Knife Valve Pneumatic Cylinder Big Bore

Knife Valve Pneumatic Cylinder

Knife Valve Pneumatic Cylinder also known as air cylinder, is a mechanical device which uses the power of compressed gas to produce a force in a reciprocating linear motion. Like in a hydraulic cylinder, something forces a piston to move in the desired direction.

1. What’s the knife gate valve?

2. The pneumatic cylinder actuated knife gate valve

2.1 The Pneumatic Cylinders

2.2 Assemble The Knife Plate On The Rod

3.Blade Postioner Mechanism

4. The Connector And Metal Air Tube

5. Manual turning wheel knife gate valve and the motorized actuated knife gate valve

6. To Contact With Us And Get The Big Bore Cylinder Quotation

What's the knife gate valve?

A knife gate valve is a linear motion type valve used to start or stop the flow of liquid in the pipe.

They are commonly used in process plants and water systems. The ability for the gate to be located completely out of the flow path when fully open reduces flow resistance through the valve. Their function mechanism allows for minim actuated strength as fluid travels through the valve, making them an excellent valve for systems requiring full flow when open.

Knife Gate Valve consist of the actuator, the closing component(Knife blade), and the valve bracket. The valve bracket hold the actuator and the knife blade.

The knife gate that moves in a vertical direction perpendicular to the fluid flow. This operation enables a reliable seal when the knife blade is pushed down to close the valve.

The actuator have three type: the commonly used pneumatic cylinder, the manual turning wheel and the electric motor.

Knife Valve Pneumatic Cylinder

A pneumatic gate valve uses a pneumatic actuator instead of a hand wheel or electric motor. By utilizing compressed air, the actuator can drive the stem to raise or lower the gate. This allows it to be operated remotely with no user onsite but requires a simplified pneumatic system on site.

The Pneumatic Cylinders

1.The Cylinder Bore Size

Aluminum Cylinder Barrel (More Than 320mm Bore Size)

Bore size 100mm : barrel thickness : 3.5mm; Theoretical Force: 6154N

Bore size 120mm : barrel thickness : 3.5mm; Theoretical Force: 8862N

Bore size 160mm : barrel thickness : 5.0mm; Theoretical Force: 15755N

Bore size 200mm : barrel thickness : 5.0mm; Theoretical Force: 24617N

Bore size 250mm : barrel thickness : 6.0mm; Theoretical Force: 38465N

Bore size 320mm : barrel thickness : 8.0mm; Theoretical Force: 63021N

The maximum bore size is 320mm for the aluminum alloy actuator barrel.

The Barrel was made by6063-T5 aluminum alloy material. The material is similar with the automobile hub. It had very good ductility performance. And be hard processed. We had adopted the barrel for twenty years. And no any accident that leaded by the barrel.

The max working pressure : 8bar=116Psi

The proof pressure: 12bar=232Psi

The max pressure we had tested is 20bar=290Psi

Steel Cylinder Barrel (More Than 320mm Bore Size)

The maximum bore size of the aluminum barrel is 320mm, so if the bore size more than 320mm, we will adopt the steel barrel to instead. The max boresize is 450mm.

How do we do to prevent the corrosion of the cylinder barrel?

We adopt the powder painting treatment.

In simple words, a plastic corrosion resistant material coverage will be paint on the steel cylinder barrel. That’s will prevent rusting effectively.

Bore size 400mm : barrel thickness : 5.0mm; Theoretical Force: 98470N

Bore size 450mm : barrel thickness : 6.0mm; Theoretical Force: 124624N

The Pressure Parameter

The max working pressure : 8bar=116Psi

The proof pressure: 16bar=232Psi

The max pressure we had tested is 30bar=435Psi

2.Assemble The Knife Plate On The Rod

We may meet the problem of valve blade can’t stretch to the bottom of the inner sealing seat, so that the valve can’t be shut off. And some times it may be too tight, thus lead to the damage of the seal.

Due to the stroke of the cylinders are fixed when it were designed according to the valve port size, it’s hard to adjust the stroke anyway. What we do if the valve gate blade can’t reach the bottom of sealing socket?

OUR PROPOSAL TO RESOLEVE THIS PROBLEM

Figure-3

Y Joint And Hexagon Milling Work On The Stem

We add a Hexagon Milling work on the piston stem as shown in the figure-3.

Therefore, you can adjust the height by rotate the cylinder stem through a wrench. So that to adjust the degree of the closure tightness of the valve blade. And then tighten the fixation steel nut, it’s for locking the Y joint when you finished the adjustment of the valve.

