Can anyone show me what a proportional valve schematic symbol looks like? - Page 1
Forum section: electronics / projects

author: jgbena
author_rank: Contributor
timestamp: October 11, 2013, 05:41:21 pm
content: Can anyone give me an example of what a proportional valve looks like in an electrical schematic? I have symbols for solenoids but i cant find one for a valve like that.Anyone?Thank you for taking the time to help!

author: IanB
author_rank: Super Contributor
timestamp: October 11, 2013, 05:45:39 pm
content: Do you mean a valve for regulating fluid flow? If so, yes, I can show you. I'll find some links to post shortly.

author: jgbena
author_rank: Contributor
timestamp: October 11, 2013, 05:49:35 pm
content: Yes, Its for a hydraulic valve.

author: IanB
author_rank: Super Contributor
timestamp: October 11, 2013, 06:02:31 pm
content: Here's an example:It's from this link:https://controls.engin.umich.edu/wiki/index.php/PIDStandardNotationIn an instrumentation context there is more detail that could be shown about the actual valve and valve positioning arrangements, but the picture above shows the simplest standard notation that can be understood in a generic sense.

author: IanB
author_rank: Super Contributor
timestamp: October 11, 2013, 06:14:11 pm
content: Here is a useful document:http://www.samson.de/pdf_en/l101en.pdf

author: jgbena
author_rank: Contributor
timestamp: October 11, 2013, 07:20:54 pm
content: Oh ok, I knew of that symbol but I thought it was only for a hydraulic schematic. It works for both then correct?

author: IanB
author_rank: Super Contributor
timestamp: October 11, 2013, 09:10:12 pm
content: Typically electrical schematics and piping schematics are shown on separate sheets, but symbols can cross over and be shown on both sheets where they overlap. Very often the control schematic and the piping schematic are shown on the same sheet, in which case this is known as a piping & instrumentation diagram (P&ID).The basic valve symbol consists of two parts, the valve part and the actuator part. They can be combined in different ways as appropriate:

author: AlfBaz
author_rank: Super Contributor
timestamp: October 12, 2013, 12:12:58 am
content: I've seen a lot of schematics with PV's in them and I don't think I've seen anything "standard" often enough to stick in my mind.This is probably due to the varying electrical control schemes for them. Usually there will be a power supply, signal in and some form of feedback which can be an analogue signal or simply a high/low error line. Most modern PVs have built in control electronics

author: IanB
author_rank: Super Contributor
timestamp: October 12, 2013, 03:33:15 am
content: There are standards for such things, for example the PDF I linked to above draws from various DIN standards, but there are other standards, such as ISA S5.1:http://www.purduecal.edu/cpmi/NSF%20Courses/ECET-462/HANDOUTS/P&ID.pdfWhile major industries will follow such standards you can't be sure that small shops will necessarily adhere to them.In the control world it is rare to get down to the details of actual electrical wires. Control interconnect schemes are standardized and a control signal will be abstracted to a single line on a diagram even if it requires two or more wires to implement it.For instance, you send a signal to a valve that says "I want the valve to be 50% open". At the valve there is an automatic positioner or actuator that moves the valve with a local power supply and feedback loop until it reaches the desired 50% position. There is usually no need to show the gory details of how this all works on a control and instrumentation diagram. If you really want to know what's going on inside the box you would need to look up the electrical circuit diagram for that component.Without standard interfaces it would be impossible to design interconnected systems.

author: AlfBaz
author_rank: Super Contributor
timestamp: October 12, 2013, 04:45:59 am
content: I agree completely with what your are stating but I was under the impression the OP was talking about the electrical schematic side not the pneumatic/hydraulic side.Even with the latter situation the types of drawings you are referring to seem to be of the generic/overview type and would do little to aid in the installation/faultfinding of the types of systems I'm referring to such as detailed pneumatic and or hydraulic systems where proportional valves are drawn indicating there functionality (see attached picture)

author: AlfBaz
author_rank: Super Contributor
timestamp: October 12, 2013, 04:50:23 am
content: oh and in the types of drawing I'm talking about a tank would simply be like this

author: mjrandle
author_rank: Contributor
timestamp: October 12, 2013, 05:04:56 am
content: If it's a hydraulic valve as in fluid power, then I would draw the electrical schematic as per the proportional solenoid part of the hydraulic symbols as posted by AlfBaz. Just makes it obvious that it's a fluid power rather than process valve.Cheers,Mike

author: IanB
author_rank: Super Contributor
timestamp: October 12, 2013, 08:25:17 am
content: I see, it all depends on the context. In some industries or industrial areas such as pneumatic or hydraulic servo control there are different schematic symbols in use with much more detail in them.In the first post jgbena may be thinking of something like one of these:http://www.ascovalve.com/Applications/Products/ProportionalControl.aspxI would say however that even on an electrical schematic or a circuit diagram one may still show a floating valve symbol without any of its process connections just to indicate where the electrical signals go.