Actuator minimum air pressure increase

Can someone explain what are the consequences if the available instrument air minimum pressure in the plant is increased?.

Will it affect negatively to the valve actuators?

What is a minimum pressure and how do you change it?

Supply air is usually provided through a proportional regulator, which attempts to hold a setpoint pressure. The actual pressure will droop (drop lower) with increasing load. The regulator's setpoint is not really a minimum pressure, it is a setpoint pressure.

I'm not sure what you mean 'minimum pressure'. Do you mean the kick-in point for the compressor, where the compressor motor starts because the pressure switch has sensed that the resevoir pressure is is at the low point?

Or are you talking about changing the setpoint on the regulator that supplies the actuators?

Or something else?

The instrument air supply for our plant comes from another plant.
We have been informed that the minimum instrument air supply have been increased from 3.5 bar to 5.5 bar.
I want to understand what will be the consequences of this change regarding existing valve actuators

soyxan said:

The instrument air supply for our plant comes from another plant.
We have been informed that the minimum instrument air supply have been increased from 3.5 bar to 5.5 bar.
I want to understand what will be the consequences of this change regarding existing valve actuators

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Do you not have regulator on your incoming supply or each machine, if you do just turn it down to 3.5 bar and nothing changes, or am i missing something ?

Unfortunately i don't think anybody will be able to help with this one unless you list EVERY type of valve actuator you have in your plant.

tragically1969 said:

Do you not have regulator on your incoming supply or each machine, if you do just turn it down to 3.5 bar and nothing changes, or am i missing something ?

Unfortunately i don't think anybody will be able to help with this one unless you list EVERY type of valve actuator you have in your plant.

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I am sure that someone could give a general idea.

I can understand that if the maximum air supply pressure is increased we will have to check if the pressure regulator of the actuators could handle it. But what about an increase in the minimum pressure?

The actuator will just operate a little faster. Is that a problem ?

Is it just the minimum pressure that is increasing or the maximum as well ? almost as importantly , what is the normal supply pressure ? The reason for asking is that you may have pressure boosters on some of your equipment if it requires more than the current minimum pressure . If these have been fitted ,then the new min. supply may make these redundant and their removal improve reliability . You should also check if the air quality will change - instuement air is normally clean and moisture free .
Pal

I'm hoping all your machines have a main pressure regulator. When they switch you over to 5.5 bar, turn the regulator down to match your previous 3.5 . I suspect many of your regulators are cranked up all the way.

Why? I work in maintenance, everything gets cranked up when it doesn't work.

I agree, all your machines should have a main air regulator w/pressure switch.
Or just put a combo kit in: filter, regulator, gauge, Pressure switch. This is a standard for us. Compressed air is not always very clean.

Most solenoid valves are rated for a maximum inlet pressure of about 7 bar (100 PSI). Large orifice valves may have a lower maximum of about 4 bar (60 PSI).
The increase from 3.5 Bar (50 PSI) to 5.5 bar (80 PSI) may cause some valves to stick closed.
As others have posted, we expect machines to have a pressure regulator for the incoming air. On these machines, there won't be a problem. You won't see any difference in operation.

keithkyll said:

The increase from 3.5 Bar (50 PSI) to 5.5 bar (80 PSI) may cause some valves to stick closed.

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Please can you explain what you mean by "stick closed" and why?

keithkyll said:

As others have posted, we expect machines to have a pressure regulator for the incoming air. On these machines, there won't be a problem. You won't see any difference in operation.

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We have pressure regulators in control valves, but not in on/off valves. Do we have to expect any issue with them?

Thanks to everyone for your replies!

Air pressure will help hold the valve disc C against the seat D. The solenoid needs to overcome this pressure. You can calculate the amount of force by figuring out the total surface area of the disc.
How a solenoid valve works link.

The manufacturer makes maximum pressure available in spec sheets

Maximum pressure for solenoid valves is all over the map. Just look at the variety of maximum pressures for a handfull of solenoid valves.

soyxan,

It all depends on what you call instrument air.
if you are talking about plant air, some valves may not operate correctly, depending on the type.

if you are talking about test instrument air, that's a big problem if you do not have an air regulator in front of the test instrument. the increased air pressure will throw the test results off depending in what the machine does.

we constantly have to monitor the air pressure to our lab equipment.

james

generally, each actuator have an input pressure regulator that accepts pressures from the instrument air supply and feed the actuator with a constant air pressure: an exemple when the instrument air network pressure is between 3.5 and 8 bar, 3.5 bar being the minimum instrument aire pressure, the input air pressure regulator to the actuator will be set around 2.5 or 3 bar (depending on the manufacturer) so it will be no problem for the air pressure to be from 3.5 to 8 bar. so for existing actuators you will have nothing to fear as long as the air pressure is within those values. if the air pressure will raise above the max limit here you have to check the inlet pressure regulator can work in this pressure. raising the minimum instrument air pressure for the network will be beneficial in the case when you will install new actuators, for there seizing will result in smaller ones (actuators) comparing to those specified for lower minimum air pressure.