Hey there guys. Paul here from theengineeringmindset.com. In this video, we're going
to be learning the basics of how solenoid valves work. Coming up, what do they look like? Why are they used? Where are they used? And how do they work? If you are working with solenoid valves, you're going to want to
download the Magnetic Tool app from Danfoss, who have
kindly sponsored this video. The app makes it easy to test that your solenoid valve
is working properly and works with both AC and DC versions.
You can download it for
free for Android and iPhone using the link in the
video description below. Solenoid valves are used to
convert electrical energy into mechanical energy. Solenoid valves have quite a
distinctive look about them. As you would expect,
they have the valve body, but on the top they have a block, which will have some cables coming out once the valve is installed. This top part is the solenoid, and the bottom part is the valve, therefore making a solenoid valve. Here's a small real-world solenoid valve, and in the next solenoid video, we're going to actually cut
this one open to look inside as well as make a very simple
solenoid valve ourselves to understand the mechanics
of how it operates. Now these valves do come in a
variety of shapes and sizes. I'll just show you some examples here.
The shape variation depends
on the capacity of the valve, the pressure it's working with, and the different internal mechanisms, which we'll look at
later on in this video. Why do we use solenoid valves? Well these valves allow
engineers to autonomously and remotely control the flow
of fluid within a system. This fluid can be a liquid or a gas, for example, water, air,
natural gas, oil, steam, refrigerant, etc. The list goes on and on. The solenoid coil on the top
is used to operate the valve by passing an electrical
current through it to create an electromagnetic field and operate the valve. This means, if it is
connected to a controller, it can be operated autonomously and remotely by a computer, without the need for engineers
to physically run around, opening and closing valves.
This allows systems to
run much more efficiently and safely. So where do we use or
find solenoid valves? The short answer is everywhere. Solenoid valves can be
found in everything, from washing machines up to space rockets, although we're going to
focus on the industrial and HVAC applications for this video. Let's have a look at some examples. In commercial refrigeration systems, we're almost certainly going to find at least one solenoid valve in the system, and it's usually found in the liquid line near the expansion valve. We've also covered how
expansion valves work in a previous video.
Do check that out. Links are in the video description below. You can see this example here
from the air handling unit which I was recently working on. This has a double direct
expansion cooling coil inside to control the temperature
of the air being sent around the building. The top expansion valve and cooling coil is always on when the system operates. But the second expansion
valve and cooling coil only come on in the summer, when the cooling load is too large for the single coil to handle. The solenoid valve is therefore used here to isolate the second coil
and the expansion valve until it is needed. The controller then sends
a signal to the valve to open and provide
the additional cooling. Another very common
application for solenoid valves in refrigeration systems is
in the hot gas defrost line to control the flow of hot refrigerant into the evaporator
during the defrost cycle. When the moisture in the air condenses on the tubes of the evaporator, it will freeze and cause a buildup of ice. We need to remove this to
ensure efficient operation, so we open the solenoid valve to send hot refrigerant
from the compressor through the evaporator
instead of the condenser.
Then, once the defrost has completed, the solenoid valve shuts
and the system continues as normal in cooling mode. In industrial applications,
we can use these valves to precisely control the
flow and mixing of fluids, for example, to pour a
perfect amount of fizzy drink into a bottle on a production line. We might also find
solenoid valves being used in a production line to
detect and prevent leaks. If a sensor detects a
leak from the pipework, then a controller will tell
the solenoid valve to close to shut that part of
the production line off and prevent product being wasted and also protect the
manufacturing equipment until engineers can get there and fix it. So how do they work? As we saw earlier in the video, there are a few variations
in how the valve operates, depending on the required capacity and the pressures it's working with. We're going to focus on the
directly operated valves, which is the simplest version.
With a direct operated valve, we have the solenoid on top, which is basically a coil of wire. As you may have seen in
our electrical videos, when you pass an electrical
current through a coil, we generate an electromagnetic field. This magnetic field is what
we'll use to control the valve. We have two types of valve, the normally open and
the normally closed type. Let's look at the normally
closed type first. So inside the valve we have the armature. The solenoid is placed over this and completely surrounds the armature so that it's at the centre
of the magnetic field. Inside the cylinder of the armature is the plunger and spring. The spring pushes the plunger down in a normally closed type valve. Because the plunger is
pushed by the spring, it will sit in the down position to close the valve indefinitely.
But if the coil receives
an electrical current, then it would generate
an electromagnetic field, and this magnetic field
passes through the plunger and will cause it to move upwards, against the spring,
therefore opening the valve. At the centre of the coil, the magnetic field lines
are the most compact, and therefore the strongest. This is why we place the
plunger in the centre. Once the electrical current is stopped, then the magnetic field disappears and the spring will force
the plunger down again to close the valve. With normally open valves, we again have the coil
sitting around the armature, but this time the spring
pushes the plunger in an upwards position so
that the valve is always open, unless the solenoid coil is powered on.
There are a few different designs, but one of the simplest to understand is if we pass a current through the coil in the opposite direction, it again creates an electromagnetic field, but this time the field pushes the plunger instead of pulling it. When the plunger is pushed, it will close the valve
and stop the flow of fluid in the system. When the electrical current is stopped, the spring will then
force the plunger back to the upwards position
and open the valve again. In this very simple version, the direction of the
current flowing in the coil is what determines whether
the coil produces a pulling or pushing force on the plunger. Now we're going to look at that in much greater detail in our next video, and we're going to even
make a simple solenoid coil ourselves to see how this operates.
Can you think of any
interesting application for these valves? If so, then please let me know in the comments section down below. I just want to remind you to
download the Magnetic Tool app from Danfoss for free using the link in the video description below. Okay, guys, that's it for this video, but if you want to continue your learning, then check out one of
the videos onscreen now, and I'll catch you there
for the next lesson. Don't forget to follow
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TheEngineeringMindset.com.
