FAQ - Compressed air preparation

Service units

Regulators/filter regulators

On-off valves

Filters

Lubricators

Dryer

Pressure amplifier

...

Service units

Does a service unit have to be fitted with a manual on-off valve?

In accordance with EN 983, Section 5.1.6, the systems must be designed in such a way that there is a complete separation of energy sources and also degradation of energy in the pressurised medium in the system, to prevent unexpected start-up. For example, in pneumatic systems this can be achieved by separating the energy supply and reducing the pressure in the system. The appropriate shut-off mechanism, which has a pressure relief vent, must be lockable.

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Based on what criteria is the connection size of a service unit selected?

In the case of service units, you should pay attention not only to the connection size but also the flow rate values and the control range. If the control range is ok, the correct choice of service unit ultimately depends on the air flow rate.
Although no harm is done in using a bigger service unit than necessary, this leads to unnecessary costs.

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Regulators/filter regulators

Can multiple pressure regulators be fitted in series?

Standard regulators are not usually fitted in series, as each regulator fitted later in the control range would be restricted by the regulators before it.

For this reason, Festo offers regulators known as lockable pressure regulators which are appropriate for such applications.

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Does Festo have regulators for the vacuum branch?

Festo's product range does not include vacuum regulators.

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Can standard pressure regulators be operated with nitrogen?

Nitrogen can be used as a pressure medium if the following constraints are adhered to.

  • The nitrogen used must be available in a gaseous state
  • The operating pressure and operating temperatures must comply with the values specified for compressed air on the data sheet
  • Contamination of the nitrogen used in terms of residual humidity, residual oil content etc. corresponds to the specifications in the catalogue for operation with compressed air

Provided that these parameters are adhered to, the products can be operated without any significant restriction to their service life.

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What type of lock is used in the case of D series pressure regulators?
Pressure regulators with a lockable knob in the D series are all fitted with an E11 lock.

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Can a regulator and/or filter with a manual condensate drain be converted to an automatic condensate drain?

Yes, if the entire filter bowl is replaced. You will find a spare parts catalogue on the Internet site. The correct part number can be selected here.

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Is the padlock LRVS-D for locking the controller available as an E11 lock or for use with a master key?
No, the padlock is not available as an E11 lock or for use with a master key. With around 30,000 possible locking mechanisms, it can usually be assumed that no two locks within any one delivery will be able to be opened with the same key.

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Is the knurled nut part of the scope of delivery for a regulator of the type MS?

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.

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.

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Are D-Maxi pressure regulators available with increased return venting?
The pressure regulators LR-D-...-Maxi are designed with an increased return flow as standard.

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Are D-Micro pressure regulators available with increased return venting?
The pressure regulators LR-D-...-Micro are designed with an increased return flow as standard.

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Is an assembly position defined for filter regulators?
As filter regulators are fitted with a filter bowl for condensate, these devices must always be installed vertically. It is possible that the automatic condensate drain will no longer close properly, if there is a deviation of more than 5°.

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

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

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Why in the case of some pressure regulators is there a choice between a short and long rotary knob?
With service units in the MS series you have a choice of a long or short rotary knob for pressure regulators. The total height of the regulators with different rotary knobs is identical. The difference is that part of thread and lock nut are visible in the case of the shorter rotary knob. This variant is, for example, suitable for installation in control panels. In contrast, the longer regulator knob covers the thread, protecting it against contamination.

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On-off valves

What malfunctions could occur when using the safety valve MS6-SV?

- Operating pressure less than 3.5 bar
- Enable signals not OK
- Internal error
- For versions below revision 03, the simultaneity has been set at 1.5 ms. A couple of emergency off devices in this market segment do not meet this simultaneity.

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Do all circuit examples listed in the catalogue for the safety valve MS6-SV conform to safety category 4?

As a rule, all circuit examples listed in the catalogue conform to safety category 4. However, if connections are made using the plug MP1 (both signals 24 V), the two signals must be physically separate from each other (to avoid cross-circuits).

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Is the safety valve MS6-SV BG (trade association)-certified?

