GB/T 20080-2017General specification for hydraulic filter elements (English PDF)

1 Scope

China's national general specification for hydraulic filter elements. It specifies the general technical conditions for filter elements together with the requirements for testing, inspection, marking, packaging and storage, and it applies to elements using hydraulic oil as the working medium. Contamination is what destroys hydraulic systems. The clearances in a servo valve, a piston pump or a proportional valve are a few micrometres, and particles of that size erode the surfaces that form them, so the cleanliness of the fluid determines the life of every expensive component in the circuit. The filter element is what maintains that cleanliness, and it is the cheapest part of the system - which is why it is also the part most often substituted with something that looks the same and is not. This standard exists to make the difference measurable. It classifies elements and sets the requirements on the properties that matter: the filtration ratio, which states how efficiently the element removes particles of a given size and is determined by the multipass test rather than by any nominal rating; the dirt holding capacity, which decides how long the element lasts before the bypass opens; the differential pressure against flow characteristic; the collapse and burst pressure rating, since an element that collapses under a cold start pressure surge discharges everything it has collected straight into the system; the fabrication integrity and bubble point, which detect a hole in the medium or a failed seam; the compatibility of the materials with the fluid; the resistance to flow fatigue, since flow in a hydraulic system pulses; and the end load rating. Each is referred to its own test standard, so a claimed performance can be checked rather than believed. Issued on 12 May 2017 and in force since 1 December 2017, it replaces GB/T 20080-2006.

This Standard specifies the general technical conditions for hydraulic filter elements (hereinafter referred to as filter elements), as well as the requirements for testing, inspection, marking, packaging and storage. This Standard applies to filter elements that use hydraulic oil as the working medium.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 1184-1996, Geometrical tolerancing -- Geometrical tolerance for features without individual tolerance indications

GB/T 1800.2-2009, Geometrical product specifications (GPS) -- Limits and fits -- Part

3 Terms and definitions

For the purposes of this document, the terms and definitions defined in GB/T 17446 as well as the followings apply.

3.1 filter element rated flow The flow rate that a clean filter element can pass under the specified oil kinematic viscosity (generally 32 mm2/s) and specified pressure drop.

3.2 filter element pressure drop When oil passes through the filter element, a pressure difference between the upstream and downstream of the filter element.

3.3 filter element characteristics of pressure drop versus flow Characteristic curve of filter element pressure drop versus flow rate.

3.4 filtration ratio The ratio of the number of pollutant particles larger than a given size x (c) per unit volume of oil upstream and downstream of the filter element is expressed as betax (c). It is calculated using the following formula. Where, Nu - The number of particles larger than x (c) microns contained in the unit volume of oil upstream of the filter element; Nd - The number of particles larger than x (c) microns contained in the unit volume of oil downstream of the filter element.

4 Classification

4.1 Classification by installation location.

a) Suction filter. a filter element installed in the oil suction port or oil suction filter in the oil tank;

b) Return filter. a filter element installed in the oil return port or oil return filter in the oil tank;

c) Pressure line filter. a filter element installed in the pressure line filter;

d) Other filter elements. filter elements with comprehensive performance, such as suction and return filter elements.

4.2 Classification by filter material used.

a) Glass fiber filter element. the filter material is glass fiber filter material;

b) Paper filter element. the filter material is plant fiber filter paper;

c) Metal mesh filter element. the filter material is metal wire mesh;

d) Other filter elements. including chemical fiber filter element, metal fiber felt filter element, sintered powder filter element, polymer material filter element, etc.

6 Test requirements

6.1 Filter element filtration ratio test It shall be carried out in accordance with the provisions of GB/T 18853.

6.2 Filter element dirt holding capacity test It shall be carried out in accordance with the provisions of GB/T 18853.

6.3 Filter element structural integrity test It shall be carried out in accordance with the provisions of GB/T 14041.1.

6.4 Compatibility test between filter element material and liquid It shall be carried out in accordance with the provisions of GB/T 14041.2.

6.5 Filter element pressure drop flow characteristics test It shall be carried out in accordance with the provisions of GB/T 17486.

6.6 Filter element structural strength test It shall be carried out in accordance with the provisions of GB/T 14041.3 and GB/T 14041.4.

6.7 Filter element flow fatigue characteristics test It shall be carried out in accordance with the provisions of GB/T 17488.