This article discusses about control valve uses. Control valve as the name suggests, controls the flow rate and related properties of flowing fluid such as pressure and temperature.
What is a control valve?
As discussed above, a control valve is a device that controls the flow rate and related properties such as pressure and temperature.
The control action takes place as directed by the signal from controller. It opens and closes which helps in controlling the fluid flow in the passage.
What are different types of pressure control valves?
Pressure control valves are most commonly found in every hydraulic and pneumatic system.
The different types of pressure control valves used in industries are as follows-
- Pressure relief valves– Usually the hydraulic system and pneumatic systems work in a specified pressure range. When the pressure goes beyond this range, that is when relief valves come into picture. They avoid the components from getting damaged by controlling the pressure differential.
- Sequencing valves- If the circuit has more than one actuators then it is necessary for these actuators to move in a sequence. This can be achieved by using limit switches, timers or digital control devices with sequencing valves.
- Pressure reducing valves– The name itself implies that these valves are used for reducing the pressure of the fluid that is flowing. This ca be achieved in a single stage as well as two stages depending upon the application. This provides a better repititive accuracy. In hydraulic applications, there may be blockage of flow due to oil contamination.
- Counter balance valves– Counter balance valves are not used directly, they are used passively. That means they are closed valves which maintain a set pressure in certain portion of a flowing circuit. This is done usually to achieve counter balancing of weight. The design of this valve is perfect for counter balancing an external force or counter act a weight as in a press to keep it from free falling.
What is a directional control valve?
Directional control valves or DCVs are the most important parts in both hydraulic and pneumatic systems.
Directional control valves allow the fluid to flow in different passages from one or multiple sources. These valves are actuated by the action of a spool whose position restricts or permits the flow of fluid.
What is a spool in directional control valve?
Spool is responsible for controlling the fluid flow.
It is used to regulate/control the flowing fluid and connects internal passages and port. Its design includes lands and undercuts which are encased in precisely machined housing. The lands and undercuts will open and close flow paths once the spool shifts.
Classification of directional control valves
The classification of directional control valves or DCVs is done as follows-
- According to number of ports– Depending on the number of ports, directional control valves are classified as 2-way, 3-way or 4-ways valves.
- According to type of spool– Depending on the type of spool used, they are classified as poppet, rotary and sliding valves.
- According to actuating method used– The position of the valve is changed by the actuating the handle which can be done manually, mechanically or electronically.
Directional Control Valve benefits and features
The features of directional control valves make them beneficial for industries to use them.
The features and benefits of directional control valve are as follows-
- Custom porting is available.
- It is light in weight as aluminium is used for construction.
- Blocked, open and power beyond options are available.
- High flow options are also available.
Directional control valve uses
Hydraulic directional valves are used in many agricultural and Mobile industries to have smooth operation and low pressure drop.
The directional control valves are used in many applications such as-
- Car carriers
- Assembly line
- Energy production
- Construction machines
- Material handling cranes
- Trucks and rigs
What are the things to be considered while choosing a directional control valve?
The following points should be considered while analyzing the performance of a directional control valve-
- Dynamic power limit.
- Static power limit.
- Resistance to flow
- Switching time
What is a differential pressure control valve?
Differential pressure valves or DPCVs are valves that are used in heating or cooling systems to regulate sub-circuit pressure to desired or given maximum.
A differential pressure control valve reduces energy consumption, provides silent operation and has simple commissioning process.
How does a differential pressure control valve work?
A differential pressure control valve includes a capillary tube, spring and a diaphragm.
A DPCV controls or regulates differential pressure in the circuit depending on the impulse of pressure coming from the inlet and direct pressure from the outlet side. The spring force will be equal in magnitude as the differential pressure force across the circuit.
Differential pressure control valve uses
Differential pressure control valve sets the differential pressure in the circuit to a maximum due to which we get following uses of differential pressure control valve-
- Extremely efficient
- Reduces noise and provides a silent operation.
- Reduces energy consumption.
- Makes the commissioning process less complex.
- As they are pressure relieved so low force actuators can be used.
- Keeps high controllablity in the system.
- Reduces pump head.
What is PICV?
PICV stands for Pressure independent control valve.
These valves are used in heating applications where differential pressure exists, by adding an actuator these valves act as flow limited control valves that balances the system and hence provides the best possible indoor comfort and energy efficiency.
What are the features and benefits of pressure independent control valves ?
PICV provides similar features and benefits as that of DPCV.
The features and benefits of pressure independent control valves are-
- Stable room temperature– It eliminates the overflow situations at partial load conditions that helps in maintaining stable room temperature.
- Improved indoor comfort– As the room temperature becomes more and more stable, the indoor comfort increases. The desired temperature is accurately met which also increases the productivity of employees.
- Energy savings– A perfectly balanced system increases the energy savings and cost savings.
- Reduced maintenance costs– As these valves ensure perfect working conditions, the actuators require few movements which in turn reduces the need of maintenance.