FAQ

Flow is a function of three parameters: the size of the orifice(s) inside the regulator, the pressure upstream of the valve, and the pressure downstream of the valve. For Aqua Environment’s 415 and 873 series regulators, we have flow charts as these regulators effectively have two orifices that constrict the flow. Using the Regulator Flow Charts here and knowing the application’s upstream and downstream pressures the flow can be calculated. For Aqua Environment’s other regulators and valves, only a single orifice constricts the flow. Each valve’s O&M sheet or technical bulletin will list the effective orifice size for that valve. With the orifice size and the equation given in our application note “Equations for Flow Through Orifices” the flow through the valve can be calculated based on both the upstream and downstream pressures. We are happy to provide assistance calculating the flow for your application – please call or email the factory.

Yes, different gases will flow at different rates based on their molecular weight. The equation in our application note Flow Through Orifices assumes the medium is air; however, correction factors for several other gases are given. If your gas is not listed in the note, please contact the factory to determine the correction factor for the gas you are using.

As with any valve or piping system, flow only occurs if there is some pressure drop. For most applications, pressure drop becomes negligible (about 1% of line pressure) when the flow is about 30% of that shown on the technical note Regulator Flow Charts or flow is about 10% of that given by Equations for Flow Through Orifices.

The temperature range of any given valve can be found in the online catalog; however, there are some general guidelines. The lower limit is usually determined by the o-rings – as they become cold they lose their pliability and ability to provide a seal. Viton o-rings, our standard, we rate down to -15 degrees F. We provide buna o-rings for low-temperature applications that we can rate down to -50 degrees F and special low-temperature o-rings that we can rate down to -65 degrees F. The high-temperature range is limited by the properties of aluminum. At higher temperatures, aluminum loses significant strength. As these are high-pressure valves, we wish to ensure no strength reduction and as such recommend our valves are used at temperatures no higher than 200 degrees F. For further information, please consult with the factory.

Freeze-up is related to a large number of factors including the flow requirements of the system, the pressure drop through the valve or regulator, the presence of moisture in the flow, design, and maintenance of moisture separators, maintenance of drying agents, ambient temperatures, and other factors. It is extremely difficult to predict how all these issues will factor into possible freeze-up problems with a regulator. In general, most systems do not experience freeze-up. One exception is natural gas systems using the filtered or standard cartridge in the 873 lines of regulators. For this reason, we developed the non-filtered version of the cartridge. For extreme cases, we offer a heating manifold that can be attached to the 873 body and allows the system designer to pass hot water through the body thereby keeping it warm. For further discussion see our application note: “Avoiding Regulator Freeze-up” or contact the factory.

Gas compatibility is a function of the materials used to assemble the regulator or valve. In the O&M sheet for each valve or in the online catalog the materials used are listed. Commonly used gases that are fine with our regulators include air, nitrogen, natural gas, helium, hydrogen, and argon. All these have no compatibility issues with our regulators. Natural gas has some special issues which we address in the natural gas compatibility question below. Oxygen can be used in some of our valves but requires special considerations. Some of these are discussed below. If you need to know about the compatibility of other gases please contact the factory.

Natural gas is compatible with all our valves. Sometimes issues arise due to the other components or contaminants within the natural gas. Some of these can have deteriorating effects, especially on the o-rings used for seals. Some customers prefer Viton seals, other customers prefer buna seals. Each group claims their favored material holds up better with their particular variation of CNG. We can provide our valves and regulators with a variety of seals to meet each application’s needs.

We generally recommend using the non-vented version of our regulators when used with natural gas or any other toxic gas as the vented versions vent to the atmosphere. If the regulator is located outdoors this may not be necessary, but if the vented gas is in a confined space then the vented gas could become a hazard. Additionally, we manufacture a non-filtered version of our 873 cartridges. Generally, the filter helps prolong the life of the cartridge; however, these filters can freeze up and crush in natural gas applications due to the extreme JT cooling effect inherent with natural gas. The non-filtered version will not have the freeze-up problem but to prolong the life of the seat we recommend installing our T-filter upstream of the 873 regulators. For more about cooling see the application note “Avoiding Regulator Freeze-Up“.

When the pressure downstream of a vented regulator exceeds the set pressure by some amount (this varies based on the regulator) that excess pressure is vented out of the regulator to the atmosphere. A non-vented regulator will not vent excess pressure downstream of the regulator. The choice of vented or non-vented is application specific. Please contact the factory if you have any questions about your application. We recommend having a relief valve downstream of all regulators, vented or non-vented.

Any regulator can fail, particularly if it is not properly maintained or the gas flowing through the regulator is dirty or contaminated. If the regulator fails in an open mode – a mode that allows gas to continue to flow through it – then the components downstream of the regulator may be subjected to pressures higher than their design pressure. A relief valve is a simple safety device that acts as a backup to prevent catastrophic failure of those downstream components. It should be set a few percent over the downstream pressure for the system.

In general, gas analyzers require only a few psi of pressure at their inlets. To step down from high pressure to just a few psi requires two stages of regulation. One of our regulators (generally we recommend either the 1247 or 969 regulators) can be used to step the pressure down to about 150 psi. Then a low-cost, shop air regulator can be used to step the pressure down to the desired final pressure. Please protect the regulators using relief valves. See our application note “Controlling Pressures in the 2 to 200 PSI Range” for more details and part numbers.

