untitled BRITISH STANDARD BS EN 1804 3 2006 +A1 2010 Machines for underground mines — Safety requirements for hydraulic powered roof supports — Part 3 Hydraulic control systems ICS 73 100 10 ���������[.]
General requirements
General
Hydraulic control systems of hydraulic roof supports shall comply with the safety requirements of
EN 982 except for the deviations listed in normative Annex B
Hydraulic control systems of hydraulic powered roof supports which are designed according to this part of
EN 1804 shall also meet the requirements of the other parts of EN 1804, if relevant
Hydraulic control systems of hydraulic powered roof supports should comply as appropriate with
EN ISO 12100-1:2003 and EN ISO 12100-2:2003 for hazards which are not covered in this document.
Hazard areas
Hydraulic control devices must be designed and positioned to ensure that personnel do not need to be in the vicinity of the operated support units, such as by utilizing an adjacent control system.
Arrangement of the control devices
Hydraulic control devices must be designed and positioned to prevent unintentional operation from the travel way, ensuring they do not obstruct this path (refer to section 5.1.1 of EN 1804-1:2001) Additionally, information and warning devices, such as symbols and pressure indicators, should be clearly visible from the travel way.
Dead man's control
The hydraulic powered support's controls for lowering, advancing, and setting will halt movement immediately upon release This mechanism also applies to other functions that could potentially restrict the travel way or affect alignment.
Automatic hydraulic control system
The automatic hydraulic control system shall control the movement of the hydraulic powered supports
(lowering, advancing and setting) only if they are fitted with pre-start warning and emergency stop devices
This also applies to other automatically hydraulic controlled functions which may lead to the narrowing of the travel way Excluded from this requirement is the automatic guaranteed setting control.
Automatic guaranteed setting control
The automatic guaranteed setting control shall not come into operation until a minimum pressure of 80 MPa
(bar) is reached in the leg The automatic guaranteed setting control shall be capable of being switched off.
Shut-off devices
It shall be possible to isolate each support unit from the hydraulic pressure supply.
Pressure indicator
Hydraulic circuits of each leg of the support unit shall be fitted with a device indicating the pressure in the leg.
Pipe and hose assemblies
Pipe and hose assemblies for hydraulic control systems of hydraulic roof supports shall be designed to withstand the maximum permissible working pressure in that system
Hose assemblies must satisfy one of the following conditions: a) They should adhere to the standards set by ISO 6805:1994, and for type 4 hoses, sizes DN 6 and DN 10 must also meet the specifications outlined in Table 2.
Maximum working pressure MPa (bars)
Pressure for additional 5 000 a cycle test MPa (bars)
Pressure at which all hoses are tested
DN 10 380 655 800 a The test requirements shown above are additional to those test requirements for Type 4 hoses in ISO 6805:1994
Type 6 hose assemblies shall be pressure impulse tested either:
in accordance with the requirements of ISO 6805:1994 or;
with 400 000 cycles at 1,33 times of the maximum working pressure at 100 °C b) hose assemblies shall meet the mechanical requirements of EN 853, EN 854, EN 855, EN 856 and
According to EN 857, hose assemblies of type 2 ST (EN 853) and 4 SP (EN 856) that primarily experience static loading can have their maximum permissible working pressure increased to 1.4 times the nominal pressure specified in EN 853 and EN 856.
NOTE 1 Special requirements for underground hose assemblies with respect to their fire and electrical resistance properties, currently being developed by CEN/TC 305, should be taken into account
NOTE 2 Preferably, the requirements of option a) above should be met a) pipes and hose assemblies shall be arranged, assembled and, if necessary, also fixed and protected so that external damage is minimized and ejecting fluids are deflected.
Hydraulic fluids
Hydraulic control systems for roof supports in coal mines and other potentially explosive environments must be engineered to utilize non-toxic and fire-resistant fluids, as outlined in the SHCMOEI 7th report.
Hydraulic control systems must be designed to accommodate either fire-resistant fluids of category HFA, as specified by the roof support manufacturer in accordance with ISO 7745:1989 and ISO 6743-4:2001, or water without additives, suitable for temperatures ranging from +5 °C to +60 °C.
