Purge Systems for enclosures play a very critical role in industries that deal with explosive gases or dust. General purpose equipment cannot be used in these areas due to safety requirements. The NFPA Code 496 has established rules to allow purging of enclosures to reduce the internal classification.
Triad Control Systems (“Triad”) builds its purge systems to meet the ISA and NFPA codes that require a specific quantity of positive air flow to eliminate any hazardous gas or dust that may be present. The purge system then maintains a positive pressure within
the enclosure to prevent gas or dust from re-entering.
This process allows the use of less expensive NEMA 4 enclosures because the internal atmosphere is safe. The Z purge allow use of general purpose equipment inside the enclosure. Type X and Y purges require hermetically sealed equipment or explosion proof equipment that has a lower rating.
Purge types and area class reductions are as follows:
Reference NFPA Code 496, and ISA Code S12.4 for additional information.
Triad Purge Systems are constructed of:
316 S.S. Mounting Plates, Tubing, Fittings, and Needle Valves.
Non-corrosive materials are used for:
Regulators, Gauges, Flowmeters, Pressure Switches, and Vents.
Special materials and designs can be provided to handle specific applications. (Consult Factory)
Triad Purge Systems include:
Right-Hand or Left-Hand Mounting Plate, Bowl Filter-Regulator, Supply Fitting, Adjustable Flow Indicator, Pressure Indicator with Warning Label.
Enclosure area not to exceed 10 cubic feet. With adjustable flowrate, and bulkhead vent.
For enclosures up to 10 cubic feet plus pressure switch for alarm contacts, and bulkhead vent.
Enclosure area exceeds 10 but does not exceed 50 cubic feet plus pressure switch for alarm contacts. 1” spark arresting vent required.
Enclosure area exceeds 50 but does not exceed 150 cubic feet plus pressure switch for alarm contacts. Spark arresting vent required.
Installation Kit: Stainless Steal Bolts, Nuts, Pre-bent Tubing and Bulkhead Fittings. Specify Right-Hand or Left-Hand Mount.
1 inch NPT Spark Arresting Vent, Aluminum Construction.
1 inch NPT Spark Arresting Vent, Stainless Steel Construction.
2 inch NPT Spark Arresting Vent, Aluminum Construction.
2 inch NPT Spark Arresting Vent, Stainless Steel Construction
Note: Enclosures to be fitted with type, Y Purge Systems need to comply with NFPA Code 496 Article 2-4 and ISA Code S12.4 Article 5.2 Z Purge Systems need to comply with NFPA Code 496 Article 2-3 and ISA Code S12.4 Article 5.1
Type X is the most complex of all the purge systems. It is used in areas which have hazardous vapors or dust present at all times. The start-up instructions are critical and must be followed precisely.
The system detects when the flow is sufficient to start purging. The panel is deenergized until a predetermined time has elapsed, then energized as long as a safe pressure is detected. Pressure loss below the safe level will cause the system to deenergize and open the alarm contacts shutting down power to the enclosure.
Enclosure area does not exceed 10 cubic feet. Panel vent included (167).
Enclosure area exceeds 10 but does not exceed 50 cubic feet. Panel vent included (167).
Enclosure area exceeds 50 but does not exceed 150 cubic feet. Panel vent included (267).
Options: See above.
Note: Enclosures to be fitted with Type X Purge Systems need to comply with NFPA Code 496, Article 2-4 & ISA Code S12.4, Article 5.3