The Mark 518 is a back pressure regulator for use in low pressure gas and liquid services. With a selection of six pressure ranges, set points can be chosen to control back pressures from 1" w.c. to 7 psi (3mbar to 0,5 bar). For critical applications, the Mark 518 can be provided with soft PTFE or Viton seats for ANSI Class VI bubble-tight shutoff. The valve is also leak-proof under vacuum conditions.

The Mark 518 back pressure relief valve is used for maintaining the pressure of air and gases in the positive inches w.c. (mbar) pressure range.