Safety Interlocks and Used Equipment

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A functional evaluation for the earlier limit-switch interlock configurations and/or for the newer invisible detection means, often required actually simulating behaviors that are hazardous; that is, simulating reaching into a moving machine, opening a hinged guard when the machine is on, or functioning on/off switches at what could be inappropriate times. Rockford Systems (a provider of safety hardware and training) publishes a check list for light curtain installations that states: “Light curtains should be function-tested at every set up, operator and shift change, as well as every time after maintenance is performed. A third wave of safety interlocks, that are reportedly self-checking, are documented in the patent literature generally starting around the mid-1980s and into the 1990s. 2) Eighty (80) or 72% of the respondents indicated that all safety interlocks got exercised/ tested every time a machine is placed into production, and 31 or 28% indicated that safety interlocks do not get exercised/ tested when machines are placed into production. , springs, gravity, counterweights…) as basic elements of their design. Since all of these safety interlocks still required some surveillance to determine their functionality, it was often deemed useful to check these interlocks by exercising them and/or testing them on some timebased frequency. Of course pull back devices and two hand controls that were mis-adjusted and/or mis-positioned would not provide a consistent level of safety, hence the need to regularly examine their performance. These devices may not have had the same mechanical switches, alignment, and/or jamming considerations of the prior generation of mechanically activated switching mechanisms of earlier designs, but they too require some sort of functional testing. ”9 This standard language leaves the frequency of testing somewhat poorly defined and this was confirmed through contact with one of the major interlock suppliers who referenced ISO 13489, section 4. But in either case, it would seem reasonable that the brakes have been tested, what airbags are there work, and the seatbelts are compliant. While the survey resulted in a rate of 17 out of 100 respondents indicating their approval of using an interlock for the control of hazardous energy under LOTO conditions, this is not the current policy of OSHA. , Negative Mode monitoring senses guard is closed and allows machine to operate; Positive Mode monitoring senses the guard is not closed and that prevents machine from operating. 4) Over 77% indicated that the machine provider did not provide a frequency on which to test safety interlocks. Verification of the performance of safety interlocks did not guarantee future performance, but provided an opportunity to correct malfunctioning safety mechanisms, potentially before an accident. Often these sellers do not know of the past service life or intended service application of the used hardware forcing them, to some extent, to rely on the integrity of the original design, and the care of the new owner. , a motor will not be able to run), there is still a possibility of electrocution if the electrical power itself is not eliminated. That is the equipment was more of a salvaged item, perhaps to be used for spare parts or significant modification and upgrading by the purchaser. This may be due to possible mechanical, hydraulic, pneumatic, and/or electrical reasons. Questions concerning machine safety, safety interlocks, and used equipment safety included the issues of: the testing and/or exercising of safety interlocks, manufacturer’s directions on the frequency of testing and/or exercising safety interlocks, the need for testing of safety interlocks on used equipment, the implementation of “alternative” means over more traditional lockout/tagout procedures, the expectation that used equipment would have all the necessary safety equipment, and the failure of an interlock causing and/or contributing to an injury. This does not mean that if we purchase a 1964 car we expect it to have seatbelts (pre-mandatory seatbelt requirement), or that the purchase of all 2012 cars will give us the protection of airbags all around