46 CFR 62.35-50: Monitoring and safety controls for specific systems

Last reviewed: November 9, 2026

This section lists the minimum instrumentation, alarms and safety controls for specific types of systems in table 1 to § 62.35-50. It also lists the ABS Marine Vessel Rules required for engineering systems. Paragraphs (a) through (k) set specific safety control and alarm requirements.

What it says

  1. Navigating bridge primary propulsion control systems must have safety limit controls, as § 62.35-5(c) addresses.

    46 CFR 62.35-50(a)“Safety limit controls must be provided in navigating bridge primary propulsion control systems.”
  2. All main boilers must have safety trip controls and alarms, regardless of mode of operation, as § 62.35-20(a) addresses.

    46 CFR 62.35-50(b)“Safety trip controls and alarms must be provided for all main boilers, regardless of mode of operation.”
  3. Main propulsion turbines and main propulsion diesel engines must have loss of forced lubrication safety trip controls.

    46 CFR 62.35-50(c)“Loss of forced lubrication safety trip controls must be provided for main propulsion turbines and main propulsion diesel engines.”
  4. Main propulsion or generator steam or gas turbines, and diesel engines, must not have override of overspeed and loss of forced lubrication pressure safety trip controls. See § 62.35-5(e)(2).

    46 CFR 62.35-50(d)“Override of overspeed and loss of forced lubrication pressure safety trip controls must not be provided for main propulsion or generator steam or gas turbines, or diesel engines.”
  5. Interlocks must prevent engines or turbines from starting while the jacking or turning gear, if installed, is engaged. See § 62.25-5(a).

    46 CFR 62.35-50(g)“Interlocks must be provided to prevent the starting of engines or turbines while the jacking or turning gear, if installed, is engaged.”
  6. Main and remote-control stations, including the navigational bridge, must give visual and audible alarms if a fire occurs in the main machinery space.

    46 CFR 62.35-50(h)“Main and remote-control stations, including the navigational bridge, must provide visual and audible alarms in the event of a fire in the main machinery space.”
  7. Minimally attended and periodically unattended machinery plants must have a personnel alarm that sounds on the bridge if the watch engineer does not acknowledge it. See § 62.50-20(b)(1).

    46 CFR 62.35-50(i)“Minimally attended and periodically unattended machinery plants must be provided with a personnel alarm that annunciates on the bridge if not acknowledged by the watch engineer.”
  8. All automatic controls and alarms must be failsafe to the least critical consequence for the particular system. See § 62.30-1.

    46 CFR 62.35-50(j)“All automatic controls and alarms must be failsafe to the least critical consequence for the particular system.”

Common questions

Which boilers must have safety trip controls and alarms?

All main boilers must have them, regardless of mode of operation.

“Safety trip controls and alarms must be provided for all main boilers, regardless of mode of operation.”

Can I override the overspeed trip on a main propulsion diesel engine?

No. Override of overspeed and loss of forced lubrication pressure safety trip controls must not be provided for main propulsion or generator steam or gas turbines, or diesel engines.

“Override of overspeed and loss of forced lubrication pressure safety trip controls must not be provided for main propulsion or generator steam or gas turbines, or diesel engines.”

What fire alarms are required in the main machinery space?

Main and remote-control stations, including the navigational bridge, must provide visual and audible alarms for a fire in the main machinery space.

“Main and remote-control stations, including the navigational bridge, must provide visual and audible alarms in the event of a fire in the main machinery space.”

Where is the operating or tripped status of vital auxiliary boilers indicated?

It must be indicated at the ECC. The text refers to part 63 of this subchapter.

“The operating or tripped status of vital auxiliary boilers must be indicated at the ECC.”

The text of 46 CFR 62.35-50

Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR

Tabulated monitoring and safety control requirements for specific systems

The minimum instrumentation, alarms, and safety controls required for specific types of systems are listed in table 1 to § 62.35-50. The ABS Marine Vessel Rules (incorporated by reference; see § 62.05-2) required for engineering systems are also listed in table 1 to § 62.35-50.

(a) Safety limit controls must be provided in navigating bridge primary propulsion control systems. See § 62.35-5(c).

(b) Safety trip controls and alarms must be provided for all main boilers, regardless of mode of operation. See § 62.35-20(a).

(c) Loss of forced lubrication safety trip controls must be provided for main propulsion turbines and main propulsion diesel engines.

(d) Override of overspeed and loss of forced lubrication pressure safety trip controls must not be provided for main propulsion or generator steam or gas turbines, or diesel engines. See § 62.35-5(e)(2).

(e) Transfer interlocks must be provided for main propulsion systems capable of remote and local control.

(f) Semiconductor controlled rectifiers must have current limit controls.

(g) Interlocks must be provided to prevent the starting of engines or turbines while the jacking or turning gear, if installed, is engaged. See § 62.25-5(a).