Lifting points
Lifting points in hydraulic control systems must be appropriately designed for their specific applications They should have a minimum safety factor of 4 based on the average tensile strain relative to their load capacity Additionally, these lifting points must be clearly and permanently marked with their load carrying capacity, such as through welding.
Design requirements
Protection against ejected fluids
Hydraulic control systems shall be designed, located or guarded to minimize the risk from ejection of fluid.
Roof contact advance
Hydraulic control systems shall be designed so that the facility to advance the support unit in contact with the roof may be incorporated.
Pressure limiting
Hydraulic control systems designed for loading through convergence or horizontal shear must include safeguards against excessive pressures Isolated pressurized compartments should be equipped with pressure limiting valves for effective protection.
Interruption of the operating pressure
Any interruption or restoration of the operating pressure shall not lead to unintentional movements of the support unit.
Travel speeds
Hydraulic control systems must ensure that the movement speed of individual parts of the support unit does not exceed 30 cm/s, specifically at the extremities of canopies and anti-spalling devices This speed limitation is not applicable in support operating areas where personnel are not present.
Actuating forces
The actuating forces for the hand-operated hydraulic control systems shall not be less than 10 N nor exceed
Resistance to back pressure
Hydraulic control systems shall be capable of operating safely up to the maximum permissible back pressure in the return system.
Adjustable valves
Adjustment of valves shall only be possible by tools, as specified by the manufacturer.
Requirements of type A valves
General
Type A valves shall meet the test requirements as defined in Annex A.
Leaktightness
Type A valves shall be leaktight up to 94,5 % of the yield pressure.
Yield pressure
The measured yield pressure of type A valves can differ by a maximum of ± 5 % from the specified yield pressure This requirement applies to ambient and fluid temperatures of 20 °C to 40 °C.
Opening pressure
The opening pressure at a flow rate of 0,04 l/min can exceed the specified yield pressure by a maximum of
Closing pressure
The closing pressure can fall below the specified yield pressure by a maximum of 10 %.
Pressure pulses
Type A valves shall not fail when pressure pulses occur.
Impact resistance
The function of type A valves shall not be impaired by mechanical impacts.
Pressure flow behaviour
The volume flow rates for type A valves are specified in Table A.1 and must align with the required roof support yield parameters For volume flows ranging from greater than 0.04 l/min to 60 l/min, the opening pressure should not exceed the yield pressure by more than 20% and must not drop below the yield pressure by more than 10%.
> 60 l/min are intended, this requirement shall apply
Generally, one valve is used Where an arrangement of valves is used, at least one valve shall satisfy this requirement.
Operating reliability
Type A valves shall continue to meet the requirements of 5.3.2 to 5.3.5 after 10 500 opening and closing cycles.
Temperature effects
The influence of the temperature on the function of gas-charged type A valves shall be specified by the manufacturer.
Resistance to back pressure
The yield pressure of type A valves that support the roof remains unaffected by back pressure Additionally, back pressure in the return circuit does not increase the yield pressure of other type A valves.
Requirements for type B and C valves
General
Type B and C valves shall meet the test requirements given in Annex A.
Leaktightness
Type B valves shall be leaktight in the closed position up to 1,5 times their maximum permissible working pressure
Type C valves shall be leaktight in all switching positions up to 1,5 times their maximum permissible working pressure.
Resistance to pressure
Type B valves shall be capable of being loaded in the closed position up to 2 times the maximum permissible working pressures without bursting
Type C valves shall be capable of being loaded in all switching positions up to 2 times the maximum permissible working pressure without bursting.
Switching behaviour
Type B and C valves, when switching, shall not produce pressure peaks greater than 1,5 times the permissible working pressure.
Operating reliability
Type B and C valves shall continue to meet the requirements of 5.4.2 to 5.4.4 after 30 000 switching cycles.
Resistance to back pressure
Type B and C valves shall not undergo any switching up to the maximum permissible back pressure in the return system circuit.
Requirements for type D valves
Where type D valves contain elements or assemblies found in type A, B or C valves, then the corresponding requirements of 5.3 and/or 5.4 shall be met.
Materials
Metallic materials
Only metals that meet the material characteristics specified by the manufacturer shall be used as the material for hydraulic control devices.
Light metal
Surfaces made of light metals or their alloys, including those with paints and coatings, used in actuators for potentially gaseous mines must comply with the standards outlined in clause 8 of EN 13463-1:2001.
Other materials
Other materials shall conform to the material specifications laid down by the manufacturer of the hydraulic control devices Non-metallic materials shall meet the requirements of clause 7 of EN 13463-1:2001.
Seals
Hydraulic control device seals must be specifically designed for their intended application, taking into account dimensions, pressure range, fluid compatibility, and temperature Additionally, these seals are required to comply with the testing standards outlined in Annex A.
6 Verification of the safety requirements
Type testing
One hydraulic control device specimen must undergo type testing as specified in Annex A, ensuring compliance with the outlined test requirements Additionally, all necessary documents for the type test must be provided.
data relating to the material characteristics;
specification of the seals used;
NOTE The specimen which has been tested according to Annex A should not be placed on the market.
Additional tests
If Annex A does not include specific tests for verifying the requirements in clause 5 of this standard, verification must be conducted through inspection, functional tests, or by referencing documentation or standards The safety requirements verification is detailed in Table 3.
Table 3 — Test for verification of the safety requirements
5.1.2 *Inspection/comparison with manufacturer's drawings
5.1.4 *Inspection/comparison with manufacturer's drawings
5.1.5 *Inspection/comparison with manufacturer's drawings
5.1.7 *Inspection/comparison with manufacturer's drawings
5.1.8 *Inspection/comparison with manufacturer's drawings
5.1.9 *Inspection/comparison with manufacturer's drawings and documentation 5.1.10 *Inspection of manufacturer’s test documentation
5.2.2 *Inspection/comparison with manufacturer's drawings
5.2.3 *Inspection/comparison with manufacturer's drawings
5.2.4 *Inspection/comparison with manufacturer's drawings
5.2.5 *Inspection together with support unit/comparison with manufacturer’s drawings 5.2.6 * Force measuring using a recording device
5.2.7 *Measurements/comparison with manufacturer’s drawings t
5.2.8 *Inspection/comparison with manufacturer's drawings
5.6.1 *Inspection/comparison with manufacturer’s material specification
5.6.2 *Inspection/comparison with manufacturer’s material specification
5.6.3 *Inspection/comparison with manufacturer’s material specification
General requirements
The hydraulic control system manufacturer shall provide user information meeting the requirements of clause
6 of EN ISO 12100-2:2003 and clause 7
User information must be presented in one of the official languages of the country (restricted to EU and EFTA) where the hydraulic control system will be utilized.
User information is essential for a comprehensive hydraulic control system, encompassing all details necessary for its safe application This information will be compiled into an instruction handbook, as outlined in section 6.5 of EN ISO 12100-2:2003.
The user information in clause 7 of EN 1804-1:2001 also applies to EN 1804-2 and prEN 1804-4 2 and is complemented, as appropriate, by corresponding clauses in those parts
Care shall be taken to ensure that the user information is available to the user on receipt of the hydraulic control system.
Technical and application data
Introduction
The user information shall describe the intended use of the hydraulic control system under normal conditions and for operations as described by the manufacturer
The operating instructions must encompass all essential design and performance data required for both users and manufacturers of hydraulic powered roof supports This information is crucial for evaluating the suitability of the equipment for specific applications and environments, as well as for identifying necessary energy supply requirements and additional ancillary facilities.
General description
This article provides a clear and logical overview of the hydraulic control system, detailing its overall function along with its special features, markings, and characteristics It includes general arrangement drawings and function block diagrams to enhance understanding.
Performance data
The principal dimensions, weights and performance data of the hydraulic control system shall be given.
Hydraulic data
The article outlines the required data for defining the hydraulic supply system, including a list of hydraulic fluids specified by the manufacturer of the hydraulic control system.
List of additional drawings and documents
A comprehensive list of all drawings, illustrations, and documents provided separately from the user information must be included, along with appropriate cross-references to the relevant sections of the user information.
Handling, transport and storage
Introduction
This section of the user information shall include information and instructions for the safe handling, transport and storage of the hydraulic control system or its components.
Handling and transport
The article should detail the mass and outline dimensions of the hydraulic control system, along with precautions for handling and transportation It must also indicate potential damage risks to the system during these processes Additionally, it should provide information on the quantity and rated load of any ancillary lifting equipment, such as shackles and eye bolts, that are not supplied but are essential for the safe lifting and installation of the hydraulic control system.
Storage
For the effective storage of the hydraulic control system, both on the surface and underground, it is essential to provide detailed methods of preservation and clear instructions for preparing the system for use after the storage period.
Installation and commissioning
Installation
The installation of the hydraulic control system shall be described together with details of any special tools which may be required
Reference shall be made to the user information supplied for the support unit.
Commissioning
Before connecting to the pressure supply, ensure the correct installation and follow the required cleaning and flushing procedures Next, connect the hydraulic pressure supply and proceed to commission the hydraulic control system, testing each individual function for proper operation.
Operation
This section of the user information shall include the information and instructions necessary for the safe operation of the hydraulic control system
The instructions on correct use shall include details on the scope of use and the prevention of impermissible applications.
Maintenance
Introduction
This section provides essential information and instructions for maintaining or restoring the hydraulic control system to a safe working condition, in accordance with guidelines 7.6.2 to 7.6.5.
Technical description
This article provides a detailed functional overview of the hydraulic control system and its key components, accompanied by clear illustrations for better understanding It emphasizes the importance of safety devices and measures implemented to mitigate potential hazards resulting from equipment malfunctions.
Maintenance instructions
The article will provide comprehensive instructions, complete with illustrations, on the methods and procedures for both preventative and corrective maintenance Key topics will include dismantling and reassembly, replacement and adjustment, a parts identification list, special tools and additional equipment, as well as potential hazards and necessary precautions when working on high-pressure components.
Fault diagnosis and correction
Information and instructions shall be included on fault diagnosis and correction.
Preventative maintenance schedules
Schedules shall be provided and include information on the nature and frequency of inspections, tests, maintenance and discard criteria required to keep the hydraulic system in safe working order.
Parts identification lists
A comprehensive parts identification list will be supplied, featuring part numbers and detailed descriptions to ensure accurate identification of all assemblies, sub-assemblies, and components within the hydraulic system.
The list shall also identify: a) those parts which the manufacturer envisages being changed in the working environment, and b) those parts which the manufacturer recommends should be held as spares
Parts identification lists shall be illustrated by drawings, photographs, etc as appropriate, so that each component listed may be readily identified and located.
Marking
! a) the business name and full address of the manufacturer and, where applicable, his authorised representative;"
NOTE If space is restricted, the registered company logo or trademark can be used b) year of manufacture;
! c) designation of the machinery;" d) serial number, if any; e) maximum permissible working pressure of type B, C and D valves; f) yield pressure of type A valves; g) all connections in accordance with the drawings.
Residual risks
The user information shall inform the user of the residual risks when using the hydraulic control system
Tests for verification of the safety requirements
Load tests
General
Tests will be conducted on individual components, hydraulic control systems, or various valve combinations The manufacturer will specify the hydraulic fluid to be used, in accordance with section 5.1.10 The filter rating must fall within the range of 15 µm to 40 µm.
As a result of the test described below, no defects shall appear that would impair the function of the control system All results from the test shall be recorded.
Lifting points
Lifting points shall be tested for at least 1 min at 4 times the rating specified by the manufacturer
No failure of the lifting point or damage shall occur.
Testing of type A valves
Before testing, fluid shall be passed through the valve at least once
For type A valves with variable yield pressures, testing requires two valves: one calibrated to the lowest yield pressure and the other to the highest yield pressure.
For a type A valve, if different springs are used as a prestressing element, for example, the test shall be carried out using each of the spring variations
For tests according to A.1.3.2, A.1.3.3, A.1.3.4 and A.1.3.6, the hydraulic circuit to the valve shall contain a volume of 2 l to 5 l (see Figure A.1)
Tests according to A.1.3.3 and A.1.3.8 are for valves where exhaust fluid passes directly to atmosphere
The A.1.3.9 test is an additional assessment conducted alongside the A.1.3.3 and A.1.3.8 tests for valves that allow the exhaust flow to be redirected into the return line.
The valve shall be tested three times with 95 % of the specified yield pressure for 5 min each, and the pressure drop shall be no more than 2 %
The valve will undergo an 8-hour test at 95% of the specified yield pressure while maintaining a consistent ambient temperature During the initial 3 hours, the pressure drop must not exceed 3%, and for the subsequent 5 hours, there should be no additional decrease in pressure.
A.1.3.3 Testing of the yield, opening and closing pressures at ambient temperature
See Figure A.1 for the test arrangement
The yield, opening, and closing pressures of the valve must be tested at the ambient temperature of the hydraulic fluid and the valve body The upstream pressure should be gradually increased until the valve opens, ensuring that the pressure increase does not exceed 10 MPa (bar)/s within the last 50 MPa (bar) After the valve opens, fluid should flow through it for 1 minute at a rate of 0.04 l/min Following this, the hydraulic fluid supply must be halted, and the closing pressure should be measured over a 5-minute period The pressure versus time characteristics should be recorded and plotted, as illustrated in Figure A.2.
The yield and opening pressures must not exceed the specified yield pressure by more than 5%, while the closing pressure should not drop below the specified yield pressure by more than 10%.
Figure A.2 — Example of a pressure/time characteristic curve for a type A valve
A.1.3.4 Testing of yield, opening and closing pressures of valves with a pressurized volume of gas
For the test, the hydraulic fluid and the valve shall be at a temperature as specified by the manufacturer Subsequently, the tests shall be carried out as specified in A.1.3.3
Type A valves are classified in the 4 categories depending on their performance (see Table A.1)
Table A.1 — Classification of type A valves
II > 150 l/min ≤ 400 l/min III > 400 l/min ≤ 1 000 l/min
Category Ia valves are only permitted for the protection of annular areas of actuators
NOTE The ratio between piston area and annular area ensures that the volume flow of the yield valve cannot be exceeded
The valves will undergo a pressure pulse test conducted three times, where the pulse pressure will be raised from 60% of the specified yield pressure to the minimum values outlined in Table A.2.
Table A.2 — Pulse pressure for type A valves
Ia + Ib 1,5 x specified yield pressure
II 1,4 x specified yield pressure III 1,3 x specified yield pressure
The pulse pressure increase shall be within 5 ms to 25 ms, the valves shall open until the given pulse pressure is attained
The characteristic of the whole pulse pressure test shall be recorded After the test, the valves shall be fully functional and shall meet the requirements of A.1.3.2 and A.1.3.3
During the impact test, a volume flow of 0,04l/min shall be passed through the valve
The firmly fixed valve shall be subject to three pendulum impact tests A test body made of steel of a mass of
1 kg shall be fixed to a 500 mm long thread (see Figure A.3) The impact test shall be carried out from a swinging angle of 45° from the vertical
The opening pressure shall remain within the tolerance range given in A.1.3.3 during and after the impact tests
The closing pressure shall remain within the tolerance range given in A.1.3.3 after the impact test
A.1.3.7 Testing of the flow-related pressure behaviour
To test the flow-related pressure behaviour, hydraulic fluid shall be passed through the valve at gradually increasing flow rates from 0 l/min up to the manufacturer's specified flow rating
The flow rates will be gradually decreased to zero, while the valve opening pressures will be measured and documented It is essential that these pressures do not exceed the specified yield pressure by more than 20% and do not fall below it by more than 10%.
For the endurance test, the valve shall be tested with 10 500 load cycles Of these, 5 000 load cycles shall be applied comprising the following load cycle operations:
hydraulic fluid passing through the valve at a rate of 0,4 l/min;
interrupting the flow and reducing the pressure to zero
A further 5 000 load cycles comprising the same load cycle operations shall be carried out, however, with a volume flow rate of 0,04 l/min
The total duration of a load cycle operation shall be at least 10 s; the volume flow passing through the valve shall take at least 5 s
After 10 000 load cycles, the requirements according to A.1.3.2, A.1.3.3 and A.1.3.7 shall be met
Following this, an additional 500 load cycles will be conducted using the same operational procedures, ensuring a flow time of no less than 5 seconds at a volume flow rate of 30 liters per minute Each work cycle will have a total duration of at least 10 seconds.
After completing 500 load cycles, the valve will undergo three tests at a pressure of 85% of its rated yield pressure, each lasting 5 minutes During these tests, the pressure drop must not exceed 2% of the test pressure.
The valve shall be connected into a circuit so that a pressure of 60 ± 5 bar is maintained behind the valve (return line)
The intake pressure of the valve shall be increased until the valve opens Fluid shall then pass through the valve for 1 min at a flow rate of 0,04 1/min
The measured yield and opening pressures shall not differ more than 5 % from the yield and opening pressures measured according to A.1.3.3
The closing pressure shall not differ more than 5 % from the closing pressure measured according to A.1.3.3.
Testing of type B valves
One test specimen of a type B valve shall be tested
This test shall be carried out in two steps
Type B valves must be connected to a test ram for normal operation, as illustrated in Figure A.4 The test ram is then subjected to pressure tests at 20 bar, 100 bar, and the maximum permissible working pressure (± 5 bar) Once the designated pressure levels are reached, the pressure supply is halted It is essential to maintain the pressure between connection ports (a) and the test ram for a minimum of 5 minutes at each pressure level.
2 Connectors as present during normal operation of roof support a Hydraulic ram (leg) connection ports b Control circuit connection ports c Pilot release connection ports
Figure A.4 — Test circuit for type B valves
Hydraulic tests will be conducted using a reservoir with a volume ranging from 2 to 5 liters The connection parts, typically subjected to normal operating pressure, will be pressurized to 1.5 times the maximum allowable working pressure This hydraulic pressure must be sustained for a minimum duration of 5 minutes.
1 Reservoir with 2 l to 5 l hydraulic volume
2 Connectors as present during normal operation of roof support a Hydraulic ram (leg) connection ports b Control circuit connection ports c Pilot release connection ports
Figure A.5 — Test circuit for type B valves (example)
The tests of the 1st and 2nd step shall be carried out twice No pressure drop > 2 % shall occur during the tests
The valve's connection ports must be pressurized to the maximum allowable working pressure and maintained for 8 hours at a consistent ambient temperature In the initial 3 hours, a pressure drop of up to 3% is acceptable, but after this period, no additional pressure loss should occur.
The pressure test requires the valve in operational switching and connection combinations to endure 1.5 times the maximum permissible working pressure through connection ports (a), (b), and (c) as illustrated in Figure A.5 This hydraulic pressure must be sustained for a minimum of 3 minutes for each type of connection port The pressure tests are to be conducted twice, and post-testing, the valve must still comply with the standards outlined in sections A.1.4.2 and A.1.4.5.
Tests will be conducted at twice the maximum allowable working pressure, performed only once While the valve's function may be affected, it must not rupture, and no components should be expelled.
The valve must be linked to a test ram calibrated to 60% of its maximum allowable working pressure Subsequently, the valve connection ports, which could be affected by back pressure during standard operation, should endure a pressure of 80 ± 5 bar for one minute It is essential that the pressure in the test ram does not decrease by more than 2%.
The valve must be connected to a test leg featuring a piston diameter of at least 250 mm and an extended travel length of 800 mm, as illustrated in Figure A.4 The leg should be adjusted through the valve to the maximum permissible working pressure.
The valve must be released twice, utilizing both hydraulic methods and an auxiliary device if available It is crucial to ensure that pressure peaks at connection ports (a) do not exceed 1.5 times the maximum permissible working pressure.
For the endurance test, the valve shall be connected to a test leg as described in A.1.4.5 and shall be subjected to 30 000 working cycles comprising the following operations:
set the leg with the maximum permissible working pressure;
release the valve and retract the leg by 10 cm
During the endurance test, the hydraulic fluid shall be supplied by a pump that can deliver at least 70 l/min at the maximum permissible working pressure
After the endurance test has been completed, the requirements of A.1.4.2 shall continue to be met.
Testing of type C valves
One type C valve shall be tested
Type C valves must be connected in the neutral position to a hydraulic supply over a reservoir with a volume between 2 to 5 liters They should be tested at pressures of 20 bar, 100 bar, the maximum permissible working pressure, and 1.5 times the maximum permissible working pressure (± 5 bar) Each pressure level must be maintained for a minimum of 5 minutes, and the tests should be conducted twice, ensuring that there is no pressure drop greater than 2% during the tests.
The valve must undergo testing at the maximum allowable working pressure for 8 hours under consistent ambient temperature conditions During the initial 3 hours, a pressure decrease of up to 3% is acceptable, but after this period, no additional pressure drop is permitted.
The valve must undergo pressure testing under all operational switching and connection combinations, excluding the return line, at 1.5 times the maximum permissible working pressure The return connection should be adjusted to the maximum allowable back pressure Hydraulic pressure must be sustained for a minimum of 3 minutes for each connector and switch position, with the tests conducted twice Following these tests, the valve must still comply with the requirements outlined in A.1.5.2 and A.1.5.6.
The valve, excluding the return connection, must undergo testing at twice the maximum permissible working pressure, ensuring that it does not burst and that no components are ejected.
For the endurance test, the valve shall be tested for a total of 30 000 working cycles comprising the following operations:
opening of the valve and passage of the hydraulic fluid through it for at least 5 s in all directions occurring during normal operation;
If the valve is operating both mechanically and hydraulically, then 15 000 cycles shall be carried out for each type of operation
The hydraulic fluid shall be supplied by a pump that can deliver at least 70 l/min at the maximum permissible working pressure
After the endurance test, the requirements of A.1.5.2 shall continue to be met and the valve shall operate correctly
With the valve in the neutral position, each service port shall be connected to a hydraulic reservoir of 2 l to
5 l volume Than, each port shall be supplied with a pressure of 150 bar
Those valve connections which can be influenced by back pressure (i.e return and pilot connections) shall be tested with a back pressure of 60 ± 5 bar for 1 min
The pressure at the service ports shall not be higher than the back pressure value
The test shall be repeated with the supply pressure equal to the maximum permissible working pressure
With the valve in the neutral position, each service port shall be connected to a hydraulic reservoir of 2 l to
Each service port shall be tested with a pressure equal to the maximum permissible working pressure
The valve shall then be operated
No pressure peaks shall occur at the service port exceeding 1,5 times the maximum permissible working pressure
The switching shall be carried out with each service port and with all possible manual overrides.
Testing of type D valves
One type D valve shall be tested
Type D valves shall be tested in accordance with A.1.3 to A.1.5 as far as they can be classified as type A, B or C valves
General
The primary function of hydraulic roof support is to safeguard workers at mining faces from rock and coal falls originating from the strata and goaf area This system must effectively support the strata while shielding travel and working zones from potential hazards Consequently, personnel must remain within the operational range of the hydraulic roof support However, it is generally prohibited for individuals to occupy the working area of a support unit during the control of its maneuvering functions.
The hydraulic powered roof support prioritizes the reliable support of strata and the protection of workers at the working face from rock and coal falls, ensuring safety in mining operations.
The protective objectives outlined in EN 982 for fluid-powered systems focus on safeguarding against hazards associated with these systems However, these objectives cannot be fully implemented in the operation of hydraulic roof support systems.
