Hi All, we have a MAC 45A-AA1-DDBA-1BA control valve for controlling a double acting actuator, what would be the best way to control exhaust, there are 2 flow control valves on the actuator, do we have to also control the exhaust? Pic of current setup that is being replaced due to age.

 

What aspect of the exhaust are you trying to control? If you put another valve or flow control on the exhaust port of the main valve, you risk ext/retract happening at the wrong speed - or not at all if the exhaust is restricted. If you just want to control where the exhaust takes place, you can run the exhaust through a line and put that brass muffler in a different location.

Also, to be clear, is that a pressure sensor at the bottom of the container, attached to the line right off the extend port?

 

Thanks for the reply Dave, this is all being reworked, none of us are particularly familiar with pneumatics , so, new actuators, double acting Bimba 094 DP new SMC speed control valves and new MAC valves, basically duplicating what’s there.
Exhaust port. replace with a brass muffler, correct ?
lower speed control valve controls the piston extension speed
upper control control valve retraction speed.
Yes, that is a pressure sensor, I guess that it some sort of a safety, always N/C and has never been activated and apparently that switch is no longer mfg.
We are interested in your input.

 

In the MAC valve in your picture, there is a supply inlet and the exhaust outlet right next to each other on the top side of the valve. That brass muffler installed in the exhaust port just diffuses and silences the exhaust air, but when the cylinder extends, the air can easily flow out of the retract port. Vise versa for the other direction.

I still want to make sure I'm addressing your original question about the exhaust control. If you are just replacing the MAC valve with a similar type, that part number has the IN, EX, A, and B. As long as you install the brass muffler on the EX port, you are fine.

This is a really common setup, called a 4-way, 4-port (some have a separate exhaust port for A and B, that's called a 5-port), 2-position spool valve. When the solenoid energizes, it automatically reverses which outlet gets the air pressure supply, and which one freely opens up to the exhaust. So the good news is, you don't need to worry about doing anything extra to control that exhaust.

Those SMC flow valves will do a fine job of controlling the ext and retract speed, so if you add anything else to that EX port besides the muffler, you risk restricting the air even more and that may mess up your whole system. That muffler is good.

 

The MAC valves are on back order but will be replaced. do we need that pressure sensor? We are supplying air to this system via a portable compressor capable of about 150PSI. we are currently supplying the actuators with about 50 PSI . These actuators are controlling a shaft that has a 12’ RR crossing gate arm for a ride around RR, we have replaced all of the a tubing with the hope that increased pressure will give us better control for raising and lowering the gate arms, I’ll post a pic at some point.

 

Sounds like a fun project! I don't think removing the sensor is a good idea, not knowing what it does.

Since it's on the extend side, looking at the plate on the shaft, extending the rod brings the gate arm down? If so, that pressure sensor probably verifies that you aren't closing the gate on some obstacle, so the controller probably checks the sensor during the extend stroke, but then once it reaches the end of the stroke, the pressure will rise, but it's safe at that point.

 

I may reconsider the sensor, one other question, to adjust the piston extension speed, we start off with both control valves closed, air pressure applied, slowly open the extend valve and adjust to a smooth extension and gate arm closure, do the same with the opening or retracting of the piston.
currently we have counter weights on the arms, hoping to remove some of it , if we apply more pressure to the actuator will that give us more closing force ?

 

Yes, it will have more force in both directions, and also more speed since the air will be forced into the ext/ret ports with that higher force. But as long as you are adjusting the control valves with that new higher pressure, you should be set!

 

Thanks for the support, it will be a few days before we get to the adjustment.

 

Good morning, another question has popped up, we are planning on running 1//4” OD 5/32 ID tubing approximately 50’ between the compressor location and the gate control, what we currently have, definitely 1/4” OD not sure of the ID, would there be any need to increase this supply?
Thanks
Geo

 

Don't remove the counter weights, there used for balancing the forces. Your actuator is small, unless you require extreme opening or closing speeds, 1/4" is okay. You might want to use an air filter and provide a tee and a liquid drain valve on the airline as a precaution should you have high humidity in the area..

 

The counter weights will stay, I did think of a filter, what would you suggest?

 

A typical valve filter regulator to limit the pressure as needed (actuator supplier will advise), and to allow draining of any condensates.

 

Update, we installed the new actuator, 4 way valve, muffler on valve, system works better, and has better control, however we still have quite a bit of bouncing gate arm when gate is lowered, tried adding and removing counter weights but that didn’t seem to help much, currently we have enough counter weight to keep the gate arm at about a 45* angle from pole when disconnected from actuator, I took a video but lost it somehow, will try again later.
One other question, the extend control valve should not have any effect on the retraction function, correct?
Any thoughts?
Thanks