Pressure regulators

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Pressure regulators set the operating pressure
on a system to a maximum value and compensate for
pressure fluctuations.


Functional principle

Pressure regulators work according to one of two main functional principles: the directly actuated diaphragm regulator and the pilot actuated piston regulator.

Directly actuated diaphragm control valves

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On these regulators, the main spring exerts a force on a diaphragm. This force can be adjusted by turning the regulator knob. In the centre of the diaphragm is a sealing element, which is pressed tightly against the front side of the piston regulator because of the force of the main spring and the regulator piston spring.
By readjusting the main spring, the regulator piston is pushed downwards and the lower seal seat is released, whilst the front side of the regulator piston continues to be sealed off by the sealing element in the diaphragm. This enables the flow from the pressure to the working lines for supply and exhausting of the system. Small pressure fluctuations can be compensated for through slight movements of the regulator piston and the related changes in flow on the lower seal seat.
If the pressure on the working line rises above the set working pressure, this generates a force on the underside of the diaphragms which pushes the diaphragm. This pushes the diaphragm upwards and compresses the main spring. The spring makes the regulator piston move upwards; it closes the lower seal seat completely, but cannot extend as far as the seal seat in the diaphragm.
The air then escapes past the sealing element in the diaphragm and through an exhaust port on the housing of the compressed air regulator. This procedure is known as secondary venting.

 

Pilot actuated piston regulators

The overall function is the same as that of the directly actuated compressed air regulating valve.
However, the difference is that the function of the diaphragm is carried out by a piston, the pilot piston.

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In the starting position, the pilot and regulator piston are in their upper end position; the lower seal seat is therefore closed. If air now flows from the supply port into the valve, it first flows around the lower part of the regulator piston. The air flows into the interior of the pilot piston via a small connection hole (∅ approx. 0.1mm) and therefore onto the upper side of the pilot piston. The resulting force then opens the lower seal seat and thus enables flow to the working line.
In this "normal operating position", the pressure in the working line is regulated so that the different pressure conditions between the input and output pressures lead to movement of the regulator piston, which in turn regulates the flow on the lower seal seat. In this state, the operating pressure in the regulator is the maximum set pressure.
In order to reduce pressure, excess air escapes to the outside via the connection hole, the interior of the regulator piston and the open seal seat.
The valve in the pilot piston has a damping function for the movement of the regulator piston. It can rapidly generate pressure compensation between the upper and lower sides of the pilot piston; this has a positive cushioning effect on the regulation behaviour of the valve.

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The maximum exhaust flow is achieved in two steps. The pressure chamber can be very quickly exhausted on the side of the working line through the automatic opening of the non-return valve. The higher pressure that is still on the inside of the regulator piston and on the upper side of the pilot piston can only slowly be reduced via the very small connection hole. This creates
a force which pushes the regulator piston down and thus keeps the entire cross section open for exhausting purposes.

 

Filter regulators

A combined filter and regulator

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In the filter regulator, the regulator is positioned in the upper part while the filter with the filter bowl and integrated condensate drain are housed in the lower part.

Did you know?

Can pressure regulators be fitted in series?
Standard regulators are not usually fitted in series, as each regulator fitted downstream in a series assembly is restricted by the upstream regulators. Festo offers regulators, known as manifold assembly pressure regulators, specifically for such applications.(LRB)

Can standard pressure regulators be operated with nitrogen?
Provided the following parameters are adhered to, the products can be operated with nitrogen as the pressure medium without any significant restriction to their service life.
The nitrogen used must be available in a gaseous state.
The operating pressure and operating temperature must comply with the values for compressed air specified on the data sheet.
Contamination of the nitrogen used by residual humidity, residual oil content etc. must comply with the specifications in the catalogue for operation with compressed air.

Can standard pressure regulators be operated with oxygen?
When using components with oxygen, a couple of rules must be kept to. One of these rules is that our standard components are not suitable for use with oxygen. You can obtain information as to which components are suitable from the Technical Hotline.

What kind of closure does the lockable pressure regulator have?
Pressure regulators with a lockable knob in the MS and D series are all fitted with an E11 lock.

Is the lock LRVS-D for locking the MS regulator or manual On/off valve, keyed alike or so called E11?

No, the padlock is not keyed alike or E11. With approx. 30000 possible keys, it can be assumed in normal case that there is no equal key within a delivery.

Is the knurled nut included in the scope of delivery of a regulator?
In the case of pressure regulators in the MS series, sizes 4 and 6, types LR-... and LRB-..., the knurled nut (aluminium) is included in the scope of delivery, as it is in all pressure regulators in the D series.
In the case of filter regulators LFR-... and FRC-..., the knurled nut is not included in the scope of delivery because the mounting bracket is usually used for mounting. A hex nut (aluminium) can be ordered as an accessory.

Can Festo pressure regulators be used for water?
All Festo regulators are designed for inert gases and are therefore not suitable for liquid media.

Can a regulator LRP be integrated into a working line?
A working line normally flows in both directions. Since the regulator LRP does not have an internal return flow, this function is provided using a parallel-installed non-return valve.