Switch loading

Note Section A-5-6.3 of the 1996 edition of NFPA30 (reiterated in NFPA385) contains erroneous information about switch loading. 

Is switch loading in operation If so, have the hazards been recognized ... 

Switching loads Loads imposed by the operation of both opening and closing of switchgear. 

Problems may arise with switch-loading of road tankers, ships or pipelines and with the use of returnable containers. The important considerations for safety are ... 

Doer Locks Temperature Turbidity Float switches Load... 

Figure 1. GC/MS analysis of a methanol extract ofS-5 fuel from switch-load testing of o-rings immersed in JP-5 followed by immersion in S-5.

Through the use of switch-loading tests and an analytical method based on methanol extraction followed by GC/MS analysis, several possible compounds were identified for individual testing as possible swelling agents for synthetic... 

PILOT DUTY RELAY - A relay used for switching loads such as another relay or solenoid valve coils. The pilot duty relay contacts are located in a second control circuit. Pilot duty relays are rated in volt-amperes (VA). 

A computerized power-demand controller provides an effective method of managing peak demand. A controller can analyze the options available and switch loads as needed to maintain a relatively constant power demand from the utihty company. Such systems are programmed to recognize which loads have priority and which loads are nonessential. Power demand then is automatically adjusted by the computer, based on the rate schedule of the utility company. 

Switch loading occurs when a tank tmck carries a low flash point material such as gasoline and then carries a liquid (such as heating oil) with a higher flash point without first purging the vapor space. This practice can create static ignition hazards because the heavier material can absorb some of the vapor left behind from the low flash product. Hence, the vapor space may no longer be fuel rich and an explosive mixture may form. 

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