Aquatic Plant Forum banner

21 - 40 of 43 Posts

·
regulator
Joined
·
928 Posts
in the less general case of pressurized tanks and regulator connections - it seems the only place I see evidence of taping cylinder threads being advised - is in Milwaukee instructions and people who quote them. Or is that wrong? Welding shops and welders around here say its wrong to tape cylinder connections to the regulator. Is it a central Indiana thing or is that typical for regulator-tank connections everywhere? Do your welding shops say tape reg connection or not to? :)

I looked into the thread situation for the CO2 bottles and regulators before I spoke even thou I thought I knew the answer from doing piping for years, many years ago. They are what is called NPT = National Pipe Thread. Same as on piping. They do have a taper. Hydraulic lines tend to use ferrels to seal the connection. Pipe dope is used all the time on water, steam and gas.
 

·
Registered
Joined
·
3,136 Posts
ashappard,
The only place I've ever seen teflon tape used on regulators is on the gauges and other connections. I've been in manufacturing engineering for over 25 years and seen lots of equipment. Teflon tape and various types of teflon paste and pipe dopes are used all the time on water, steam and gas piping. You do need to becareful not to overtighten.

As soon as I need to remove my MA957 to refill the bottle I will be removing the teflon tape.
 

·
Registered
Joined
·
1,461 Posts
I looked into the thread situation for the CO2 bottles and regulators before I spoke even thou I thought I knew the answer from doing piping for years, many years ago. They are what is called NPT = National Pipe Thread. Same as on piping. They do have a taper. Hydraulic lines tend to use ferrels to seal the connection. Pipe dope is used all the time on water, steam and gas.
pipe dope is perfectly fine on all those lines, infact its recomended. Those are also relativly low presure systems

On hydrolic or high presure lines it will get red taged and failed.( atleast in CA)
 

·
regulator
Joined
·
928 Posts
ashappard,
The only place I've ever seen teflon tape used on regulators is on the gauges and other connections. I've been in manufacturing engineering for over 25 years and seen lots of equipment. Teflon tape and various types of teflon paste and pipe dopes are used all the time on water, steam and gas piping. You do need to becareful not to overtighten.

As soon as I need to remove my MA957 to refill the bottle I will be removing the teflon tape.
just trying to keep the discussion relevant - I can understand all the myriad ways that piping connections are made -- in the case of regulator to cylinder, tape isn't advised when I talk to welders. These folks say need for tape means the reg isn't sealing proper, I cant really argue with that. I taped my MA957s for quite a while and took flack at the shops for it, but mostly shrugged it off, because the forum guys and my Milwaukee instructions said thats how to do it. So if anything hopefully this is a discussion about how to get a great seal without lots of hassle?

When I came across permaseals it was excellent. Quicker changeover, less worry about leaks and no more taping. I have had to change o-rings on permaseals. They get ragged after a while. Lucky for me, I got the shop I exchange tanks with interested in permaseals and they now stock the orings and the two brass pieces that make up the seal.

seems the board is lighting up recently with pressurized CO2 discussion. Nice.
 

·
Registered
Joined
·
3,136 Posts
Maybe when I do my weekly maintenance on Monday on my 75 I will take the regulator off.It wont be empty for about a year. I'll take a picture of the nipple and nut connection used on that. No washers/seals, just brass on brass -never had a leak. I think its an argon/CO2 nipple with a female compesssion nut. It was being used this way on a CO2 tank some welders were using to weld 316ss pieces.
 

·
Registered
Joined
·
216 Posts
I have a friend who has worked for years with medical O2 tanks, regulators, etc on a daily basis. He told me that we should never, ever use tape (or dope) on the high pressure connection between the cylinder and the regulator. Any of the low pressure parts are fine to be taped, though. I totally trust his 15 years of experience with high pressure gas systems.
 

·
Premium Member
Joined
·
8,540 Posts
Discussion Starter #29
My welding shop also says NO TAPE. I check with Orlando at Greenleafaquariums.com and he also said no tape. He also said no pipe dope.

What I know is that I don't tape, or dope. I use permaseals on two tanks and the nylon washer on the other. No leaks, they last a long time. It's working for me- not broke so I'm not gonna fix it. :D
 

·
Registered
Joined
·
3,136 Posts
Yeah, I've never seen a taped connection for the regulator to the tank valve and I'm not sure why Milwaukee tells you to do so but its odd that after a tank hydrotest they always put new tape or dope the threads on the valve stem to the cylinder - steel anyway. I'm not sure about aluminum as you cant see the valve stem threads as it is a different style valve.
 

·
Registered
Joined
·
2,156 Posts
This is something that I wasn't told until I talked with my local welding supply ... The difference between dual (or two) stage regulators and single stage regulators. They are basically two regulators in one.



