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STD2000 Bench Testing

13.01.2006

The following positions can be marked as basic ones:

  • carrying out of tests for static strength of a shield and its assemblies under test load Pt = 1.2 Pnom, where Pnom is nominal load;
  • shield test under action of both symmetrical and asymmetrical loading, in the course of which bending and torsional tensions occur in the shield assemblies, which leads to a rather considerable (3-6 times more) growth of equivalent tensions in a number of assemblies;
  • shield test under cyclic load action, which value varies within 0.25:1.05 Рnom; the total quantity of load cycles can be 10,000:30,000;
  • shield test at simultaneous action of vertical and horizontal loads (which is 30% of vertical one), which in some cases leads to a considerable increase of tensions in the shield assemblies.

In addition, requirements for operating resistance of supports have been established. They were differentiated by three types of roof and operating seam thickness. According to world tendencies of roof support construction, values of support's operating resistance are increased considerably as compared to the previous standard.

Taking into account the above stated, it becomes evident that companies producing powered roof supports urgently need a bench with functional and power characteristics, which comply with requirements of new European, Russian and Ukrainian standards.


The analysis of the above standards, existing designs of benches and scientific studies on this subject, which was made by employees of Dongiprouglemash Institute, allowed establishing as follows:


Comparative characteristics of benches for testing powered roof supports


Parameter

DBT, Germany

OSTROJ, Czech Republic

MRS, USA

KOMAG, Poland

STD, Ukraine

Vertical load mode

passive

passive

active

active

active

Vertical load force, tf

2,000

1,360

1,600

1,950

Horizontal load mode

passive

passive

active

active

active

Horizontal load force, tf

600

720

450

585

Maximum height of tested shield, m

5

4.8

6

When developing STD bench, the target for provision of the bench operation in the “active” mode of horizontal and vertical load was set at testing sections 0.6-6.0 m high, which are intended for operation on seams with all types of roofs according to standards.

фото к новости_01.07.2007_фото 1.jpgфото к новости_01_07_2007_фото 2.jpg

A design solution on the bench was made; its superstructure is a rigid frame structure of the gallery. The design of the bench gallery represents a box structure, which includes basement “1” with six columns “2” of flat-topped cross section installed in two rows. The columns of each row are connected between themselves by boxes and sheets, forming a one-piece metal structure intended for accommodation of vertical and horizontal forces and bending moments. The mobile floor structure of bench “3” is located over the basement and its guide brackets “4” are inside each column. Cylinders of vertical load hydraulic jacks “5” are located in the guides of the floor structure brackets; their rods are pinned in columns “2”.


Platform “6” is located on the bench basement; it is installed on idlers with a possibility of movement on the basement and receiving platform “7”. The platform is intended for arranging the roof support shields. Horizontal load hydraulic jacks “8” with a possibility of force interaction with platform “6” are installed on the basement brackets. Hydraulic polyspast mechanism “9” is located on receiving platform “7”. It moves the platform in the course of the shield installation on the bench and its removal from the bench.


For the purpose of providing required strength parameters of the bench, its 3-D computer model was developed and studies of the bench operation were performed as a whole and its separate assemblies in different load modes. The model studies were carried out on the basis of the finite element method using Visual Nastran software.


Operation of STD test bench is performed as follows. The support shield is installed on the platform located on the receiving platform. Supports for this load diagram implementation are installed, if necessary, between the shield basement and platform. It is also possible to install spacer plates on the shield floor structure for implementation of relevant load diagrams. If it is necessary to make measurements and record loads on the shield (in particular, when determining the shield resistance) spacer plates - piezoprops are installed.


The bench height is changed step-by-step: by step-by-step rearrangement of support beams of each of vertical load hydraulic jacks with the help of a lever mechanism of special design and further rearrangement of the bench floor structure using these hydraulic jacks.


The platform with a shield is installed in the bench using a polyspast mechanism. In order to perform bidirectional effect on the shield, rods of horizontal load hydraulic jacks are connected with the platform. Initial vertical setting load is performed in the bench floor structure by extending its hydraulic props. If necessary, initial horizontal setting load of the shield is performed using horizontal load hydraulic jacks with the shield's floor structure rest on a bracket of the bench floor structure.


Active vertical load is applied to the shield by operating pressure feed to six or four vertical load hydraulic jacks (depending on required force). The value of active horizontal force acting on the shield is determined by pressure regulated in the piston cavity of horizontal load hydraulic jacks. It is also possible to create load by feed of required operating pressure to hydraulic props of the support shields through a booster (passive mode). The electric-hydraulic control system provides creation of the shield cyclic load mode in the intermittent load mode within the range of 0.25:1.05*Рnom. In the process of loading, deformations and forces in assemblies and elements of the shield tested are controlled by special sensors.


The electric-hydraulic control system of the bench manages, controls and records results in the course of all performed operations. Information coming from sensors located on the bench is collected and processed by an industrial computer with special software and hardware. Incoming information is visualized on the computer monitor. One of the control system functions is check of compliance of a number of control parameters with established standards and emergency shutdown of operations when unallowable deviations occur.


Controlled and registered parameters include as follows:

  • pressure in chambers of vertical and horizontal load hydraulic jacks, as well as hydraulic jacks of lever mechanisms;
  • pressure in delivery and discharge main lines;
  • value and rate of vertical load hydraulic jack advancing;
  • value of forces in piezoprops;
  • readings of deformation and force transmitters in shield assemblies;
  • readings of lever mechanisms' endpoint sensors, etc.

Summarizing the above stated it is necessary to note as follows:

  • STD bench is a single test bench available now on the CIS territory; it allows carrying out tests of powered roof support shields according to requirements of standards to the fullest extent.
  • Per totality of functional and power characteristics, width of operating range of shields tested, STD bench outgoes existing world analogues and provides, in particular, active vertical and horizontal load of support shields 0.6:6 m high with maximum vertical force of 19,500 kN.
  • STD bench creation opens up ample opportunities for carrying out R&D and experimental works required for development and testing of new structures of powered roof supports.
  • STD bench provides an opportunity of testing support shields within the maximum wide range of load diagrams and parameters with record of all values required for determination and confirmation of strength characteristics of a support, which determine its operational reliability and life cycle.
In September 2005, STD bench developed by Dongiprouglemash Institute and produced by Druzhkovsky Engineering Factory underwent preliminary tests and state certification.

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