Gas pressure regulator question. - Page 1
Forum section: electronics / projects

author: DTJ
author_rank: Super Contributor
timestamp: September 14, 2019, 10:36:19 am
content: It's a little off topic but I know people here know about all sorts of stuff!I'm using Sodastream CO2 cylinders with my infrequently used MIG welder.I purchased a new MK4 Kegland gas regulator (https://www.kegland.com.au/co2-gas-regulator-mk4-dual-gauge-multi-gas-type-30.html).It behaves a strangely. If the output is set to say 10 PSI and the gas is flowing it is fine. However the if the gas flow is stopped (by the solenoid in the welder) the secondary pressure in the regulator climbs until its nearly full scale. The over pressure relief valve then opens, and the pressure drops right back. This cycle repeats with the pressure slowly oscillating wasting gas.Do some regulators work this way? I think its faulty and the internal diaphragm operated valve has a slow leak causing the oscillation when the output is dead-headed.Thoughts?

author: jpanhalt
author_rank: Super Contributor
timestamp: September 14, 2019, 10:46:30 am
content: That is not normal operation. Sounds like the pressure control valve (a needle valve inside) or diaphram in the regulator is faulty. In the US, getting regulators repaired is almost impossible because of liability/regulatory concerns. One simply replaces them.

author: tautech
author_rank: Super Contributor
timestamp: September 14, 2019, 10:48:10 am
content: Good regulators don't creep however as they age some do.Cleanliness of the bottle and reg fittings prior to mating is important to keep crap out that might damage the regulator valve seat.For MIG you're better off with a flow meter type regulator like this one:https://www.wish.com/product/5948c1df7f90b37287b024ec?hide_login_modal=true&from_ad=goog_shopping&_display_country_code=NZ&_force_currency_code=NZD&pid=googleadwords_int&c=%7BcampaignId%7D&ad_cid=5948c1df7f90b37287b024ec&ad_cc=NZ&ad_curr=NZD&ad_price=23.00&campaign_id=1643927955&gclid=Cj0KCQjwn_LrBRD4ARIsAFEQFKu4dfADaJkLcKUUo9jQ3GBcFa61vI65gVG3CHuZJtHjY7Z2-n1-L2AaAv3VEALw_wcB

author: DTJ
author_rank: Super Contributor
timestamp: September 14, 2019, 12:45:02 pm
content: Thanks tautech & jpanhalt. It sounds like I've got a dud regulator.I thought (wrongly) that perhaps there might be some cheap arse regulators that only regulate while there is flow. I'll have a look at it in the morning and probably take it back. It was cheap, only $50.I've got an old medical O2 rotameter in a drawer somewhere I should dig it out and see if it matches the flow rate for the MIG.

author: jpanhalt
author_rank: Super Contributor
timestamp: September 14, 2019, 12:54:40 pm
content: A leaky regulator can be very dangerous as it may expose whatever it is attached to to full tank pressure.I don't know about the connector you have. CO2 has at least two standard connectors in the US. One (less common) is flat faced and uses a sealing washer. The other is a more standard looking CGA type with a washerless seal. Switching from one regulator connection to another type (e.g., CO2 to O2) is done, but regulatory agencies frown on that practice. Good luck.

author: DTJ
author_rank: Super Contributor
timestamp: September 14, 2019, 01:44:38 pm
content: Yeah I had thought of that. Full cylinder pressure is dangerous stuff.It seems the standard for CO2 here in Australia is called an Type 30 connection. Its a flat face connection with a plastic sealing washer.TYPE 30 0.860” WHIT RH, 14 T.P.I. Flat end sealing face, thread O.D. 21.8mmThanks.

author: jpanhalt
author_rank: Super Contributor
timestamp: September 14, 2019, 01:57:47 pm
content: That CO2 fitting sounds like what we have here. Our CO2 cylinders are relatively low pressure. You may consider switching to argon/CO2. The CO2 percentage is non-standardized. 20% is common. The cost difference from my local dealer for similar sized bottles is only about $2 per refill (I own the bottles).

author: FreddieChopin
author_rank: Regular Contributor
timestamp: September 14, 2019, 06:15:43 pm
content: Stable gas flow is very important for doing proper welds. Get a two stage regulator with flowmeter, I can recommendPerun regulators. They are pretty affordable and of superb quality when compared to chinese turds. I'm using 2RBArg-0.15 model and it serves me well doing TIG welds. I think I'd never put a dodgy chinesium regulator onto a pressurized cylinder.

author: amyk
author_rank: Super Contributor
timestamp: September 14, 2019, 06:56:23 pm
content: If it's new there could just be some dirt (possibly left over from manufacturing) in there. You can set the output pressure to 0, cap off the output, and it should stay at 0. Try to clean the seat and valve first.

author: tautech
author_rank: Super Contributor
timestamp: September 14, 2019, 08:29:40 pm
content: Quote from: jpanhalt on September 14, 2019, 01:57:47 pmDTJ hasn't said what he is welding and what wire he's using and if ordinary MIG wire I agree with you.However if he's using gasless wire and CO2 as I've seen some engineers do this combo produces really nice welds.

author: DTJ
author_rank: Super Contributor
timestamp: September 15, 2019, 12:52:22 pm
content: It seems Amyk was right - there may have been crap inside the reg from manufacture.I was planning to return it to the shop today.Before doing that I cranked the pressure right up and flushed a heap of gas through. The regulator has an over pressure valve with a pull ring on it. I unscrewed that and let the gas flush it out. After this it seems to work OK.I did a pile of welding today (0.6mm MIG wire + CO2) and the Sodastream bottle is still almost full so I'm pleased with the outcome.

author: lwatts666
author_rank: Unknown
timestamp: September 22, 2019, 03:50:46 am
content: If the Sodastream bottle is not upright, liquid CO2 may be getting to the regulator needle valve and flashing into solid CO2 on the low pressure side. When the solenoid valve closes, the solid CO2 continues to evaporate, increasing the pressure.Large flow rate CO2 regulators often use electric heaters to prevent this effect.

author: DTJ
author_rank: Super Contributor
timestamp: September 22, 2019, 04:34:59 am
content: Thanks lwatts666, I was not aware that that was an issue (I had not thought about it).I've got the bottle vertical and am drawing off slowly so hopefully it wont happen. It's working well at the moment. I'm surprised how little gas I'm using.