DYNTTS - Setting Up the System

Connecting Hardware

Hydraulic connections

DYNTTS GDS systems are supplies with Legris nylon hydraulic tube and Swagelok-type hydraulic tube fittings. All hydraulic connections mentioned in this handbook should be done according to the instructions provided in Helpsheet 78 -Hydraulic connectors, included in this handbook (after this section).

Bolts

The normal use of a DYNTTS system will require the user to tighten or remove bolts for different operations. On all variants, this will be a requirement for the removing and replacement of the sample pedestal and feedthrough blanking ports. The 150mm and the high-pressure variants of the DYNTTS will use bolts to seal the triaxial cell instead of tie rods.

All bolting operation shall follow the guidelines given in helpsheet 224 - Torque Settings and Bolting procedures, included in this handbook (after this section)

Setting up the Triaxial Cell

The two digital pressure controllers should be connected to the cell via the valves on the side of the cell, using the supplied hydraulic tube and the swagelock-type connectors fitted to the DYNTTS cell bowl.

For systems with the Sig-3 Pressure controller upgrade, this controller is already connected hydraulically to the Cell base. The valve labelled ‘Back pressure’ will be used with a 1/8” tube and connector. Once the controllers have been filled, the EMPTY function on the pressure controllers should be used to run de-aerated water through the connections to flush out any air in the tubing.

Open

The cell top is placed on top of the cell base and screwed down by tie rods, or by the sealing bolts for the 150mm and High-Pressure variants of the DYNTTS.

Open

Photo, showing cell top placement on cell base

 

To remove any backlash effect on the load ram adjustment assembly, at the top of the triaxial cell during a dynamic test the bolts at the top of the assembly, they are to be tight. Also, on the side of the turning ring, used to set the ram at a certain height, there are two grub-screws that need to be ensured are tight.

Sig 3 Controller and piping kit installation (only applicable for Sig 3 upgrade systems)

A pressure transducer provided with Sig 3 controller is connected to the de-airing block on the triaxial cell and the lemo plug is plugged into the matching colour on the ADVDCS box channel.

The Pressure Controllers

Typically two GDS Pressure Controllers (cell pressure and back pressure), are required and should be hydraulically connected to the triaxial cell. Please follow the manual for the GDS Pressure/Volume controllers for setting these up.

Each pressure controller senses pressure from a pressure transducer inside the controller pressure cylinder, converts this into digital form and then turns the stepper motor to increase or decrease the pressure as required.

Please refer to the relevant controller manual (provided separately) for detailed information on your controllers.

Setting up the Standard/ Advanced Pressure Controllers (USB)

The ‘v2' version of standard pressure controllers (STDPCv2) or the 'new’ Advanced Pressure Controller (ADVDPCv4) have a USB interface, rather than an RS232 interface. The controller is to be connected to the PC via a USB cable – then once GDSLab is opened with the correct .ini file, the correct controller can be selected by clicking on the controller in question and choosing the necessary controller serial number from the drop down menu.

Setting up the Advanced pressure controllers (RS232/ IEEE)

If provided with an IEEE interface, each advanced pressure controller must be setup with the correct IEEE address corresponding to the controlling software. To change (or check) the IEEE address on the controller, perform the following keystrokes:

RESET, 0, 1

If the Advanced controller is set up with an RS232 interface, you must set up the communication parameters as detailed in the GDSLab handbook. A 25 pin to 9 pin RS232 cable will be supplied – this should be connected to the serial port on your PC.

To set the communications parameters on the controller itself (4800, odd, 8, 2), simply perform the following keystrokes: “RESET”, “0”, “ENTER”, “RESET”, “9”.

Setting up the computer system

Reference should be made to the appropriate computer manuals.

When using a standard USB interface, simply connect the USB cable to your computer and select the drop down box within the ‘Object Display’ window on GDSLab.

If using Advanced IEEE controllers, use IEEE cables of minimum length to link the computer to the digital controllers. Ensure that the device codes are set as indicated in the GDSLAB object display. Where there is a conflict of device codes the system will malfunction, e.g. if both digital controllers have IEEE addresses = 8 it will not be possible to run the system.

If using a Advanced Serial controllers, these should be connected to the computer, either directly using two 9-25 pin serial cables to Commports 1 and 2, or via a serial to USB converter.

Power on the devices making that sure the computer is powered on last. This sets all the devices on the bus into the correct state for subsequent bus operations.

Install the software

PC System Requirements

The AdvDCS unit is connected to the computer using a USB cable.  Acquired data is stored locally on the AdvDCS and passed to the controlling computer by a separate communications process.

Please follow the instructions referred in the section “Calamari Drivers” in the helpsheet below to install the software.

Windows Power management recommended settings.

Calculate transducer zero offsets

There are two similar pressure transducers connected to each of the two pressure controllers as follows:

• Cell pressure controller

• Back pressure controller

In addition, there is a third transducer measuring pore pressure. A Sig 3 controller, if shipped, comes with a separate pressure transducer. The measurement of these transducers is routed through the 8 channel data acquisition pad (AdvDCS v2).

Naturally there will be small differences between measurements of the same pressure made by these transducers. This is because they have slightly different accuracies (their specified deviation from a standard value) and calibrations (actual relationships between a standard value and the read value). This is quite normal and should be taken into account when interpreting your results because you do not have any control over these inherent discrepancies.

You do, however, have control over setting the common zero or datum of pressure measurement. This is so that all four pressure measuring systems (i.e. the transducers and their associated analogue-digital conversion) measure pressure from the same “base line”. This is how you do it.

First you need to set up your datum of pressure measurement. Normally this will be an elevation equal to the mid-height of the triaxial test specimen. Probably the best way of doing this is to connect a short length (say 300mm) of small bore nylon tubing to the back pressure connector of the cell. This is the connection to the top cap drain. Fill the cell with water. You will not have a test specimen in place for this procedure. Apply a small positive cell pressure using the cell pressure controller. You can do this by setting a target pressure. Open the valve to the back pressure line. Water will flow out of the cell from your short tube. Stop pumping when the tube is full of water and water drips out of the open end. Fix the open end of the water-filled tube at an elevation corresponding to the mid-height of the test specimen (or the base of the test specimen if you prefer)

Now the water in the cell is at a pressure corresponding to this elevation head. Connect your back pressure controller to the base pedestal pore water port and open the valve. Now the cell pressure controller, back pressure controller and pore pressure transducer all share the same pressure set by the external tube. You can now zero the displays of these values. Now all displays of pressure are zeroed to the same datum of pressure measurement!

To overcome this you need to zero both devices at the same time and using the same datum as described in this section.