Dual plate check valves vs swing check valves are two main types of check valves that are usually compared side by side, but what are the similarities and differences between the two, and how do you decide which is best for you?
Either of these valves help to prevent a fluid reversal in a pumping system used in the oil and gas industry.
As such, they ensure that the mechanical equipment within these pipes is safe.
But what do these check valves for water do?
Let’s take a closer look.
What are Check Valves?
Check valves are automatic valves that open when fluid flows forward but closes when fluid flow reverses backwardly.
These valves do not rely on operators since they perform automatically based on the forward or reverse movement of the fluid.
Similarly, check valves produce a slamming effect as they restrict reverse fluid flow.
Why are Check Valves Important?
Check valves are important for a number of reasons and some of these include:
- They protect the mechanical component in a piping system through the stoppage of fluid reversal.
- They prevent the massive backflow of water if in any case the pipe breaks.
- Check valves also prevent backflow to a lower pressure which helps in reduced energy consumption.
Check Valves Slamming Effect
Generally, slamming effect in valves is caused by a sudden pump stoppage which results in a forward-moving fluid flowing backward rapidly.
As the fluid reverses and comes in contact with the check valve that is trying to close fully, it is blocked by the valve.
The effect is given off as noise in the form of a slam and water hammering.
Researchers have attributed this check valve slam to two processes and these are:
- Pump stoppage occurs, the fluid flows backwardly and lands on the check valve that is trying to close
- The closure member slams the valve suddenly which stops the backflow
Thus, check valves are either closed rapidly or slowly which has given rise to two basic types of check valves.
These are the dual plate check valves and swing check valves.
What are Dual Plate Check Valves
Dual plate check valves are more popularly used in certain regions since they have a low slamming effect.
What are Swing Check Valves
Swing check valves, on the other hand, are an economic type of check valve.
Their closure or disk is mounted on the seat and it usually moves around the hinge.
Also, the closure is opened as a result of water forcing it to swing.
That is to say, the force of water flowing forward will see the swing open of its own accord while backward flow tends to shut it which gives off a high slamming effect.
Differences Between Dual Plate and Swing Check Valves
1. Slamming Effect:
Slamming effect is evident in check valves and in some more than others.
An instance is the case of the dual plate check valves which has a lower slamming rate in comparison to the swing check valves which is an advantage over the latter.
Dual plate check valves are closed rapidly even before a fluid reversal occurs. The rapid closure is made possible by closing the check valve disk with the help of a spring’s force. As a result, the motion of closing the plates is supported by the spring.
Swing check valves, on the other hand, are closed slowly when reverse flow begins using the disk’s weight force which is slammed on the seat thereby giving off a high slamming effect. As a consequence, dual plate check valves are more popular than swing check valves.
2. Cost
When a dual plate check valve’s total cost is considered, it is considerably lower than that of a swing check valve.
The total cost includes the installation cost, energy cost, and maintenance cost.
An instance of an estimated cost that can be incurred through the use of either the dual plate or swing check valve is given below:
a. Dual plate check valve:
- Installation Cost: $2000
- Energy Cost: $22,400
- Maintenance Cost: $6,000
- Total Cost: $31,200
b. Swing check valve:
- Installation Cost: $8500
- Energy Cost: $30,800
- Maintenance Cost: $24,000
- Total Cost: $63,300
The above shows that a swing valve’s total cost can be twice as high as that of a dual check valve.
In the same vein, more energy consumption and pressure drop in a pumping system that uses a swing check valve mean a higher energy cost.
The high maintenance costs can be attributed to the weak connection of the disk of the swing check valve to the body which increases the potential for the disk to break down while it is in use.
3. Design
When it comes to a wafer type check valve design, dual check valves can be made to be more compact in comparison to swing valves.
A dual valve also has its disk weight distributed among two parts instead of one which could help in saving space.
How to Prevent Operational Problems Due to a Minimum Flow Condition
A dual check valve comes with several advantages over a swing check valve, but that does not mean it cannot pose its own issues.
That is to say, minimum or lower flow operational risks can occur which could lead to an increase in energy consumption and wear of the valve.
The latter can be attributed to the minimum flow capacity being unable to produce the required pressure as the dual plate check valves are in use.
Here, the minimum flow is regarded as lower than the minimum critical flow that is sufficient to open the valve fully.
Thus, to prevent these problems from occurring, the following considerations should be given:
1. Avoid Minimum Flow Capacity:
Operate the dual plate valve at a sufficient flow velocity which will ensure that the disk of the valve is always pushed to be fully opened.
This is because if the valves are not fully opened, more pressure is lost and the energy consumption is increased unlike when the valves were in an opened state.
On the contrary, operating at a minimum flow that is below the critical flow will cause the disk to vibrate which leads to repeated slams that could wear and tear the valve and shaft bearing.
2. Install the Valve on the Horizontal Line:
It is better to install the check valve on a horizontal line instead of a vertical line.
For instance, installing the valve vertically with the fluid moving downward will always keep the valve open.
Trying it the other way round by using the same vertical installation but the upward flow will pose a difficulty when the valve is to be opened.
Thus, horizontal installation is the best way to go.
3. Reduce Valve’s Size
One more way operational risks can be avoided is by reducing the size of the valve which can help the disk to open efficiently.
The same can be said about reducing the spring torque behind the disk.
Conclusion
After taking a closer look at the dual plate check valves vs swing check valves, their pros and cons can easily be pointed out.
While swing valves are known to be economic valves, their high slamming makes them an unpopular choice compared to dual plate check valves.
The latter comes with the benefits of reducing total cost while also allowing fluid flow in the piping system without damaging its mechanical equipment.
Backed with this information, you too can make a choice on which can serve you with the least noise produced while you save on cost that would’ve been tied to the check valve’s installation, maintenance, and high energy consumption.
