English term (edited): non-tank vessel, nontank vessel

Только такой описательный перевод адекватен, поскольку понятие "nontank vessel" официально введено сравнительно недавно - и только в США
Русский эквивалент отсутствует

Определения из официальных источников:
1.
AS 46.04.900(11) - "non-tank vessel" means a self-propelled watercraft of more than 400 gross registered tons; in this paragraph, "watercraft" includes commercial fishing vessels, commercial fish processor vessels, passenger vessels, and cargo vessels, but does not include a tank vessel, oil barge, or public vessel
West Coast Oil Transfer Regulations Table
page 5
http://www.oilspilltaskforce.org/docs/project_reports/OilTra...

2.
"nontank vessel" means a self-propelled vessel of 400 gross tons as measured under section 14302 of title 46, United States Code, or greater, other than a tank vessel, that carries oil of any kind as fuel for main propulsion and that
(A) is a vessel of the United States; or
(B) operates on the navigable waters of the United States
Clean Water Act Section 311 - Oil and Hazardous Substances Liability
http://www.epa.gov/region7/public_notices/CWA/section311.htm

Редко встречающееся словосочетание
"non-tanker vessel"
не имеет четкого официального определения по причине, понятной из следующего фрагмента официального документа:

Tankers constitute a significant percentage of vessel source oil spills as compared to non-tankers. [ US Code Section 2101 (39) defines a “tank vessel” as a vessel carrying oil or hazardous materials in bulk or residue including a tanker as defined in section 2101 (38). US Code Section 2101 (38) defines “tanker” as a self-propelled tank vessel that has been constructed or primarily adapted to carry oil or hazardous material in bulk in the cargo spaces. This vessel is a subclass of tank vessel, which is defined in section 2101 (39).
Oil Spill Prevention and Response: The U.S. Institutional System in the Coast of California
page 14
http://www.institutofranklin.net/sites/default/files/fckedit...
Т.е. существуют
- широкий класс "наливное судно" (tank vessel), включающее напр. (несамоходные) нефтеналивные баржи
- его подкласс "танкер" (tanker) - самоходное нефтеналивное судно

Таким образом,
- non-tanker = не танкер (но, возможно, "tank vessel")
- nontank vessel - не нефтеналивное судно, в том числе non-tanker (но не только)

Отсюда ясно, что называть
non-tank vessel
словосочетанием
non-tanker vessel
неверно
Например, по официальной классификации, нефтебаржа это "tank vessel" и одновременно "non-tanker vessel"