3-Way Valves vs. 2-Way
Valves in Chilled Water
Systems
Introduction
Chilled water control valves are important components in fluid pipelines because
they regulate the flow of a fluid by varying the size of the opening through which
the chilled fluid passes. Control valves are made up of three parts: an electronic
controller that houses the modulating elements, a positioner that determines
how far the valve opens, and an actuator that initiates the mechanical movement
of the controlling element. The control valve, as an essential component of any
fluid pipeline, helps regulate fluid flow between the minimum required and the
maximum installed capacity of the pipeline. These valves are also known as final
control elements.
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Actuators for Cold Water Valve
Actuators are an essential component of a control valve. In a chilled water system
environment, the chilled water actuator valve initiates a physical change in the system by
moving a modulating element such as a ball or a butterfly. Actuators are classified into several
types; the type used will be determined by the method used to create the control action. The
most common type of actuator is a pneumatic actuator, which uses air signals from the
controller to initiate mechanical movement of the modulating element. A spring return
actuator, on the other hand, makes use of spring force. Because of the spring motion used,
such actuators are unidirectional. Meanwhile, double-acting actuators use pistons and can
move in both directions. Finally, hydraulic actuators achieve mechanical movement by using an
incompressible fluid, such as water, rather than air.
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The Distinctions between 3Way and 2-Way Valves
Valves can also be classified according to the number of openings they have. Two-way
valves and three-way valves are two of the most common types used in chilled water
systems. A two-way valve is a simple device with two openings, one for inlet and one
for outlet. These chilled water control valves work as on/off devices and simply regulate
the flow of fluid through them by varying the size of the valve opening. As the name
suggests, a 3-way valve has three openings. These valves can be used to mix fluids when
used in a two-inlet, single-outlet system. They can be used as diverting chilled water
valves in a single-inlet, two-outlet system to redirect a portion of the flow in another
direction.
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Converting a 3-Way Valve
to a 2-Way Valve
Within certain industrial systems, a three-way
valve may be used as a two-way valve. In
layman's terms, this entails closing one of the
three valve openings; the bypass line is blocked,
so fluid entering through one side has no choice
but to exit through the other. However, once this
is completed, the actuator must be recalibrated,
as it is calibrated to show its maximum value
when the valve is fully open.
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Control Valves for Cold
Water
Both 3-way and 2-way valves have numerous applications. As previously stated, they are both
used in chilled water systems. The choice between a 2-way and 3-way valve is made during
the design stage, based on application-specific design and cost considerations. For example,
using a 2-way valve at the chiller's outlet allows you to modulate the supply to the cooling
load based on the load requirement. This can result in cost savings because the load on the
secondary pump is reduced. Two sets of pumps, however, are required in this case for a
constant flow supply to the chiller and a variable flow supply to the cooling load. A variable
flow chiller can also be used as an alternative. A 3-way valve is ideal for applications that
require a constant flow rate. These valves are also ideal when fluid mixing within the process
flow is required.
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