norman filter company

Norman Filter Company

Media Type Descriptions◦ Woven Wire Mesh◦ Porous Sintered Metal◦ Random Metal Fiber

Element Construction◦ Pleating◦ Welding◦ Core/Collapse◦ Custom Design/Manufacturing

Acceptance Testing (Bubble Point)◦ ARP 901 Test Description◦ DEN 02-12 “NFC Bubble Point Specification”

NFC Internal Cleaning Capabilities

Introduction Surface Filtration – Removes particulate from stream

by stopping it at surface of filter media. Pleatable, Manufacturable in different forms

(cylindrical elements, cones, punched discs, etc.) Typically used where components must be

protected from particulate 10 microns and larger.

Materials of Construction◦ 316/316L Stainless Steel◦ 304/304L Stainless Steel◦ Titanium (Down to 20 um)◦ Inconel 625◦ Nickel 200/201

Micron Grades *◦ Nominal – “Subjective” rating defined between 90-

95% efficient at the nominal rating.

◦ Absolute – The largest spherical particle that will pass through the filter at controlled test conditions.

Standard Micron Filtration**

* Source: G. Bopp (main supplier of raw material

woven wire mesh)

** Nonstandard micron grades available for

custom designs

Nominal Rating Absolute Rating Wire Count

2X 10 325x2300

5 15 200x1400

10 18 165x1400

20 25 165x800

40 75 40x560

75 101 150x150

100 150 100x100

150 178 80x80

200 300 60x60

Dutch Twill Weave◦ Lower Micron Rating◦ Higher Strength◦ Higher Pressure Drop◦ Lower % Open Area

Square Weave◦ Higher Micron Rating◦ Lower Pressure Drop◦ Typically used as

support layer.◦ Higher % Open Area

Introduction Depth Filtration – Removes particulate by

trapping within structure of filter media. (Tortuosity)

Non-Pleatable, Typically manufactured in cylinder, rolled and welded cylinder, or discs.

Typically used where components must be protected from particulate in range of 0.2 to 20 microns.

Materials of Construction◦ 316/316L Stainless Steel◦ Bronze◦ Nickel 200

Micron Grades *◦ Note: Media Grades have efficiencies based off

testing performed per ASTM F795 (liquid) and IBR E304 (gas) shown below:

* Source: Mott Corporation (Porous

Sintered Metal Provider)

Porous Sintered Disc

Same Disc – 90X Magnification

Advantages◦ Much lower micron capabilities

Dis-Advantages◦ Larger pressure drops across media

◦ More difficult to clean and re-use.

Introduction Depth Filtration – Removes particulate by

trapping within structure of filter media(tortuosity).

Pleatable in most cases, Manufacturable in different forms (cylindrical elements, cones, punched discs, etc.)

Typically used where components must be protected from particulate in range of 1 to 100 microns.

Materials of Construction◦ 316/316L Stainless Steel

RMF Swatch

Same Swatch – 90X Magnification

Typical construction consists of:1. Element Media (single or multiple layers)

2. Core Tube (strengthens/supports media)

3. Weld Rings

4. End Fitting

5. End Plug

4 5

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Pleating Machine Pleated Wire Mesh

Pleating of the filter media is used to increase the effective filtration area within a given envelope size.

Since there is more media for a given fluid to pass through differential pressure through the filter element is lower.

Pleating can be incorporated into cartridge style elements and filter discs.

Three types of welds performed during elements manufacturing.◦ Mesh to Mesh (Resistance Welding or Micro-Tig

Welding)

◦ Mesh to Metal (Tig Welding)

◦ Metal to Metal (Tig Welding)

Allows the manufacture of “all welded” elements. Eliminates the use of epoxies that have fluid incompatibilities.

All welding performed by qualified procedures.

NFC manufactures the majority of our core tubes in house.◦ Spiral Wound and Welded◦ Machined

Spiral Wound◦ 316 or Nickel◦ Typical wall thicknesses .060” and .120”◦ Allows for collapse ratings greater than 4500 psid

Machined◦ Any material required based on design.◦ Thicknesses based on design.◦ Allows for tightly controlled collapse requirement.

Custom design completed through NFC engineering department to fit element into your system.◦ Cone shaped filters◦ Flat filters◦ Basket type filters

In house manufacturing allows short lead times on custom tooling required to assemble elements.

In house testing allows for quick validation of design.

ARP901 “Bubble Point Test Method” is the most common industry specification used/referenced for bubble point testing filter elements.

ARP901 is intended for wire mesh media, specifically twill dutch weave filter media.

Test sequence from ARP901 can be used for other medias, however, calculation values within the standard cannot.

Bubble Point testing used to ensure manufacturing process was completed as designed.◦ Correct Mesh Used

◦ Welding Imperfections have not occurred. (i.e. tigweld blow throughts or seam weld imperfections)

Bubble Point can be completed at mesh level, sub assembly level or full assembly level.◦ NFC employs BP testing depending on product to

maintain quality assurance through build process.

Wire Mesh Products◦ Swatch BP tested when raw material received.

◦ BP tested at sub assembly prior to welding end plug and end fittings.

◦ BP tested at final assembly post heat treatment.

Sintered and Random Metal Fiber Products◦ BP tested when raw material received.

◦ Product not BP tested at assembly level, instead microscope inspection takes place at weld joints to ensure blow throughs have not taken place.

Recommended Practice for measuring the largest pore size of a wire mesh element.

ARP901 Specification Describes◦ Test Setup◦ Test Method/Procedure◦ Science behind correlation of bubble point to pore size

(for wire mesh elements)◦ Equations to calculation largest pore size for twill dutch

weave mesh only.

Two test methods described in specification.◦ Precision “Referee Test”◦ Simpler Quality Assurance “go-no go” test (NFC Internal

Document DEN02-12 written off this test)

For dutch twill mesh the corresponding micron size can be calculated using the equation.◦ P=207/BPT (where 207 is constant for dutch twill mesh)

Example. Bubble point value found to be 22.3 in H2O◦ P=207/22.3

◦ P = 9.3 microns

NFC internal document DEN02-12 is used as NFC internal test standard and is based on ARP901. DEN02-12 accounts for wire mesh, sintered material, and random metal fiber material.

NFC Standard Operating Procedure:

Tests performed at swatch level, sub-assembly level, and full assembly level.


Tests performed at swatch level. One representative unit from lot tested at assembly level to ensure correct media used. Visual

inspection under magnification performed on remainder of lot to ensure blow through during welding did not occur.


Swatch test conducted prior to manufacturing/assembly. After swatch test visual inspection under magnification used post assembly to

ensure blow through has not occurred.

NFC developed internal document OPMF-500 “Hardware Cleaning” which covers piece part and assembly cleaning for all hardware manufactured at NFC.◦ Available for customer review upon request.

Current capabilities do no include certified cleaning and particulate counts.◦ If needed NFC will outsource certified/precision

cleaning to an NFC or customer approved vendor.

Hardware cleaning consists of typical hardware degreasers/part agitators and high pressure rinses post machining processes.

Element cleaning consists of ultrasonic baths using a variety of aqueous solutions depending on application.◦ Nitrogen purged drying completed on all elements

to ensure aqueous solution retention (and subsequent rusting/corrosion) within the mesh/media of parts do not occur.

norman filter company

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