Filter Testing

Product validation is important in any industry, but no more so than the filtration industry. In many cases, filter elements and assemblies are the final opportunities to stop any particulate from contaminating your vital system components.

Norman Filter Company has a variety of in-house test stands that we operate to both internal and industry specifications. Whether you need non-destructive strength testing such as proof pressure or helium leak, or filter element micron size validation such as bubble point testing, we have you covered.

We also perform destructive testing, such as burst testing, that is carried out to the filters failure, in order to understand the filters performance and material behavior under different pressure ratings. NFC performs these types of tests to determine the filters ability to retain liquids and or gasses that may flow through the component through the most critical of times.

NFC also has the ability to design and construct a specialty test stands to test our filters to the precise requirements you need.

Proof and Burst:

Proof and Burst Testing is performed to validate the working pressure of filter housings and pressure vessels. Proof and Burst Pressure Testing is performed using hydraulic oil in accordance with in-house testing procedures. Proof pressure testing is typically performed at 1.5 times the maximum allowable working pressure of the filter housing for a pre-determined period of time to ensure the filter housing performs as designed.

Burst pressure testing is utilized for new housing designs to determine the pressure at which the filter housing fails. Our in-house test stand operates up to 50,000 PSI and all data is electronically logged.

Testing Specifications:

  • Test Pressure: 0-50,000 PSI Maximum
  • Duration: 15 minutes (Typical)
  • Procedure: OPMF-56 – Hydraulic Proof Burst Pressure Set-Up & Test (Typical)

Helium Leak Test: Non-Destructive

Helium Leak Testing is set to validate seals and weld joints of filter housings and pressure vessels. Our Ii house helium leak testing is performed by submerging the filter housing into deionized water, raising helium pressure to the desired testing specification and observing sealing surfaces and welds for bubbles. This method of detection is valid to a leakage rate of 1×10-4 cubic centimeters per second at standard temperature and pressure. Testing is typically performed for 1 minute in increments of 25%, 50%, 75%, and 100% of the working pressure. Our in-house test stand operates up to 22,500 PSI and all data is electronically logged.

Testing Specifications:

  • Test Pressure: 0-22,500 PSI Maximum
  • Duration: 1 minute at each of 25%, 50%, 75%, and 100% MAWP (Typical)
  • Procedure: OPMF-62 – Pneumatic Proof Pressure & Bubble Tight Leak Set-Up and Test (Typical)

Flow Test: Non-Destructive

Gas or Liquid Flow Testing is set to validate pressure drop across housing and filter elements. Norman Filter Company has the ability to perform flow testing using water for liquid applications and nitrogen or helium for gaseous applications. Filter flow testing is performed to understand the differential pressure from the inlet of the filter housing to the exit of the filter housing. All flow testing is performed on NFC built test stands which utilize electronic data logging to record system pressure, system temperature, and differential pressure.

Liquid Test Stand Capabilities:

  • Flow Rate: 0-350 GPM maximum
  • Fluid: Water

Pneumatic Test Stand Capabilities:

  • Flow Rate: Contact NFC Engineering Department
  • Fluids: Nitrogen or Helium
  • System Pressure: 0-2,000 psi *

We offer high-pressure test stands can be constructed for flow testing. NFC has the ability to design and construct test stands to meet requirements outside the ranges noted above.

Bubble Point Testing: Non-Destructive

Bubble Point Testing is typically performed using the industry standard SAE ARP901 “Bubble Point Test Method”. Bubble point testing is used by NFC as standard manufacturing quality control check for our stainless steel woven wire mesh elements, and welded disc assemblies. The tests are performed to ensure the welding process and filter mesh elements being used are up to our strict quality standards.

NFC has several bubble point test fixtures, dependent on the type of product being tested in-house. Bubble point testing consists of attaching a clean, dry compressed air line through a seal at the filter inlet, the pressure is then slowly raised using a pressure regulator until the first steady stream of bubbles is observed. A manometer is used to measure the pressure at which the first stream of bubbles occurs. This measurement is related to the largest pore size of the filter element.  

Although ARP901 is a “Recommended Practice”, Bubble Point Testing is used as an industry standard to determine the largest (absolute) micron size of a given filter element. This test is typically used as an acceptance test when a stringent requirement is needed for aerospace applications. NFC’s standard manufacturing process includes bubble point testing at several different manufacturing stages conducted using sampling size with a zero-defect policy.

Specialty Testing:

Our team has the ability to design and construct various types of other test stands depending on our customer’s requirements.

Some projects may require testing above and beyond NFC standard testing. In these cases, NFC has the ability to design and construct a specialty test stands to validate filter design requirements. NFC also maintains a list of approved suppliers to ensure your testing needs can be met.

The following examples are test stands constructed at NFC for non-standard tests:

Dirt Loading (hydraulic) – This NFC built test stand allowed ISO 12103-1 fine test dust to be added during the test to determine the maximum amount (by weight) that could be added before the filter element under test catastrophically collapsed. 

Contaminated pressure drop (pneumatic) – This NFC built test stand allowed ISO 12103-1 fine and coarse test dust to be added during the test to determine the maximum amount (by weight) of particulate that could be added before the filter under test could no longer pass contaminated pressure drop requirements.

Slam Start (Pneumatic) – This collaborative effort with Purdue University Zucrow Laboratory utilized high-frequency pressure sensors and a fast-acting solenoid valve to quickly release 0-4000 PSI Helium across the filter under test in under 10 ms.

The following are examples of non-standard tests conducted at approved NFC sub-tier test houses:

Cryogenic Sealing Test – This test was conducted by submerging a filter assembly into liquid nitrogen where the filter soaked for a given time period to ensure all surfaces were at the desired soak temperature, then helium leak testing was conducted at this temperature to ensure the seal operated as designed.

Shock Testing MIL-S-901 – Several T-Type filters have been tested and approved per MIL-S-901 “High Impact for Mechanical Shock”.

To learn more about Norman Filter Company and our engineering capabilities please visit us at!

Norman Filter Company was established in 1978 as a manufacturer of hydraulic filters and filtration systems for the industrial and aerospace markets. Over time, design and testing capabilities have been added to provide maximum value to our customers. Norman Filters offers a diverse filtration product line including high, medium and low pressure inline and T-Type standard filtration solutions. In addition, Norman Filters provides custom design and manufacturing solutions to meet our customer’s unique needs. All product is designed and manufactured at our Bridgeview, IL facility.


AS9100D • ISO 9001 Certified


Engineered, Manufactured & Tested in the USA


Have questions, or can’t find what you are looking for?

Contact Us