What is the gate valve?
08 Feb,2022

Gate valves are commonly used in various applications and can be installed both above and below ground. Not least for underground installations, selecting the correct type of valve is critical to prevent high replacement costs.

Gate valves are available in two configurations: completely open or fully closed. They’re used as isolating valves in pipelines and should never be used to control or control valves. The stem of a gate valve is rotated either clockwise to close (CTC) or clockwise to open (CTO) to operate the valve. The gate on the threaded portion of the valve stem moves up or down while it is operated.

Gate valves are used in a variety of applications.

If there is a need for minimal pressure loss and a free bore, gate valves are often used. A distinctive gate valve has no obstacle in the flow path when completely open, resulting in very low-pressure loss and allowing the use of a pipe-cleaning pig. The gate valve is a multi-turn valve, which means it has a threaded stem used to operate it. The slow operation also prevents water hammer effects because it has to turn several times from open to close.

Gate valves are suitable for a wide range of fluids. The gate valves from AVK are suitable for the following applications:

• Temperature between -20 and +70 °C, overall five m/s flow rate, and up to 16 bar differential pressure for potable water, wastewater, and neutral liquids.

• Gas: temperature range of -20 to +60 °C, the maximum flow velocity of 20 m/s, and differential pressure of up to 16 bar.

By-pass valves for gate valves

By-pass valves are commonly employed for three reasons:

• With the main valve closed and the by-pass open, a continuous flow is permitted, preventing potential stagnation, lowering the valve’s torque requirement, and allowing one-person operation.

• Pipeline filling is taking longer than anticipated.

Wedge-shaped vs. parallel-shaped gate valves

Parallel and wedge-shaped gate valves are the two primary types of gate valves. A flat rate is used between two parallel seats in parallel gate valves, and a common form is the knife gate valve, which has a sharp edge on the bottom of the gate. Two inclined seats and a slightly mismatched inclined gate are used in wedge-shaped gate valves.

Although most AVK’s gate valves are solid wedge-shaped, we also have knife gate valves for wastewater conduct and parallel slide valves for gas supply.

Gate valves with metal seated vs. resilient seated seats

Gate valves with a metal seated wedge were commonly used until the hardy seated gate valve was hosted to the market. A depression in the valve bottom is needed by the annular sealing devices of a metal seated wedge and the conical wedge design to confirm a tight closure. Sand and pebbles are embedded in the bore at this point. Regardless of how thoroughly the pipe is flushed during construction or repair, it will never be completely free of impurities. As a result, any metal wedge’s capacity to be drop-tight would deteriorate over time.

The plain valve bottom of a resilient seated gate valve allows sand and pebbles to move freely through the valve. If impurities move through the valve as it closes, the rubber outward may close around the impurities. When the valve shuts, a high-grade rubber compound captivates the impurities, which are flushed out when the valve is opened again. The rubber outward would return to its original form, ensuring a leak-proof seal.

While resilient seated gate valves account for the overwhelming majority of AVK’s gate valves, metal seated gate valves are still in demand in some markets, so they remain part of our water supply and wastewater treatment range. Series 54 can be found here.

Gate valves with growing stems versus non-rising stems

Rising stems are attached to the gate and rise and fall together as the valve is opened and closed, providing a visual indicator of the valve location and allowing the stem to be greased. The threaded stem is pushed by a nut revolving around it. This form is only suitable for installation above ground.

Threaded through the gate, non-growing stems rotate with the wedge rising and falling within the valve. Since the stem is contained inside the valve shell, they take up less vertical space. AVK provides gate valves with a factory-installed valve location indicator on the upper end of the stem. Non-rising stem gate valves can be used in both above-ground and underground applications.

While most AVK’s gate valves have a non-rising stem, we also provide rising stem gate valves for water, wastewater, and fire safety applications.

Gate valve with a knife blade

Knife gate valves are industrial valves with a design that ensures minimal contact between valve components, minimizing wear and tear. Knife gate valves have certain characteristics, such as avoiding sliding contact between the body and the gate, allowing the flushing of media to form the valve interior, and non-sliding motion. And when there are solid particles at the bottom of the body, the valve’s bottom edge will provide a strong shutoff. Knife gate valves are unidirectional valves that can cut through moving media and dislodge and close any material in the seating region. These valves are used in mining, steam, and chemical applications because they can withstand high temperatures and abrasive slurries.

What are the benefits of a gate valve?

  • The gate valve opens and closes very slowly, which prevents fluid hammer and piping damage.
  • The best choice for on-demand service
  • Bidirectional flow with low-pressure drop

What are the applications of gate valves?

These valves can be used for gas, slurries, steam, oil, and corrosive liquids. They are appropriate for high-pressure and temperature applications. They cannot be quickly opened or closed. They need a large space for installation, operation, and maintenance.

Sum Up

Gate valves can’t be used for control because the disc can be damaged when partially open, and when completely open, they reduce the pressure drop around the valve. If the fluid flow must be in a straight line with minimal restriction, gate valves may be used. All gate valves are bidirectionally sealable and can be mounted in any direction; however, pressure-relieving valves can only be installed in the direction indicated by the arrow.

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