The safety valve MS6-SV conforms to the requirements of the standard DIN EN ISO 13849-1. It is certified by the trade association.

Max. possible performance level = "e"/category 4.

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Which mounting bracket do I need to mount the safety valve MS6-SV?

The safety valve MS6-SV can only be mounted using the mounting bracket MS6-WPB.

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What do I need to change if I cannot select an MS6-SV in the MS modular system configurator?

If it is not possible to select a safety valve MS6-SV in the MS configurator, this is usually because the short mounting bracket (WP) is selected in the basic configuration. The mounting bracket WPB must be selected for use with the safety valve MS6-SV.

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How do I monitor a malfunction with the MS6-SV soft-start/quick exhaust valve?

One way of monitoring a malfunction is with a pressure switch. A "valve with integrated pressure switch" variant is available. Alternatively, the pressure switch can be integrated into the service unit via a branching module.

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Can you use the signal contact for the soft-start/quick exhaust valve MS6-SV as a malfunction indicator?

No. This signal contact simply signals whether the valve is operational, i.e. that it is ready to switch on. If there is a malfunction, the device is not ready to switch on.

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What is the purpose of the signal contact on the safety valve MS6-SV?

The signal contact on the safety valve MS6-SV is designed to signal whether the valve is ready to be switched on, i.e. the valve runs a self-test after switching on. If everything is in order, the signal contact switches to the high state. The valve with two enable inputs can now be switched on. The signal contact can be connected into the feedback loop of a safety control system.

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A 9-pin Sub-D connector should be used for the electrical connection of an on-off valve type MS6-SV. The device isn't working. Is there a fault?

There could be a fault, depending on the application.

Conventional Sub-D connectors must not be used. A special Festo plug connector must be used for the electrical interface; see accessories..

The ...-MP1 plug must be selected for 24 V at both enable inputs (static or dynamic signals). The ...-MP3 plug is used when one enable input is supplied with 24 V and the other with 0 V.

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How do I acknowledge an error with the soft-start/quick exhaust valve MS6-SV?

To acknowledge that an error has been recognised on the MS6-SV soft-start/quick exhaust valve, switch off the power supply then switch it back on again (voltage interrupted at pin 8). This ensures that the error will also be registered.

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What protection class does the coil of the electrical on-off valve of the MS series correspond to?

The coil of the electrical on-off valve of the MD series has IP protection class 65.

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What is the power consumption of the coils of the electric on/off valves HEE-... of the D series?

The 24 V DC coil has a power consumption of 2.5 watts.
The 110 V and 230 V AC coils each have a switching power of 5 VA and a holding power of 3.7 VA.

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Is the electric on-off valve MS4/MS6-EE also available with detenting manual override?

The standard variants of the electric on-off valve MS4/MS6-EE are only available with non-detenting manual override. This variant has the type designation…-10V24-… .
Use the modular product system to select a variant which includes both non-detenting and detenting manual override. This variant has the type designation…-V24-… .

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Filters

Can a regulator and/or filter with a manual condensate drain be converted to an automatic condensate drain?
Yes, if the entire filter bowl is replaced. You will find a spare parts catalogue on the website. That's where you can select the correct part number.

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Do filter bowls have to be fitted with a metal bowl guard?
According to section 8.4.1 of ISO 4414, non-metal filters and separator casings must be fitted with anti-burst protection.

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Can VAF-... vacuum filters also be used in the positive pressure range?

The vacuum filters VAF-... cover a pressure range up to 7 bar.

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How is excess water removed from the compressed air?
The only correct solution is to use a dryer. If a dryer cannot be used, there is the option of removing at least part of the water from the compressed air via filters. To do so, we recommend the use of a filter combination with at least a 1 µ prefilter and a subsequent 0.01 µ filter.

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Does Festo have coalescing filters in its product range?

Our fine filters (1 µm) and micro filters (0.01 µm) are coalescing filters.

