DTH Hammer Lubrication: Oil Type and Application
To ensure optimal performance and longevity of DTH (Down-the-Hole) hammers, a specific type of oil with unique properties is required during operation. These properties include:
- Compatibility with compressed and humid air: The oil must function effectively in the presence of moisture and compressed air without degradation or separation.
- Sealing capabilities: The oil should fill clearances within the hammer mechanism, creating an effective seal that minimizes air consumption and improves efficiency.
- Excellent lubrication and anti-wear properties: The oil must provide superior lubrication to prevent metal-to-metal contact, reducing wear, and delaying component failure.
- Thermal stability and oxidation resistance: The oil must withstand high temperatures generated during operation without breaking down or oxidizing, ensuring consistent performance and extended service life.
- Good fluidity at low temperatures: The oil must maintain adequate flow properties even in cold environments, enabling reliable operation in various climates.
- Excellent corrosion resistance: The oil should protect hammer components from corrosion and pitting, preventing premature failure and maintaining structural integrity.
Suitable oils for DTH hammer lubrication are commonly referred to as “rock drill oils,” offered by various companies under different brand names. Examples include “Moteh Oil” from Behran Oil Company (Iran), “Pars Rock Drill Oil” from Pars Oil Company (Iran), as well as products from international companies like Shell and BP. In colder seasons with temperatures below 25°C, oils with a viscosity of 46 to 68 are recommended. For warmer seasons and temperatures above 25°C, oils with a viscosity of 150 to 220 should be used.
The importance of using the correct oil is evident. In extremely cold temperatures, antifreeze additives should be employed to maintain oil fluidity and prevent freezing.
Oil Consumption:
Oil consumption can be determined using the following table:
Hammer Size | Pressure (BAR) | Air Consumption | Oil Consumption (Liters/Hour) |
---|---|---|---|
DS 2.5 | 7 | 2.2 | 0.2 |
DS 3.5 | 7 | 3.6 | 0.3 |
DS 4 | 16 | 14 | 1 |
DS 5 | 16 | 17 | 1.2 |
DS 6 | 16 | 24 | 1.7 |
Note: The values provided are for normal operating conditions. If water is injected into the hammer, increase oil consumption by 50%.
Avoid using used or burnt oil for hammer lubrication. Used oil has diminished lubrication properties and may contain harmful suspended particles that can accelerate wear and even cause component failure.
A proper lubrication system should be integrated into the drilling rig. If not available, a separate system should be installed to ensure continuous oil flow through the air line, lubricating the hammer during operation. The oil reservoir should have adjustable settings and a visual gauge to monitor oil levels and prevent depletion.
Recommendation: When installing a new hammer or adding a new drill rod, pour approximately 0.25 liters of oil into the new rod. This creates a protective internal coating and prevents the hammer from running dry.