GB/T 47716-2026Heavy mechanical - Design specifications for hydraulic system (English PDF)

Foreword

This document was drafted in accordance with the rules given in GB/T 1.1-2020 “Directives for standardization — Part 1: Rules for the structure and drafting of standardizing documents”.

This is the first edition of the standard: it does not replace an earlier document.

Attention is drawn to the possibility that some of the content of this document may be the subject of patent rights. The issuing body of this document takes no responsibility for identifying them.

This document was proposed by, and is under the jurisdiction of, the National Technical Committee on Metallurgical Equipment of Standardization Administration of China (SAC/TC 409).

Drafting organizations: China National Heavy Machinery Research Institute Co., Ltd.; Taiyuan Heavy Industry Co., Ltd.; Xi'an Jiaotong University; Yanshan University; Zhejiang University.

Principal drafters: Qiu Mingjun, Xie Zenggang, Ning Bo, Liu Jie, Wang Xin, Wang Yaqiang, Wu Jiahao, Lin Qiyin, Wang Chen, Yao Jing, Chen Jinfeng, He Bo, Wu Liang, Liu Zhaoqi, Yan Ying, Zhen Yongfu, Li Xianghui, Zhang Qiang, Zhang Yongfeng, Chen Guofang, Fan Yulin, Zhang Libo, Guo Yong'an, Hou Yongchao, Duan Lihua, Zhang Jun, Wang Zhelin, Qiu Lipeng, Hu Yanghu, Xu Bing, Wang Tao, Li Xinqiang, Wang Wenxue, Liu Yunfei, Ji Jiang, Su Zhenhua, Zhao Teng, Yao Chenggong, Zhang Chao, Wang Shijie, Liu Lei, He Qian, Ma Haikuan, Zhang Jun, Xue Hongwei, Liu Junping, Wang Pei, Yang Shuai, Ren Zhongkai.

1 Scope

This document specifies the design criteria, the design procedure, the system composition and the design requirements of the hydraulic systems of heavy machinery, referred to below as hydraulic systems.

It applies to the design of the hydraulic systems of heavy machinery.

NOTE: heavy machinery mainly includes metallurgical equipment, heavy extrusion and forging equipment, mining machinery and similar plant.

2 Normative references

The content of the following documents constitutes, through normative reference in this text, indispensable provisions of this document. For dated references, only the edition corresponding to that date applies; for undated references, the latest edition (including all amendments) applies.

GB/T 786.1 Fluid power systems and components — Graphical symbols and circuit diagrams — Part 1: Graphical symbols · GB/T 786.2 Fluid power systems and components — Graphical symbols and circuit diagrams — Part 2: Circuit diagrams · GB/T 1047 Pipework components — Definition and selection of DN (nominal size) · GB/T 1048 Pipework components — Definition and selection of PN (nominal pressure) · GB/T 3766 Hydraulic fluid power — General rules and safety requirements for systems and their components · GB/T 4458.1 Mechanical drawings — Representation of views · GB/T 4459.1 Mechanical drawings — Representation of screw threads and threaded parts · GB 5083 General rules for designing the production facilities in accordance with safety and health requirements · GB/T 7935 General technical rules for hydraulic components · GB/T 8163 Seamless steel tubes for liquid service · GB/T 14039 Hydraulic fluid power — Fluids — Method for coding the level of contamination by solid particles · GB/T 14043.1 Hydraulic fluid power — Valves — Identification code — Part 1: Mounting surfaces and cavities · GB/T 14976 Seamless stainless steel pipes for fluid transport · GB/T 16898 Guidelines for the use of fire-resistant hydraulic fluids · GB/T 17395 Dimensions, shapes, masses and tolerances of seamless steel tubes · GB/T 17446 Fluid power systems and components — Vocabulary · GB/T 17490 Hydraulic control valves — Identification of ports, subplates, control devices and solenoids · GB 18613 Minimum allowable values of energy efficiency and energy efficiency grades for motors · GB/T 20079 Specifications for hydraulic filters · GB/T 20663 Accumulator pressure vessels · GB/T 25133 Hydraulic system assemblies — Methods of pipe flushing · GB/T 36997 Hydraulic fluid power — Identification of manifold assemblies and their components · GB/T 37400.3 Heavy mechanical general technical specification — Part 3: Welded parts · GB/T 37400.10 Heavy mechanical general technical specification — Part 10: Assembly · GB/T 37400.11 Heavy mechanical general technical specification — Part 11: Piping · GB/T 37400.12 Heavy mechanical general technical specification — Part 12: Painting · GB/T 37400.16 Heavy mechanical general technical specification — Part 16: Hydraulic system · JB/T 10607 Specification for the use of working fluids in hydraulic systems

3 Terms and definitions

The terms and definitions given in GB/T 17446 apply to this document.

4 Design criteria

The design criteria of a hydraulic system are: a) safety — of personnel, of equipment and of production operation; b) reliability — redundancy and fault-tolerant design, fail-safe design, margin design; c) technical advancement — digitalization, intelligence, green design; d) inheritance — preference for mature technology, modular reuse, design by analogy; e) supportability — ease of maintenance, modularity, standardization; f) economy — economical scheme, economical selection, economical operation and maintenance.

5 Design procedure

The design of a hydraulic system should proceed in five stages: a) scheme demonstration; b) overall scheme design; c) schematic design; d) structural design; e) test verification. The design procedure is set out in Annex A.

6 System composition

A hydraulic system is made up of the power section, the control section, the actuating section, the auxiliary devices and the working fluid, as shown in Figure 1.

7 Design requirements

7.1 General requirements. The system shall comply with GB/T 37400.16 and GB/T 3766; pressure ratings are selected to GB/T 1048 and the nominal sizes of pipes, fittings and in-line valves to GB/T 1047; motor energy efficiency grades shall meet GB 18613; accumulators shall be used in accordance with GB/T 20663; noise and vibration shall meet GB 5083; painting shall meet the process specification and GB/T 37400.12 or the manufacturer's recommendation; and the system should carry components for fault diagnosis, to make digital and intelligent control possible.

7.2 Safety requirements. The design shall meet the safety provisions of GB 5083 and GB/T 3766 and shall take preventive, control or protective measures for the safety of people and machines. Clear and durable warning marks shall state high-pressure hazards, hot surfaces, operating instructions and emergency steps. Critical electrical points shall be connected to an emergency supply so that the safety functions keep working during a power failure. The system shall have complete safety interlocks — hydraulic control interlocks, interlocks with the main machine and forced interlocks in maintenance mode — an obvious pressure-relief point or device in an accessible position, and, against the risk of pressure loss or pipe burst at critical parts, a quick shut-off device in the circuit.

7.3 System schematic diagram. Schematics follow GB/T 786.1 and GB/T 786.2 and the port letter codes of GB/T 7935, GB/T 14043.1 and GB/T 17490. Near a pipe connection the function letter code, the connection type and the nominal bore shall be marked, a numeral being added after the letter where circuits run in parallel. Table 1 fixes the function letter codes: S for suction lines, P for pressure lines, T for return lines, A and B for the two working lines, L for drain lines, X for control-oil supply and Y for control-oil return. Typical circuit designs are given in Annex B.

7.4 Hydraulic pumps and pump sets. Pumps are selected with reduced pressure, speed or power to improve reliability and life; a pump should have its own cooling and flushing circuit to avoid overheating. A system that runs continuously, is safety-critical or is costly to shut down shall have a standby pump set with condition monitoring and automatic changeover. The suction line shall satisfy the pump's suction conditions, and the pump should be mounted below or beside the tank. On a high-pressure, high-flow pump unit the inlet shall have a rubber elastic compensating connection and the outlet a high-pressure hose; the base shall have elastic anti-vibration pads and the coupling between pump and motor shall be flexible. Exposed rotating shafts and couplings shall be guarded, and the pump set laid out so that it can be dismantled, adjusted and maintained with enough space around it.

7.5 Accumulator sets. Selection, design and use follow GB/T 20663. The nominal pressure of an accumulator shall be not lower than the maximum working pressure of its circuit, and the effective volume is calculated from the function required — leakage compensation, damping of pressure pulsation, emergency power source, energy recovery — with an appropriate margin. Bladder accumulators suit the absorption of pulsation, shock reduction and short-term flow make-up, the bladder material being compatible with the fluid; diaphragm accumulators suit small capacity and high-frequency response; piston accumulators suit large storage and long high-pressure holding, and should have a nitrogen bottle group matched to the capacity. The set should carry a gauge or pressure transducer with monitoring and alarm, a relief valve or pressure-relief device able to release the pressure safely at shutdown or maintenance, protection against vibration and shock, and a clear statement of gas type, charging pressure and charging procedure.

7.6 Hydraulic valves and valve stands. On loss of power or pressure the valves shall bring the circuit to a safe state. The minimum stable flow of throttle and speed-control valves shall meet the lowest stable speed of the actuator; circuits subject to severe pressure shock shall use shock-resistant valves with an increased nominal pressure margin; and the rated flow of a relief valve shall be not less than the maximum overload flow of the circuit it protects. Valve stands should be modular and standardized, clearly and compactly laid out, with the oil paths obvious so that pressure loss and leakage risk are reduced. The mounting height of the components used in operation and checking — manual directional valves, pressure adjusting handles, gauges — should be between 0.8 m and 1.6 m; space shall be left for dismantling between valves and adjacent parts, with a clear distance between the bodies of stacked or adjacent valves of not less than 15 mm. The stand shall stay stable under vibration and shock, carry pressure test points where the circuit pressure changes, have a drip tray to keep oil off the floor, and be surface-protected or made of corrosion-resistant material where the atmosphere is hot, humid or corrosive.

7.7 Hydraulic cylinders, motors and their assemblies. Cylinders with large inertia or high speed shall have cushioning to soften the end of stroke; the stroke shall allow for manufacturing tolerances, installation error, thermal distortion and elastic deformation so that the mechanism works reliably at its limit positions; cylinders shall be checked for bending and off-centre loading; and the seal selection shall prevent stick-slip at low speed. Motors shall be selected for starting torque and low-speed stability, the circuit shall have an independent drain line keeping the motor case at low pressure and always full of oil, and a motor that rotates continuously or starts and stops often should have an independent brake control line.

7.8 Working fluid. The fluid is chosen in accordance with JB/T 10607; mineral hydraulic oils follow GB/T 37400.16 and fire-resistant hydraulic fluids follow GB/T 16898.

7.9 Tank assembly. The tank follows GB/T 3766, and the welding of open rectangular and cylindrical tanks follows GB/T 37400.3. A level gauge shall be fitted near the pump suction, level switches should monitor and signal the high and low limits, and an oil temperature sensor shall be fitted. The tank volume is obtained from the total rated flow of the system multiplied by an empirical coefficient — 2 to 4 for low-pressure systems, 5 to 7 for medium- and high-pressure systems, 7 to 10 for metallurgical hydraulic systems and 6 to 12 for extrusion and forging systems, the higher values suiting systems with many actuators or large displacement — and the result is rounded to the nominal series of Table 2, which runs from 2.5 L and 16 L up to 10 000 L; above 10 000 L the R10 series of GB/T 321-2005 is used.

7.10 Piping. Piping design, workmanship and pressure testing follow GB/T 37400.11 and GB/T 37400.16, and the nominal outside diameter and wall thickness of steel tube follow GB/T 17395. Servo and proportional systems should use seamless stainless steel tube. Threaded connections should not be used on high-pressure lines working above 31.5 MPa, and pipes exposed to strong heat radiation or to very low temperatures shall be insulated. The minimum wall thickness is calculated from the maximum working pressure, the internal diameter and the permissible stress of the material, the permissible stress being the tensile strength divided by a safety factor: 6 or 8 below 7.0 MPa, 6 from 7.0 MPa to 17.5 MPa, and 4 above 17.5 MPa. Tensile strengths are taken from GB/T 8163 and GB/T 14976.

7.11 Sealing. Parts containing seals shall be protected during welding, high-temperature painting and assembly. Seal materials for control components and accessories follow the manufacturer's recommendation and, in its absence, are chosen for compatibility with the fluid, the temperature range and the pressure rating. Seals working at high pressure, under high-frequency vibration or under alternating load shall be of an anti-extrusion form, so that the material is not forced into the clearance and fails.

7.12 Hydraulic units. Assembly follows GB/T 37400.10. Modular design shall suit transport, the mass and overall dimensions of a single module matching the transport method chosen. Manifold assemblies and the components mounted on them are identified to GB/T 36997. Electrical interfaces, cable routes and fixing points shall be arranged for easy wiring and shall meet the required degree of protection; sensitive valve groups shall be insulated, protected against damp or kept warm where the environment demands it; and the unit shall have a drip tray. Typical structural cases are given in Annex C.

