TSHD - Computing and Displaying Production

Computing and Displaying Production

Definitions

Tons Dry Solid (TDS) measures the hopper-load's volume and weight in order to determine the quantity of "dry solids" that it contains. By applying the values for the dry solid's specific density and the in situ water's density in a formula with the hopper-load's weight and volume (which indirectly measures the hopper-load's average density), the total quantity of the dry solids can be calculated.

The displacement or displacement tonnage of a ship is the ship's weight. The name reflects the fact that it is measured indirectly, by first calculating the volume of water displaced by the ship, and then calculating the weight of that water. By Archimedes' principle, this is also the weight of the ship.

Displacement should not be confused with other measurements of volume or capacity typically used for commercial vessels such as net tonnage, gross tonnage, or deadweight tonnage.

The process of determining a vessel's displacement begins with measuring its draft.This is accomplished by means of its "draft marks" (or "load lines"). A merchant vessel has three matching sets: one mark each on the port and starboard sides forward, midships, and astern. These marks allow a ship's displacement to be determined to an accuracy of 0.5%.

The draft observed at each set of marks is averaged to find a mean draft. The ship's hydrostatic tables show the corresponding volume displaced.

To calculate the weight of the displaced water, it is necessary to know its density. Seawater (1025 kg/m³) is more dense than fresh water (1000 kg/m³);so a ship will ride higher in salt water than in fresh. The density of water also varies with temperature.

The hopper volume of a vessel is given in the form of a so-called hopper table, or "sounding hopper table". This is the calculated volume versus the average level in the hopper. As long as the walls of the hopper are vertical the trim has no influence. On some ships, the wall at the top of the hopper is inside; this results in a (limited) error in the volume.

The status of the dredging cycle is determined by a PLC. This is a small computer receiving signals referencing valve positions and proximity switches etc.. The point in the dredging cycle is determined on the basis of these signals. The output is a number representing the status.

Computation of TDS

Different methods of computing TDS

Using mixture velocity, mixture density and suction pipe diameter. Trip volume and load are computed based on these parameters.
Using hopper levels, displacement and volume.
1. Hopper volume is computed using the average height of water levels in the hopper and "hopper tables".
2. Displacement is computed using draft measurements and a "displacement table". The draft of the hopper dredge is directly related to the weight of the dredge, plus loaded water and sediment. The draft can be related to vessel displacement with a draft/displacement table typically available from the shipyard. The total weight of material in the hopper is equal to the weight of bin water in the hopper before the load is taken plus the slurry load added. This total weight divided by the volume that the material occupies in the hopper is the average density of the material in the hopper.
3. The empty weight of the vessel is calculated right after dumping by subtracting from the displacement plane to dump after subtracting the weight of the water in the hopper and the trim tank.

QINSy does not, at time of writing (July 2016), support computation of volume and displacement. These parameter values must be read from the dredge PLC.

Database Setup - Sensor Input

In Database Setup define Dredging sensor observations including:

Displacement
Hopper volume
Hopper levels (multiple locations)
Dredging status
Mixture velocity (port and starboard)
Mixture density (port and starboard)
Flag (e.g. PMO status)

Also define Underwater sensor observations including:

Draft (draught) fore and aft

And define a Dredging System as follows:

Make sure to check 'Enable density/velocity sensors' and 'Enable TDS Calculation'.

Make sure to enable dredging status and define a translation table.

Make sure to assign velocities and densities observations for both dredge heads:

Make sure that 'TDS Calculated by' is set to QINSy.

Online

Computation Settings

Make sure to enable the Dredging System:

In Session Setup click on Storage and then on Sounding Grid.

Create a new sounding grid or load an existing grid.

Assign systems to different layers.

In Session Setup, click on Dredging and then Design.

Set the Design Properties by selecting:

One of - From Grid File, From QGF File or From Mapping File (PRO).
The correct file and layer.

Enter - a clipping depth if appropriate and dredge tolerances.

In Session Setup, click on Dredging and then Production.

Select Automatic for Volume Mode.

In Session Setup, click on Dredging and then Various.

Enter a value for Spill.

Generic Display

In the Controller click on the

icon to add a new Generic display.

In the opening dialog click on the

icon to open the Layout Editor.

In the Layout Editor click on Results Data and then on the Dredging button.

Click on Add.

Select a Dredge System and a particular head.

Select the sub-items as shown in the image.

