The versions available with the CL31 are:

• CL31N – The CL31N is a constant pressure loaded regulator that utilizes a pilot with no internal relief (N).  This regulator can be used where psig to psig regulation is required with no internal relief
• CL31R – The CL31R is a constant pressure loaded regulator equipped with a pilot internal relief valve.  The pilot relief valve is not designed for “full capacity” relief, but rather to limit the loading chamber pressure to a safe value in the event of a failure
• CL31IMN – The CL31IMN is a constant pressure loaded regulator featuring Internal Monitoring (IM) operation with no pilot internal relief (N).  It provides the important added advantage of a second, bubble-tight lock-up seat in series with the primary seat.  If the primary seat fails to close or control the gas flow, the Internal Monitor seat assumes control of the downstream gas pressure
• CL31IMR – The CL31IMR provides the same features as the ‘IMN’ model but with token pilot relief valve backup of the monitor orifice if both the primary seat and monitor seat fail simultaneously
• CL31IMRV – Operation is identical to the ‘IMR’ except that at no flow position of the monitor orifice a small volume of gas is vented through the relief valve to serve as a signal that the regulator is on monitor operation and the primary seat has failed.  No gas is vented until the gas load is less than the volume going through the orifice vent hole and the regulator is on monitor operation