Medium Air Pressure DTH Hammers

Products
DTH Drilling Tools
DTH Hammers (Medium Air Pressure)

DTH Hammers (Medium Air Pressure)

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

SPM medium air pressure DTH hammers feature an internal structure designed according to advanced rock drilling theory, ensuring efficient energy transfer, faster drilling speed, and lower air consumption. They are widely used in geotechnical engineering for drilling medium-hard to hard rocks and other tough formations that are difficult to drill.

Request a Quote

Applications

In practical use, medium air pressure DTH hammers are recommended for drilling medium-hard to hard rocks in geotechnical engineering. Typical applications include 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

Model	Top sub connection thread	Wrench flat, mm	Hammer OD, mm	Length (W/O bit), mm	Weight (W/O bit), kg	Bit shank	Hole range mm	Piston weight, kg	Recommended rotation speed, rpm	Feed force, kg	Air consumption, m³/min
Model	Top sub connection thread	Wrench flat, mm	Hammer OD, mm	Length (W/O bit), mm	Weight (W/O bit), kg	Bit shank	Hole range mm	Piston weight, kg	Recommended rotation speed, rpm	Feed force, kg	5bar	10bar	12bar	14bar	15bar	17bar
SPM825	Special M42x10x1.5	48	58	715	9.5	SPM825	65-70	2	35-60	390-630	2.5	3	4	-	-	-
SPM830	DZ50 Box	47	67	808	15	SPM830	75-85	3.4	35-60	450-780	3	3.5	5	-	-	-
SPM930	Special M48x10x3	60	80	822	22.5	SPM930	90-130	4.7	35-60	550-1200	3.5	4	6.5	-	-	-
SPM930C	Special 48x10x3	60	82	782	21	SPM930	90-130	4.8	35-60	550-1170	-	6	-	8	-	-
SPM940	API 2-3/8 REG Box	75	98	910	35	SPM940	110-135	7.4	35-60	660-1250	-	5.5	-	-	9	-
SPM950	API 2-3/8 REG Pin	75	126	970	64	SPM950	138-152	12	35-60	850-1380	-	7.5	-	-	12	-
SPM960	API 3-1/2 REG Pin	101	148	1130	100	SPM960	165-203	23	30-60	990-1850	-	9	-	-	-	15
SPM980	API 4-1/2 REG Pin	150	182	1260	180	SPM980	203-254	43	30-50	1250-2300	-	13	-	-	-	26
SPM9100	API 4-1/2 REG Pin	150	224	1260	260	SPM9100	241-311	33	20-40	1500-2800	-	14	-	-	-	26

Structure

The medium air pressure DTH hammer is illustrated using the SPM825 model as an example (internal structure may vary slightly for other models).

No.	Product name	Product No.	Qty
1	Backhead	825001000	1
2	O ring	825002300	1
3	Check valve	82004000	1
4	Spring	76002300	1
5	Distributor	825005000	1
6	Cylinder	825006000	1
7	Piston	825007000	1
8	Casing	825008000	1
9	Bearing	825009000	1
10	Rubber plugs	80016300	1
11	Spring	80016300	1
12	Pin	80017300	1
13	Key	65018300	1
14	Chuck	825014000	1

The formation consists of soft sandstone and clay (compressive strength <15 MPa). Which pressure series of DTH tools should be selected: low, medium, or high?

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.

For large-diameter pile holes with diameters greater than 800 mm, should the large-diameter series be selected regardless of the formation?

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.

A drilling rig operates at a rated working pressure of 1.8-2.2 MPa. The target formation is moderately weathered granite with a compressive strength of 15-30 MPa. Which pressure series should be selected?

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.

How should DTH bits be selected? For example, within the same medium-pressure tool series, are different DTH bits required for limestone and sand-gravel formations?

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 composite formation contains an upper sand layer and a lower hard-rock layer. Is frequent replacement of DTH tools necessary, or can one toolset handle both?

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.