Flow Indicator (Sight Glass)
The Batu Valve flow indicator (sight glass) allows the flow in a closed piping circuit to be observed visually. It shows the presence and direction of flow; it is not a measuring instrument and gives no flow rate value.
It is used in particular to check whether a steam trap is operating. The field of use is water, food, chemicals, air and other gases.
Batu Valve flow indicator
Type code: BAG-FL · BAG-Dİ
Connection: Flanged · threaded (double glass)
Size: DN 15 – 300 · R ½″ – R 2″
Pressure: PN 16 / 40
Body: Cast iron · cast steel · stainless steel
Glass: DIN 7080, tempered
Flow indicator types
Flow indicators are divided into four types according to the element that shows the flow:
- Plain glass (window)
- Flap
- Rotor
- Ball (used on vertical lines)
Installation
- The direction arrow on the body must point in the direction of flow.
- Straight pipe is allowed at the inlet and outlet; if the straight pipe at the inlet is insufficient, the moving element rotates irregularly.
- The operating limit is the maximum working pressure stated in bar on the indicator.
Fault symptoms
| Symptom | Meaning |
|---|---|
| Moving element not rotating | No flow, indicator installed in reverse, or deposits in the bearings |
| Element rotating irregularly | Insufficient straight pipe at the inlet |
| Misting on the glass | Sealing has deteriorated |
| Permanent film on the glass | The cleaning interval is shortened |
Inspection intervals
| Medium | Inspection |
|---|---|
| Clean water, air | Visual once a month; gasket and glass once a year |
| Medium with solid particles | Visual once a week; bearings every 6 months |
| Steam and hot media | Glass clouding every 3 months; gasket once a year |
| Corrosive medium | Every 3 months |
Glass, glass gasket, flange gasket and moving element are held as spare parts.
Frequently asked questions
No. A flow indicator serves to confirm visually the presence and direction of flow; it is not a measuring instrument.
It is used to monitor flow in closed piping circuits. It serves in particular to check whether a steam trap is operating.
There are three possible causes: there is no flow in the line, the indicator is installed in reverse, or there are deposits in the bearings.
Related products and documents
- Product PageFlow Indicator
- InstructionsFlow Indicator Maintenance & Safe Use Instructions
- Technical documentValve Technical Documents
See also
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