The Dawn of DTH Hammers

THE HISTORY OF DTH HAMMERS

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The Down-the-Hole hammer, also known as a DTH hammer, is used for drilling holes through a wide range of rocks and associated materials. The variety of applications in which it can be utilised, has extended, and still continues to extend, well beyond the original conception of primary blast hole drilling. The first person to commercialise the product was Andre Stenuick of Stenuick Freres Belgium in 1950.

Halco, in close co-operation with Stenuick Freres, pioneered the development and distribution of the Down-the-Hole hammer, primarily throughout the UK, Australia, New Zealand, Africa and India in the 1950s. “Down the Hole” refers to where the hammer action occurs when compared to drifter hammers, which hammer on top of the drill string, and are thus called Top Hammer or TH. The DTH hammer’s piston always makes direct contact with the drill bit and there is generally no loss of transmitted energy as the hammer drills deeper, as is the case with drifter rigs.

Prior to the introduction of DTH hammers in the early 1950s, blast hole drilling was normally carried out with drifter equipment whilst water well drilling in hard formations was done by cable tool rigs or rotary rigs using rock roller bits (Tricones). However, drifter drilling becomes progressively slower with increasing depth, which is not the case with DTH drilling. Furthermore, a DTH hammer can drill in one day what a cable tool rig takes weeks to complete. For these reasons, the quarrying, water well, site investigation, civil engineering, and mining industries throughout the world have become more and more aware of the advantages to be gained from using DTH hammers. They are not only seen as an alternative to drifters but appreciated on their own because of the higher performance when compared to conventional rotary drilling.

The DTH hammer concept proved so popular that established manufacturers of drifter steels, bits, and accessories followed Halco’s lead and developed their own range of DTH hammers and bits.

HAMMER DEVELOPMENT

The first ever DTH hammers were created with a “valved” design and had an internal liner. This valved technology, together with compressor availability, limited the air pressure capability of the early hammers, which were incapable of withstanding air pressures above 12 bar (170 psi). The valve itself had operational problems, causing hammer malfunction to occur when large volumes of water were passed through the hammers or if grit entered the hammer.

Modern hammers are generally valveless in design, with fewer internal parts requiring maintenance. The removal of the valve has eliminated the operational problems experienced previously. They are also more rigid in construction, enabling them to withstand air pressures as high as 28 bar (400 psi). Penetration rates with DTH hammers are almost directly proportional to air pressure, therefore doubling the air pressure will result in an approximately doubled penetration rates.

The further development of DTH hammers will focus on achieving lower drilling costs for the user, by increasing rates of penetration and extending the hammer lifetime. Increases in penetration rates will require delivering even higher air pressures to the hammer, as opposed to current conventional designs, or the use of alternative power sources such as water or oil. To achieve longer life for the hammer components, researching wear and impact resistant materials not normally associated with traditional hammer manufacture, will be essential.

Water powered hammers are being developed for use in underground mines. Although performance results are encouraging, the design of the hammer is limited to use on sites where large amounts of water are available and can be tolerated, but most importantly handled and cleaned for return to the hammer. Hammers powered with hydraulic oil have also been tested in some quarries, but these need a specially adapted drill rig, drill tubes, and coupling system. Spillage and potential contamination of the ground is a major consideration. Furthermore, a separate air supply is needed in order to flush the hole. Because of these limitations, water and oil powered hammers are slow to gain ground and air driven hammers still have the competitive edge.

The immediate opportunity for DTH hammers is in developing their use for applications normally drilled using other drilling methods. These may include, for example, shallow oil and gas field development, shallow wide hole piling, continuous drilling and casing systems, reverse circulation chip sampling, mole drilling and applications where holes required in mining exceed 900 mm (36”) diameter, as well as civil engineering and construction applications.

Although DTH hammers started life in quarries, they are now appreciated throughout the drilling industry. They have become the preferred option due to their significant advantages over other systems, in particular -

• Capability to drill in almost all rock types, hard to medium to soft.
• Penetration rates that can outstrip other systems.
• Reduced costs.
• Straighter/cleaner holes.
• Wide range of hole sizes available, without high expenditure.
• Quieter than other percussive systems.

