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Mass Properties

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  • Last UpdatedMar 09, 2026
  • 4 minute read

The Mass Properties for Volume, Surface, Weight and Center of Gravity can be queried from any element in the system that has graphical representation or owns elements that have graphical representation.

These Mass Properties are calculated in a variety of ways, depending on the type of element. These are namely:

  • User Input - Usually for Weight and CofG of elements such as equipment and vessels.

  • Catalogue Data - Usually for Weight of components such as Pipe fittings, tables and chairs.

  • 3D Model Calculation by the System - Weight can be calculated for such as Beams, Columns, Panels where the Volume is used in combination with the material density. Volume and Surface area are always calculated by the System.

User Input

Elements that own primitives, such as Equipment and Sub-Structure for example have the following attributes for user input:

USRWEIGHT

Normal Weight.

USRWEIGHT is an expression that evaluates to a weight. The value is assumed to be in kilograms unless a unit has been specified. For example:

USRWEIGHT (1000g)

or

USRWEIGHT (RPRO WEIG)

USRWWEIGHT

Wet Weight for in the case of equipments with fluids.

USRCOG

An optional position from the element origin for the element Centre of Gravity. If unset then the origin is used.

USRCOG is an expression that evaluates to a position with respect to the equipment origin. The values are assumed to be in millimeters unless a different unit has been specified. For example:

USRCOG ( E ( 1000 ) S ( 2000 ) D ( 3000 ) )

or

USRCOG ( E ( 1m ) S ( 2m ) D ( 3m ) )

USRWCOG

An optional position from the element origin for the element Wet Centre of Gravity. If unset then the origin used.

The above attributes can be queried using a USC--- attribute such as USCWEIGHT to expand any expression for normal weight.

for example USRWEIGHT (RPRO WEIG)

Q USCWEIGHT gives actual result, say 1000

Similar applies for all above attributes.

Catalogue Data

Elements that have a Specification Reference (SPREF) also have a Component Reference (CMPREF). The Component Weight can be set here. The setting is usually numeric such as 10 for the weight of a pipe valve. However the component can also be an expression such as (RPRO TWEI) which allows for more user control. Component wet weights can also be set in this way.

For Center of Gravity (Dry and Wet) it is possible to create a Ppoint with a Purpose attribute of COFG (or WCOG) that is used as the Center of Gravity position. Otherwise P0 is considered to be the CofG.

3D Model Calculation by the System

For Volume and Surface calculations the results are calculated by the system, using the Representation Mass level. As per drawing representation levels an element can be displayed as a very simple or complex model using different representation levels, then the same principle applies for Mass Properties. Obviously it is quicker for the system to calculate a more basic representation.

Command Window

To set the mass representation level (to level 6 for example):

REPRE MASS 6

The Arc Tolerance for graphical representation is also a controlling factor:

REPRE DARCTOL 10mm - is the default

REPRE DARCTOL 1mm - is a finer representation.

The basic commands used for calculating Mass Properties are:

  • Volume

    NVOL, GVOL, RVOL  -  For Net, Gross or Rough Volume. Net calculations consider all negatives, whereas Gross ignores negatives, and Rough is a quicker version of Gross often useful when calculating many elements or complex shapes.

  • Surface

    NSRF, GSRF, RSRF

  • Weight

    NWEI, GWEI, RWEI

    Center of Gravity

    NCOFG, GCOFG, RCOFG

    Embedded Image (65% Scaling) (LIVE)

In addition to these basic commands it is also possible to use the following syntax:

Volume

To calculate the Volume that is 'within' an area definition (AREADE) - /room1 for example:

!args[1]=‘inside’

!args[2]=/room1

!nvol=!!ce.attribute(‘nvol’,!args)

Gives the net Volume of the current element that is within the room1.

NVOL(‘inside’ /room1 )

It is as above but can be used in the standard Report Utility.

GVOL(‘outside’ /room1 )

Gives the Gross Volume of the current element that is outside of /room1.

!args[1]=‘free’

!args[2]=/room1

!gvol=!!ce.attribute(‘gvol’,!args)

Gives the Free space in /room1.

Surface

To calculate the Surface that is 'within' an area definition (AREADE) - /room1 for example:

!args[1]=‘inside’

!args[2]=/room1

!nsrf=!!ce.attribute(‘nsrf’,!args)

Gives the net Surface of the current element that is within the room1.

NSRF(‘inside’ /room1 )

It is as above but can be used in the standard Report Utility.

GSRF(‘outside’ /room1 )

Gives the Gross Surface of the current element that is outside of /room1.

Note: The 'free' option is not applicable to surface.

Weight and CofG do not currently support inside/outside qualifiers.

All command line functionality is available in the Mass Properties Utility window.

Other Options

In addition to the inside/outside options described above, there are other options; namely wet/dry and only/all for example;

NWEI('wet')

Gives the weight or a pipe or equipment including any fluid weight.

NWEI('dry')

Gives the weight or a pipe or equipment excluding any fluid weight.

NWEI('only')

Gives the weight of an element only, excluding any members of the element.

NWEI('all')

Gives the weight of an element including the weight of any members of the element.

Any of the above options can be combined in any order.

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