Check Valves
The function the check valves:
Check valve is a valve that prevents the flow reversal in a pipeline or in a piping system. By using this
valve, it could be achieved unidirectional flow. Valve closure takes place due to the weight of the check
mechanism that might be the back pressure, a spring or the combination of both.
Product Standards
Design standard: API602, ASMEB16.34, API6D
Structure length: ASME B16.10
Material and temperature: ASME B16.34
Inspection standard: API598, API6D
Major type of the check valves
Swing check valve
Lift check valve
Titling check valve
Diaphragm check valve
Butterfly check valve
Stop check valve
Swing check valve
Major parts of the swing check valve are, the valve body, bonnet, and a disc, and the disc would be
attached at the top section of the valve as shown in the figure below. The swing check valves are used
mostly in pipelines where the medium flows in one direction to avoid accident and detriment the
equipment. When the fluid comes in the forward direction then the disc swings in an open position thus
allowing the fluid to pass. When the flow of the fluid is in opposite direction then the disc swings and rests
on the seat as shown in the figure 1.
Figure 1. Swing check valve.
The swing check valves are mostly used where full flow is required. They are mainly used in petroleum,
chemical, pharmaceutical, fertilizer, power, and another pipeline.
This type of valve should generally be installed horizontally in the pipeline. But it is not preferable to use
vertically because, the disc cannot reach the stalling position where the disc is stuck in the open position.
Lift check valve
A lift check valve is an automatic valve installed within a high-flow system to prevent backflow and
cross-connection as indicated in the fig.2. It’s commonly used in steam, air, gas, and water systems in a
horizontal or vertical piping system. It is mostly used for high-pressure applications where the velocity
high. Examples of lift checks include nozzle check, silent axial check, and ball check valves. These valves
have no external moving parts and can be economical to produce and reliable in operation.
Figure 2. Lift check valve.
Silent Axial Check Valves are commonly used in high‐rise buildings and high head applications because
of their quiet closure. When the flow is initiated, the disc is pushed to the right to allow forward flow.
When the pump is stopped, the compression spring in the valve forces the valve closed before the flow
reverses, which provides silent closure. They close very quickly (in about one tenth of a second) because
of a short linear stroke, which is equal to one fourth of their diameter.
Figure 3. Solent axial check valve.
Nozzle Check Valves operate similar to Silent Check Valves but have a smooth venturi‐shaped flow path
and annular disc with lower head loss than the Silent Check Valve, but with a longer laying length. Like
the Silent Check Valve, the nozzle check has a spring‐assisted, short linear stroke, which provides the
best non‐slam characteristic of check valves. Nozzle Check Valves are commonly made in steel for high
pressure classes to meet the rigors of industrial and power plant applications.
Figure 4. Nozzle check valve.
Ball check valves contain a ball that sits on the seat, which has only one through-hole. The ball has a
slightly larger diameter than that of the through-hole (seat). When the pressure behind the seat exceeds
that above the ball, liquid is allowed to flow through the valve. But once the pressure above the ball
exceeds the pressure below the seat, the ball returns to rest in the seat, forming a seal that prevents
backflow. Ball check valves are typically preferred for use in pumping stations as they are self-cleaning
as the ball rotates during the operation and are vertically maintenance-free. If a ball check makes noise,
it is typically due to insufficient pump capacity or water hammer issues. These check valves can be used
for fluid condensate in gas or steam lines.
Figure 5. Ball check valve.
Titling check valve
In this type of check valve, a disc rotates about a hinge as shown below, the major parts of this type of
check valve are a disc, body, spring, and spring retainer. The disc would move in a plane at right angles
to the flow of the fluids, and this movement is restricted by the spring. If the force which is exerted by
the upstream pressure is more than the force which is exerted on the disc by the spring then the disc
would lift off. When the differential pressure across the valve is reduced then the spring would force the
disc back to the seat thus it would prevent the backflow. Tilting Disc Check Valve offers significant
energy savings compared to other types of conventional check valves because of its larger flow area and
low head loss characteristics.
These valves are only suitable for water service because sludge and rags in the dirty fluid would stick
onto the disc The check tilting disk check valve is a cost-effective valve with a unique design that
provides excellent tightness and minimizes water-hammering.
Figure 6. Titling check valve
Head loss is an important factor in the design and operation of fluid systems, such as pipelines, pumps
and heat exchangers. It represents the amount of energy lost as fluid flows through a system and can
have a significant impact on system performance and efficiency.
Diaphragm check valve
Diaphragm check valves, sometimes referred to as one-way valves use a flexible diaphragm to control
the flow of fluid. They are popular in industrial applications because they are durable and can handle
high pressures and temperatures. As the name implies, diaphragm check valves have a diaphragm that
controls the flow. When fluid pressure is applied to the valve from the inlet side, the diaphragm forces
open, allowing fluid to flow through.
Once the fluid pressure lessens, the diaphragm closes, preventing any backflow as illustrated in the
figure below. This makes diaphragm check valves ideal for preventing reverse flow in systems where
that could be dangerous. It can be used as tight shut off, be used for maintaining pressure and
regulating flow.
Figure 7. Diaphragm check Valve.
Butterfly check valve
Butterfly check valves have a similar construction and flow characteristics as butterfly valves. They are
often used together in flow management systems. Butterfly check valves are a specific type of butterfly
valve used primarily for preventing backflow in a pipeline. They typically have a disc that allows flow in
one direction while preventing flow in the opposite direction as shown in the fig.8. This type of check
valves is designed so the body provides enough room for easy movement of the butterfly disk. The
design allows for flexible sealing against the bore of the valve body at 45° and reduces the slamming
action. They can be used in the same applications as butterfly valves, can be installed horizontally or
vertically and can handle vertical flow.
Figure 8. Butterfly check valve.
Stop check valve
A Stop Check Valve is a combination of a lift check valve and a globe valve. These are designed to
prevent the reversal of flow in a piping system. It has a stem which, when closed, prevents the disk from
coming off the seat and provides a tight seal (similar to a globe valve) as explained in following figure.
Having a stop check valve is like having two valves in one. The internal disc, which is not attached to the
stem, performs as a lift check allowing it to freely move up and down when the stem is raised to adjust
the opening and closing as. This controls the flow rate, but when backflow occurs, the disconnected disc
functions as a lift check and quickly closes, thus preventing reverse flow. If needed, the stem can be
manually lowered for flow to be stopped or completely shut off as a globe valve.
Figure 9. A Stop Check Valve can be operated as a lift check valve and a globe valve.
Selecting a check valve:
When selecting the best check valve for your compressor or pump application, consider the following
factors:

Flow rate: Choose a valve that can handle the expected flow rate in your system.

Pressure rating: Ensure that the valve can withstand the maximum pressure in your system.

Material compatibility: Select a valve material that is compatible with the fluid being pumped
(e.g., corrosive vs. non-corrosive).

Installation orientation: Some check valves are sensitive to the orientation in which they are
installed. Ensure the valve is installed correctly.

Maintenance requirements: Consider ease of maintenance and the need for periodic inspection
and replacement.
It's advisable to consult with a valve specialist or engineer who can assess your specific needs and
recommend the most suitable check valve for your compressor or pump application. Additionally, local
regulations and industry standards may also influence your choice of valve.