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Jul . 17, 2024 14:32 Back to list

What are dual plate check valve?



1. What are dual plate check valve?
​
Dual Plate Check Valve is manufactured based on API 594 standard. To allow the installation of the stop-pin and hinge-pin of the check valve without having to drill through the valve body completely, the valve is designed to be retainerless. 

The valve plate acts as a door resting freely on the inclined valve seat surface. In order to ensure that the valve plate matches the correct position of the valve seat every time it is operated, the valve plate plays a vital role to ensure that it has enough swing space so that it is truly and completely accessible to the valve seat.

Dual plate check valve is suitable to use in various applications, including:
  1. Oil and gas: Sour gas in low temperature, cryogenic, petroleum, lubricating oil, LNG, onshore/offshore
  2. Water: Boiler feed water, sea water, potable water, water supply system, cooling water
  3. Air & Gases: Chlorine (Cl2), Hydrogen (H2), Nitrogen (N2), Carbon dioxide (CO2), Oxygen (O2)
  4. Chemical processes: paper, cement, steel, aluminium (Al), copper (Cu), pharmaceutical, sugar process, zinc (Zn)
 
 
What are dual plate check valve?
Dual Plate Check Valve
2. How does the dual plate check valve function?

When fluid pressure flows in one direction, the valve plate opens. If the liquid moves in the opposite direction, the flow will be cut off due to the pressure of the fluid and the effect of the plate on the valve seat. The reduced flow will close the plate through the action of the torsion spring without any reverse flow.

The dual valve has a cylindrical body, and its stress distribution is more uniform compared with other valve designs. The cylindrical body is designed to withstand extreme weights as large as the weight or thickness of the valve. Therefore, for severe load conditions, the valve has obvious advantages in terms of safety and economy.
 
 
3. What is non-slam check valve?
​
​The reason for dual plate check valve design is predominantly to prevent water hammer and bring out the benefit of non-slam at the same time, it enables the valve to maximize its efficiency. The swing plate is hinged on the top of the valve. When it swings to the closed position, gravity includes high inertia. Otherwise, when the plate hits the valve seat, the momentum will cause serious damage. In order to minimize the momentum frequency, the valve must use a counterweight.

Dual plate check valve contains two plates which hinge vertically in the middle of the valve, so that the valve is able to eliminate the influence of gravity when it is installed horizontally. The momentum generated when the plate moves to the closed position is a small part of the valve, because the weight of each plate is one-fourth of the weight of the swing plate, and the tip speed is less than half. In addition, during the valve closing process, with the help of the spring, the valve will reach zero flow before the return flow begins. This flow cushions the board and seat, so when it starts to close, the possibility of impact is negligible.

4. What causes valve slam?
​
Check valve slam is a situation of reverse fluid flow in the pipeline and flow through the valve disc before the valve disc is completely closed after the pump has stopped. The check valve that was closed for the reverse flow stopped instantaneously, causing a huge shock wave and water hammer in the pipeline. Therefore, it appears the noise related to slamming is not due to the effect of the valve disc violently hitting the seat, but to the rapid stretching of the pipe by the water hammer. In addition, a resilient seat check valve can emit the same metal pop sound as a metal seat valve.

To prevent slamming, the check valve must be able to close within a fraction of a second, or be equipped with an oil buffer device or actuator to control its closing time for more than a few seconds or (depending on the length of the piping system) several minutes. The dynamics of the pumping system (that is, the slowdown due to head, slope, and pipe friction) determines the necessary shutdown time. Systems with high heads, steep slopes, vertical pipes, or surge tanks require check valves to close quickly (for example, 20 milliseconds), while low-lift, relatively flat systems require a one-second closing time. This article describes how the design and geometry of a check valve affect its closing speed.
 
 
5. What is a water hammer and how its it caused?

Water hammer can occur in any piping system that uses valves to control the flow of liquid or steam. Water hammer is the result of pressure surges or high-pressure shock waves propagating through the pipeline system when the fluid in motion is forced to change direction or stop suddenly. This shock wave is also commonly called hydraulic shock, and may be characterized by a noticeable impact or knocking sound on the pipe immediately after it is closed.

Water hammer occurs when an open valve is suddenly closed, causing water to rush into it violently, or when the pump is suddenly closed and the water flows back to the pump in the reverse direction. Since water is incompressible, the impact of water will cause the shock wave to propagate at the speed of sound between the valve and the next elbow in the piping system or in the water column behind the pump.

The effect of water hammer:
​If the water hammer is not solved, it will eventually lead to catastrophic failure of the flow system. The long-term effects of water hammer include:
  • Pump and flow system damage
  • Water leakage
  • Ruptured pipes
  • External property damage
  • Accidents
  • Downtime/ maintenance
 
 
6. Why use a dual plate check valve?

The following are the advantages of installing a dual plate check valve:
  • Lightweight and therefore easier to handle.
  • It can be installed horizontally or vertically.
  • More compact and reasonable structure design.
  • Regardless of the valve pressure level, it has a low pressure drop and reduces energy loss.
  • It's not booming in nature.
  • Streamline streamline.
  • Long life and trouble-free valve operation.
  • Effective and reliable sealing under pressurized conditions. The valve closes before the zero velocity reverse flow.
What are dual plate check valve?
Dual Plate Check Valve
 
 
7. How to install a dual plate check valve?

Step 1: Valve cleaning service
You must ensure both ends of the valve are coated with anti-rust oil. The valve must be cleaned before installed into the system, and also ensure that the valve plate is free of rust/oil. 

Step 2: Determine the flow direction
The valve body consists of an arrow mark to determine the flow direction, you must ensure the flow direction of the valve body is consistent with the flow direction in the pipeline.

Step 3: Insert the valve in the horizontal piping
Insert the valve into the pipe with the pin seat in the up and down position. 

Step 4: Measure the distance between the dual plate check valve and the flange
When both flanges are connected to the check valve body, make sure that there is sufficient distance.

Step 5: Valve testing operation 
Operate the valve from the full open to closed position in minimum working pressure.

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