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ISO-aligned QC · Borosilicate 3.3 · Pan India supply network
Flapper type double window sight flow indicator with hinged stainless flapper visible through the window
Double Window Sight Flow Indicators

Flapper Type Double Window Sight Flow Indicator

Hinged flapper flow indicator, 25NB to 400NB

Double window sight flow indicator with a hinged flapper whose angle indicates fluid velocity — for uni-directional flow, mounted horizontally or vertically with upward flow.

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At a glance
Product typeFlapper type double window sight flow indicator
Body materialWCB / MS / CF8 / CF8M / CF3M
FlapperCF8 / CF8M / CF3M, 1 off
GlassToughened borosilicate 3.3 or soda lime, 2 off
GasketPTFE, 4 off
FastenersG.I. / A2 / CF8
Size range25NB to 400NB
Face to face127 mm to 850 mm, tolerance ±3 mm

Product overview

What it does, and where it fits.

A flapper is a hinged stainless plate that the flow pushes aside. The angle it takes up indicates the velocity of the fluid, so the operator reads flow rate as a position rather than a rotation speed. It settles back closed when flow stops, giving an unambiguous no-flow indication.

Because the flapper depends on flow pushing it in one direction, it suits uni-directional service only, and it must be mounted horizontally or vertically with upward flow. Within those constraints it is simpler and has fewer moving parts than a rotary wheel.

The flapper is CF8, CF8M or CF3M, in a WCB, MS, CF8, CF8M or CF3M body, with dimensions matching the standard double window model.

Features

Built into every unit.

  • Position of the flapper indicates velocity of the fluid
  • Unambiguous closed position when there is no flow
  • Flapper in CF8 / CF8M / CF3M
  • Suitable for uni-directional flow
  • Mounted horizontally, or vertically with upward flow

Benefits

Why it earns its place in the line.

  • Reads flow rate as a position — simple and immediate
  • Fewer moving parts than a rotary wheel
  • Clear, definite no-flow indication
  • Robust flanged body drops straight into an existing line
  • Glass and gaskets replaceable in situ without cutting the pipework

Applications & industries

Where it is specified.

Typical applications

  • Uni-directional flow confirmation
  • Pump discharge monitoring
  • Batch transfer verification
  • Confirming that a line is actually flowing
  • Watching for colour change, cloudiness or phase separation

Industries served

  • Chemical processing
  • Pharmaceutical
  • Dairy & food
  • Water & effluent treatment
  • Agrochemicals
  • Paper & bleaching
  • Petrochemical
  • Distillation & solvent recovery

Technical data

Specification for Flapper Type Double Window Sight Flow Indicator.

Figures below are for this product only — every item in the range carries its own dimension table.

Flapper Type Double Window Sight Flow Indicator — technical specification
Product typeFlapper type double window sight flow indicator
Body materialWCB / MS / CF8 / CF8M / CF3M
FlapperCF8 / CF8M / CF3M, 1 off
GlassToughened borosilicate 3.3 or soda lime, 2 off
GasketPTFE, 4 off
FastenersG.I. / A2 / CF8
Size range25NB to 400NB
Face to face127 mm to 850 mm, tolerance ±3 mm
Flow directionUni-directional
MountingHorizontal, or vertical with upward flow
Flange standardANSI B-16.5; BS-10 Table E, BS-10 Table F and PN 10 also available
Flapper Type Double Window Sight Flow Indicator — dimensional table
SizeOD (±3)PCDH (No.)H dia.L (±3)
25NB10879416127
40NB12798416165
50NB152121419178
80NB191152419203
100NB229191819229
150NB279241822267
200NB343298822520
250NB4063621225600
300NB4834321225650
350NB5334761229760
400NB5975401629850

All dimensions in mm. Flange drilling to ANSI B-16.5; BS-10 Table E, BS-10 Table F and PN 10 drilling are also available — see the flange standards table.

Material specification
No.DescriptionQty.Material
1Body1WCB/MS/CF8/CF8M/CF3M
2Toughened glass2Borosilicate 3.3 / soda lime
3Gasket4PTFE
4Connectors2WCB/MS/CF8/CF8M/CF3M
5Fasteners—G.I./A2/CF8
6Flapper1CF8/CF8M/CF3M

Available on request

  • Choice of body MOC
  • Different flange standards

Exploded view

Every part, in assembly order.

Item numbers match the material specification table above.

Exploded assembly view of the Flapper Type Double Window Sight Flow Indicator showing numbered components

FAQ

Questions we are asked about this item.

No. The catalogue specifies horizontal mounting, or vertical with upward flow. Downward flow would let the flapper hang open and give a false reading.

No — it is for uni-directional flow. Use a rotary wheel type where flow can reverse.

Enquiry

Tell us your line size — we'll confirm the spec.

Send the bore, the media, the temperature and pressure, and the flange standard you work to. Drawings and custom sizes welcome.

Enquire on WhatsAppChat to us on +91 90336 30547 Request the datasheetWe will email the drawing for this item Talk to a technical expertMaterial selection and duty review Send a drawingWe fabricate to your isometric or sketch Request a custom sizeNon-standard bores, lengths and drilling

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