Knife Gate Valves - DB Series | Wey Valves | Double Block & Bleed
Knife Gate Valves - DB Series | Wey Valves | Double Block & Bleed

Knife Gate Valves - DB Series | Wey Valves

WEY DB Knife Gate Valve – Double Block & Bleed

The WEY DB series is designed for positive isolation of pipelines carrying hazardous, corrosive or contamination-sensitive media. Two gates operate through a common actuator, creating two independent sealing points. The intermediate cavity includes connections for venting, draining or flushing, allowing isolation verification before maintenance work.

Technical Data

  • Nominal sizes: DN80–DN750

  • Body material: ASTM A351 CF8M

  • Gates: stainless steel 1.4404, hard chrome plated

  • Seat seal: Aflas with metallic support

  • Flange connections: ASME B16.5 Class 150

  • Face-to-face dimension: manufacturer-specific

  • Leakage test: EN 12266-1, Leakage Rate A

The transverse seal limits leakage to atmosphere and can be readjusted through the lateral compression screws while the valve remains installed. Adjustment must be uniform to prevent uneven gate loading, increased friction or restricted movement.

Actuator Options

  • DBA-HW: handwheel, DN80–DN300, up to 10 bar

  • DBA-GK: bevel gearbox, DN350–DN600, up to 6 bar

  • DBC: pneumatic cylinder

  • DBE: electric actuator

  • Hydraulic actuator upon engineering review

Applications

Chemical solutions, bleaching agents, pulp and paper processes, tank isolation and pipelines where product cross-contamination must be prevented. The DB arrangement is also used where maintenance access requires verified isolation between the process and downstream equipment.

FAQ

Is the DB series suitable for flow control?
No. It is primarily intended for full open or full closed isolation service.

What is the function of the intermediate cavity?
It allows venting, pressure monitoring, draining or flushing between the two gates, confirming that both isolation barriers are effective.

Which standards apply?
The series is available in accordance with PED 2014/68/EU and can be configured for SIL 3 capable safety functions under IEC 61508.

Standard (Options)
  • ANSI
Material (Options)
  • 1.4404
  • ASTM A351 CF8M
Pressure Rating (Options)
  • 150 lbs
Seat (Options)
  • Aflas (Metal seat)

Datasheet and documents

Description

The “double block and bleed” knife gate valve was specially developed for applications using hazardous media. The DB model is a single valve with two seat areas. In the closed position, these provide a seal against pressure from both ends of the valve, and there are purge ports to flush the cavity between the seat areas. The DB model thus makes complex and costly multiple valve systems redundant. In spite of these cost benefits, it offers zero leakage protection in difficult applications.

Characteristics

  • Nominal sizes: 80 – 750 mm
  • Material: Stainless steel, Special material
  • Pressure rating: 0 – 10 bar
  • Flange drilling: Stainless steel, Special material
  • Face to face dimension: Special length

Details

The robust metal yoke enables the optimal, simple assembly of mechanical or inductive limit switches. The yoke can be removed from one side. This makes it easier to access the mechanical parts.

Two gates provide additional security. The medium can be flushed out in the gap between them.

The robust metal yoke enables the optimal, simple assembly of mechanical or inductive limit switches. The yoke can be removed from one side. This makes it easier to access the mechanical parts.

Robust 4-post topwork for maximum load and a wide variety of actuator types.

The robust metal yoke enables the optimal, simple assembly of mechanical or inductive limit switches. The yoke can be removed from one side. This makes it easier to access the mechanical parts.

A unique transverse seal, consisting of a transverse seal profile and packing compound, makes the body bubble-tight towards the atmosphere.

The robust metal yoke enables the optimal, simple assembly of mechanical or inductive limit switches. The yoke can be removed from one side. This makes it easier to access the mechanical parts.

The transverse seal can be repacked at any time and under full pressure using the lateral packing screws.

The robust metal yoke enables the optimal, simple assembly of mechanical or inductive limit switches. The yoke can be removed from one side. This makes it easier to access the mechanical parts.

In the closed end position, the gate is also mechanically supported.

Application Areas

Pulp and paper industry

e.g. Chemical solutions, bleaching agents ...

Material Of Construction

PartStainless Steel
BodyEdelstahl CF8M
Gate1.4404*
SealAflas
TopworkCarbon steel
Stem / Piston rod430F

Other materials upon request  *hard chromed

Corrosion Protection

Topwork2 Comp. Epoxy-Polyamide Resin Primer, 2 Comp. Polyurethane-Enamel-Top Coat
ScrewsStainless steel

Certificates

SIL 3 Certificate