A hardened poppet and seat provides long life and better resistance to contamination than soft seating material.Pilot operated check valves should never be used with paired cylinders; Pilot pressure will open the valve with the least load first, transferring the combined load to the second valve doubling the load pressure on the second cylinder. This situation could prevent valve from being capable of being piloted open.Pressure at port 2 is directly additive to the pilot pressure required at port 3. For applications where high port 2 pressure occurs, it may be necessary to consider using a vented type pilot operated check valve.