DTH Hammers (Low Air Pressure)

DTH Hammers (Low Air Pressure)

Down-the-hole hammers for rock drilling in soft to medium-hard rock formations with low air pressure

SPM low air pressure DTH hammers are widely used in geotechnical engineering for drilling various soft to medium-hard rocks and other tough formations that are difficult to drill.

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Features
  • The SPM low air pressure DTH hammer is a valve-type central exhaust hammer, providing efficient removal of rock cuttings, reducing repeated crushing of debris, lowering drill bit wear, and improving drilling efficiency.
  • The internal structure is designed according to advanced rock drilling theory, ensuring efficient energy transfer. Each impact delivers high energy, resulting in faster drilling speed and lower air consumption.
Applications

Suitable for mining, quarrying, road construction, blasting hole drilling, landslide protection, dam foundation reinforcement, anchoring, geothermal energy wells, water wells, hydrological wells, and other engineering projects.

Technical Parameters
Hammer model Outer diameter, mm Length
(W/O bit), mm 		Weight,
kg 		Tubular sub thread Bit shank Hole diameter
range, mm 		Working
pressure, MPa 		Recommended
rotation speed, r/min 		Feed force,
kg 		Air consumption,
m³/min
@6bar @10bar @17bar @24bar
SPM65B 61 745 13 Square 42x10x1.5 CIR65B 68-70 0.5-0.7 40-50 340-630 2.5 - - -
SPM70 65 803 14 DZ50 Box CIR70 75-80 0.5-0.7 40-50 375-640 3 - - -
SPM70A 67 762 15 DZ50 Box CIR76 75-80 0.5-0.7 40-50 375-640 3.5 - - -
SPM80-II 67 777 15.5 DZ50 Box BR2 75-80 0.5-0.7 40-50 375-640 3.5 - - -
SPM76 67 765 15 Square 48x10x3 CIR70A 75-80 0.5-0.7 40-50 375-640 3.5 - - -
SPM80 72 795 18 Square 48x10x3 CIR80 80-83 0.5-0.7 40-50 400-650 5 - -
SPM80X 72 760 17 DZ50 Box CIR80 80-83 0.5-0.7 40-50 400-650 4.3 - - -
SPM80XD 72 797 18 API 2-3/8 REG Pin BR3 85-90 0.5-0.7 30-50 425-720 5 - - -
SPM90 80 796 20 Square 48x10x3 CIR90 90-130 0.5-0.7 30-50 450-1000 7.2 - - -
SPM90-I 80 796 20 Square 48x10x3 CIR90 90-130 0.5-0.7 30-50 450-1000 6.5 - - -
SPM110 98 840 30 API 2-3/8 REG Box CIR110 110-150 0.5-0.7 30-50 550-1200 12 - - -
SPM110-I 98 840 30 API 2-3/8 REG Box CIR110 110-150 0.5-0.7 30-50 550-1200 11 - - -
SPM130-I 116 881 49 API 2-3/8 REG Box CIR130 130-165 0.5-0.7 25-40 650-1300 12.7 - - -
SPM150 137 908 75 Internal square 76x10x3 CIR150 155-220 0.5-0.7 20-35 780-1750 17 - - -
SPM150-I 137 908 75 Internal square 76x10x3 CIR150 155-220 0.5-0.7 20-35 780-1750 16 - - -
SPM170 156 1022 90 Square 100x28x10 CIR170 175-250 0.5-0.7 20-35 875-2000 19.5 - - -
SPM170-I 156 1022 90 Square 100x28x10 CIR170 175-250 0.5-0.7 20-35 875-2000 18 - - -
SPM200-I 184 1120 165 API 4-1/2 REG Pin CIR200 200-254 0.5-0.7 20-35 1000-2030 22 - - -

The low air pressure series (working pressure 0.8-1.5 MPa) is recommended. Soft formations require lower impact energy for effective rock breaking. Low-pressure DTH hammers ensure sufficient penetration efficiency, reduced energy consumption, and slower tool wear. Medium- or high-pressure tools may cause excessive impact, increased cuttings pulverization, and higher risk of hole collapse, resulting in higher overall construction costs.

The large-diameter series is the preferred option. This series is engineered for large-diameter hole making and stable hole formation. Structural features include thicker tool walls for improved torsional strength and wider discharge channels to prevent cuttings blockage. Compatibility with high-torque output from pile-foundation drilling rigs ensures efficient, stable operation. Standard low- or medium-pressure tools may deform under load or suffer from inadequate cuttings discharge.

The medium air pressure series (working pressure 1.5-2.5 MPa) is suitable. Medium-pressure DTH tools deliver proper impact energy for medium-hard rock formations while matching the 1.8-2.2 MPa rig pressure range. Low-pressure tools provide insufficient impact, leading to slow penetration. High-pressure tools exceed the rig’s pressure capacity and cannot achieve normal performance.

Correct bit selection is essential.

  • Limestone (dense, hard rock): Use spherical-button DTH bits, which provide high wear resistance and concentrated impact points for efficient rock breaking.
  • Sand-gravel formations (loose formations with pebbles): Use flat-edge ballistic bits, which offer wider discharge grooves for rapid removal of gravel and reduced bit blockage.

Bit interfaces must match the selected DTH hammer connection standard, for example API REG threads, to ensure stable sealing and power transmission.

A medium air pressure DTH hammers paired with a composite-formation DTH bit such as a spherical-button can meet both layers’ requirements. Medium air pressure tools support efficient drilling in both sand layers and hard-rock layers. DTH bits with wear-resistant ballistic buttons and wide discharge grooves enhance cuttings removal in sand layers and improve rock penetration in hard rock.

When the lower hard-rock compressive strength exceeds 30 MPa, only the DTH hammer may be replaced with a high-pressure model while other components remain unchanged, reducing replacement cost.