7.13 Coolers and heaters. The rated heat rejection of a cooler shall be not less than the maximum continuous heat generation at thermal balance, with margins for ambient temperature change, fouling factor and performance decay. An electric heater should be fitted in a protective sheath whose surface power density does not exceed 0.7 W/cm², so that the oil is not overheated and degraded. The working oil temperature should be held between 25 °C and 50 °C and shall at no time fall outside the range 15 °C to 60 °C.

7.14 Filters. Filter selection follows GB/T 20079, and the filtration rating shall meet the cleanliness required by the components and by the system as a whole. Filters shall have a contamination indicator or differential-pressure signal, and pressure test points at inlet and outlet to show blockage. Main return and circulation filters should be duplex, so that elements can be changed without stopping the system; the nominal flow is chosen from the permissible pressure drop with a margin; a bypass protection device is used or not according to the importance of the machine; and a large pump station in continuous service should have its own cooling and circulation filtration system. Air breathers are chosen so that the pressure inside and outside the tank stays balanced at a low air velocity, and the control ports of servo and proportional valves should have their own filters matched to the valve's requirements.

7.15 Green and cleanliness requirements. The cleanliness class of the fluid follows GB/T 14039, the recommended values being given in Annex D; the design follows the industrial hygiene provisions of GB 5083; the assembly environment shall be clean and, where possible, away from welding, machining and spraying areas, with effective isolation; and energy-saving components and circuits shall be used to raise efficiency and reduce heat generation.

7.16 Digitalization and intelligence. Where these are required, the system shall provide data acquisition and sensing, condition monitoring and fault diagnosis. A uniform electrical interface and communication protocol shall be specified, and the digital parameters shall cover system parameters such as pressure, temperature, cleanliness and level; component status parameters such as spool displacement, directional valve position, filter differential pressure and motor electrical parameters; and control parameters such as positioning accuracy, repeatability and response time. Digital design and verification methods shall be used — three-dimensional modelling, system modelling and simulation, flow-field and temperature-field analysis.

7.17 Technical documentation. The documentation should include drawings, technical documents and the electrical specification. The drawings comprise the hydraulic schematic, the unit assembly drawing, the system layout and the pipe installation drawing, prepared to GB/T 4458.1 and GB/T 4459.1 with symbols and circuit diagrams to GB/T 786.1 and GB/T 786.2. The technical documents comprise the operating manual, the basic lists — component schedule and summary of wearing spare parts — the technical outline, the design calculations and the test outline. The electrical specification shall set out the action logic and control modes, the electrical closing table of the electrically controlled hydraulic components, the electrical parameters and wiring diagrams of the instruments, and the layout drawing and parameter table of the control components, giving the position of each electrical point, the wiring type and the signal specification.

7.18 Test requirements. Testing follows GB/T 7935 and shall include pressure resistance testing, leak-tightness testing, functional testing and performance testing, the performance test being carried out to the test outline.

7.19 Other. Pipe flushing follows GB/T 25133. The civil foundation of a pump station should have facilities for collecting and discharging contamination. Where energy saving is required, efficient components and circuits should be used and monitoring points provided so that energy and fluid consumption can be assessed and managed.

Annexes

Annex A (informative) sets out the design procedure of a heavy machinery hydraulic system as a flow chart. Annex B (informative) gives typical circuit designs in a table that puts an unreasonable design beside the reasonable one and explains the difference — among them the A and B port interconnection at the end of the line on large actuators that are hard to bleed, the anti-freeze bypass circuit for actuators placed far from the pump station in cold regions, the check valve upstream of the main return filter that stops shock loads from destroying it, and the small-bore bypass ball valve fitted alongside a high-pressure ball valve of DN 50 and above so that the line can be depressurised before the main valve is opened.

Annex C (informative) gives typical cases of the structural design of heavy machinery hydraulic units. Annex D (informative) gives the recommended cleanliness levels: for servo systems, solid particle contamination classes 16/14/11 or 17/15/12 to GB/T 14039, equivalent to NAS 1638 classes 5 and 6; for proportional systems 17/15/12 or 18/16/13, that is NAS classes 6 and 7; for on-off valve systems 19/17/14 or 20/18/15, NAS classes 8 and 9; and for mobile machinery, metallurgical equipment and heavy extrusion and forging equipment 18/16/13, 19/17/14 or 20/18/15, that is NAS classes 7, 8 and 9.