Solenoid valve SV-92 plays an important role in this compressor inlet separator control system. Level control valve LV-92 opens up when needed to drain liquid out of the “boot” of the separator vessel, which ideally contains only gas (vapor).

Examine this P&ID and then answer the following questions:

Questions :

1. 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.
2. Describe how this system responds to high liquid levels in the separator boot.
3. What will be the consequence of an instrument air supply failure, as it relates to the separator boot liquid level?
4. What will be the consequence of an AC power failure to LIC-92?

Answers :

1. 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.
2. 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.
3.  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.
4. 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

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