Flow Indicators let plant engineers to monitor the flow and condition of granular solids, liquids or gases in the system. Flow indicators are either sight windows or stand alone piping components affixed to vessels or tanks. Flow indicators are inserted directly into the pipeline of the system.
General Information
Flow indicators inserted in the pipeline let a user view the material flowing through a pipeline. It also offers visual confirmation of more sophisticated controllers and indicators. It can be designed for being effective at most any temperature, flow and pressure.
There are two kinds of SFIs for pipeline applications: flat-disk and cylindrical window.
Equipment Design
Cylindrical sort flow indicators allow maximum visibility however, because of strength considerations, is restricted in use. They could have either sheathed or an unsheathed window.
Unsheathed kinds are more generally inserted in vertical pipelines, although could be used in horizontal pipelines in which only restricted strains are put on the indicator. Unsheathed kinds are sealed on the ends with gaskets for preventing leakage.
Sheathed Flow Indicators are stronger and utilized in both vertical and horizontal applications. The sheathed cylindrical shaped sight flow indicator has a metal sheathing surrounding the pipe. Sheathed sorts could be end sealed with gaskets however are usually sealed with the stuffing box seals.
For the reason that they are mechanically stronger, flat-disk window SFIs cover up a much larger range of applications than the cylindrical-sort. There are five plans of flat disk window sight flow indicators: rotary, flapper, plain, drip and ball.
Flow indicators have a bi-directional flap whose position point change in flow. In most of the designs, the flap could point in either direction. They are often used for viewing the flow of slightly opaque solutions or gases or transparent. These flow indicators are not suggested for downward flow.
Flow Meter Source 