Hydromax includes a wide range of template criteria (or: parent criteria) as well as pre-defined custom criteria such as IMO, HSC, DNV, ISO and more. Hydromax uses a single dialog to control all the stability criteria. This makes it quick and easy to set which criteria should be included for analysis and to change criteria parameters. It is also possible for users to create their own custom sets of criteria. Users may save, import and edit their criteria sets. These custom criteria files may be easily transferred via email.

Criteria may be identified as intact or damage criteria (or both). This ensures that the correct criteria are evaluated and displayed during normal and batch analysis. Although all criteria are displayed in the criteria table, only criteria that are applicable are added to the report; i.e.: if the intact case is being computed, only the criteria that are selected for evaluation during an intact analysis will be evaluated and added to the report, similarly for the damage cases.

Criteria results are added to the Report after a Large Angle Stability or Equilibrium analysis. However, only the applicable criteria are added to the report (although all are displayed in the Results table); i.e. after an Equilibrium analysis only those criteria that are evaluated from Equilibrium data are added, and after a Large Angle Stability analysis only GZ based criteria are added to the report.

Help information relating to the use and parameters of each criterion is displayed in the lower right hand corner of the dialog.

Hydromax includes a wide range of criteria. These criteria are listed using in a tree control on the left-hand side of the criteria dialog. This section describes how this list of criteria can be divided up in to Parent heeling arms, Parent criteria, predefined custom criteria and user created custom criteria. This section also explains how all criteria can be divided up into two different criteria types: equilibrium and GZ curve based.

The criteria tree list

Parent Heeling Arms

In most cases a ship is subject to specific heeling moments. Those heeling moment are then used in a number of different criteria. The Hydromax criteria list contains Parent Heeling Arms that can be copied into a custom criteria folder and then cross-referenced into the stability criteria.

The advantage of using cross-referenced Heeling Arms is that a heeling arm is now defined (and edited) in only one place. This ensures that all criteria which use a specific heeling arm use exactly the same heeling arm. Another benefit is that, since the heeling arm is defined in one place, it is only displayed once in the GZ graph and not duplicated for each criterion that uses it.

Parent Criteria

The Parent Criteria group contains all the parent criteria types that are available in Hydromax. Each parent criterion allows you to perform a specific calculation; these are the fundamental criteria from which criteria for specific codes are derived.

Parent criteria are special in that you cannot rename, delete or add criteria to the Parent Criteria group. Also the parent criteria settings cannot be saved, they will always revert to their default values when Hydromax is restarted. This is because the parent criteria are intended for use as templates from which you can derive your own custom criteria. This is done by dragging the required parent criteria in to the “My custom criteria” group or any other group you create.

To distinguish the Parent criteria from your derived criteria, they are displayed in bold text in the Criteria list.

Predefined Custom Criteria

A number of criteria files containing criteria for specific codes are supplied with Hydromax. These may be found in the “HMSpecificCriteria” folder. This folder can be found in the Maxsurf root directory: c:\program files\Maxsurf.

Most specific criteria are locked; those that are not locked require your ship design data to be input.

Also see

Working with Criteria Libraries on page 123

Appendix D Specific Criteria on page 233.

You can create your own set of criteria in the tree as well. This is explained in the section on Working with Criteria on page 119.

There are two fundamental types of criteria:

Equilibrium criteria

Equilibrium criteria are evaluated after an Equilibrium analysis and refer only to the condition of the vessel in its equilibrium state For example: margin line immersion tests, freeboard measurements, trim angle, metacentric height, etc. This type of criterion is also used by the Floodable Length analysis. Equilibrium criteria can be recognised by the  icon.

Criteria derived from measurements of the GZ curve.

These are calculated after a Large Angle Stability analysis and during a Limiting KG analysis. For example, area under GZ curve between specified limits, angle of maximum GZ, etc. These criteria are often referred to as Large Angle Stability (LAS) or GZ criteria.

Note that there is some cross-over between the criteria types, notably angle of equilibrium heel. This can be measured from the GZ curve by looking for an up-crossing of the GZ=0 axis. The equilibrium heel angle is also a fundamental output of the Equilibrium analysis. The same also applies for GMt. For this reason, in some criteria sets some criteria are included twice, once in the form of an Equilibrium criterion and again as a Large Angle Stability criterion.

For a criterion to be used in the search for maximum VCG in the Limiting KG analysis, it must be a LAS criterion. This is because it is only this type of criteria that is more likely to pass as VCG is reduced. A check is also made to ensure that any selected Equilibrium criteria are passed, but they cannot be included directly in the search algorithm.

You will notice that different icons are used to differentiate between different types of criteria. These icons are derived from the parent criterion type. The different types of criteria and their icons are described below:

See next: Criteria Procedures