DUAL STAGE regulators reduce the source pressure down to the desired delivery pressure in two steps. Each stage consists of a spring, diaphragm, and control valve. The first stage reduces the inlet pressure to about three times the maximum working pressure. The final pressure reduction occurs in the second stage. The advantage of a dual stage regulator is its ability to deliver a constant pressure, even with a decrease in inlet pressure. For example, as a cylinder of gas is depleted, the cylinder pressure drops. Under these conditions, single stage regulators exhibit a "decaying inlet characteristic"; where the delivery pressure increases as a result of the decrease in inlet pressure. In a dual stage regulator, the second stage compensates for this increase, providing a constant delivery pressure regardless of inlet pressure conditions. The dual stage regulator is recommended for applications where a continuous supply of gas is required; such as the gas supplied to analytical instruments where constant delivery pressure is critical.



SINGLE STAGE regulators perform the same function as the two stage regulator using a single step reduction of source to outlet pressure. For this reason, the outlet pressure cannot be as accurately controlled as the source pressure decays. It is highly recommended that single stage regulators only be used in circumstances where the operator can monitor and adjust the regulator as needed or where the regulator is supplied a nearly constant source pressure.
 

·
Registered
Joined
·
624 Posts
My welding shop also says NO TAPE. I check with Orlando at Greenleafaquariums.com and he also said no tape. He also said no pipe dope.

What I know is that I don't tape, or dope. I use permaseals on two tanks and the nylon washer on the other. No leaks, they last a long time. It's working for me- not broke so I'm not gonna fix it. :D
I don't use either because my regulator uses a built in rubber O-ring that is on what I think is called the inlet nipple. It's the part that pressed up against the outlet hole on the Co2 tank when you tighten the nut. I checked for leaks and did not find any. It's now been over two months and I have to do my first tank refill.
 

·
Registered
Joined
·
15 Posts
ive never taped the thousands of bottles of any gas(im a union ironworker) i have ever used!
they are straight threads they seal by the fitting internally.
all other connections can/should be taped. do not get tape on the insides of the connections.
 

·
Registered
Joined
·
384 Posts
I use tape, I clean off the threads between each application and when I return bottles I clean them off. I don't see what harm plumbers tape is going to do to it.
 

·
Registered
Joined
·
15 Posts
I use tape, I clean off the threads between each application and when I return bottles I clean them off. I don't see what harm plumbers tape is going to do to it.
the harm is that the fitting isnt designed to seal at the threads. it can leak if you tape the threads.
you can split the fitting on the regulator taping the threads.
 

·
Registered
Joined
·
596 Posts
There is nothing to seal the nut against the inlet nipple so, I don't think taping the threads will provide a tight seal. If it were to leak, it would most likely leak out of the back of the nut. The nut is only there to force the flat of the nipple against the valve in the cylinder. You need the washer or permaseal at the end of the nipple to form the seal.

Putting tape on the input might cause pieces of tape to enter the regulator. Putting tape on the output won't hurt the regulator but might cause pieces of tape to enter the solenoid.
 

·
Registered
Joined
·
2,156 Posts
CGA-320 reads are not like NPT tapered threads that need pipe dope or Teflon tape for sealing. A washer fits between the male and female ends that forms a leak free seal when tightened properly.

From: http://fins.actwin.com/aquatic-plants/month.200411/msg00022.html
"Tape is neither necessary nor especially useful. It won't improve the seal and you shouldn't expect it to. The tank should have CGA 320 fitting on it with male threads and the regulator should have CGA 320 female fitting. CGA 320 fittings are *not* like standard pipe threads. With standard pipe threads, the tapered threads provide the seal and using tape or pipe dough helps ensure that the threads don't have any small gaps. But the CGA fittings *do not* seal at the threads! They seal where the flat faces of the two fittings meet and that's why you *must* have a fiber or nylon washer between the two -- to seal the joint where those to seats meet. In fact, applying tape makes it possible to bind the threads before the fittings are fully seated against the washer -- although it would take a lot of tape to do that. ..."

From: http://reefkeeping.com/joomla/index...ctors-in-out-and-everything-in-between-part-1
"The valve used in the cylinder is typically made out of forged brass and in the US has a Compressed Gas Association (CGA) connection type 320 (see diagram) that requires a flat washer to provide the seal. This washer should be replaced every time the regulator is reconnected. Do not use Teflon tape or any other type of sealant but the washer. The company filling the cylinder can provide you with new washers. Note that there are different valve and connection specifications throughout the world, so insure you check your local specifications."
 

·
Registered
Joined
·
28 Posts
I use tape, I clean off the threads between each application and when I return bottles I clean them off. I don't see what harm plumbers tape is going to do to it.
The seal from the tank to the regulator is at the CGA 320 nipple and face of the valve on the tank. The threads have nothing to do with the seal and the tape can actually prevent you from tightening the nut adequately for a good seal, then it being high pressure even though it is sealed pieces of tape can get in the regulator and clog it or you can have a slow leak. I use tape or dope on any fitting where the threads actually act as part of the seal. Just my 2 cents.
 
21 - 40 of 43 Posts
Top