The mixing unit belongs to the category of pipeline control valves. A three-way valve for heating mixes different heat carrier flows into one to obtain a stable temperature. The node divides and switches the flows to other lines with the appropriate installation scheme. The valve works automatically when there is a drive and receiving signals from control sensors.
The device and features of the three-way valve
The module is used in the liquid heating system and as part of the piping of air heaters and air coolers. Three-way regulators are divided into separating and mixing types.
The valves are similar in design and consist of parts:
- body;
- connecting flange;
- sealing element;
- link for transferring force from the drive to the shutter;
- plunger of various profiles to determine the type of adjustment;
- seat for seating the plug in the closed position.
The regulating element is a travel rod or a swivel ball. These mechanical links do not completely close the valve, leaving room for mixing or redistribution of currents.
Types by control method
The types of control depend on the working conditions and purpose. The fixing sensors of the heating main transmit commands to the controllers, and they coordinate the actions of the energy suppliers.
There are types of drives:
- with thermostat;
- electric drive;
- pneumatic;
- hydraulic.
A manually operated actuator is much less common.
Manual control
The stem is driven by a rotary knob or valve. For convenience, a control panel is installed, on which marks are applied. The risks correspond to certain thermal hydrological regimes.
- The positive aspects include:
- low cost of a manual drive;
- direct control of mode indicators;
- the ability to instantly change the order of work.
The disadvantages include the need for the constant presence of the operator for response. Manual control does not provide uniform heating of the pipeline.
With thermostat
A three-way valve for heating is equipped with a thermostat in which there is a liquid or gas. The internal environment reacts to all changes in the temperature of the streams. Heating up to the set parameters activates the thermo-valve piston system and the hot flow is blocked.
Three-way units with a thermostat are mechanical or electronic. Mechanical ones work autonomously, while electronic ones require connection of electricity or battery power. The disadvantage of the second type is compensated for by absolute automation. Electronic regulation allows you to set a change in the order of heating by days of the week, time of day.
With electric drive
An electromagnet (solenoid) is installed or a combination servo drive is used, mounted on an electric motor with a transmission mechanism. The drive is coordinated by temperature or pressure meters that are installed in the piping loop.The unit is immediately equipped with a servo drive or delivered without it, which makes it possible to choose the optimal device for actuation.
The technical characteristics of current, voltage, power, overload capacity are taken into account. They choose economical and reliable, without high operating costs, pay attention to the working conditions and safety requirements.
Hydraulic
The three-way valve for heating with a thermostat is supplied with a thermostat installed inside the housing. The device operates according to the parameters of the outlet water temperature, which are set at the factory. The hydraulic actuator includes a disc-shaped diaphragm housing.
The low price belongs to the positive aspects of use. The negative side is the need to select a hydraulic drive for the temperature of the liquid in the heat line. The second disadvantage is the impossibility of changing the heating mode set at the factory.
Pneumatic
The pneumatic actuator automates the operation of the control valve and is used for remote control. The actuators are a cylinder with a piston that moves under the action of compressed air.
Benefits of using pneumatic drives:
- fast control when environmental conditions change;
- simplicity of design and interchangeability;
- the change in force is achieved by simply limiting the air pressure in the actuator.
Pneumatic devices are more commonly used for valves. Requires additional installation of a compressed air compressor for operation.
Three-way valve working principle
The force from the actuator is applied to the valve including the seat and plug. The piston blocks a portion of the port, which reduces the flow through the valve. The flow rate increases and the static pressure in the pipeline decreases. The plunger is placed in the seat when fully closed, and the coolant flow is shut off, there is no water pressure downstream of the valve.
Single-seated and double-seated valves are available, while the piston is rod, needle or poppet type. Double-seat are used more often due to the good balance of the valve and effective tightness. They are used to change the pressure up to 6.3 MPa in lines with a diameter of up to 300 mm.
The principle of operation of a three-way valve for heating with a cage action is that the saddle simultaneously serves as a guiding device (cage) and a place for fixing the hollow valve when closing. The flow rate of the medium is regulated by perforation in the walls of the cage.
Diaphragm valves use external or built-in hydraulic or electric actuators. In the case of a separate actuator, the force is applied to the rod bearing through the diaphragm, then to the control link. After the pressure drops, the membrane returns to its original position. With a built-in actuator, the water flow is coordinated by closing the hole in the diaphragm.
In three-way spool valves, the coolant flow rate is regulated by turning the movable element at a certain angle. The modules are used as control devices.
Installation features
Manufacturers do not always assemble an actuator and a valve into one design. Sometimes it is necessary to replace the valve without dismantling the feeder.
The following steps are taken:
- Loosens the locknut on the valve and coupler. The locking element is unscrewed down when pressing the piston with the rod. Unscrew the coupling and nut downwards.
- The ring nut and the connector are removed by the thread from the drive. The nut slides over the piston rod.
- The actuator is installed upward of the valve and secured with a nut.
- The information table of the actuator specifies the description of the control signal range and the type of device.The safety position is determined and the module is placed in the “actuator stem extended” position.
- In the safety position, air is supplied to the connection of the lower chamber under pressure corresponding to the start of operation. The position is changed to "actuator stem retracts" and is pumped into the upper compartment of the diaphragm compartment, its value corresponds to the end of the adjustment.
The fixing sleeve is turned until it comes to the actuator, then screwed on by ¼ of the turn and secured with a lock nut. The connector is put in and screwed until it stops. The travel indication scale is aligned with the top of the coupling.
The nuances of valve selection
The three-way regulator is selected taking into account the results of the hydraulic and thermal engineering calculation of the heating main - the circuit where it will be installed. Attention is drawn to the pressure, water temperature, heat carrier flow per hour.
In addition, the following characteristics are taken into account:
- type of shutter mechanism;
- control method;
- scope of application;
- valve material.
The diameter of the connecting pipes and the method of connecting the mixer (flanged or threaded) matter.
Popular manufacturers
Five leaders stand out among the manufacturers. They manufacture plumbing fixtures, thermostatic systems and state-of-the-art technologies.
- IMI-HEIMEIER (Germany).
- ESBE (Sweden).
- HERZ (Austria).
- Danfoss (Germany).
- Valtek (Russia, Italy).
Valtek is a separate project of joint work of Russian and Italian engineers. The products are adapted to the conditions of Russian heating mains. It is characterized by an affordable cost.
