Frequently Asked Questions
Why the name “Petram”?
Petram is latin for “rock”.
How do I use your service? Can I be a reseller?
We sell our service through value-added resellers or licensed franchisees. Please contact us if you are interested in ordering or providing services.
How does the discharge wave propagate?
Some researchers indicate that the pressure emitted from the discharge depends on the spatiotemporal distribution of the electric power deposition and on shock wave propagation through the media. Therefore, we can theoretically control the amplitude and profile of the generated pressure wave. Experimentation is needed to match the energy release rate conditions during the discharge and the generated pressure wave characteristics for the specific material being fractured.
Can you discharge multiple holes at one time or at timed intervals?
Testing has focused on discharging one hole, but it is possible to use multiple holes at one time or at timed intervals using our technology. We will begin this research in q4 2018.
Does it work for both vertical and horizontal holes?
Yes, the discharge works for both vertical and horizontal holes. For each discharge, approximately one ounce of water-cornstarch is required. In the case of horizontal holes or pre-fractured rocks with cavities, more care is needed to keep the fluid in place. The cornstarch mixture or probe rubber plugs may be needed for horizontal applications. In addition, a slurry, like the one used in the oil industry could be used to fill cracks before discharging, if this proves necessary.
How does the technology perform when working with fractured rock?
It depends on the fractured rock. Although not a purposeful part of the experimentation to date, results indicate that pre-fractured rock was easier to fracture. However, if the fracture volume or cavities are too great, pressures can be dissipated causing a decrease in efficiency. Optimization based on material type and pre-fractured geometry is necessary to determine if our technology will enhance or degrade the results. Simulations will need to be done followed by actual field demonstrations. It may also be possible to add extra water-cornstarch and use multiple discharges in the same hole depending on probe condition. , there may also exist a subtle optimum with respect to the tensile vs. compression strengths/pressure of the rock media as a function of the rock media the blasting probe is in. For the initial quarter-wave current rise-time, dl/dt, if the rise time is too quick and intense, compressive bore wall material collapse may occur and may absorb too much energy, making yield less effective.
Do you have to chain down the probe so it doesn’t fly away?
The probe, which weighs about 5 pounds, would recoil without constraint. When attached to a construction vehicle weighing on the order 1000x, the recoil will be minimal.
What is the power supply required for this technology?
The power supplied to the rock is through a capacity bank discharge. The total energy is on the order of 1GW for 30 microseconds or approximately 0.01 kW-hr. If we assume that 100 shots are needed per 8-hour shift the energy supplied is on the order of 1 kW-hr. The size of the power supply will be dependent on how fast you want to recharge the capacitor bank. For practical purposes, it will be somewhere between the size of a car battery and perhaps ¼ the size of the back of a pick-up truck.
Have you investigated the application of this technology in addressing oversize in block cave mining?
We have not addressed block cave mining. However, the technology’s first mining applications have been targeted at the secondary blasting market to blast oversized rocks that were previously blasted but are too large for rock crushers at quarries or major excavations.
How do water connections between the discharge site and location of the discharge operator impact the technology?
Electrical safety is of utmost importance. Proper cabling, system design, and redundant safety interlocks have yielded a very safe design. The water connections must be analyzed electrically for grounding or stray currents. They also must be analyzed physically. If they block access, longer cabling may be necessary.
Can I reduce oversize chunks of rock to sizes compatible with the transport equipment in use?
This is an extremely good match for the technology. Please note that all answers given are based on current configuration/design of the equipment. In any solution, tradeoffs of cost vs. size vs. time vs. performance can be made to optimize the key factor desired.
How long would it take to reduce a refrigerator-sized rock to a manageable pile of smaller rocks assuming that the equipment and supplies need to be brought in from a storage area about 200m away?
Roughly 15 minutes. Our products will be mounted to the back of a pick-up truck. Assuming a very slow speed of 5 km/hr, the transportation back and forth 200m away will take approximately 5 minutes round-trip. Assuming a refrigerator-sized rock is 2m x 1m x 1m, it will take three holes and therefore three discharges to fracture the rock, which can be done simultaneously or in series (which takes more time and is therefore a worst case). Each hole, which is 25mm in diameter and 25cm deep, takes 1 minute to drill. Setting up the probe with one ounce of the water-cornstarch mixture takes about 3 minutes. The drilled hole can be cleared of debris using either compressed air or water blast. After inserting the probe, safety checks must be conducted. Setting up and discharging each hole takes about 4 minutes. Therefore, the total time is roughly 15 minutes.
What is the size and weight of the equipment?
We are designing the system to be transportable in a heavy-duty pickup truck like a Ford F-150 or a super-duty F-250 including optional drilling equipment, generator or battery, air-compressor, and water-cornstarch media. The heaviest parts of the system are the capacitor banks (250 kg) and an optional energy storage battery system which may weigh an additional 250 kg.
How much training would an operator of this equipment need?
We estimate a two-day training session, which would contain an overview of:
- System principles
- Introduction to high voltage safety, capacitors, hearing and eye
- Pre-operation system/component condition inspection (cables, probe and tip)
- Operation (determining discharge power, connecting cable to power source and probe to cable, drilling and clearing holes, prepping and inserting water-cornstarch)
- System safety (system start, self-checks, arming, firing, aborting, post-firing inspection of tips)
- Personal safety (first-aid, CPR certification, automated external defibrillators (AED) certification)
- Maintenance and support
- Hands-on experience, observation, and competency evaluation
How do capacitors work?
Here is one example: