Short Description

Model No.: Double-Offset-Butterfly-Valve

China Valves Manufacturer www.sfutube.com offers Double Offset Butterfly Valve.

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Key Specifications / Features

Type: double offset butterfly valve
Material: A536,A126,WCB,LCB,CF8,CF8M.CF3.CF3M,CN7M,904L
Size: 1″ (DN25) – 80″ (DN2000)
Pressure:  Class150~1500LBS (PN16~PN160)
Connection type: Wafer Double Offset Butterfly Valve, Lugged Double Offset Butterfly Valve, Flanged Double Offset Butterfly Valve
Kind of drive: wrench, gear, electric actuators and pneumatic actuators
Operating temperature: -100℃ – 190℃
Working medium: water, gas, oil,concrete, Sulfuric acid and hydrochloric acid
Testing: API 598, ISO 5208
Pressure-Temperature Rating: API 609
Value Design: ASME B16.34, MSS-SP-68
Anti-Blow-Out Stem: API 609
Facc-to-Face: API 609, MSS-SP-68, ISO 5752
Fire Safe: API 607
Low Fugitive Emission Gland Packing System: DIN3780, MSS-SP-143
Marking: MSS-SP-25, API 609
Top Mounting: ISO 5211
Suitable Flange:

  • ANSI 150Ib, 300Ib
  • DIN: PN10, 16, 20, 25, 40, 50
  • JIS: 10K, 16K, 20K, 30K, 40 K


Standard

  • Design Standard: API 609, MSS SP-67, MSS SP-68, BS 5155
  • Face to Face: API 609, ASME B16.10, BS 5155, EN1092
  • End Connection: DIN PN10/16/25, ANSI B16.1, BS4504
  • Inspection and Test: API 598

What is a Double Offset Butterfly valve?

A double offset butterfly valve comprising a valve body, a valve seat carried by the valve body, and a valve disc mounted on a shaft rotatably journaled in the valve body, the shaft being eccentric both to the centerline of the body and to the centerline of the valve disc (double offset). The periphery of the valve disc has a substantial knife edge which contacts the valve seat without rubbing. As the valve disc rotates, the knife edge remains out of contact with the valve seat until the knife edge contacts the seat at full closure.

Classification By Connection Type

  • Based on the connection there are four main types of high performance or double offset butterfly valves.
  • Wafer type ends.
  • Lug type ends.
  • Both flanged ends.
  • Butt-welded types end.

Wafer Type: The wafer type of the double offset butterfly valves is constructed to provide a strong sealing, safeguard against bi-directional pressure differentials, and to prevent any backflow in devices that were built for unidirectional flow. This is done by the use of a tightly fitted seal material, such as an O-ring, gasket, precisely machined, along with a smooth valve face on the downstream and upstream parts of the valve.
Lug Type: In the lug body type of the butterfly valve configuration one end of the pipeline can be removed without impacting the other side of the valve. This can be achieved with threaded inserts, flanges, and two sets of lugs (bolts) that do not use nuts so each flange has its bolts. In a Lug type connection, you do not have to shut down the whole device to inspect, clean, repair, or replace the lug butterfly valve.
Flanged End Type: The flanged end type butterfly valve uses a flange at both ends of the valve to be attached with pipe flanges. This type of end connection is used for the very large size of the butterfly valve.
Welded End Type: The welded end type butterfly valve is used where the system is under very high pressure. These types are generally used for small size butterfly valves.

How does Double Offset Butterfly Valve Work?

Double-offset butterfly valves have a two-offset disk which can be used up to 1,480 psi (10 MPa) Compared to the single-offset design, the double-offset butterfly valve uses a stem which is present behind the disk. In the high-performance butterfly valve, the second offset stem is pushed back to one side from the middle of the disk. This offset geometry allows the disk to be rubbed over the seat with just 1° to 3° of 90° rotation.
The action of the double offset butterfly valve refers to the cone profile while sealing the valve. The configuration of the disk and shaft offsets produces the cam action of the disk in the seat, minimizing the torque required to operate the valve.

