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Troubleshooting Gas Regulator

Troubleshooting Gas Regulator


Components in a typical gas regulator :

1. Inlet (High) Pressure Gauge
2. Inlet Connection
3. Safety Valve
4. Outlet Connection
5. Outlet (low) Pressure Gauge
6. Regulator Body
7. Diaphragm Valve




Introduction to Gas Regulators.

Why do we even need regulators? Regulators take a high pressure gas, and reduce it to a useable pressure for various applications like running an instrument (GC, GC-MS, ICP-MS, AAS, calorimeter bomb, incubator, etc), pressure testing, hydraulic charging, gas piping, welding, bubbling, sampling system and many other applications. A typical gas cylinder is filled to a pressure of about 200 bar (3000 psi) and need a gas regulator to reduce pressure down to say 5 bar (70 psi) to run a GC analysis. 

Another type of pressure regulator is installed with a flow gauge or flowmeter instead of a pressure gauge. These pressure regulators take a tank pressure of 200 bar (3000 psi) and drop it down to where the gauge reads in liter per minute (LPM) . Mig and Tig welders have regulators that display LPM.

People are often mistaken when they see a pressure regulator with two gauges. They will refer to them as "two stage" regulators. A two stage regulator will have kind of a bulb on the back and this houses a second regulator or "stage". These regulators keep the outlet pressure at a consistant level even as the cylinder pressure lowers. Research labs will frequently have this syle of regulator in tandem with test equipment. These pressure regulators are sometimes called dual stage or multistage regulators. 

Carbon Dioxide CO2 Regulator / Flowgauge

What is Co2? It is a colorless gas made up of carbon and oxygen. Carbon Dioxide is one of the more versatile gases. It can be used as a shielding gas for welding, carbonation for sodas, dispensing beer, in cell culture incubators and even making dry ice. These are just a few of its uses.

Cylinders of Carbon Dioxide or CO2 are different than most gas cylinders. Oxygen, nitrogen, helium and argon for example are pumped into cylinders as a gas at about  200 bar (3000 psi) for larger cylinders.
 

Carbon dioxide is pumped into the cylinder as a liquid and the pressure reaches only about  70 bar (1000 psi). As the CO2 warms it will fill the top of the cylinder with gas and the lower portion of the cylinder will remain a liquid until a time comes where the head pressure drops and allows more of the liquid to become gas.
 

CO2 regulators are probably one of the more misunderstood regulators. The tank pressure gauge seems like it is always almost full and then before you know it the tank is empty. It gives you a false sense of security seeing the tank pressure reading full then suddenly the needle drops to show that you are almost out of gas. What is happening is the liquid CO2 in the lower portion of the cylinder is changing to a gaseous state creating head pressure then it is used. This process is continued until the liquid is almost gone. Without the liquid to make the gas the cylinder pressure falls fast.
 

If the tank pressure is so unreliable how can you tell how full the cylinder actually is. The best way is to check the weight. Just like the LPG tanks we use for cooking, as the gas is depleted, the gas tanks will be lighter in weight.


Carbon Dioxide Regulator

CO2 regulator with flowmeter

Even though this flow gauge looks radically different than the one previously discussed, their operation is the same with one exception. This regulator is used in a high flow applications.

CO2 is extremely cold. If the regulator is controlling a high rate of CO2 the body of the regulator becomes cold enough that it doesn't allow the CO2 in the cylinder to warm enough to create CO2 gas. If the flow gauge isn't able to warm the liquid to a gaseous state it will spit out small pieces of dry ice.
 

The fins on the flow gauge create more surface area so that the flow gauge allows the ambient air to warm the regulator thus creating CO2 gas. There are times when the flow rate is so great that these will even freeze up. If this is the case then there are CO2 regulators with heater that you can plug into a socket outlet to power an internal heater.
 

There are CO2 regulators that do not have the float tube but use a dial gauge instead. Either way they will read flow rate in liter per minute (LPM). Be careful not to get a flow regulator confused with a pressure regulator. A pressure regulator will read in BAR/PSI/kPA and not liter per minute (LPM).
 

NEVER Use Oil on any Gauges or Regulators.

If you look closely at a regulator gauge you will see the instructions USE NO OIL. There is a reason for this. If pure oxygen or high pressure gas comes in contact with oil it can ignite and cause a fire.

Oil and Oxygen Don't Mix

The following demonstration is an example of mixing oil and pure oxygen. The dropping of the weight is an example of the high pressure of the gas coming in contact with the oil. Repeat NEVER use oil on regulators.

It Seems Like the Cylinder of Gas Didn't Last Very Long

What is Wrong with my Regulator?

This can happen when cylinder valves are not shut off after use. Small leaks can also happen at any place where two parts come together. How do you find leaks on a regulator? There are those in the industry that will look for leaks like you would in an innertube and that would be to use soapy water. When it comes to finding a leak in high pressure cylinders or regulators... DON'T USE SOAP. If you look at the label you will likely see the soap is made out of some sort of oil or petroleum based product. Remember DO NOT MIX OIL AND OXYGEN. 

There are products that are safe for leak detection. We carry leak detector that is non-oil based.

Snoop!

Finding Gas Leaks Safely

Snoop is a totally safe liquid that is applied to places where two pieces come together. At the base of gauges, inlet nipple, tank nipple or any place you feel that needs to be checked. Checking joints for leaks might save you a lot from losses from gas leaks but most important it might save lives.

My Regulator Gives Me the Creeps!!!

Probably the most major problem that a regulator can have is when the outlet gauge starts to rise and just keeps going till it is pegged. When this happens the diaphragm is shot and needs to be replaced. If you have a good regulator (Victor, Smith, Harris) in most cases they are worth repairing. Ask for a quote on the repair and the price of a new regulator and then decide on which option to take.. If it is a cheapo regulator just ditch it and get a new one. More than likely parts aren't available for them.

What Happened to my Gauges?

Periodically the needles get bent, don't return to zero or even get totally pegged and stay. This is an easy fix. Just order up the exact size and pressure gauge as the defective one. Most gauges are 1/4 pipe thread and the 1 1/2" gauges are 1/8 pipe thread. Remove old gauge, remove any dried lock tite and wrap the threads of the new gauge with a couple of wraps of teflon tape and install. You can request us to replace the gauge for just the price of the gauge and not charge labor. We believe in saving costs for our customers.

Apply Leak Detector... Now what?

Simply look for the bubbles. They can be very tiny bubbles that look almost like foam for small leaks or larger bubbles for larger leaks. if the leaks are coming from the regulator where the gauges are screwed in, these can be backed out and teflon tape can be applied and gauge turned back into regulator.

The same can be done for the nipple going into the regulator. Be aware that from the factory these parts are installed with loctite and can be difficult to remove. Most regulators are made of brass and the parts can be damaged very easily.
 

If the bubbles are coming from where the nut of the regulator meets the cylinder it can sometimes be corrected by tightening the nut more to cinch it down and seal it. Be careful not to overtighten and never use teflon tape where the nipple meets the cylinder valve.
 

If there is a large leak coming from the body of the regulator through holes in the body or through an external safety there has been a rupture in the safety and should be sent back to us for checking and repair.

External repairs :

The external repairs of regulators are pretty simple, yet if done wrong can be dangerous. If you make the mistake of putting a low pressure gauge where the high pressure inlet is you will make that gauge explode. Remember be careful, do not use oil, replace gauges one at a time with the exact pressure reading gauge as the stock equipment.

For more information on compressed gases, please surf Gasworld (www.gasworld.com)