(h) Main and remote-control stations, including the navigational bridge, must provide visual and audible alarms in the event of a fire in the main machinery space.

(i) Minimally attended and periodically unattended machinery plants must be provided with a personnel alarm that annunciates on the bridge if not acknowledged by the watch engineer. See § 62.50-20(b)(1).

(j) All automatic controls and alarms must be failsafe to the least critical consequence for the particular system. See § 62.30-1.

(k) The operating or tripped status of vital auxiliary boilers must be indicated at the ECC. See part 63 of this subchapter.

Table 1 to § 62.35-50—Minimum System Monitoring and Safety Control Requirements for Specific Systems System Service Instrumentation Alarm Safety control See alsoparagraph Main (Propulsion) boiler ABS Marine Vessel Rules Part 4-9-6 tables 1A, 1B and 5A ABS Marine Vessel Rules Part 4-9-6 tables 1A, 1B and 5A ABS Marine Vessel Rules Part 4-9-6 tables 1A, 1B and 5A

(a) Burner seating Failure Burner auto trip

(b) Trial for ignition Status Failure Burner auto trip

(b) Manual trip

(b) Low fire interlock Status Program control interlock Status Main (Propulsion steam) turbine ABS Marine Vessel Rules Part 4-9-6 table 2 ABS Marine Vessel Rules Part 4-9-6 table 2 ABS Marine Vessel Rules Part 4-9-6 table 2 Manual trip

(c), (d) Main propulsion, diesel ABS Marine Vessel Rules Part 4-9-6 tables 1A, 1B and 5A ABS Marine Vessel Rules Part 4-9-6 tables 1A, 1B and 5A ABS Marine Vessel Rules Part 4-9-6 tables 1A, 1B and 5A Manual trip

(c), (d) Main propulsion, remote control Failure Manual trip Auto safety trip override Activated Starting power Pressure (voltage) Low Limit

(a) Location in control Status Override

(c) Shaft speed/direction/pitch See § 113.37 of this chapter. See § 113.37 of this chapter. See § 113.37 of this chapter. Clutch fluid Pressure Low Main propulsion, electric (1) ABS Marine Vessel Rules Part 4-9-6, tables 4A and 4B ABS Marine Vessel Rules Part 4-9-6, tables 4A and 4B ABS Marine Vessel Rules Part 4-9-6, tables 4A and 4B ABS Marine Vessel Rules Part 4-9-6, tables 4A and 4B

(f) Main propulsion, shafting Stern tube oil tank level Low Line shaft bearing Temperature High Forced lubrication Pressure Low Main propulsion, controllable pitch propeller Hydraulic oil Pressure High, Low Temperature High Generators Ship service ABS Marine Vessel Rules Part 4-9-6, table 6 ABS Marine Vessel Rules Part 4-9-6, table 6 Starting pressure/voltage Low Tripped Emergency 2 Turbogenerator ABS Marine Vessel Rules Part 4-9-6, table 6 ABS Marine Vessel Rules Part 4-9-6, table 6 ABS Marine Vessel Rules Part 4-9-6, table 6 Manual trip Diesel ABS Marine Vessel Rules Part 4-9-6, table 6 ABS Marine Vessel Rules Part 4-9-6, table 6 ABS Marine Vessel Rules Part 4-9-6, table 6

(d) Manual trip Auxiliary boiler Run Trip

(k) Gas turbine 3 ABS Marine Vessel Rules Part 4-9-6, Tables 3 and 6 ABS Marine Vessel Rules Part 4-9-6, Tables 3 and 6 ABS Marine Vessel Rules Part 4-9-6, Tables 3 and 6 ABS Marine Vessel Rules Part 4-9-6, Tables 3 and 6

(d) Engines and turbines Jacking/turning gear Engaged

(g) Fuel oil ABS Marine Vessel Rules Part 4-9-6, tables 5A and 6 ABS Marine Vessel Rules Part 4-9-6, tables 5A and 6 ABS Marine Vessel Rules Part 4-9-6, tables 5A and 6 Remote/auto fill level High Auto trip or overflow arrangement Hi. press. leakage level High Bilge Pump remote control Run Pump auto control Run Excessive operations Level High/location Machinery space Class 3 (power-operated) watertight doors Open/closed Fire detection Machinery spaces Space on fire

(h) Fire main Pressure Low Personnel Deadman Fail to acknowledge

(i) General, control and alarm systems Power supply Available (pressure) Failure (low) System function Failure

(j) Console air conditioning Failure Built in test equipment Active Sequential interlock Activated Safety control Activated Auto trip/limit

(j) Redundant auxiliary, system, power supply Status Auto transfer 1 See subparts 111.33 and 111.35 of this chapter. 2 See subparts 112.45 and 112.50 of this chapter. 3 See § 58.10-15(f) of this subchapter.

Sections it refers to

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.