Help - Looking for very reliable pressure switches


Thread Starter


We had installed several high end snap-action pressure switches from a well known manufacturer over the years. These switches were used on natural gas system, dry, clean and ambient temp is within specification. Generally the sepoint ranges are ~ 7psig lo/22psig hi.

We have been experienced non-responsive diaphragm problem from time to time with these switches. The process pressure is regulated and therefore seldomly activated the high gas pressure switches (may be only once a year). During a normal maintenance check, we discovered that some of these switches do not respond. It appears that the diaphragm/spring built up a memory after few years in service (2 -3 years). Failure rate is ~ 3 out of 8 over the 12 year period.

We then replaced them with solid state microproscessor based switches recommended by the same company. We had 3 failures on the solid state recently. This time it is related to cycling power on/off to the switches or overvoltage, we do not know for sure. Failure rate is 3 units out of 8 during a 5-year period.

We are ready to change all of these electronic switches out.

I am looking at a different manufacturer, someone with history of reliablity and performance. In my opinion a reliable switch should last more than 10 years with normal maintenance.

Please post your comments. I am looking forward to hear from you.

Thank you for your assistance.

Rahul P Sharma

Our experience with Custom Controls Systems Inc.'s switches has been excellent... We use them in our Turbines... and two of these Turbines use CCS made switches, which were supplied with the Turbine Package... I must say that in last twenty years (20 Yrs...!!) of the Turbine run, we've never faced a single switch failure... (Wonder how these guys can do business with such a low failure!! kidding...) In annual Preventive Maintenance Calibration Schedules too, it's more like checking the setpoints and never adjusting (or calibrating) the setpoints... The switches are truly low drift switches and can be relied upon... Atleast that's what my experience is...

I 2nd Rahul's comments on CCS switches. We're on the Texas Gulf Coast so both process and environment "test" our instruments. Maintenance uses these to replace other brands that fail or are found to be changing with age and we try very hard to get them bought on the front end of new projects (not too hard as CCS has VERY competitive pricing).

If you want to make this more reliable, I would recommend you using a pressure xmtr connected to a switch. Say a Rosemount 3051 for instance. This is quite common these days to replace pressure switches outright with xmtrs....for some of the reasons you mentioned. Especially where safety is a concern. They also provide a continual 4-20, so you know they are responsive..before you do a maintenance check to find out they are dead. They will cost more initially, but eventually pay for themselves on the maintenance side of things.

Just my .02$ worth.