Yes, but this is the worst way to do it if using servo control. I repeat, the hydraulic designers do not know how to design for servo control.The pistons are mounted (upside down) in real the same way as in the drawing, a heavy load is attached to the rod, so I suppose the CBC is for avoid the rod and load to descend when the hydraulic is not active.
I would use energized open blocking valves. POCV are acceptable just not optimal. It also makes a big difference where the POCV is piloted from.I thought the pilot valve was there not to lose oil to the tank if the hydraulic is not active?
OK, but have you done it and how does the the Atos valve know about the CBV?Can the pilot valve be ommited or place somewhere else with the same functionnality?
Max pump pressure is 240 bar.
I know that atos can parametrize the surfaces of the cilinder into the electronic valve
Why? A POCV is better in this case and a energized open blocking valve better yet.Peter,
I doubt very, very much that you will legitimately be able to CE mark a press without a CBC valve located where this one is in this press.
Hopefully? You don't know?The circuit could be improved I don't doubt, but the CBC has to stay put, hopefully it is physically where required.
Are you sure?Valves that require a control input to achieve the same function would not be acceptable for the relevant safety standards.
Why not? Usually the blocking valve is powered by a series of relays so that if any relay loses power the blocking valve loses power and shuts. This means that you can put the press in a safe condition if any number of things fail. A CBV closes only one the pressure goes away and that wouldn't be as fast as an electrical circuit.Peter,
I don't believe that a valve that requires electrical energising will meet the requirements to CE mark the press as safe, it MUST default to the closed circuit position under the failure of control signals
Even and energized open blocking valve?I am sure that a valve that requires a control input to prevent fluid from leaving a cylinder which is required to suspend a load would not be acceptable under the requirements for the safety requirements of a power press under CE marking requirements.
Of that I am ALSO sure.
Read again, I said energized open. If power is lost they close by springs. The CBVs have springs in them too and close when there isn't enought pressure to keep the valve open.OK Peter,
Once again I can't comment on your posts in the manner I would like.
It seems you are suggesting a valve that requires power to close the fluid line, this is NOT acceptable.
The controller doesn't know what the CBV is doing and the CBV interferes with the flow. The CBV will work only if it is piloted by a constant pressure source so it stays open but they the CBV is being used as a POCV. As it is now you can see the CBV is piloted by the pressure on the cap side of the cylinder. What plc-user has now will never work right.I can see why the CBC valve is an issue, but it is not insurmountable I don't think.
This particular design of valve may be unacceptable, but there are others that will function correctly I am sure.
I can't believe who ever is making the rules over there can be that stupid but maybe they are. Is so bad 4U good 4 us.Peter,
I did not get from your posts that the valve was default closed with no electrical input.
However, I don't care what you say or have done, in the US, nor what I have or have not done.
You must use a hydraulically controlled counter balance valve, of "some" sort, to comply with current CE requirements in the EU as far as I know, having worked for a hydraulics control systems manufacturer, of global standing, this is what our internal specs required, as interpreted by our legal and product specialists to meet the requirements for equipment for use, sale, or being put onto the market in the EU.
Why not? Emergency stop and all sort of safety mechanism rely on fail safe electronics. Jets fly by wire?I don't believe this has changed since I left them.
Whilst I agree the circuit is not correct, I do not agree that a purely electrically controlled valve in the place of the CBC valve is acceptable.
It is clear the CBV is powered by the cap side of the cylinder and this is very bad.From where I am, I don't have enough information on the machine, or the system to make concrete recommendations for what is acceptable.
It is simple. You can't have two devices controlling flow when one works without knowledge of what the other is doing. In plc_user's case it is bad because the Atos valve doesn't know about the CBV so it can't take that into account when computing force. On top of that the CBV better be fast or it too will delay any response.For example, if the press is an Annexe 4 machine under the Machinery Directive, the requirements will be different to those if it is not.
Unless you have information that is not in this thread, or a crystal ball, neither of us can say that at this time.