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Jul 2019

Semiconductor Wafer Fabs Improve the Safety of Bulk Oxygen Gas Systems with Mott’s Penta® Nickel Porous Metal Filters

Nobody wants to see this scene, let alone be the cause of it.

What Happened?

High pressure Oxygen systems are susceptible to adiabatic compression ignition when materials that cannot withstand a high ignition energy, like Teflon, are used in the system. As you can see, the results can be catastrophic.

According to Compressed Gas Association’s (CGA) Oxygen Pipeline and Piping Systems: Filter elements are impingement locations that are considered high risk, due to their particle-retention function. Elements are also "high surface area to volume" components which, depending on the material used, might easily ignite. As such, element material selection requires additional care.  Systems should be designed to avoid the likelihood of filter or strainer operation in reverse flow. Common filter-element materials include, but are not necessarily limited to, sintered nickel.

What is Adiabatic Compression Ignition?

Adiabatic compression is also known as the “GAS HAMMER” effect or Metal Fire.

In a high pressure Oxygen system at 99.5% purity, when a valve is opened quickly, the oxygen will rush into the high-pressure tubing and adiabatic compression can occur when it reaches the end of the tubing at the next valve or regulator; there, the pressure will briefly be much higher than the filling pressure of the Oxygen source.

It is adiabatic because the compression happens without any heat input from the outside.  However, the result is that compression heat is generated locally, so that we see higher than normal pressure and increased temperature, making the materials in contact with the Oxygen that much more critical; normally non-flammable materials become flammable when in contact with high pressure Oxygen at higher temperatures.

Avoid Oxygen Ignition, Improve Performance, and Reduce Your Cost of Ownership

Sintered Nickel powder provides the best protection against Oxygen ignition.

  • Nickel has a higher ignition temperature than plastic, Teflon or 316 Stainless Steel
  • The high surface area of a Nickel Filter Element acts as a heat sink to quench any potential flame

Added benefits of Nickel include:

  • Nickel has hydrophobic qualities, resulting in 2 hours of dry down rather than days
  • The cost is comparable to Teflon at higher flows, for a higher integrity material that lasts longer than Teflon, therefore minimizing your cost of ownership while maximizing your safety

Note: Attempts to use Nickel screens in front of Teflon filters are wholly inadequate and potentially dangerous because the screen does not help to reduce the high temperatures of adiabatic pressure buildup.

The Mott Solution

Mott Porous Bulk Gas FilterGASSHIELD® POINT-OF-USE PENTA® NICKEL BULK FILTERS

  • Hydrophobic, resulting in dry time to 10 ppb of H2O in minutes, not hours
  • 1.5 nm Filtration (industry standard is 3 nm)
  • Proven in fabs for over 15 years
  • PENTA® Nickel Media
  • Lower dp
  • Available in flow rates from 1500 SLPM to 60,000 SLPM
  • Comparable in cost to Teflon at higher flow rates

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