Type S251C
Fisher Controls
Instruction Manual
Type S251C Pilot-Operated Regulators
March 1978
Form 5101
WARNING Fisher regulators must be installed, operated, and maintained in accordance with federal, state, and local codes, rules and regulations, and Fisher instructions. If the regulators vents gas or a leak develops in the system, service to the unit may be required. Failure to correct the trouble could result in a hazardous condition. Call a gas service technician to service the unit. Only a qualified person must install or service the regulator.
INTRODUCTION Figure 1. Type S251C
This instruction manual provides instructions and parts lists for the Type S251C regulator, including the main regulator and pilot.
Description The Type S251C is an accurate, pilot-operated pressurereducing regulator, intended for general gas pressure reduction service such as domestic and small commercial applications using pressure-factor measurement (fixedfactor billing).
Specifications Table 1 lists the specifications for Type S251C constructions. The following information is stamped on the regulator at the factory: orifice (seat ring) diameter, maximum inlet pressure, outlet pressure setting, and pressure factor.
ŠFisher Controls Comany 1978
INSTALLATION WARNING Personal injury or system damage may result if this regulator is installed, without appropriate overpressure protection, where service conditions could exceed the limits given on the regulator nameplate. Regulator installations should be adequately protected from physical damage.
CAUTION Like most regulators, the Type S251C regulator has an outlet pressure rating lower than its inlet pressure rating. If actual inlet pressure can exceed the outlet pressure rating, outlet overpressure protection is necessary. However, overpressuring any portion of a Type S251C regulator beyond the limits in table 2 may cause
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