Level sight glass
A vertical glass tube against a vessel wall, tagged LG. Mechanical-only level indication for the operator at the equipment. No wires, no PLC channel, never on the I/O list.
Read one of your own drawings.
Drop a P&ID, instrument index, or schedule. Tagsight reads it to the tag and opens a workspace you keep when you sign in.
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How it’s drawn.
A glass tube drawn against the vessel wall, tagged LG. It is a mechanical local indicator the operator reads at the equipment, with no signal and no actuator. It often appears alongside an electrical level transmitter on the same vessel.
Typical usage.
Vessel side-mount for operator local indication, redundancy alongside an electrical level transmitter, regulatory requirement on certain SIS-classified storage vessels. The LG always shows on the instrument index but never on the I/O list.
Telling it apart.
- A sight glass is local indication only. It has no signal behind it and is read by eye at the vessel.
- An LG and a level transmitter can sit on the same vessel. The glass is the manual backup to the electrical measurement.
- Mechanical indicators like this are drawn for the operator at the equipment, not as a remote reading.