Unidirectional Knife Gate Valve

A typical Unidirectional Knife Gate is one of the few application-specific designs among the industrial valves which features a single-piece rugged and compact cast body design that offers optimum performance and serves from general to complex demanding applications for material flow purposes. An economical, easy to operate shut-off valve that regulates the flow in the piping system of high viscous fluids. Its design ensures minimum contact between moving parts and is achieved by having the gate, which is practically held between a few layers of gland packing, not touching the body parts during most of its travel. The gate and seat final sealing is achieved with non-sliding motion aided by gate wedges located in the body. This feature enables the valve to handle abrasive particles in the media better than other designs. The beveled bottom edge of the gate from which the name KNIFE is derived enables positive closure of the valve, even when solid particles tend to settle at the bottom of the body. As an effective solution for the leakage problem in Media containing particles, Knife gate valves are used in various sectors of industries.

Salient features of Unidirectional Knife gate

Beveled edged gates cut across the tough solid materials

• Easy to actuate, due to lower thrust
• Low weight easy to handle and install.
• Multilayered gland sealing design
• No dead pockets
• One-piece, rugged and compact, cast body.
• Round port for better flow and low-pressure drop
• Metal and replaceable soft seat options
• Ground finish stainless steel gates for better sealing and low friction against the gland packing provide a better life to the packing.
• Knife gate valves are pressure/leak tested as per MSS-SP 81 Standard.
• Cost-effective isolation
• Low operating torque
• Gate hardening options for abrasion resistance.
• Lubricant injection port for smooth operation
• Less Face to face dimensions

Typical applications of Unidirectional knife gate valves

• Paper and pulp industry
• Chemical/petrochemical plants
• Sewage/Wastewater treatment plants
• Mining
• Food and beverage industry
• Cement plants
• Silo emptying
• Thermal Power plants
• Steel and metal plants

Design characteristics

As in other valves, the operational components are

1.Valve body

The heavy-duty single-piece Integral Cast body, rugged and compact is available in Cast Iron, Ductile Iron, Cast Carbon Steel, Stainless Steel & Alloy Stainless Steel. The valve is available from 50nb to 1500nb sizes fully lugged/Wafer & flanged design conforming to the dimensions of MSS-SP-81 Face to Face for easy interchangeability. Wide choice of international flange drilling standards ANSI, BS, JIS, etc… The valve round port far exceeds the 90% minimum requirement of schedule 40 pipe ID bore which provides much better flow rates and minimizes pressure drop across the valve. The integral seat design provides lesser room for the settlement of solids.

2.Gate

The high-quality, ground finish stainless steel gates with gate edge radius design reduce packing stress, friction, and operating force, thereby improving the packing life for optimum sealing and low maintenance. Generous Gate Thickness, well supported by packing, resists distortion or deflection and is less likely to bend in upset process conditions resulting in the lesser gland or seat leakages. The beveled bottom Knife Edge of the gate cuts through solid particles that tend to settle at the bottom of the valve. The gates are available in various Stainless steel grades suitable for the service conditions and are also hardened suitably.

3. Valve seat

Clear, relieved upstream area with jams. This eliminates dead pockets in the body where suspended solids/media tends to settle in the bottom of the valve, not allowing the gate to seat properly. Unidirectional Knife Gate valves are pressure-assisted face sealing valves. Metal to Metal integral as well as a replaceable seat for slurries, replaceable resilient seats for clean fluids and light-duty slurries, and V-Notch replaceable seats are available for throttling applications.

4.Stem

Rising stems are available as standard design. Non-rising stems are also available for tight spaces and to provide increased operational safety. A rotating part of the valve shafts is connected with the gate and handwheel. Stem hoods with rising or non-rising stems are lubricated, dust-free is maintained for efficient performance.

5. Handwheel or actuators

As the name denotes, handwheels are used for rotating purposes to move the gate for opening and closing in the unidirectional knife gate valves. With up or down movement, the flow of fluids is maintained. It can be operated manually, electrically, pneumatically, or using hydraulic operation systems. Some accessories include scraper, air injection ports, heating jacket, flushing holes, mechanical locking device, connection box, gearbox, emergency actuators, and others are available as accessories. As a whole, they all together function as a single well-organized system.

Maintenance of Knife gate valves

V-tork develops unidirectional knife gate valves with minimal maintenance and durability in operation.

• Always mount the knife gate valve in the vertical position with the actuator upwards.
• If not used regularly, cycle the valve components for better performance.
• Release the system pressure before repair and maintenance
• Use compatible detergents for all valve components. Non-metallic parts can be washed with pure water or alcohol.
• The parts dismantled should be cleaned to remove dust, dirt, grease, oil by immersion methods.
• Lubricate the parts at regular intervals with optimum lubrication agents.
• Do not assemble immediately after the washing process is done. Dry the components completely without rusting and install them.
• Check for no extrinsic particles present in the internal valve body.
• Follow V-tork guiding principles for perfect reassembly.

Internal maintenance

1. Release the upstream and downstream pressures.
2. Retain the valve at the full closed position.
3. Conduct an airtightness test after replacement.

Quality standards for gate valves at V-tork

V-tork follows stringent quality tests for each part of Unidirectional knife gate valves. The flawless and seamless performance valves are only delivered to the clients.

Our quality tests

Body shell test

Each gate valve body is tested hydrostatically with a given pressure of 1.5 times the working pressure for no visible leakage.

Valve seat test

The valve gate is closed and normal test pressure of 40 PSI is given against the seat and checked for leakage. The maximum allowable leakage is 40cc per inch per minute.

Functional test

Each ideal assembled valve is operated for one complete cycle ie., close to fully open and vice versa for validation of operation.

Gate test

To ensure gate material integrity, the valve is tested with the gate closed at the rated pressure.

How to choose the best unidirectional knife gate valves?

Among innumerable ball valve manufacturers available in the market, choose the best gate valves that fulfill your demand and requirements in the industry. The unique design, assembly of parts, working conditions, and valve functionality should suit your industrial purpose. Key points to be remembered while selecting are

• Size range
• Temperature range
• Pressure rating
• Body materials
• Seat materials
• Actuator type
• End connection

Why choose unidirectional knife gate valves from Vtork?

V-tork is a well-established gate valve company that delivers products with perfection and high-level customer satisfaction. We are ISO certified knife gate valve manufacturers striving in the industry since 2008. We provide high-quality valves at affordable prices. Our valves with zero downstream leakage, high performance, 100% bubble tight isolation, and precise shut-off will maximize your production process. Get premium quality gate valves at V-tork!