Filter medium
The present invention relates to a filter medium comprising a substrate and a fine fiber layer on top of the substrate, wherein the substrate comprises a first layer comprising first fibers having a first average diameter and a first maximum fiber length; a second layer comprising second fibers having a second average diameter and a second maximum fiber length; and a third layer comprising third fibers having a third average diameter and a third maximum fiber length; wherein the boundary area between the first and the second layer forms a first blended area comprising first and second fibers; and the boundary area between the second and the third layer forms a second blended area comprising second and third fibers; and wherein the first and the third average diameters are each larger than the second average diameter.
1. A method for the use of a filter medium in filtering a fluid, in particular in heating ventilation and air conditioning filters and gas turbine intake air filtration applications, said fluid comprising particles, said filter medium comprising a substrate and a fine fiber layer on top of the substrate, wherein the substrate comprises
a first layer comprising first fibers having a first average diameter and a first maximum fiber length;
a second layer comprising second fibers having a second average diameter and a second maximum fiber length; and
a third layer comprising third fibers having a third average diameter and a third maximum fiber length;
wherein
the boundary area between the first and the second layer forms a first blended area comprising a first homogeneous mixture of first and second fibers; and
the boundary area between the second and the third layer forms a second blended area comprising a second homogeneous mixture of second and third fibers;
and wherein the first and the third average diameters are each larger than the second average diameter; and
wherein the method comprises the steps of:
a. introducing the fluid to the filter medium at an entry side corresponding to the third layer,
b. passing the fluid through the third layer to capture a first amount of the particles having a first average particle size,
c. passing the fluid through the second layer to capture a second amount of the particles wherein said second amount of the particles has a second average particle size,
d. passing the fluid through the first layer,
e. passing the fluid through the fine fiber layer to capture a third amount of the particles, and
f. removing the fluid from the filter medium at an exit side corresponding to the fine fiber layer.
2. A method for the use of a filter element including a filter medium in filtering a fluid, in particular in heating ventilation and air condition filters and gas turbine intake air filtration applications, said fluid comprising particles, said filter medium comprising a substrate and a fine fiber layer on top of the substrate, wherein the substrate comprises
a first layer comprising first fibers having a first average diameter and a first maximum fiber length;
a second layer comprising second fibers having a second average diameter and a second maximum fiber length; and
a third layer comprising third fibers having a third average diameter and a third maximum fiber length;
wherein
the boundary area between the first and the second layer forms a first blended area comprising a first homogeneous mixture of first and second fibers; and
the boundary area between the second and the third layer forms a second blended area comprising a second homogeneous mixture of second and third fibers;
and wherein the first and the third average diameters are each larger than the second average diameter; and
wherein the method comprises the steps of:
a. introducing the fluid to the filter medium at an entry side corresponding to the third layer,
b. passing the fluid through the third layer to capture a first amount of the particles having a first average particle size,
c. passing the fluid through the second layer to capture a second amount of the particles wherein said second amount of the particles has a second average particle size,
d. passing the fluid through the third layer,
e. passing the fluid through the fine fiber layer to capture a third amount of the particles, and
f. removing the fluid from the filter medium at an exit side corresponding to the fine fiber layer.
3. The method of claim 1 , wherein the second average particle size is smaller than the first average particle size.
4. The method of claim 1 , wherein the step of passing the fluid through the first layer decreases a face velocity of the third amount of the particles.
5. The method of claim 1 , wherein the filter medium has been pleated.
6. The method of claim 1 , further comprising the step of:
g. reversing the fluid flow to effectively clean the filter medium.
7. The method of claim 1 , wherein the filter medium has a bending stiffness of at least 500 mg.
8. The method of claim 1 , wherein the filter medium has an air permeability of at least 5 cfm.
9. The method of claim 1 , wherein the filter medium has a filtration efficiency of more than 35% against 0.4 μm particles.
10. The method of claim 2 , wherein the second average particle size is smaller than the first average particle size.
11. The method of claim 2 , wherein the step of passing the fluid through the first layer decreases a face velocity of a third amount of the particles.
12. The method of claim 2 , wherein the filter medium has been pleated.
13. The method of claim 2 , further comprising the step of:
g. reversing the fluid flow to effectively clean the filter medium.
14. The method of claim 2 , wherein the filter medium has a bending stiffness of at least 500 mg.
15. The method of claim 2 , wherein the filter medium has an air permeability of at least 5 cfm.
16. The method of claim 2 , wherein the filter medium has a filtration efficiency of more than 35% against 0.4 μm particles.