Balancing valves are accessories that are not only essential in distributing flow but in metering hydraulic systems as well. The process is pretty straight forward: the valve has a cavity, in which fluid circulates, and a spigot. The hoses from the metering device are connected to two pipes that extend to the valve body, one upstream and the other downstream from the cavity.
The metering device reads the variance between the pressure found in the system and a basic flow value that’s predetermined by the valve manufacturer. It’s important to understand that the variance in pressure can differ from one valve model to another and therefore cannot be compared or associated with another model. In fact, the flow depends on the construction characteristics of the valve that’s fabricated by the manufacturer.
That’s why it’s essential to refer to the diagram that corresponds to the valve being used. This diagram, which is specially designed by the manufacturers based on the valve’s fabrication characteristics, establishes the ΔP vs. balancing valve flow relationship and, as a result, can only be used with its corresponding model.
Balancing a hydraulic system
Balancing a hydraulic system is performed in three stages: testing, balancing and adjustments. It’s critical to perform these operations to ensure equipment in a hydraulic system functions properly.
First, testing helps confirm whether system components hold the desired capacities and performance. Testing means taking various readings, such as pressure, flow, temperature, electric current and pump motor voltage. These tests are performed to compare the results with the required design values.
Then, balancing must be performed to obtain proper flow distribution and achieve desired capacities. This step consists of regulating fluid distribution across system equipment based on values established during the design phase.
Finally, minor adjustments must be applied to the system’s basic components to obtain optimal efficacy. In practice, the defined theoretical flow values may prevent desired results from being obtained. Readjusting balancing valves for certain system clients must be performed to obtain better operation.
Where should balancing valves be placed?
Many flow distribution problems, permanent or transient, are attributed to control loops, when in fact their causes are hydraulic. The source of the problem is often tied to water flow disparities in relation to design values. Most of these problems can be detected and, in general, resolved, if balancing valves are placed in strategic locations.
Here is a brief list of hydraulic system equipment and components that require balancing and/or an adjustment:
- Process equipment
- Water coolers
- Water towers
- Unit heaters
The importance of balancing
Balancing a hydraulic system must not only be performed when a new system is started up, but also when any major changes have been made to the system. Adding a new line to an existing system can be harmful to equipment if balancing is not performed quickly. In certain cases, this newly added portion can be less restrictive and, as such, can provoke a short circuit in the flow, which can cause a shortfall in existing equipment.
Moreover, without proper balancing, the system’s total flow often exceeds the suggested design flow to adequately meet the needs of users at the end of the system. The system pump therefore operates with more flow, less pressure and in a less effective range (based on its operating curve) than standard operating values. Although a simple balancing can often solve many problems, other solutions may have to be considered, such as increasing the diameter of the pump impeller or replacing the pump to compensate for the lack of flow for certain users. It should be noted that a good flow distribution leads to great savings in pumping power required to satisfy all system clients and increases pump life by operating in an ideal range.
Hydraulic balancing should be the preferred solution if equipment overheats in a cooling system. Unfortunately, the blame is often placed on exchangers that are too dirty or control valves that do not function properly when, in fact, the problem is often marked by a lack of hydraulic flow caused by system imbalance. A balanced system can therefore also prevent unfortunate production shutdowns caused by overheating equipment.
Profitability from balancing valves isn’t even an issue! Not only are they necessary for the system to function properly, but they help achieve substantial pumping savings.