Double Eccentric Off-Set Disc Butterfly Valve

DOUBLE ECCENTRIC OFF-SET DISC BUTTERFLY VALVE

... A New Generation of Butterfly Valves

A NEW GENERATION OF PAL BUTTERFLY VALVES

On going research and development of a unique design of butterfly valve, capable of handling higher pressures and temperatures and more aggressive process conditions than conventional butterfly valves.

An ideal substitute for ball and plug valves.

OPTIONS:

Various gland packing options.

Splined or recess keyed.

Metal to metal class IV shut-off.

Class 150 - 20 bar rated or Class 300 - 50 bar rated.

High temperature version.

MATERIAL SELECTION & CONSTRUCTION
A SIMPLE NUMERICAL/ALPHABET SYSTEM TO IDENTIFY MATERIALS OF CONSTRUCTION.

Ref no.
Pipe size

Body
Material

Disk
Material

Shaft
Material

Body
Seal

Body & Shaft
"O" rings

Operation

6"(150mm)

Carbon Steel
(ENP)

304 ss

PTFE

Nitrile

Bare Shaft

8"(200mm)

CF8M Stainless
Steel

316 ss

Filled
PTFE

Viton

Gear
Operator

10"(250mm)

EN57(17-4PH)

UHMWPE

Silicone

12"(300mm)

CD4 MCu. Duplex
Stainless Steel

CD4

Peek

FEP

14"(350mm)

904L

Metal

16"(400mm)

Alloy20-CN7M

PAL 28

Pal 20

PAL 28

MONEL 400

CB7-P.H.

RUTHALLOY

Monel-M35

RuthAlloy

Example: 6" (150mm) Alloy 20 Valve with 904L shaft, reinforced PTFE body seal ring, VITON body and shaft seals with bare shaft. By using the legend the above description is converted to a type:

Size	Body-Disk-Shafts	Body seal	"O" rings	Operation
#6	6 6 5	R	V	BS

MATERIAL CHARACTERISTICS
CF8M:	Commonly used Alloy for a wide range of applications covering weak to mild acids, alkalies and where product contamination resistance is essential.
CN7M:	A higher nickel, chrome alloy for improved corrosion resistance for various acid application showing particularly good results for sulphuric acis across a wide range of temperatures and concentrations.
CD4:	A high chrome super stainless or "Duplex" stainless steel for improved resistance against chloride environments and stress corrosion, often more suitable for higher temperature acids and salts.
PAL28:	An alloy similar to CN7M (Alloy 20) but containing higher nickel, chrome and molybdenum contents for improved corrosion resistance for strong acids deaerated and where chloride are present.
CB7:	A chrome nickel steel which precipitation hardened for applications where high abrasion rates are anticipated.
WCB:	A common refinery type cast carbon steel alloy for high temperature conditions. Bodies and discs electroless nickel coated for corrosion resistance. Suitable for non corrosive conditions such as diesel and petrol..

VALVE SPECIFICATIONS

F-F dimensions are to API 609 CLASS B

Body flanges suitable for BS4504 T25,T40, T64, ASME/ANSI B16.5 CLASS 300, BS 10 F&H.

Mounting pads and offset square on shafts are to ISO 5211 standards.

Serrated spiral finish on faces are to ASME/ANSI B16.5P

AL BUTTERFLY VALVE DESIGN FEATURES

A high strength durable and compact butterfly valve capable of working in high pressure and temperature environments.

Valves are manufactured in a wide range of standard and exotic materials for corrosion resistance against various aggressive chemicals, acids, alkalies and gasses.

The shafts being eccentric to the disc combined with low coefficient of friction seals and bearings, results in the valve having lower operational torques compared to other designs of butterfly valves. Substantial savings are thus guaranteed when considering the costs of valve automation.

The self energising body seal ring as described below combines the unique strength of PTFE, UHMWPE and PEEK with the resilience of elastomeric type "0" rings, resulting in a long life zero leakage simple to replace at low cost valve seal.

A positive disc to drive shaft connection using a keyed or spline drive system, which eliminates the use of taper pins or fasteners. This also allows for simple and quick disengagement for maintenance purposes.

The one piece shaft offers superior strength under higher pressure conditions.

THE NEW PAL BE-AX PRESSURE ENERGISED BODY SEAL


Figure 1	Figure 2	Figure 3
The diagram shows the valve in assembled condition, opened and under no pressure. The lock ring and butterfly body have shoulders which loosely capture the "T" shaped seal. The seal is positively retained in position by an "0" ring.	The diagram shows the valve in a closed position but under no pressure conditions and contacting the integrally machined disc seat. The seal ring being dimensionally slightly smaller than the disc bore, compresses itself and forces the "0" ring to compress further. The "T" seal moves away from the body and seat ring shoulders. The "0" ring exerts an upward force that continually energises the body seal maintaining contact between seal and seat.	The diagram indicates pressure applied from one side of the disc in a closed position. The line pressure automatically exerts an upward force on the underside of the 'T" seal, increasing the pressure of the seal at the contact face. The higher the pressure, the tighter the seal. When the disc moves to an open valve position the tension is lost and the components revert to a relaxed position.

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