A regulator operates by balancing pressures and spring forces. All regulators, whether they are balanced or unbalanced, will be unbalanced to at least a small degree to ensure the regulator seat closes and prevents flow when the set pressure is met or exceeded. Hence the inlet pressure is acting to shut the regulator. This unbalanced closing force must be countered by the spring that opens the valve. The third piece of the puzzle is the outlet pressure, which is also acting to close the valve. As the outlet pressure increases the valve must close when the set pressure is met. The inlet and outlet pressures are both acting to close the valve while the spring is acting to open it. As the inlet pressure decreases, there is less force to close the valve while the spring force opening the valve remains the same. Hence the outlet pressure required to close the valve increases. The net result is that as the inlet pressure falls, the outlet set pressure will rise.

The ratio of rise to fall depends upon the regulator. For each regulator, we have listed the outlet variation based on inlet variation in both the O&M sheets and the online catalog. In general, the lower outlet versions will have the least amount of outlet pressure variation due to inlet pressure variations. The balanced regulators will have less variation than the unbalanced regulators and our high-accuracy pilot-operated regulator minimizes outlet variation.

Finally, the 1247 line of regulators is the exception. Their outlet pressure decreases with decreasing inlet pressure as they are unbalanced in the opposite sense regarding outlet pressure.

A balanced regulator has the inlet pressure acting on two opposing areas that are of nearly the same size, this way variations in inlet pressure have a minimal effect on outlet pressure. Unbalanced regulators are simpler and have pressure acting from one direction only. This effectively requires greater outlet pressure variations with inlet pressure variations. Be aware that even balanced regulators require a small degree of unbalancing force to ensure the pressure closes the seat of the valve. See the discussion regarding outlet variations with inlet variations.

Some of our valves and regulators are Oxygen compatible but not all. Be advised that there are two issues with valves in oxygen service: the materials used must be oxygen compatible and the valves must be oxygen cleaned. Aluminum is NOT oxygen compatible. Buna o-rings are NOT oxygen compatible. However, we manufacture many of our valves with all brass wetted surfaces (meaning the sections of the valve that contact high-pressure oxygen is brass) and we use Viton o-rings for most applications. Viton is oxygen compatible. When selecting a product for oxygen service ensure you are selecting a brass version (usually containing -B in the part number) with Viton o-rings.

WE DO NOT OXYGEN CLEAN OUR VALVES. THE VALVES AS SHIPPED ARE NOT TO BE USED IN OXYGEN SERVICE WITHOUT FIRST OXYGEN CLEANING THEM.

For further information regarding the use of valves and regulators with oxygen please refer to our application note: “Use of Valves and Regulators with Oxygen Gas (PDF 338KB)“.

There are many companies that offer oxygen cleaning. We have a vendor that provides oxygen cleaning and we can ship your valves directly to them and either have them bill you or do the billing through Aqua Environment. Please contact the factory for further details, prices, and the time required.

A back pressure regulator senses the pressure upstream of the valve. It remains closed, blocking flow until the pressure upstream of the valve exceeds the set pressure. Then the valve opens and allows flow. Typically these are used just after filter/separator systems that function optimally at minimum pressure.

A reducing regulator senses the pressure downstream of the valve and maintains that pressure at the set value as long as possible. If the upstream pressure falls below the set pressure the valve will simply stay open allowing the gas or fluid to pass with a minimum restriction. A vented valve will, in addition, vent excess downstream gas if the downstream pressure exceeds the set pressure by an amount that varies with each valve model. Non-vented valves will not vent off excess downstream pressure.

Aqua Environment Co. Inc. decided to use a metal-to-metal seat in its back pressure regulators. This is in contrast to a metal-and-plastic seat that is used in our reducing regulators. The advantage of a metal-to-metal seat is that it has far superior resistance to regulator freeze-up. The cooling effect of gas at high flows through a back pressure regulator can cause significant freeze-up issues and the metal-to-metal seat solves these issues. The disadvantage of a metal-to-metal seat is that they do not seal as reliably. At Aqua Environment we have researched ways to minimize the leakage through the seat when it is closed and have achieved a minimum of leakage; however, some leakage, especially after the BP regulator has seen many hours of service, is to be expected. The back pressure regulators are not designed to be shut-off valves and a shut-off valve should be placed before or after the back pressure regulator if it is desired to maintain pressure in the system upstream of the BP regulator for long periods of time between usage.

The application notes, “Use of Sequence Valve 1018 for Cascade Bank Filling (PDF 198KB)” and “Use of Sequence Valve 1018 to Priority Fill from Cascade Banks” detail how to use the 1018 or 1085 for cascade systems. For high-flow systems replace the 1018s in the diagrams with 1085s and the other low-flow components with their high-flow equivalents. Please do not hesitate to contact our factory if you need any assistance with the diagrams or your specific application requirements.

This is typically because the sensing line that goes to the open control port of the 1018 or 1085 is not actually sensing the pressure of the tanks being filled. This line should be plumbed as close as possible to the tanks being filled and after any restrictions in the system. It’s also important the valves on the fill whips be fully opened. If the sensing line is too far upstream from the tanks being filled the pressure at that point in the system may be much higher than the pressure in the tanks to be filled and the sequence valves are fooled into thinking they need to open the high-pressure cascade banks.

Typically when a regulator’s pressure is set in static or no flow conditions and then flow is allowed to pass through the regulator, the downstream pressure will drop by some small percent of the set pressure. This pressure reduction is normal and often referred to as droop.

Static conditions refer to the state of the system (pressures primarily) when there is no flow of gas or liquid through the system. Dynamic conditions refer to the system when the gas or liquid is flowing.