Conventional Valves -

Butterfly Valves

Butterfly Valves

SIGMAFLOW Butterfly valves have widespread usage among diverse industries and applications such as water supply, wastewater treatment, fire protection, gas supply, fuel handling, pharmaceutical, chemical and oil, food etc. These valves are available in very large sizes and are suitable for handling slurries, and liquids with relatively large amounts of solids at low pressures.

Butterfly valve is essentially a quarter turn, shut-off valve with a relatively simple construction. In closed position, the disc blocks the valve bore; while in open position, the disc is turned to allow flow. The valves can be operated by levers, gears or actuators according to your specific need.

Manufacturing & testing conformity :

  • General Design & Manufacturing : IS13095/API609/EN593(BS5155)
  • Valve Inspection & Testing : IS13095/API598/EN12266

Advantages of SIGMAFLOW Butterfly valves :

  • Allows bi-directional flow of fluid and provides air tight shut-off at full rated pressure
  • Ease of operation, low operating torques
  • Compact, light-weight
  • Can be easily installed or replaced
  • Need very little maintenance

Salient features of SIGMAFLOW Butterfly valves :

  • Valve body and disc can be of ductile cast iron, grey cast iron and MS fabricated.
  • Rigid and sturdy design with minimum loss of head across the valve
  • Surface protection with epoxy
  • Long and short face-to-face length
  • Long service life; Wear resistant
  • Corrosion proof seat with plasma deposit

Wafer-style [50 NB to 300 NB]

A wafer-style butterfly valve is the most economical version and it is sandwiched between two pipe flanges. The pipe flanges are connected through long bolts that cross the entire valve body. The sealing between the valve and pipe flanges is accomplished via gaskets, O-rings, and flat valve faces on both sides of the valve.

Lug-style [50 NB to 600 NB]

The lug-style butterfly valve has threaded inserts (lugs) outside the valve body. Two sets of bolts connect pipe flanges to each side of the bolt inserts without nuts. This design enables the disconnection of one side without affecting the other for dead-end service. The lug-style butterfly valves, unlike the wafer-style, carry the weight of the piping through the valve body.

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Flanged end[150NB to 2400NB]

The double flanged body pattern ensures precise installation in pipeline, and can be used as an end to the line valve if required. The unique feature of this valve is its adaptability for lined pipes, due to negligible disc protrusion beyond the body laying length. The unique design enables easy change over from hand lever operation to actuated operation when required.



Butterfly valves can be concentric or eccentric depending on the location of the stem in relation to the disc and the seat surface angle on which the disc closes.

  • Concentric : In a centric or concentric butterfly valve, the stem passes through the centre-line of the disc which is in the centre of the pipe bore and the seat is the inside diameter periphery of the valve body. Here, the disc comes into contact with the seat at around 85° during a 90° rotation. These are used for low pressure ranges.


  • Single eccentric:In this type, the stem does not pass through the centre-line of the disc, but instead behind it (opposite of flow direction). When the stem is located right behind the centre-line of the disc, the valve is called single-offset. This reduces the disc contact with the seal before full closure of the valve and thus improves service life of the valve.


Installation of Butterfly valve


  • Check and verify that the dimensions of the valve and pipeline matches.
  • Spread the flange enough to allow the valve with disc in closed position. This prevents the damage of disc and seat during installation.
  • Insert the bolts through the two bottom pipe flange holes to rest valve on during installation.
  • Insert the remaining flange bolts after aligning the valve with flanges and tighten the bolts partially.
  • Open the valve completely and tighten the flange bolts evenly with adequate torque to prevent the leakage between flange and valve.
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