Advantages:

HJG(BD DRILL) High Air Pressure Deep Hole Rotary Pneumatic Drilling DTH hammer without foot valve for COP MISSION DHD QL SD.

The optimum range of hole size for blast hole drilling with DTH is 90 mm to 254 mm (3 ½"-10″). Smaller blast holes are generally drilled using tophammer, and larger holes generally use rotary machines.

In other applications, like foundation drilling, DTH hammers can be used with single bit in hole sizes up to . 750 mm (30″). With multiple hammer units CD (Cluster drills) drill holes up to 70″ or 1778 mm.

As a rule of thumb, the smallest hole diameter a DTH hammer can drill is its nominal size. A 4 inch hammer will drill a 4 inch (102 mm) hole. The limiting factor is the outside diameter of the hammer, because, as hole diameter reduces, airflow is restricted. Maximum hole size for production drilling is the nominal hammer size plus 1 inch, so for a 4 inch hammer the maximum hole size is 5 inch (127-130 mm).

Choosing the right hammer is largely determined by hole size and type of rock formation. Ideally, the size of the hammer should match the required hole dimension as closely as possible, leaving just enough space for cuttings to evacuate the hole.

PARAMETERS:

Length(exclude bit)

Weight(exclude bit)

External Diameter

Bit Shank

Hole Range

Connection Thread

1183 mm

92.00 kg 

Φ146 mm  

QL60

Φ155mm _ Φ203mm

API 3 1/2'' Reg 

Working Pressure

Impact rate at 0.5 MPa

You will get efficient and thoughtful service from KSQ Technology.

Recommended Rotary Speed

Air Consumption

1.0 MPa

1.8 MPa

2.4 MPa

1.0_2.5 MPa

25 Hz

20-30 rpm

9 m³/min 

18 m³/min

26 m³/min

Factory View:

 

Frequently Asked Question:   

1.Are you a manufacturer or a trade company?

We are a manufacturer of rock drilling equipments and pneumatic tools in China over 17 years.

 

2.How many workers in your factory?and what is your company scale?

We have more than 700 employees, including factory workers,sales people,QC ,R&D and management team.
With a land area of 110,000SQM(=1,184,068 square feet) and workshop sapce of 50,000SQM(=538,213 square feet).We are equiped with over 1,000 sets of different advanced equipments and facilities required for manufacturing rock drilling machine and pneumatic tools.Our annual output value is over US dollars 50 million.Over 50-70% for export which covers most of the global markets including Korea,Malaysian,Australia,Russia,Middle Asian,East,Europe,South America,and Africa etc..

 

3.Where are your company?

We are located in Changsha city,Hunan province,where our first chairman Mao was born.1 and half hours by car from the nearest Huanghua international airport,2 and half hours by CHR express from Guangzhou nan station to Changsha city.

 

4.Why choose HJG DRILL?

1)We have more than 17 years of researching,developing, manufacturing  and exporting high quality rock drilling equipments and penumatic tools to the global market.

2)High quality compatible with Sandvik, Atlas Copco,Ingersoll Rand etc...

3)Unbeatable price

4)Excellent service.

 

5.Which port do you shipping from?

We usually ship container from Shanghai port.Guangzhou port is available too.

 

6.Can you accept OEM & ODM ?

Yes, both of them are acceptable.

 

7.What is your minimum order quantity?

Our MOQ are 1pc or 1 complete set, the price may rely on the order quantity.

 

8.What is your payment term?

We can accept T/T, L/C at sight, West union and in cash.

 

9.How about the delivery time?

It all depends,generally it takes about one month both in peak and off season.

10.Could we make a schedule of an appoinment with your company?

Definitely.You are the most welcome.Please inform us your arrival time in any place of China and initial routine in advance.We can reserve the hotel,offer pickup service from Changsha Huanghua airport or the CHR Express station unpon your arrival and after the appoinment.Be our guest then!

Weclome our dearest customers to Visit our factory and to choose our great product ranges!

For more information, please visit High Pressure DTH Hammer.