Solenoid Controlled Systems

Solenoid SV-115 vents all actuating air pressure from flow control valve FV-38 whenever its coil is de-energized. Thus, SV-115 is “normally energized” to maintain actuating air pressure to FV-38.

Solenoids SV-111, SV-112, and SV-113 act to prevent fuel gas from reaching the incinerator’s burner assembly when the Burner Management System (BMS) sends a trip signal. SV-111 and SV-112 are block valves, while SV-113 is a bleed (“vent”) valve, making this a “double-block and bleed” valve arrangement. A similar solenoid valve arrangement can be seen on the pilot burner gas line with solenoids SV-101, SV-102, and SV-103.

{\bullet} Identify the statuses of SV-92 and LV-92 when the separator boot liquid level is at or below the normal level of 1 foot 4 inches.

LV-92 will be closed, and SV-92’s coil will be de-energized.

{\bullet} Describe how this system responds to high liquid levels in the separator boot.

If LT-92 senses a high liquid level, controller LIC-92 will respond by applying electrical power to SV-92. When SV-92 actuates, it sends instrument air to the diaphragm actuator of LV-92 to cause that drain valve to open. As LV-92 drains liquid out of the boot, the level sensed by LT-92 decreases over time, eventually to a point where controller LIC-92 stops sending power to the coil of SV-92.

{\bullet} What will be the consequence of an instrument air supply failure, as it relates to the separator boot liquid level?

Without instrument air supply (IAS), the level drain valve LV-92 can never open and the separator boot liquid level will rise unabated. Eventually LSHH-231 will detect the high-high level condition and command the Emergency Shut-Down (ESD) system to turn the compressor off in order to avoid damaging that machine.

{\bullet} What will be the consequence of an AC power failure to LIC-92?

Without AC power to energized the coil of solenoid SV-92, the level drain valve LV-92 will never be commanded to open by SV-92 and the separator boot liquid level will rise unabated. Eventually LSHH-231 will detect the high-high level condition and command the Emergency Shut-Down (ESD) system to turn the compressor off in order to avoid damaging that machine.

{\bullet} The typical status of the output switch contact on TY-135 (NO or NC)

TY-135’s output must typically be conducting (switch contacts closed) in order to pass AC power on to the coil of the solenoid valve and maintain its “normally energized” status.

{\bullet} The effect of an AC power loss from breaker #4

The solenoid coil would de-energized, venting air pressure from the input of TV-135 and causing that process valve to go to its “fail” (closed) position.

{\bullet} The effect of the solenoid vent becoming plugged or accidentally capped by a technician

If ever the discrete controller TY-135 commands the solenoid valve to trip, it would force TV-135 to hold its position rather than close as it should.