The Wassara technology uses water to power the down-the-hole (DTH) percussion hammer.
This makes it the superior choice for many drilling applications where air-powered DTH hammer, top hammer or rotary drilling equipment are normally used.
Drilling technologies over the years
The mechanised drilling in mining operations started some 140 years ago with the invention of the pneumatic top hammer. Productivity demands have forced development in new technologies, and the possibility to drill long and straight holes gave a huge step in this direction. The most recent major innovation in drilling came with the water-powered DTH hammer from Wassara.
Wassaras water-powered DTH hammer is the most environmentally friendly percussion drilling method existing today. The DTH hammer is powered by water. No oil is used for lubrication, meaning no contamination of air or water. The water is effectively suppressing dust as well.
The incompressibility of water is a key factor allowing the features of the Wassara hammer system. It also gives a major energy cost saving compared to air DTH technology, and reduces the energy demand to power the hammer
A selection of applications where drilling with Wassara makes a difference:
- Grout holes in dams and ground engineering
- Jet grouting
- Sensitive formations
- Casing advancing
- Precollaring in mineral exploration
- Long holes in underground mining
The DTH hammer
The Wassara hammer is ideal for use in hard, stable rock drilling applications and overburden drilling applications that require casing systems. Compared to conventional air-powered DTH hammers or top hammers, water-powered DTH hammers offer a wide range of advantages, including low energy consumption, a cleaner environment, minimal hole deviation, deeper drilling capabilities, a high power output ratio and minimal impact on the surrounding ground.
Wassaras DTH hammer consist of only two moving parts: the piston and the valve. With so few moving parts, the smart solution delivers reliable high performance drilling in the most challenging conditions.
Water, at up to 180 bar delivery pressure, is used to power the impact mechanism of the hammer at a high frequency rate. When the water leaves the hammer, it loses the pressure and keeps a low flush velocity. This however is still adequate to bring any cuttings to the surface and clean the borehole. Additionally, the hydrostatic column, which is created above the hammer, helps to keep the hole stable while preventing potential collapse. This also prevents water from being drawn into the borehole, which increases hole stability and prevents potential environmental issues.
The piston in a DTH hammer always strikes directly on the drill bit. A top hammer, on the other hand, loses approximately 4-6 % of impact energy at each drill rod connection, as the percussion unit is located on the drill rig.
When comparing an air-powered DTH with a water-powered DTH, which, in principle, work the same way, there are significant differences. The energy per blow can be expressed as follows: 𝐄 equals the piston mass, 𝐦 times the piston impact velocity, 𝐯 squared and divided by 2.
The output power 𝐏 equals the pressure 𝐩 of the medium powering the piston, times the pistons pressurized area 𝐀, times the piston impact velocity 𝐯, all divided by 8. The piston mass and the pressurized area are determined by the diameter of the hammer case and are therefore rather fixed. The impact velocity depends on the piston material characteristics and is therefore also a parameter which cannot be significantly improved. But the pressure of the medium powering the DTH hammer is a parameter that can be considerably increased/ improved, for a hydraulic hammer.