By-pass valves are generally used for three basic reasons:
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AVK offers gate valves with by-pass in dimensions from DN 450, see series 55/30 and 06/30.
Gate valves can be divided into two main types: Parallel and wedge-shaped. The parallel gate valves use a flat gate between two parallel seats, and a popular type is the knife gate valve designed with a sharp edge on the bottom of the gate. The wedge-shaped gate valves use two inclined seats and a slightly mismatched inclined gate.
Most of AVK's gate valves are of the solid wedge-shaped design, but we also offer knife gate valves for wastewater treatment and parallel slide valves for gas supply.
Before the resilient seated gate valve was introduced to the market, gate valves with a metal seated wedge were widely used. The conical wedge design and angular sealing devices of a metal seated wedge require a depression in the valve bottom to ensure a tight closure. Herewith, sand and pebbles are embedded in the bore. The pipe system will never be completely free from impurities regardless of how thoroughly the pipe is flushed upon installation or repair. Thus, any metal wedge will eventually lose its ability to be drop-tight.
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A resilient seated gate valve has a plain valve bottom allowing free passage for sand and pebbles in the valve. If impurities pass as the valve closes, the rubber surface will close around the impurities while the valve is closed. A high-quality rubber compound absorbs the impurities as the valve closes, and the impurities will be flushed away when the valve is opened again. The rubber surface will regain its original shape securing a drop-tight sealing.
The vast majority of AVK's gate valves are resilient seated, however metal seated gate valves are still requested in some markets, so they are still part of our range for water supply and wastewater treatment. See series 54.
Rising stems are fixed to the gate and they rise and lower together as the valve is operated, providing a visual indication of the valve position and making it possible to grease the stem. A nut rotates around the threaded stem and moves it. This type is only suitable for above-ground installation.
Non-rising stems are threaded into the gate and rotate with the wedge rising and lowering inside the valve. They take up less vertical space since the stem is kept within the valve body. AVK offers gate valves with a factory-mounted indicator on the upper end of the stem to indicate the valve position. Gate valves with non-rising stems are suitable for both above-ground and underground installations.
The majority of AVK&#;s range are designed with non-rising stem, but we also offer gate valves with rising stem for water, wastewater and fire protection applications.
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