My company is attempting to determine the best practices for designing our control systems. We mainly design for the automotive industry, so customer requirements largely decide our fate. One area that I haven't found mentioned (probably because most of the specs are eons old) concerns manifold fluid power valves. The main questions are:

1> Some customer specs require the cylinder & valve to be shown at rest with no power. Others require us to draw them at 'home' position. Does anyone have an opinion on which is the 'better' approach?
2> We would like to line up the 'home' positions at the same side of the valve bank to make it easier to troubleshoot. I don't see that it should matter whether we choose the A or B port, except that the B port is on the left when the bank is mounted vertically. Is there an unwritten rule about which to choose?
3> I have heard that it is bad practice to draw a cylinder with the ports crossed. If one wants to show the cylinder as it sits on the machine, it is often necessary to draw the supply lines crossed. Any comments?

thanks for any comments or suggestions. I will post a summary of the results.
John Staub
Senior Controls Engineer
Process Equipment Co.

 

John,

No matter how you do it you will always have a customer who makes you change it to "their way". For instance, we have a customer whos spec.'s say "All valves shall be mounted horizontally with space to access the manual actuators" and " All valves and cylinders shall be drawn in their "home" positions. The cylinder direction must be indicated and any switches that indicate the cylinder position." ANSI /B93.11M "Pneumatic fluid
power-Systems standard for Industrial Machinery" 15.32.1.2 "Spring Returned Valves"-"Where the mounting position of a spring returned valve places the main element of the valve in a vertical plane, the spring force applied on the main element should be in a downward direction. Circuits shall use this returned position of a spring returned valve as the preferred, de-energized position". Lines crossing are normally allowed and illustrated ISO Fluid power Graphic Symbol.................................................


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