For some significant Iranian shipowners such as NITC and IRISL the sanctions meant that they were placed completely off limits to charterers, cargo interests, and - crucially - insurers by asset freezes.  Besides those shipowners subject to asset freezes, any Iranian owned (or even chartered) vessel was prevented from obtaining the services of EU based surveyors, flags or classification societies.   EU oil and chemical tankers were off limits to Iranian charterers.  Sales of key equipment and technology for the maritime industry, including marine propulsion engines, propellers and, indeed, compasses, were all banned from export to Iran.