When to use Double offset butterfly valve?

The double-offset butterfly valve is designed to be used in applications requiring greater resistance to the pressure. The disk is placed in the center of the pipe bore and designed to improve the sealing capability and minimize valve wear.
High-performance butterfly valves are suitable for application in water, wastewater, oil, steam and gasses in a cost-effective, compact build. Their corrosion-resistant, single-element thrust bearing and disk spacer eliminates body wear and helps maintain a positive centering of the disk in the valve bore.
Double-offset butterfly valves can be operated manually using a handle, or with gears or actuators. These devices rotate the valve disk to the ideal location for effective sealing or complete opening of the valve. High-performance butterfly valves are used mostly in the water, chemical and petrochemical industries and can also be used in fuel handling & control and many other applications.

Difference Between Double and Triple offset butterfly Valve

The double offset butterfly valve has two offsets at the center that produce cam action at the time of the application process.
Triple offset butterfly valves (TOV) have three different offset valves. Two offsets are located at the centre whereas the third is on the seat surface which creates the shape of the disk and seat form of the cone.
The double offset Butterfly valve can be used for an application of up to 325°C and can be used in pressure as high as 50 bars. While a Triple Offset Butterfly valves can be used for a demanding & long-term application of up to 932°F (500°C) and the valve is designed to withstand a high pressure of up to 725 psi (50 bar).
Double offset butterfly valve seat is made up of soft material while in triple offset butterfly valve seat is made of hard metal.
One of the key distinctions between the two butterfly valves is their appearance. In the double offset butterfly valve, the two offsets of this type of valve allow easy opening and retain their strong sealing strength.

Specifications of double offset butterfly valve

Description
BUTTERFLY VALVE

High Performance Double Offset Fire Safe

Design Code API 609 / EN593
Size Range NPS 2” – 50” / DN 50- 1250
Maximum Pressure/Rating 20 bar – 150#/ 50bar – 300#
Design Temperature -50°C to +500°C (MOC Dependant)
End Connections Wafer / Lug
Body Seat PTFE / RPTFE / Metal

Materials of Construction

Body Carbon Steels inc. Low Temp
Austenitic/ Super Austenitic Stainless steels
Aluminium bronze
Duplex/ Super Duplex alloys (1A-6A)
Hastelloy B, C, Inconel
Monel, Alloy 20
Others upon request
Shaft AISI 410, AISI316, 17-4Ph, Monel K500, UNS32760, Titanium
Seat PTFE, RPTFE, Inconel 625, SS316

We focus on valves in standard and special materials as customer request.

Our main materials show as the follows:

Any request for other materials, please contact our machinery sales or engineering team on email.

Special Material Titanium or Titanium alloy series Titanium(Gr.2,Gr.3,Gr.5,Gr.7,Gr.12)
Nickel alloy series Ni6,Ni200,Ni201
Monel 400,Monel k500
Inconel 600/625/690/750
Incoloy 800/825/800H/800HT
Hastelloy B3/C/C4/C22/C276/G30
Zirconium alloy series Zirconium 702/703/705
Bronze alloy series Nickel aluminum bronze C95800
(Super)Duplex Steel ASTM F51/F53/F55
Other corrosion resistance Alloy 20,AISI 321,310,904L
Normal Material Carbon Steel WCB,WCC,LCB,LCC,A105N,LF2
Alloy Material(Low Temperature) LC1,LC2,LC3,LF3
Alloy Material(High Temperature) WC1,WC6,WC9,C5,C12A
Stainless Steel CA15,CF8,CF8M,CF3,CF3M

Drawing of double offset butterfly valves

2008109175711834 - Double Offset Butterfly Valve

Dimensions
DIN2501(DIN2534 – ISO2084 PN25
DN L     L2 H H1 D1 n-φd1
50 43 265 330 250 125 4-16
65 46 265 362 267 145 4-16
80 49 265 375 275 160 8-16
100 56 320 410 295 190 8-20
125 64 320 425 305 220 8-24
150 70 340 465 320 250 8-24

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