The other advantage is we could adjust the blade continuely when the sealant were abrasion.

We could supply both kind of Y joint: two pins or one pins fixation. The material could be stainless steel or normal carbon steel with zinc plated.

Blade Postioner Mechanism

The valve positioner is a feedback mechanism. It allows valves to be positioned precisely in accordance with the output signal of the controller, in the presence of major disturbances caused by unbalanced forces acting on the valve stem, changes in actuator temperature, etcetera. Even a relatively small actuator, that otherwise would have to be bench-set to an unacceptable degree, can be stroked precisely when a valve positioner is used to signal the valve position.

Magnetic Switch

Figure-4

The Magnetic Switch

To add the magnetic switch , or reed switch on the cylinder, So that to control the piston blade location.

If so, we need to assemble a magnetic ring on the cylinder piston. When the piston run to the postion of where the switch are installed, it will trigger the switch to output a signal.

The signal could applied by the control center to shut off the solenoid valve and thus stop the cylinder action. Or to actuate other series actions of other system.

One or multiple switches could be installed on the cylinder to realize different aims.

Attention

But we need to pay attention to one issure, that’s the control element must be intalled neer the cylinder. As the overlong wire will reduce the signal of the magnet switch.

Postioner Valve

Position Valve

Adopted the valve positioner to control the pneumatic cylinder, the function is to control the postion of the knife blade by control the positioner Valve. It will help the work to control the flow rate.

Work Principle

As a common control valve accessory, the valve positioner delivers pressurized air to the valve actuator so that the position of the valve stem or shaft corresponds to the set point from the control system. Valve positioners are typically pneumatic or analog I/P and are used when a valve requires throttling action. They require position feedback from the valve stem or shaft and deliver pneumatic pressure to the actuator to open and close the valve.

The Connector And Metal Air Tube For The Knife Valve Pneumatic Cylinder

Copper tube and fittings

Stainless steel tube and fittings

Stainless steel tube and fittings: they are always used in the corrosive environment to connect the air solenoid valve and the cylinders.

Copper tube and fittings: The other choice to connect the control valve and cylinders, especially for the application when assenmbled outdoors.

PU hose and tube fittings: The cost-effective choice, for outdoor application, we should pay attention to the aging problem.

Manual turning wheel knife gate valve and the motorized actuated knife gate valve

Manual turning:

The valve knife blade is fixed with a screw rod, and on the other end , the screw rod was assembled with a metal wheel. When try to open or close the valve, the worker need to turn the wheel to lift or push down the blade. For most big bore pipe line it’s really tough work for the operator, especially in the hostile environment. Other unfavorable factor is the response time. As you can’t regulate a worker to open or shut down the valve in a certain time. Due to the uncertainty, fewer and fewer system adopt this kind of valve.

The motorized actuated valve:

Instead of the manual wheel, a electric Motor is installed to drive the screw rod to lift or push down the valve blade.

It’s a other labor-saving method. But we always face three problems, working in the explosive environment, hard to maintain and cost consideration.

The Advantage Of the Pneumatic Knife Gate Valve

1. They’re cheap, easy to actuate, and light.

2.They widely used in the situation where there are explosive gas.

3.As it acutated by the compressed air, so with lower power consumption.

4.Compared with the manual wheel operated gate valve, it response fastly.

5.It’s easy to repair and maitain.

To Contact With Us And Get The Big Bore Cylinder Quotation

Contact: Benc Zhu

Email: Benc@dg-pnetic.com

Wechat: 13867843985

Skype：Benc0432

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Knife Valve Pneumatic Cylinder Big Bore

Knife Valve Pneumatic Cylinder

Table of Contents

What's the knife gate valve?

Knife Valve Pneumatic Cylinder

The Pneumatic Cylinders

1.The Cylinder Bore Size

Aluminum Cylinder Barrel (More Than 320mm Bore Size)

Steel Cylinder Barrel (More Than 320mm Bore Size)

The Pressure Parameter

2.Assemble The Knife Plate On The Rod

OUR PROPOSAL TO RESOLEVE THIS PROBLEM

Y Joint And Hexagon Milling Work On The Stem

Blade Postioner Mechanism

Magnetic Switch

Postioner Valve

Position Valve

Work Principle

The Connector And Metal Air Tube For The Knife Valve Pneumatic Cylinder

Copper tube and fittings

Stainless steel tube and fittings

Manual turning wheel knife gate valve and the motorized actuated knife gate valve

The Advantage Of the Pneumatic Knife Gate Valve

To Contact With Us And Get The Big Bore Cylinder Quotation