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Lubricators

Does compressed air have to be enriched with oil?
An increasing number of users no longer wish to use lubricators. Festo components are lubricated for life and can therefore be operated unlubricated. There are some components that must only be operated without lubrication (please refer to the catalogue specifications). However, in some situations we recommend lubricated compressed air, for instance with extremely fast cylinder movements. If components which are usually operated without lubrication, are operated with lubricated air even once, then the air must always be lubricated from then on because the oil washes away the life-time lubrication.

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Are bio-oils approved for lubricating Festo components?
Bio-oils contain ester and are a popular choice for applications such as compressor lubrication. Such oils alter the properties of various materials and are therefore not suitable for lubricating pneumatic components (see FAQ "What type of oil is approved?").

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How can the lubricator LOE be refilled with oil?

D series – Mini: to top up oil:

The lubricator can remain under pressure during refilling.

  • Unscrew the vent screw at the top of the lubricator beside the oil sight glass; the valve will vent the lubricator bowl
  • Unscrew the lubricator bowl and top it up with oil: fill it with a maximum of 45 ml of oil

 

D series – Midi: to top up oil:

The lubricator can remain under pressure during refilling.

  • Unscrew the vent screw at the top of the lubricator beside the oil sight glass; the valve will vent the lubricator bowl
  • Unscrew the lubricator bowl and top it up with oil: fill it with a maximum of 110 ml of oil

 

D series – Maxi: to top up oil:

The lubricator can remain under pressure during refilling.

  • Unscrew the vent screw at the top of the lubricator beside the oil sight glass; the valve will vent the lubricator bowl
  • Unscrew the lubricator bowl and top it up with oil: fill it with a maximum of 190 ml of oil

 

D series – Micro: to top up oil:

The lubricator must be free of pressure during refilling.

  • Vent the system
  • Unscrew the lubricator bowl and top it up with oil: fill it with a maximum of 6.5 ml of oil

 

MS series – MS4: to top up oil:

The lubricator can remain under pressure during refilling.

  • Unscrew the vent screw at the top of the lubricator beside the oil sight glass; the valve will vent the lubricator bowl
  • Unscrew the lubricator bowl; pull the blue catch on the bayonet lock downwards while simultaneously twisting the lubricator bowl
  • Top up the lubricator bowl with oil: fill it with a maximum of 30 ml of oil (36 ml in the case of a metal bowl)

 

MS series – MS6: to top up oil:

The lubricator can remain under pressure during refilling.

  • Unscrew the vent screw at the top of the lubricator beside the oil sight glass; the valve will vent the lubricator bowl
  • Unscrew the lubricator bowl: pull the blue catch on the bayonet lock downwards while simultaneously twisting the lubricator bowl
  • Top up the lubricator bowl with oil: fill it with a maximum of 75 ml of oil (80 ml in the case of a metal bowl)

 

MS series – MS12: to top up oil:

The lubricator can remain under pressure during refilling.

  • Unscrew the vent screw on the top of the lubricator beside the oil sight glass: the valve will vent the lubricator bowl
  • Unscrew the lubricator bowl: pull the blue catch on the bayonet lock downwards while simultaneously twisting the lubricator bowl
  • Top up the lubricator bowl with oil: fill it with a maximum of 1500ml of oil

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What oil is approved for the lubricators?

We recommend the following type of oil:

Festo special oil (1-l container), type OFSW-32, order no. 152 811

 

Other suitable types of oil are as follows:

  • ARAL Vitam GF 32
  • BP Energol HLP 32
  • Esso Nuto H 32
  • Mobil DTE 24
  • Shell Tellus Oil DO 32

Viscosity range: 32 mm²/s (=cSt) at 40°C; ISO class VG 32 in accordance with ISO 3448

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Dryer

Is the cartridge for the membrane dryer available as a spare part?
No, because providing the cartridge as a spare part would cost nearly as much as an entire unit.

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What happens when an adsorption dryer or membrane dryer is pushed beyond its limits?

Each dryer performs at its best as long as the quantity of air flowing through the dryer does not exceed a certain amount.
If this maximum permissible air quantity is exceeded, the dryer is "overdriven". As a result, the dryer ceases to work efficiently and the air is not dried as much as required.

