Q.What is class memorandum to the ship owners and how is it different from condition of class ?

Ship need to be designed, built and maintained as per the standards and requirements of a classification society.

But sometimes a ship may fall short of these standards. For example, let us say that a ship had a collision. The ship had a big hole on its hull, above the water line. 

Can the ship sail ? Is the ship seaworthy ? Off course not. The ship need to be docked and the hull need repairing. But for the ship to arrive at the nearest dry dock requires sailing time of 2 days. What can be done in this case ? 

Another example. Vessel had issue with the Governor of ship's engine. Because of this ship cannot be manoevered from the wheelhouse or from Engine control room. It can only be manoevered from the local station in the engine room. To get the required spares on board need time of around 15 days. Do the ship need to wait for those spares.

What I am trying to say is that there may be situations that require a ship to sail for few days with a notable deficiency. 

In this case, Classification society may recommend some temporary measures to the ship owners. After these measures are implemented, the class may allow the ship to sail for few days or to the next port.

Classification society in this case will issue a "condition of class" to the ship. This is not a nice thing to have. Even Oil majors do not accept a ship with 'condition of class".

Now what is "class memorendum" ?

Classification society's memoranda to the ship owners are the notes for them. These notes highlight something to the ship owner that is within the acceptable limits but may require their attention because it can go out of the limit in near future.

Let us see few of the examples. 

Let us say during annual class survey, the surveyor found an indentation on the ship's hull. This indentation is within the acceptable limits as per the rules of classification society. But they want to remind ship owners that though this is within acceptable limit, it is better to repair this at next available opportunity. This fact will be entered as a "memoranda for the ship owners".

 Another common example. A memoranda may be issued for any new requirement that the vessel need to comply in near future.

As I said, memorandum are the notes from the class for the ship owner. There is nothing to worry about these memorandum but any memorandum related to hull structure is taken seriously by the third parties.