IPG high power fiber lasers in rock and concrete processing application

High power fiber laser ( kw ) in the last one or two years has been rapid development, with the price declining, power increases (now has reached 5 kilowatts, is expected in recent years and is expected to reach 50 kilowatts ), its application field is constantly expanding. From interior decoration, gas well drilling, deep sea access to new energy, nuclear power plant maintenance and many other fields have a wide range of applications.

In eight years of in the past, GTI ( Gas Development Technology Research Institute ( USA ) ) in the use of high power laser on rock cutting and crushing and other aspects of the in-depth study. Recently on natural gas exploration by using high power fiber laser has conducted in-depth research the concept, they produced by IPG 5 kilowatts of ytterbium-doped fiber laser, under atmospheric pressure and shallow layer near surface conditions of silicate and carbonate rock excavation of a number of experiments. The experimental results including the use of lower energy in sandstone and limestone drilled, a depth of 300 mm. The success of the laser cutting rock application has opened many new industrial applications.

The initial use of the GTI high power laser and obtained a lot of military technical level of success, but because the price is high, no way in the field of commercial promotion. GTI focus on the use of commercially available laser, research results show that, the industrial laser in rock cutting can be achieved with existing mechanical effects on the same level ( energy levels ), and has higher efficiency.

Optical fiber laser application on construction site is superior to any other types of laser, including in mining, tunneling, cutting and drilling, rock and concrete. Optical fiber laser can pass through the long fiber will be enough energy is transmitted to a remote target. Optical fiber laser ultra high electro-optic conversion efficiency ( 30%), good beam quality, vehicle maneuverability and stability of the equipment and maintenance etc. makes it in such fields as the best choice.

There are a lot of high power fiber has been used in the practical field in recognition. For example, the US military in Afghanistan successfully installed in Hummer Jeep 2 kilowatt laser remote explosives to clear. Study of Edison welding design of 4 kW concrete drilling system in the United States California seismic belt of the hospital building reinforcement project of the successful application.

The use of laser rock removal required energy data comparison

The chart above the blue and Brown said that Berea gravel, limestone, the ordinate is the removal of a CC required energy ( KJ ). The results show that the fiber is the most effective laser source, the effect is much better than that of traditional gas and solid laser.

They use the continuous laser focusing on common quarry limestone stone were penetration, penetration depth of >300 mm. Perforation is mainly through calcination, under 825 OC CaO3 into CaO and CO2. Because CaO melting temperature of 2570OC, so CaO is difficult to be fluid.

The same depth of penetration, their impact on Berea sand experiments, the main components for quartz sand, SiO2, they observed the most energy saving method of spalling, it only need 400-800 OC, at this temperature, due to the higher temperature gradient caused by temperature stress will make different minerals form different expansion, causing particles connected bond breaking.

Different from limestone, when Berea quartz particles temperature exceeds 1610 OC, will melt. This leads to a beam of energy from the peeling to melting, so that the cutting can greatly reduce the efficiency of! In order to avoid melting occurs, you can change the energy transfer rate and cutting time limit in the rock, energy accumulation in.

The Berea rock used in optical fiber laser drilling experiment

In a 300 mm square Berea experiments on stone. Drilling will be mainly used for steel pipe embedded in the full absorption of liquid rock, generation of oil, natural gas or water production channel. The traditional mechanical method on rock structure and fluid lines caused irreparable damage.

The experiment they used 300 micron fiber, and then the beam is 25 mm, 75psig ( 517Kpa ) compressed air through a 6.35 mm stainless steel pipe nozzle, their distance from the target object 25 mm. The lens and the nozzles are fixed on the robot arm, and at the same time with the speed of 22.6RPM 25.4 mm round orbit. The nozzle with the increase of depth of constant adjustment. Based on past experience, they will be the power of the laser is set to 3.2 kilowatts, with 1 minutes of continuous emission laser as a spacer, fired a total of 6 times, then you can cut 150 mm in depth, and then they will be turned from experimental rock, the other side in the same way to play another half. The result is dug a 300 mm pipeline, this is up to now the use of lasers in Berea punch records, pipeline diameter of about 50 mm, the total amount of movement of the material for the 210cc.

From the two cutting can reduce the boundary effect, and they were single penetration experiments, but the existence of boundary effect, including when approaching complete penetration, energy expenditure is increased apparently, thermal conductivity is also changed. These changes in previous experiments have also been observed, and the same sample geometry and experimental settings has the very big relations.

Conclusion the show

In all of the laser / rock experiment, specific energy ( SE ), the energy required per unit volume ( KJ/cc ) is an important parameter. They are cutting more than 300 mm stone SE value for 5.5KJ/cc. The spalling experiments with laser energy for 1155KJ, or 0.32KWh ( KWH). The wall of the pipe is not observed in mineral melting traces, and did not observe any damage, which in traditional drilling method is not to be!

Prospect prospect

Further studies are being carried out, including a combination of liquid jet technology and more than 2000psig high voltage experiment, the next experiment included in the hole of the operating equipment prototype, laboratory and field construction site use. The experimental device will be integrated in complex and large drilling integrity system. Other uses of lasers in different geological material cutting, drilling and other experimental results will cover energy, mineral, homeland security, military, aerospace, building and emergency rescue and disaster relief and other fields.