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How does a membrane dryer (type LD) work?

The dryer consists of a large number of coated hollow fibre membranes, positioned in parallel to one another in a longitudinal direction. Air flows through these fibres in the longitudinal direction and molecules of water can then penetrate the sidewalls of the hollow fibres. Some of the air that has already been dried is released along the external surfaces of the fibres. This drier air absorbs the moisture already located on the outside of the fibres and carries it along into the atmosphere (drying current). The drier external surfaces of the hollow fibres gives rise to a concentration gradient between the moister air within the fibre and the drier air outside of the fibre. This leads to the diffusion of water from the internal surface to the external surface of the fibre.

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Can air that is insufficiently lubricated damage devices downstream?

A low pressure dew point does not shorten the service life of Festo's products. There is also no need for additional lubrication.

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How is the excess water removed from the compressed air?

The only correct solution is to use a dryer.
We recommend using an adsorption dryer of the series PDAD-...

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Pressure amplifier

Can the pressure intensifier (pressure booster) be installed in the working line between the valve and the cylinder?
No because the pressure booster cannot vent itself. (Tip: insert VLO-3-.... in the working line and connect the actuation circuit upstream of the DPA, paying attention to the permissible pressure range for the valve.)

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By how much can the supply pressure be increased using a pressure booster?
Festo pressure boosters increase the supply pressure by about 100 %. The maximum output pressure is 16 bar, depending on the size of the pressure booster.

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What must be noted in the context of compressed air preparation?

Operating conditions and standards in pneumatics

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How much does air weigh?

One cubic metre of air (1000 litres) weighs 1.292 kg (DIN 1343).

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Are condensate drains semi-automatic or fully automatic?

All pneumatically actuated condensate drains on Festo service units are fully automatic.
If the pressure flow is switched off, the condensate drain reacts in the same way as a semi-automatic condensate drain.

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Why does air always escape through the automatic condensate drain?

Equipment with an automatic condensate drain must be installed vertically. There must not be a deviation of more than 5° here, as the condensate drain will otherwise no longer close properly.

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Do automatic condensate drain valves also operate when no compressed air consumption is taking place?

Only very few requirements need to be fulfilled in order to ensure correct operation of automatic condensate drain valves. These requirements do, however, include vertical installation and a minimum air flow rate at switch-on of 125 l/min. If the air flow rate is below this figure, the condensate drain valve, which is open under no-pressure conditions, may not close.

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Are reservoirs approved for vacuum?

All air reservoirs from the stainless steel series (CRVZS-...) can also be used for vacuum down to –0.95 bar.

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What do the quality classes for compressed air indicate?

Classification of quality classes for compressed air in accordance with DIN ISO 8573-1


class
1. Solids

Max. particle size
[mü]


Max. particle density
[mg/m³]
2. Water content

Max. pressure dew
[°C]
3. Oil content

Max. oil concentration
[mg/m³]
1 0,1 0,1 -70 0,01
2 1 1 -40 0,1
3 5 5 -20 1
4 15 8 +3 5
5 40 10 +7 25
6 - - +10 -
7 - - not defined -

 

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How accurate are pressure gauge measurements?

At a reference temperature of 20° C, the total measurement deviations must not exceed the values in the table.

Precision class Error limit
(percentage of the measurement range)
0,1 +/- 0,1%
0,25 +/- 0,25 %
0,6 +/- 0,6 %
1 +/- 1 %
1,6 +/- 1,6 %
2,5 +/- 2,5 %
4 +/- 4 %

 

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What is the cost of compressed air?

On average it costs around 3 cents for every 1000 l.

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May an HEE-... on-off valve be used as a 2/2-way valve?

No, this is not permitted. If the exhaust air of this valve is sealed, the valve no longer functions properly.

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May an HE-... on-off valve be used as a 2/2-way valve?

No, this is not permitted. If the exhaust air of this valve is sealed, the valve no longer functions properly.

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Does Festo have a condensate collecting bowl in its product range?

Festo has no condensate collecting bowl in its product range. We recommend using filter silencers type LFU.

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