In addition to the requirements found in ASME CSD-1 (incorporated by reference; see § 63.05-1), the following requirements apply for specific control systems:

(a) Primary safety control system. Following emergency safety trip control operation, the air flow to the boiler must not automatically increase. For this condition, postpurge must be accomplished manually.

(b) Combustion control system. A low fire interlock must ensure low fire start when variable firing rates are used.

(c) Water level controls and low water cutoff controls. Water level controls must be constructed and located to minimize the effects of vessel roll and pitch. Float chamber low water cutoff controls using stuffing boxes to transmit the motion of the float from the chamber to the external switches are prohibited. No outlet connection other than pressure controls, water columns, drains, and steam gages may be installed on the float chamber or on the pipes connecting the float chamber to the boiler. The water inlet valve must not feed water into the boiler through the float chamber. The boiler feed piping must comply with the applicable requirements of § 56.50-30 of this subchapter.