Therefore, this standard specifies requirements to minimize the risk of hazards for persons working in this hazardous area, particularly in the case of incorrect operation and hose failures
High-pressure hoses used for fluid supply at the working face can only be partially safeguarded, as the hydraulic support units shift relative to one another during regular operations.
Due to the high number of hydraulic-powered support units and limited space at the working face, it is recommended to monitor hydraulic fluid cleanliness outside this area Effective filtering of hydraulic fluid before it reaches each roof support control unit can be achieved using compact and straightforward solutions.
For effective roof support sequence control, it is essential to utilize a combination of pressure sensing, travel sensing, and time-dependent controls This integrated approach not only meets the strata control requirements but also ensures a high safety standard while accommodating the necessary speed of the function sequence.
Symbols designed for easy understanding by individuals without specialized hydraulic knowledge have been created for labeling the valves that manage roof support functions Nevertheless, these symbols are not appropriate for use in hydraulic circuit diagrams.
The required deviations from EN 982:1996 for the hydraulic control system are described below:
Mechanical movements, whether intended or unintended (including effects from e.g acceleration, deceleration or lifting/holding of masses), shall not result in a situation hazardous to persons
Unintended mechanical movements e.g by convergence or horizontal shear of the strata may lead to a hazardous situation
Systems shall have a means of controlling the fluid cleanliness level to ensure safe operation of the system and its components
Means should be provided to show when a filter or separator requires servicing
If blocking of a filter could lead to a hazardous situation, clear indication of such blockage shall be given
To ensure compliance with ISO 4021, it is essential to provide a method for obtaining a representative fluid sample to assess fluid cleanliness If a sample valve is installed on a high-pressure line, it must be clearly labeled to warn of high-pressure jet hazards and should be adequately shielded for safety.
The hydraulic powered roof support installation must include filters equipped with blockage indicators for hydraulic fluid supply However, filters that are directly attached to the support unit do not need these blockage indicators.
If the failure of a flexible hose assembly constitutes a whiplash hazard for persons, it shall be restrained or shielded
If the failure of a flexible hose assembly constitutes a fluid ejection hazard for persons, it shall be shielded Permitted deviation
The requirements of 5.3.4.3.2 of EN 982:1996 have been considered and possible measures representing the present state of the art of hydraulic powered roof supports have been added
Sequencing by position sensing shall be used wherever practicable and shall always be used when a sequencing malfunction of a pressure or time lapse control, on its own, could cause a hazard
Generally, combined controls are permitted
B.6 7.3.4.1 Non-electrical control mechanisms (EN 982:1996)
Valve control mechanisms and their functions shall be plainly and permanently identified with the same identification used on the circuit diagram
Valve controls must be clearly and permanently labeled with universally recognizable pictograms for each function Circuit diagrams should include symbols that comply with ISO 1219-1 standards, and these symbols, along with their corresponding pictograms, must be displayed on the diagrams.
! Relationship between this European Standard and the Essential
Requirements of EU Directive 2006/42/EC
This European Standard was developed under a mandate from the European Commission and the European Free Trade Association to ensure compliance with the Essential Requirements of the New Approach Directive 2006/42/EC concerning machinery.
Once cited in the Official Journal of the European Union and implemented as a national standard in at least one Member State, compliance with this standard's normative clauses provides a presumption of conformity with the relevant Essential Requirements, excluding ESR 1.5.8 and 1.7.4.2 u) of the Directive and associated EFTA regulations.
WARNING — Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard."
The Luxembourg Report by the Safety and Health Commission for the Mining and Other Extractive Industries outlines the requirements and tests for fire-resistant hydraulic fluids utilized in power transmission and control systems, including hydrostatic and hydrokinetic applications This document, titled "Mine Rescue and Mine Fires," is part of the Working Group and Experts' Group efforts, and it represents the seventh edition published in April 1994.
[2] ISO 4021, Hydraulic fluid power – Particulate contamination analysis – Extraction of fluid samples from lines of an operating system
[3] EN 60079-0, Electrical apparatus for explosive gas atmospheres - Part 0: General requirements (IEC 60079-0:2004)