PurityPlus® producers are a group of Independently Owned Specialty Gas producers in North America working through the Independent Welding Distributors Cooperative. A key part of the PurityPlus program is it's consistent Standard Operating and Quality Assurance Procedures that all producers must pass. Our comprehensive SOP/QA program was originally designed, tested and coordinated by AsteRisk, LLC., a gas-industry consulting company organized by a long-term employee of Union Carbide/Praxair. PurityPlus® continues to utilize AsteRisk for its third-party auditing, as well as operations and safety consulting. http://www.asteriskllc.com/
Elemental to the program are a sequence of levels or tiers that define the qualifications of each partner. These tiers define the process and analytical capabilities necessary to supply gases of defined purities, aligning with generally accepted impurity maximums and analytical tolerances. For example, all certified PurityPlus® producers can package and certify nitrogen and argon to grade 5.0 (ultra high purity.) Moving up in the tiers usually requires the purchase of further analytical and gas-filling equipment to fill higher purity atmospheric gases. Calibration and verification is carried out through NIST-traceable standards, most typically SRM’s, and verified by annual round-robin testing.
Single-stage regulators reduce pressure in a single step to effect pressure within a specific range. Regulators designed in this way will show a slight variation in delivery pressure as the cylinder pressure falls during use. This is why single-stage regulators are most appropriate for jobs where a constant outlet pressure is not crucial, where an operator can supervise and readjust pressure, or where inlet pressure is steady.
Dual-stage regulators perform the same function as single-stage regulators. That said, delivery pressure holds constant as cylinder pressure decreases. Greater accuracy in pressure control is kept because the pressure reduction is achieved in two steps. Dual-stage regulators are favored for applications necessitating a constant outlet pressure for the life of a gas cylinder.
In our terms, we refer back to two definitions:
• NIST - Traceability can be defined as an unbroken record of documentation ("documentation traceability") or an nonstop chain of measurements and associated uncertainties ("metrological traceability"). As used here, the word "traceability" always means "metrological traceability."
• ISO 17025 - “property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty”
PurityPlus® specialty gases’ specifications are traceable back to NIST’s Standard Reference Materials where such comparative gas standards exist. When particular SRM’s do not exist, equivalent comparative standards are used, either directly sourced from another designated national government agency outside the US, or by having a gas standard analyzed and certified by NIST or other designated entity.
PurityPlus® Specialty Gases offers several grades of calibration gas standards – Custom Mixtures, Certified Standards, and Primary Standards to meet the level of accuracy for your laboratory or production process. All PurityPlus® Specialty Gases are custom-mixed and analyzed, and then properly labeled in one of our independently audited laboratory facilities. Each PurityPlus® Production facility conforms to a strict set of quality-assurance measures and standard operating procedures. Each of these labs have been thoroughly inspected, certified and documented to be compliant with FDA, DOT, OSHA, and EPA requirements - among others - by AsteRisk, a globally known, reputable, independent certification company headquartered in the U.S.
Exposure to hazardous chemicals results in steep fines, penalties, and a compromised workforce. PurityPlus® Specialty Gases meets regulations and ensures compliance with all primary and certified standards.