Sub Item	Description
General State	Sailing Empty - Hopper is sailing but empty Dredging" - Pumping up material Sailing Loaded - Hopper is sailing, fully loaded with material Dumping Pumping Ashore Unknown (General State item is head independent)
Time	Update time of the dredging driver (Time item is head independent)
Design State	Above - Head footprint is above design (including tolerance) On Target - Head is on design level (within tolerance levels) Over Dredge - Head is below design level (including tolerance) Usually bad news for contractor... Not Used - Unknown/not used possible when grid data is not available
Mixture Density	Current mixture Density from production sensor, (c-o) already applied
Mixture Velocity	Current mixture velocity from production sensor, (c-o) already applied
Trip Volume	Current volume inside the selected dredging system
Trip Load	Current load inside the selected dredging system
Current Production	Current production, derived from production sensors Unit: [Cubic meter In situ material/sec] [Tons of dry material/sec]
Height Above Design	Actual height minus the design height at footprint of the selected head. Positive value means the head is above level. Negative value means head is below level. Design can be manual or from a sounding grid.
Design Height	Height of design at footprint of the selected head. Design can be manual or from a sounding grid.
Dredged Layer Thickness	Amount of removed soil. Will be zero when head is above bathy layer.
PMO Valve Time	Total time that PMO (Poor Mixture Overboard) was open (Spilling overboard).

Modify sub-item properties as necessary.

Click on DTM and then the Sounding Grid button.

Click on Add.

Leave the choice of Source to 'Active Sounding Grid' or select a specific grid.

Select the grid layer to reference.
Select the node to reference, e.g the drag head reference node.
Choose the computation and whether to deskew position or not.

Source:	Active Sounding Grid This will be automatically the sounding grid as selected in the Controller's Session Storage Setup. This option is not available when the generic layout is for export. [ Browse...] User must browse and select an existing sounding grid
Filename:	The selected sounding grid filename. This option is only visible when the source is not the Active Sounding Grid. The filename is displayed in red when the (last) selected file is not found
Layer:	Select the layer for retrieving the DTM Depth or other attribute values from. Notice that the layer for the active sounding grid may not be know yet, when defining the generic layout while being offline.
Node:	Select here the Node Position. The first entry is always [Steered Node] Notice that this selection is not supported (yet) when layout is for Export The second entry depends on the layout purpose: [Computation Setup] when layout is for Driver or Log File. The node must be selected in the Controller's Computation Setup, under shortcut Output Node [From Display] when layout is for Display. The node must be selected in the display itself, under pull-down menu item Edit, Display Node... Further notice that no computation can be selected, it will always be the one from [Priority List] [Export Settings] when layout is for Export. *This selection is not supported (yet)* The rest of the list will show all available nodes, existing in the current selected QINSy database (see General Layout Information about loading a QINSy database). The vessel name is displayed in front of the node name
Deskew:	No Node Position for the time as calculated by the PositionFilter. Yes Skewed to the time of output/trigger time, using the current Node Position (Horizontal), Time, SOG and COG. Notice that the SOG and COG depends on the Controller's Computation Setup, Object COG/SOG - Prediction Parameters Settings. The height value is not deskewed, but then again, the height component is never used for any line offset calculation.

Select sub-items as per the list below.

Sub Item	Description
Comment	Normal Text Your own free plain text Binary Enter one or more ASCII character codes, comma or space separated, in the range between 1 and 127. For example '2' for a binary STX character, '3' for a binary ETX character, or '13, 10' for CR+LF. See table ASCII Codes for an overview of all possible characters.
Status	A number between 0 and 7 indicating the status of the selected Sounding Grid, Layer and / or Node 0 means all okay, a valid DTM value was extracted successfully for the current node position 1 means no active sounding grid file has been selected in the Controller's Session Storage Setup 2 means that no grid file was selected 3 means that the selected grid file was not found 4 means that no layer has been selected 5 means that the selected layer was not found in the current sounding grid 6 means that no node was selected, or that the selected node has no valid position 7 means that the current node position is inside a bin with no valid DTM values
Sounding Grid	The file name of the selected (or active) sounding grid file Path is default not included. Will be empty when the selected grid file can not be found, or when there is no active grid selected in the Controller's Session Storage Setup
Layer	The name of the selected layer
Bin Size	The size of the smallest bin (level 0) of the selected or active sounding grid
Node Name	The name of the selected node Will be empty when no node has been selected
Node Altitude	The height of the node above the DTM Depth for the current node position Formula: Node Altitude = Node Height (on Chart Datum) - DTM Depth The DTM Depth value will be (default) the mean depth value from the bin (level 0), but may also be the deepest and/or shallowest depth value if that attribute exist in the current layer
DTM Depth	This is the mean (default) depth value from the bin (level 0) for the current position, but may also be the deepest and/or shallowest depth value if that attribute exist in the current layer. The value will be empty if the status (see above) is not zero, or if the selected attribute deepest/shallowest is not a property of the selected layer.
DTM Attribute	The value depends on the selected attribute The value will remain empty if the selected layer does not have the selected attribute as property, or if the status (see above) is not zero.

Set sub-item properties as necessary.

The final Generic Display could look something like this:

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