endations for pneumatic valves to achieve safety PLd/SIL3

[cottagewood]

I have an actuator operating a clamp that requires PLd/SIL3,

I’ve seen some SMC double valves with feedback, but they are described as dump valves.

I don’t need to dump the air, I just need to prevent the clamping. Is it feasible to do this with 2 valves in series and fit limits to the actuators themselves to get the feedback?

Does anybody have any recommendations for valves or methods that they have used
Ideally whichever valve I use, it needs to be in a Sistema library

 

[JeffKiper]

If you have access to Ross Controls they have complete safety line of valves. I know they have manufacturing all over the world.

PLd isn't a problem. I've done several applications with them. I've used safety valves with rod locking cylinders on an application that required absolutely no way to even move the cylinder when the system had a safety demand on it.

 

[Puddle]

Do you have to have two valves in series? I know the specification is for two relays/contactors, but I've never had cause to look into safety on pneumatics.
The way I've seen it done in the past is a dump valve on the safety circuit, then anything that has any potential of moving is run through a double actuated valve.

 

[cottagewood]

Do you have to have two valves in series? I know the specification is for two relays/contactors, but I've never had cause to look into safety on pneumatics.
The way I've seen it done in the past is a dump valve on the safety circuit, then anything that has any potential of moving is run through a double actuated valve.

Dump Valve is required for an Estop to remove any pressure in the system (provided it is safe to do so.)

This is for a safety function to prevent injury from the clamp, as long as the clamp can’t extend there is no risk, we don’t care if the clamp is already extended and retracts. PLd requires redundancy and feedback, a pneumatic actuator is no different to a motor in that respect

 

[cottagewood]

If you have access to Ross Controls they have complete safety line of valves. I know they have manufacturing all over the world.

PLd isn't a problem. I've done several applications with them. I've used safety valves with rod locking cylinders on an application that required absolutely no way to even move the cylinder when the system had a safety demand on it.

I have been given a contact at Ross Controls and I will speak to them. I was just looking for any alternatives that people may have used.
It makes me nervous when there is only one company that has a solution.
I’m always surprised that there isn’t more availability of products for this type of application. It’s common with electric motors and easy to implement but Hydraulics and Pneumatics seem to get overlooked by a lot of machine manufacturers

 

[Puddle]

This is for a safety function to prevent injury from the clamp, as long as the clamp can’t extend there is no risk, we don’t care if the clamp is already extended and retracts.

I was thinking with a dump valve and a double actuator, the clamp requires air pressure in either direction to move, so should just stop where it is when the safety circuit is broken.

PLd requires redundancy and feedback, a pneumatic actuator is no different to a motor in that respect

That makes sense. Sounds like you do need a certified valve for feedback, otherwise you'd have to use an auxiliary for feedback and I doubt you'd get the required response time.

 

[JeffKiper]

If you look at the clamping force there is a Ross valve that allows you to use reduced force when clamping until the operator is outside of the hazardous zone. Imagine using 2 bar for the initial force and then using 5 bar for the final clamping. If an operator gets in the hazardous area the syatem will use the lower pressure.

 

[PLCDontUQuitOnMe]

The way I have usually seen it done is there is a regular air supply and a "safety" air supply that goes through a dump valve. When the operator is in the safety zone, the dump valve drops the "safety" air supply. Use this air supply for the clamp. Not sure if this would work for your particular application.

 

[kamenges]

Originally posted by cottagewood:

I was just looking for any alternatives that people may have used.

Festo also makes a line of safety pneumatic products. Generally speaking it is their normal valve lines on custom manifolds with various monitoring options.

Keith

 

[cottagewood]

Festo also makes a line of safety pneumatic products. Generally speaking it is their normal valve lines on custom manifolds with various monitoring options.

Keith

I decided to go with Ross Controls, whilst the likes of Festo and SMC do make Safety products, finding a distributor who knows or understands safety applications is difficult, here in the UK anyway. They don’t inspire me with much confidence.
With Ross Controls, it’s their main business, they know about safety and are very helpful. It’s worth paying the extra cost for that.