A-A-2953
3.1.1 UL 499 Conformance. Acceptable evidence of meeting the requirements of UL 499 shall be a UL label or listing mark, or a certified test report from an independent testing laboratory acceptable to the Government, indicating the electrical materials and components offered have been tested and conform to UL 499.
3.1.2 NFPA Conformance. Acceptable evidence of meeting the requirements of the National Fire Protection Association (NFPA) National Electrical Code Standard No. 70 shall be the manufacturer’s certified statement that the sealing machine conforms to the applicable NFPA requirements.
3.2 Construction. The sealing machines shall be of the jaw type, equipped with an electric impulse heating element, providing a heat flux density of not less than 250 W/in2 (0.1613 W/in2) for the heating element and uniformly heating the entire sealing area. The design of the machine shall allow for lubrication of friction points, easy replacement of parts, free operation of jaws at all temperatures, and protection of the operator from contact with parts at elevated temperatures. Both jaws shall have replaceable covers of polytetrafluorethylene glass cloth, or equivalent, to prevent adhesion of the work to the jaws.
3.2.1 Sealing cycle. During operation of the sealing cycle, both the heating and cooling timers shall not be interruptable or the times changeable after the operating switch has been activated except by activation of the master switch.
3.2.2 Master switch. A readily accessible master switch shall be provided to energize the control unit and provide emergency termination of the sealing cycle.
3.2.3 Indicator lamps. A red indicator lamp shall indicate that the controls are energized and thr sealing machine is ready for operation. An amber indicator lamp shall indicate a sealing cycle is in progress.
3.2.4 Timers. The sealing machines shall have timers to control the heating and cooling periods. The heating timer shall have a variable range from 0 to 2 seconds. The cooling timer shall have a variable range from 0 to 6 seconds. Both timers shall have scale calibration intervals of 1/10 to 1/2 second.
3.2.5 Fuses. Electrical heating elements shall be protected by a separate circuit switch with a fuse or manual reset circuit breaker.
3.2.6 Spring tension. The electrical impulse heating elements shall be firmly and securely held in place by springs under tension.
3.2.7 Jaws. At least one of the jaws shall have a resilient silicone, or equivalent, rubber cushion to compensate for variation in thickness and wrinkled lap joints.
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