High level switch

Install high-high level switch in receiving vessel interlocked to feed and/or emergency dump... 

Active—Using controls, safety interlocks, and emergency shutdown systems to detect and correct process deviations e.g., a pump that is shut off by a high level switch in the downstream tank when the tank is 90% full. These systems are commonly referred to as engineering controls. 

High-level switch on storage tank which shuts off transfer system... 

LC Level controller LDV Let down valve LHV Lower heating value LH2 or LH2 Liquid hydrogen LN2 or LN2 Liquid nitrogen LNG Liquefied natural gas LSH High level switch LP Low pressure LT Level transmitter... 

Standard control methods are used for the WFI tank. A water high level switch (LSH) turns the WFI still off or on depending on whether the water level is at or below the LSH point. A water low level switch (LSL) is interlocked to the recirculation pump to shut it off should the level reach the LSL point. 

Using the T-lOO example once more, the control maybe a high-level switch that shuts off the incoming flow. The demand would be a requirement that the switch be activated when the liquid in T-lOO reaches a certain level. If this control fails then the likelihood of a tank overflow occurring is increased because this barrier has been overcome. 

Pumping must be from a redundant system with a UPS, because the collection tank usually has little extra volume and can easily overflow. A high-high level switch is normally used to activate the standby pump. 

It is important that silos be equipped with high-level switches and an alarm—either audible or visual—to alert personnel that the silo is full and avoid a situation where material backs up and clogs the fill line. It is, of course, always advisable to assure that the empty volume in a silo is sufficient to hold a truck load of resin prior to calling for delivery. 

A high-level switch must be utilized with this unloader. Most often, the rotating paddle type is used. The switches themselves are mounted in the silo deck with the paddles mounted on extension shafts. Extensions must be used because of the angle of repose the material adopts when loaded into the silo. When material contacts the paddle, the unit is shut off. The pumping system itself utilizes a positive displacement motor/blower assembly. The inlet of the pump is fitted with a two-stage secondary filter. The purpose of this filter is to prevent... 

The loader control panel, which may be mounted on the unit or at a remote point, contains motor starters, timers, high- and low-level switch lights and, on multiple silo systems, a selector switch to energize the proper high-level switch for automatic operation. When the operator wishes to change from loading one silo to another, the flex-hose connections to the material and vacuum line of the new tank must be changed and the tank selector switch on the control panel must be positioned to the new silo. The system is then ready to run. 

Overfill protection alarms or shutdown systems using high level switches or other two-state detectors may be inactive for long periods and may develop unrevealed faults. Such faults cause the system to fail to danger when required to operate. 

A high-level alarm on a knockout drum immediately ahead of a compressor, a high—high level switch to shut down the prime mover, and an alarm to indicate that the machine has shut down. 

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