:
Thu Mar 22, 2018 9:51 am
And as stated which is the most confusing to me (it may not be as confusing to someone with more experience) is the fact that pressurized air is pushing back out from the waveguide to my regulator.
Let's suppose you're pressurizing 1,000 feet of 3-1/8" transmission line... that line has a volume on the order of 50 cubic feet, or about thirty times the volume of a size-300 bottle of nitrogen tank. When you pressurize the line, you're essentially filling a very large tank (albeit at a fairly low pressure). No surprise, then, that when you disconnect the fitting you will get the gas you put in, coming back out.

It's not so much that the transmission line is elastic (like a balloon)... it's that nitrogen gas is easily compressible.

Jeff
Okay that makes sense, but in terms of a leak in my waveguide, if I did indeed have a leak, would any pressurized air in the waveguide escape through the leak. So in theory when I remove my nitrogen input to the waveguide, I wouldn't feel air pushing back out if I had a leak?

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