PurityPlus® producers are an organization 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 satisfy. Our thorough SOP/QA program was originally defined, tested and coordinated by AsteRisk, LLC., a gas-industry consulting company administered 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/
Integral to the program are a sequence of levels or tiers that define the capabilities of each member. 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 qualified 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 lower pressure in a single step to produce pressure within a defined range. Regulators devised accordingly will show a small variation in delivery pressure as the cylinder pressure falls during use. For this reason, single-stage regulators are most appropriate for applications where a constant outlet pressure is not urgent, where an operator can supervise and readjust pressure, or where inlet pressure is stable.
Dual-stage regulators perform the same function as single-stage regulators. However, delivery pressure holds constant as cylinder pressure declines. Increased accuracy in pressure control is kept because the pressure reduction is delivered in two steps. Dual-stage regulators are favored for applications calling for a constant outlet pressure throughout the life of a gas cylinder.
In our terms, we refer back to two definitions:
• NIST - Traceability can be established as an unbroken record of documentation ("documentation traceability") or an uninterrupted chain of measurements and associated uncertainties ("metrological traceability"). As applied 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 trackable back to NIST’s Standard Reference Materials where such comparative gas standards exist. When particular SRM’s do not exist, equivalent commensurate 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.