The Fisher 64 series high-pressure (pounds-to-pounds) LP-gas regulators are usually used to reduce tank pressure to pressure to an intermediate pressure for use by another regulator. The basic regulator version doesn't have a relief so it should always be used with a downstream regulator and/or separate relief devices in compliance with NFPA 58 over-pressure protection requirements. The 64SR versions include an internal relief valve so they may be used as a First-Stage regulator when set at 10 psig (0.69 bar). They are also used for Final-Stage service on high-pressure burners in crop dryers and tobacco curers, as well as other medium sized commercial or industrial applications.

One model (64SR-122) is a commercial automatic changeover regulator, designed for large capacity multi-cylinder or tank installations. These regulators are used on applications such as bakeries, motels, restaurants and grain dryers. The manifold portion of the assembly consists of two 64SR series regulators and a direct mounted 803 series indicator.

Specifications include maximum inlet pressure of 250 psig (17.2 bar), emergency outlet pressure of 220 psig (15.2 bar), and propane flow capacities up to 5,250,000 BTU/hr. Connections are 1/2in female NPT inlet and outlet with a 1/4in female NPT side outlet for gauge. Operating temperature range is -20 to 150°F (-29 to 66°C). The regulators are UL listed, CRN certified, and CE approved.