Comparison of the pros and cons of two common horizontal booms of rock drilling rigs

The horizontal boom is an extremely critical working part on the rock drill rig. A reasonable horizontal boom structure has a significant impact on the performance of the rig. We compare the key technical parameters of two mainstream horizontal booms structure, and combines with the theoretical basis and practical production applications to summarize and summarize the relevant experience of rock drilling rigs horizontal boom.

１. Common horizontal boom structures

1.1 Double-triangle structure

The double-triangle horizontal boom is one of the commonly used boom structure for rock drilling rigs. The theoretical basis can be found in the reference Double triangle hydraulic horizontal boom translation mechanism design. This type of boom is completely horizontal with a large lifting angle, which can realize polar coordinate and rectangular coordinate positioning. Epiroc BUT series booms and Hong Yuan CYTJ series booms fall into this category.

Figure 1 Double-triangle boom

1.2 Approximate horizontal boom

The approximate horizontal boom is positioned in rectangular coordinates, and there is a certain angle error. It is commonly used on Sandvik rock drill DD320, DD421, DD531, and DT720.

Fig 2 Approximate horizontal boom

In addition, some manufacturers, such as Furukawa (FURUKAWA), have made the lifting mechanism into a completely horizontal form, and the swing arm mechanism is made into an approximate horizontal movement. There are similar products in China.

２. Key technical parameters and comparison of horizontal boom

2.1 Key technical parameters of horizontal boom

The ultimate design goal of the horizontal boom is to quickly send the propeller to the positioning under the premise of ensuring the coverage area, while shorten the overall length and dimensions, and reducing the hydraulic system cost as much as possible. It helps to ensure the processing technology and improving versatility.

The key technical parameters of the horizontal boom include: coverage area, lifting angle, swing angle, telescopic stroke, moving position, gross weight, positioning method, etc.

2.2. Comparison of key parameters of two types

By comparing Eprioc and Sandvik under the same type,  it can be more clearly found that different types of booms has different impact on key parameters of the entire product.

Table 1 Parameter comparison

It is not difficult to find that under the same applicable section, most of the technical parameters of the double-triangular boom (BUT29) are better than the approximate horizontal boom (SB40).

2.3 Comparative analysis

(1) For the same horizontal length, by increasing the lifting angle, the overall length for the double-triangular horizontal boom can be reduced. With the same boom length, the coverage height of the double-triangular boom is about 20% higher than that of the approximate translation arm (Figure 3). In addition, through long-term practical comparison, it is difficult for the approximate horizontal boom to break through 45° due to the hinge point arrangement, space limitations and torque requirements.

(2) Under the same drilling height requirement, the double-triangular boom can be shortened compared to the approximate horizontal boom because of the large lifting angle. Less boom length means shorter overall machine length, more compact structure, lighter overall machine weight, smaller turning radius, and lower cost. This is very important for miners with limited space.

(3) The positioning of the double-triangular boom is more accurate. Due to the structural limitation, a support cylinder (such as Sandvik's early B26 drill boom) needs to be added if the coverage area exceeds a certain extent. Meanwhile, the position of the twisting point is needs to be adjusted when the boom is forced to swing. Translation and lifting are related to each other (such as Sandvik's TB/SB series boom). The consequence is that while the boom is raised up and down, it is pulled by the swing cylinder and deflected. The double-triangular translation boom does not have such a problem.

(4) The hydraulic system of the approximate horizontal boom is relatively complicated. The hydraulic system of the approximate horizontal boom requires a special customized control valve group to control the translation relationship, and two additional collision valves are added to control the limit swing angle. At the same time, the lifting cylinder of the translation part also needs to be made into a special form, which means an increase in cost. However, there are not so many problems with the double-triangle boom.

(5) The optional tilt mechanism is different. Approximate translational boom mostly uses swing angle and pitch mechanisms (Figure 4), and it is almost difficult to see the use of crank tilt mechanisms (Figure 5). Double-triangular booms mostly use crank tilt mechanisms, but they can also use swing angle tilt mechanisms. Such as Epiroc Boomer M2 double-triangular drilling rig.

Figure 4 Swing angle and pitch mechanism

Figure 5 Turn & pitching mechanism

３ Conclusion

By enumerating and comparing two types of horizontal boom structures of rock drilling rigs, the advantages and disadvantages and applications of the two types of booms are explained; and the impact of different types of horizontal booms on the entire rock drilling rig is explained. It has certain reference value and guiding significance for similar structural design.