The reliability of the shut-off valve determines the stability of the entire technological complex. In systems where the working medium contains solid impurities, fibers or has a high viscosity, standard valves often fail due to clogging of the body. In such operating conditions, an irreplaceable gate valve (knife).
What is a gate valve and how does it work?
Gate valve is a type of pipeline valve in which the shut-off element (knife) moves perpendicular to the flow axis.
- Feature: The locking element has the shape of a thin metal plate with a sharp lower edge.
- Knife function: This geometry allows the plate to literally cut through inclusions in the flow (fibers, paper, thick sediment), ensuring a tight fit to the seal.
Operating principle
Unlike classic wedge valves, the gate valve model has no “stagnation zones” inside the body. This prevents the accumulation of sediment that could block the mechanism. When closing, the spindle lowers the knife, which displaces the medium and presses against the seat, ensuring reliable tightness class «A».
Design features
The technical advantage of knife gates lies in the minimal number of moving parts and compactness.
Main design elements:
- Knife (slide): Made of stainless steel (AISI 304; 316; 316L or other grades of stainless steel). Precision polished to reduce friction and ensure high sealing quality.
- Corps: Monolithic or prefabricated (cast iron and stainless steel). Has a short construction length, which is ideal for limited space.
- Seal (seat): Elastomers (EPDM, NBR, Viton) or metal-to-metal type for high temperatures.
- Stuffing box: Ensures tightness of the spindle outlet. It is important to choose models with the ability to replace the gland without dismantling the entire valve.
Applications and working environments
The choice of gate valve is critically dependent on the type of medium. Using the wrong type of blade can lead to rapid wear of the system.
Where it is used:
- Wastewater treatment plants and sewage: Working with wastewater and activated sludge.
- Pulp and paper industry: Transporting masses with a high fiber content.
- Food industry: Pumping viscous products (molasses, wort, sugar syrup).
- Mining and quarrying: Pulps, sludge waters, bulk materials (cement, grain).
Shutter control:
- Manual: Handwheel or lever (for systems with a liquid operating cycle).
- Automated: Pneumatic or electric actuators (for lines with high frequency of opening/closing cycles).
How to choose the right gate valve
In order for the fittings to fulfill the stated requirements 10,000+ cycles, pay attention to the following parameters:
- Working pressure (PN): Typically, knife gate valves are designed for pressures from 2 to 10 bar (depending on diameter).
- Temperature: Depending on the environment, a gate valve with different seals is selected: NBR +80°C EPDM +110°C VITON +150°C and metal-to-metal over +150°C.
- Chemical aggressiveness: For mildly aggressive and aggressive chemicals, choose stainless steel grade AISI 316 and AISI 316L.
Conclusion
The gate valve is the undisputed standard for handling complex, viscous and contaminated media. Its self-cleaning capability and compact size make it the ideal choice for media with impurities.
Purchase certified gate valves that meet standards ISO and DSTU, you can in the company UKSPAR. We provide full technical support, assistance in selecting drives, and warranty service.
