According to chief scientist at the China Coal Research Institute (CCRI) professor Guofa Wang, CCRI has successfully developed more than 300 types of powered supports adapting to different geological conditions and broadening the scope of application.

Wang said China had become the biggest manufacturer in the world of powered support production, with an output of 6000 to 10000 shield supports of different types each year.

In a paper by Wang, presented at Longwall 2003 during November in New South Wale’s Hunter Valley, the professor explained China’s current stage of development in powered supports across areas of support range, yield and top coal caving supports.

Currently, Chinese support technology sustains mining heights from one metre to 5.5 metres. Yield support for high pressures, rigid beams and pump safety valves for hard roof have been developed successfully and different kinds of supports, such as mesh devices and high incline supports, have also been developed.

Progress in gate road support has improved support of face-end and created the condition for higher production and efficiency and electro-hydraulic control and pumping systems have allowed faster movement of supports on the working face.

Wang said these developments had led to the successful export of supports and equipment to America, India, Turkey, Russia and Bengal.

When designing supports Wang said three dimension mechanics mode, finite element method (FEM), CAD software, relative integrity of database, general gallery testing, general design software developed and dynamic testing of frame parameters all had to be taken into consideration.

The proportion of two-leg and four-leg supports in China is relatively even. Due to the restriction of dimension of existing equipment the centre distance of most supports is 1.5 metres and some mines have adopted 1.75 metres.

Technology advancements has also enabled the adoption of inertia gas shield welding to protect welding joints, preheating before welding and tempering after welding to eliminate welding stress and seal structure has been improved to enhance reliability.

CCRI have also developed a variety of support structures such as the use of extension bar for canopy and multi-level face guard suitable for soft rock and broken roof, anti-collapse and anti-slide set for high incline coal seam, advancing mechanism and base lift setting for rapid movement of support.

China has consistently lead the way in top coal caving technology, including the development of suitable supports. The adoption of CAD software to optimise structure parameters, CAE software to analyse the force conditions and virtual prototype software to simulate movements has made the design process easier.

CCRI have recently developed a reverse lemniscate bar top coal caving powered support with large flushboard and low operation. Wang said performed with high stability and anti-slanting load ability, greater space in tail, agile adjustment of top coal movement, high recovery of top coal caving, breaking of lump coal ability, little resistance in movement and had better adaptation to a soft floor.