Hi Guys, Need some assistance ; Could you provide me few inputs as below , I am planning to do a design Change / Modification on our interposing Relay Logic Panel . The Control Circuit is quite simple , but a barin storming is required. Most of the SOV Drives are controlled from ESD /PLC Panel. Due to Changes not Possible online which may have impact on Process , We planned to do a temporary Change. __ Powersupply +ve ( 24VDC or 120VDC ) ------- ( Fuse ) -------o o--------( SOV )-------- -ve of Powersupply. The logic would be developed in DCS based on voting (2 o o 2 or 2 o o 3) by reading the input transmitters and generate a contact output which would drive a additional SOV in field, through interposing relay. The addtional SOV would be in series in the pneumatic circuit for control valve / chopper valves. A dedicated power supply would drive the SOV which would be normally energised. Based on the DCS logic, this SOV will be de-energised and the valve will close. There will be a bypass switch to override the relay contact in case OF MAINTENENCE. Here are few of my concerns, If you have any documents ,application notes, Design Docs, BOM from your earlier projects, Wiring details related to the subject please forward. 1.Not sure if its 24vdc or 120vdc Solenoid ? What is the basic difference of using a 24VDC over 120VDC for the Solenoid or vise versa. 2.Can the solenoid be ordered without Surge suppressor doides and installed later. What type of diodes is suitable to be installed in parallel. 3.What should be the Relay type or Contact Rating? 4.The Control circuit is similar to have shown above ? Is the Basic design ok How can we rate the fuses ?Slow blow or fast blow and rating ? 5.The Cable length is approx. 150/200 Meters , Is 24VDC or 120VDC better for the Purpose. If any of you have a better approach please let me know, It would be of great help , Thanks in advance
