Pressure management of industrial gases is both vital for safe working and essential because of the high static pressures that are employed to store gases in cylinders for transport. High pressure cylinders supplied from gas producers may range in pressure depending on the size of the bottle and type of gas and this is often around 200bar but can be much higher.
These cylinders can be fitted to systems singly, in pairs or in large banks where high gas volumes or sustained deliver is crucial. Pressure regulators for high pressure cylinders are often referred to as first stage regulators as they take the 200-400bar static cylinder pressure and reduce it to a safer and more manageable level which could be between 5 and 50bar. In some cases it may be required to use a single regulator to deliver a lower pressure such as for diving equipment or breathing apparatus and in which case, a dual stage regulator is needed. This unit combines a first stage regulator with a second stage unit to deliver two steps of reduction and the only adjustment is the final delivered pressure. The intermediate pressure between stages is fixed.
First stage regulators often fit directly to the high pressure cylinders using mounting threads that are specific to certain gases or gas types. These thread types may conform to one of several international standards such as UNI 11144, DIN 477, CGA V0-1 or NF E29-650. For example:
Conventional G (BSPP) or NPT threads may also be used in certain applications or where cylinders have been connected to a high pressure manifold.
Since industrial gases are often used in critical processes and the high pressure cylinder fill volume is limited, it is often good practice to employ 2 separate cylinders or cylinder banks with a dual inlet regulator to make it easier to swap between supply sides when the supply pressure falls below a suitable minimum. Auto changeover regulators simplify this further by allowing the user to designate a primary supply side and then switch to the secondary side as the primary pressure reaches a minimum setpoint pressure. Alarms can be triggered at this point to alert the user that one supply side is exhausted and needs to be swapped before the other depletes.
Second stage regulators or intermediate pressure regulators take the reduced pressure from the first stage of up to 50bar and regulate down to the desired working pressure, anything between 1.5 and 50bar. These are the most common types of pressure reducing valves seen on sites and have to deliver accurate regulation for a wide range of desired pressures.
First and second stage regulators can often be used for liquids such as water or hydraulic oil subject to slight design variation or elastomer choice.
Third stage regulators are essential when very low pressures are needed as the second stage regulators are not sensitive enough when the desired pressure is between a few mbar and 1bar(g). Much larger diameter diaphragms are employed which makes third stage regulators easier to recognise from a distance. These regulators are most often for air or gas use only as the need for liquid pressure management at these pressures is not common.
First Stage Regulators up to 400bar
Second Stage Regulators Below 50bar
Third Stage Regulators from 5mbar
Dual Inlet Regulators
Auto Changeover Regulators
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