GB/T 7935-2005Hydraulic fluid power - General requirements for hydraulic components (English PDF)

4.1

The basic parameters and the mounting and connection dimensions of hydraulic components shall conform to GB/T 2346, GB/T 2347, GB/T 2348, GB/T 2349, GB/T 2350, GB/T 2353, GB/T 2514, GB/T 2877, GB/T 2878, GB/T 8098, GB/T 8100, GB/T 8101 and GB/T 14036.

4.2

The pressure-bearing passages of hydraulic components shall be subjected to a proof pressure test; the test method shall be in accordance with the relevant standard for each component.

4.3 Housing

4.3.1

The housing of a component shall be given an appropriate treatment to relieve internal stresses. The housing shall be free from manufacturing defects that affect the use of the component and shall achieve the strength required for the component.

Note: flaw detection should be carried out on complex castings.

4.3.2

The surface of the housing shall be even and smooth and shall be free from manufacturing defects that affect the external appearance of the component.

4.3.3

Castings shall be sand-cleaned; no residue of any kind shall remain in the internal passages and cavities.

4.4

Components shall be assembled from inspected and accepted parts and purchased parts, in accordance with the provisions and requirements of the relevant product standards or technical documents. Deformed, damaged or corroded parts and purchased parts shall not be used in assembly.

4.5

Parts shall be cleaned before assembly and shall be free from any contaminants (such as iron filings, burrs, fibrous impurities, etc.).

4.6

During assembly of components, cotton yarn, paper or other materials that readily shed fibres shall not be used to wipe the internal cavities of the housing, the mating surfaces of parts, or the inlet and outlet passages.

4.7

During assembly of components, seals that are defective or have exceeded their period of validity shall not be used.

4.8

Symbols indicating the function of each port shall be clearly marked near all connection ports of a component. Unless otherwise specified, the port symbols are as follows:

P - pressure port;

T - return port;

A, B - working ports;

L - drain port;

X, Y - pilot (control) ports.

4.9

The coating on exposed unmachined surfaces of components shall be uniform and of consistent colour. Putty shall not be applied in the pre-treatment before spraying.

4.10

After a component has passed factory inspection, all ports shall be sealed and protected against dust and leakage.

5.1 Measurement accuracy classes

The measurement accuracy of component performance tests is divided into three classes, A, B and C:

a) Class A: applicable to scientific appraisal tests;

b) Class B: applicable to type tests of hydraulic components, or to product quality assurance tests and selection evaluation tests by users;

c) Class C: applicable to factory tests of hydraulic components, or to acceptance tests by users.

5.2 Measuring system error

The permissible error of the measuring system shall conform to Table 1.

Table 1 - Permissible systematic error of the measuring system, for measurement accuracy classes A / B / C: Pressure (gauge pressure p >= 0.2 MPa), %: ±0.5 / ±1.5 / ±2.5; Flow rate, %: ±0.5 / ±1.5 / ±2.5; Temperature, °C: ±0.5 / ±1.0 / ±2.0; Torque, %: ±0.5 / ±1.0 / ±2.0; Rotational speed, %: ±0.5 / ±1.0 / ±2.0.

Note to Table 1: when the gauge pressure of the measured parameter is p < 0.2 MPa, its permissible error shall be as specified in the relevant test method standard for the component under test.

5.3 Measurement

Test measurements shall be made under steady-state conditions. Steady-state conditions exist when the variation of the mean indicated value of each measured parameter is within the range given in Table 2. Under steady-state conditions, all parameters (pressure, flow rate, torque, rotational speed, etc.) at each set point shall be measured simultaneously.

Table 2 - Permissible variation of the mean indicated value of the measured parameters, for measurement accuracy classes A / B / C: Pressure (gauge pressure p >= 0.2 MPa), %: ±0.5 / ±1.5 / ±2.5; Flow rate, %: ±0.5 / ±1.5 / ±2.5; Temperature, °C: ±1.0 / ±2.0 / ±4.0; Torque, %: ±0.5 / ±1.0 / ±2.0; Rotational speed, %: ±0.5 / ±1.0 / ±2.0; Viscosity, %: ±5 / ±10 / ±15.

Note to Table 2: when the gauge pressure of the measured parameter is p < 0.2 MPa, its permissible error shall be as specified in the relevant test method standard for the component under test.

5.4 Test fluid

a) Fluid temperature: unless otherwise specified, the fluid temperature during testing shall be 50 °C, and its permissible variation under steady-state conditions shall conform to Table 2;

b) Fluid viscosity: the kinematic viscosity of the fluid at 40 °C shall be 42 mm2/s to 74 mm2/s (special requirements to be specified separately);

c) Fluid contamination level: not higher than the fluid contamination level specified in the operating requirements of the hydraulic component.

5.5

For hydraulic components with special requirements, the test conditions and requirements shall be agreed between supplier and purchaser.

6.1

A product nameplate shall be fitted in a conspicuous position on the hydraulic component. The nameplate shall include:

- name, model and serial number;

- main technical parameters;

- name of the manufacturer;

- date of manufacture.

6.2

For hydraulic components with directional requirements (such as the direction of rotation of a hydraulic pump), the direction shall be indicated by an arrow or a corresponding symbol in a conspicuous position on the component.

6.3

When hydraulic components are packed for dispatch, the following documents shall accompany them:

- certificate of conformity;

- instructions for use (including: component name, model, outline drawing, mounting and connection dimensions, simplified structural drawing, main technical parameters, conditions of use and maintenance methods, and a list of spare parts, etc.);

- packing list.

6.4

When hydraulic components are packed, the specified accessories shall be packed together with the component and secured inside the case.

6.5

For hydraulic components with adjusting mechanisms, the adjusting springs shall be in the released condition when packed, and exposed threads, keyways and similar features shall be protected.

6.6

Packaging shall be sturdy and reliable and shall provide protection against shock and moisture.

6.7

The following information should be clearly marked in writing in a conspicuous position on the outside of the packing case:

- name and model;

- number of packages and gross weight;

- external dimensions of the packing case (length, width, height);

- name of the manufacturer;

- packing date;

- name and address of the consignee and destination station;

- transport precautions or handling marks.