NVIC 07-73: Main propulsion boiler automation problems and guidance
Last reviewed: October 14, 2026
This circular draws attention to problems seen when existing main propulsion boilers are automated. It gives guidance on avoiding them, mainly through closer coordination among the ship owner, automation contractor and boiler manufacturer before drawings go to the Coast Guard. Obtaining manufacturer guidance is not a requirement of Coast Guard regulations.
Applies toThe circular is addressed to all interested and affected members of the marine community concerning automation of existing main propulsion boilers.
What it says
The circular's purpose is to draw attention to problems from automating existing main propulsion boilers and to give guidance for avoiding them.
“to certain problems being encountered as the result of the automation of existing main propulsion boilers.”
Automation changes often require modifications to the boiler itself, and this has often resulted in boilers not operating within design limits.
“These automation changes often require that modifications be made to the boiler itself.”
The problems listed include excessive superheat temperatures, but are not limited to that one.
“The problems include, but are not limited to:”
The circular says many problems could be avoided by closer coordination among the ship owner, automation contractor and boiler manufacturer before drawings are submitted to the Coast Guard for approval.
“closer coordination between the ship owner, automation contractor and boiler manufacturer prior to submission of drawings to the Coast Guard for approval.”
Boiler manufacturers have said they would review proposed installations if the owner or his agent requests it, but their comments are guidance only and not approval or a guarantee of boiler performance.
“their comments would constitute guidance only and not approval or guarantee of boiler performance with the new equipment.”
Coast Guard regulations do not require that owners obtain this manufacturer guidance.
“It is not a requirement of Coast Guard regulations that such guidance be obtained.”
Common questions
Do I have to get boiler manufacturer review before automating a main propulsion boiler?
No. The circular says Coast Guard regulations do not require that such guidance be obtained.
“It is not a requirement of Coast Guard regulations that such guidance be obtained.”
Is a boiler manufacturer's comment an approval of my automation plan?
No. The manufacturers noted that their comments are guidance only, not approval or a guarantee of boiler performance with the new equipment.
“their comments would constitute guidance only and not approval or guarantee of boiler performance with the new equipment.”
What problems can boiler automation cause?
The circular lists excessive superheat temperatures, forced draft fans that must run constantly at full speed, improper flame patterns in the furnaces, and boiler response time not matching the new system. The list is not limited to these.
“The problems include, but are not limited to:”
The text of NVIC 07-73
U.S. Coast Guard, NVIC 07-73 (main body; enclosures not shown)
Main Propulsion Boiler Automation
DEPARTMENT OF TRANSPORTATION UNITED STATES COAST GUARD U.S. COAST GUARD 400 SEVVITH STREET SW D.C. WASHINGTON, DC 20590 PHONE: (202) 426-2160 NVC 7-73 13 JUN 1973 NAVTGATION AND VESSEL INSPECTION CIRCULAR NO. 7-73 Subj: Main Propulsion Boiler Automation
Main Propulsion Boiler Automation — Purpose. The purpose of this circular is to draw the attention of all interested and affected
members of the marine community to certain problems being encountered as the result of the automation of existing main propulsion boilers. Guidance for the avoidance of these problems is also provided.
Main Propulsion Boiler Automation — Background. Many existing vessels are currently undergoing boiler control system changes, in
most cases in conjunction with automation for reduced manning in accordance with NVC 1-69. These automation changes often require that modifications be made to the boiler itself. In many instances this has resulted in the boilers not operating within design limits and in operating procedures having to be changed significantly. The problems include, but are not limited to: a. Excessive superheat temperatures. b. Forced draft fans required to be run constantly at full speed due to wind box modifications. c. Improper flame patterns in the furnaces due to burner modifications. d. Bailer response time not matching the flexibility of the newly installed system.
Main Propulsion Boiler Automation — Discussion. It is believed that many of these problems could be avoided by closer coordination
between the ship owner, automation contractor and boiler manufacturer prior to submission of drawings to the Coast Guard for approval. To this end the Commandant has contacted the major boiler manufacturers, presenting a summary of the problem and asking if they would review proposed installations, if requested by the owner or his agent, and comment on the feasibility of achieving the desired automation without causing the boiler performance to vary from design conditions. All boiler manufacturers have indicated they would participate in such an effort, noting however that their comments would constitute guidance only and not approval or guarantee of boiler performance with the new equipment. It is not a requirement of Coast Guard regulations that such guidance be obtained. However, when combined with the normal plan review of boiler modifications required by 46 CPR 52 and 59, it can greatly assist the owner in Obtaining a reliable installation. Dist: (SDL 96) A: None B: n(45; c(l0); q(6) ; eg(3); bp(l)) C: o(6); m(4); y(2); g(1) D: i(2); K(l) E: o(3) F: ar(l) List CG-12
Sections it refers to
- 46 CFR 52
- 46 CFR 59
- NVIC 1-69
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. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.