If you use Hansen relief valves, this bulletin might be of use to you:
Hansen recently discovered that certain pressure relief valves sold to our customers for industrial use from February 16, 2011 to April 4, 2013 are more susceptible to internal corrosion when exposed to standing water inside the valve. Even though the risk is remote, the failure of a pressure release valve could conceivably result in serious personal injury and/or property damage. Consequently, Hansen has initiated a program to send replacement valves so that any valves currently at risk can be replaced promptly. Hansen has not received any reports to date of any valve failures that have resulted in personal injury or property damage, but Hansen is taking this action in the interest of safety and avoiding potential risks. We are therefore issuing this recall of all valves that may be potentially impacted.
.Specifically, Hansen H5600A, H5601, H5602, H5600R, H5602R, and H5632R valves with serial numbers 02B11 through 04B13 are susceptible, regardless of pressure setting.
You can download the notification bulletin here.