ColoradoSchool of Mines Center for Rock Abuse

Center for Rock Abuse

Standard Operating Procedure

Load Frame

Golden,August 2010

Standard Operating Procedure

Load Frame

The load frame consists of:

  1. A pressure vessel.
  2. Three ISCO pumps, which control: axial, confining and pore pressure.
  3. Two control panels.
  4. Validyne portable acquisition package.
  5. Computer.
  1. Pressure vessel:

The pressure vessel is the place where the sample of study is pressurized. There are 4 sections on the pressure head, each of them are labeled as seen in appendix 1.

Sections one, two and three are electrical leads for strain gauges, transducers, etc. while section four is for thermocouples and fluid inputs.

  1. ISCO pumps:

Consists of a syringe pump, filled with a certain fluid, generally oil. The ISCO pumps have a maximum pressure limit:

Confining pressure: 20,000 psi

Axial and pore pressure: 10,000psi

  1. Control panels:

The first control panel controls thefirst three sections of the pressure head.

The second control panel consists of a set of switches and valves that control the flow of fluids in and out of the pressure vessel for axial and confining pressure. The diagram is shown on appendix 2.

Switches: open horizontal. Close down.

Valves and wheels: open counterclockwise. Close clockwise. It is not necessary to open completely, three turns is sufficient.

  1. Validyne portable acquisition package:

The Validyne module case currently has five available SG297A strain gage amplifiers (refer to manual if necessary). These ALWAYS need to be calibrated with a shunt resistance before running an experiment. The module case is connected to the computer through a USB port, which allows data collection in the computer with Tracer DAQ software.

How to connect the sample on the pressure head

Put sample in the pressure vessel. Connect wires of the sample in the different sections, according to the experiment.

Lower the upper part of the pressure vessel with the control.Be careful not to ruin the sample or any of the cables!

When it is finally down, remove the aluminum rod to the left. Rotate the upper part of the pressure vessel clockwise for securing it.

For security reasons, lower the plastic shield

Applying confining pressure to the vessel:

Open valve 1 to fill up the pressure vessel with oil.

Open valve 10.

Open switch 5 to vent the system.

Open knob 2 to put air pressure into the oil reservoir.

Turn valve 8 towards pressure.

Once the glass tube fills up with oil, close valve 10 so that the trap does not fill up. We know that the pressure vessel is full when the tube has oil in it.

Close valves1, 10, 5 and 2.

Vent the oil reservoir, by turning valve 8. Close it when the pressure is vented.

Set ISCO pump to a pressure of 120 psi, approximately.

Press A to enter pressure value.Enter numerical value.

Press enter.

Open valve 14, topressurize the vessel.

The confining pressure is set.

After using, lower the pressure of the system in the same way, using ISCO pump.

Close valve 14.

Applying axial pressure to the vessel:

Open valve 15.

Set ISCO pump to a low pressure (10-20 psi).

Press A for entering pressure value.

NOTE: Axial pressure should ALWAYS be higher than the confining pressure.

Enter numerical value.

Press enter. Press run.

The axial pressure is set.

After using, lower the pressure of the system to 10-20 psi in the same way, using ISCO pump.

Close valve 15.

Applying pore pressure to the sample:

Open valves 16 and 17.

For one pore fluid line: open valve 18 and 20

For two pore fluid lines: open valves 18, 19 and 20.

Apply the desired pore pressure from the ISCO pump.

NOTE: Pore pressure should NEVER be higher than the confining pressure.

To remove pore pressure:

Lower the pressure of the system to 10-20 psi in the same way, using ISCO pump.

Close valves 16 to 20.

Emptying the pressure vessel-filling up the oil reservoir:

Open valve 1to fill up the oil reservoir.

Open valve 10.

Open switch 2, 3 and 4.

After the oil reservoir starts bubbling, close valve 2.

Vent system with valve 8.

After the oil reservoir stops bubbling, close valves 1 and 10.

Close switches 3 and 4.

Opening the pressure vessel

Pull up the plastic shield.

Turn the upper part of the vessel counter clockwise until the marks on the right line up.

Use the control for lifting the vessel. After lifting a bit, put the aluminum rod on the left slot of the pressure vessel. Lift up the vessel completely.

Clean the oil out of the whole system!

Refilling the main oil reservoir:

First, make sure the reservoir is vented! Make sure knob 2 is closed and valve 8 is pointing towards “Vent”.

Open valve 22 and pour oil into the reservoir.

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ColoradoSchool of Mines Center for Rock Abuse

Failure mode analysis

Load frame

Device / Failure mode / Results / Safety constraints / Solution
Pressure transducer T1 (20 kpsi) / Drifting - Misreading / Erroneous pressure measurements / Sample breaks in the vessel – Fluid will leak into pore fluid line (if any) Will it reach 35 kpsi? / Stop pump. Close pore fluid valves. Close valve 14.
Empty vessel.
Pressure transducer T2 (10 kpsi) / Drifting / Erroneous pressure measurements / Open valve that connects to reservoir and press “Zero press”
Pressure transducer T3, T4 and T5 (10 kpsi) / Misreading pressure / Erroneous pressure measurements / Change the pressure transducer
Pressure transducer T6 (20 kpsi) / Misreading pressure / Erroneous pressure measurements / Change the pressure transducer
Pressure transducer T7 (10 kpsi) / Drifting / Erroneous pressure measurements / Rupture disk R3 will break / Turn off valve connected to pore pressure pump. Stop pump.
Do not pass the maximum pressure of R3 (8500 psi)
Open valve that connects to reservoir and press “Zero press”
Rupture disk R1, R2 (35 kpsi) and R3 (8500 psi) / Exceeds max. pressure / Pressure will drop / Oil leakage / Shut off all pumps and change the rupture disk.
Omega meters / Erroneous or non-reading / Erroneous measurements / None / Check if the meter cables are plugged correctly.
Calibrate the meters with ISCO pump (Omega manual)
Check the fuse of the power cable.
Sample jacket / Breaks due to high pressures, leakage or bad jacket preparation / Pore and confining pressure will mix/equilibrate. R3 might break. / Oil leakage from R3 / Close pore fluid valves. Depressurize the vessel.

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ColoradoSchool of Mines Center for Rock Abuse

Appendix 1

Pressure head lines

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ColoradoSchool of Mines Center for Rock Abuse

Appendix 2

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ColoradoSchool of Mines Center for Rock Abuse

Legend appendix II

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