KF40CV80S is a spring-loaded vacuum check valve installable in either vertical or horizontal orientations. With a CF8M (316) body and FKM (Viton) seal combination, it offers an operating temperature of -5 to 100°C, a leak rate of 1×10⁻⁸ mbar·L/s, and a minimum opening differential pressure of approximately 7 mbar, and is used for backflow prevention in vacuum systems in semiconductor, display, solar, and laboratory applications.
Features
Used to prevent backflow in air, inert gas, and vacuum environments
Maintains vacuum protection - usable in low-pressure piping conditions
Internal spring allows vertical or horizontal installation regardless of gravity
Specifications
Size
KF40
FLANGE
KF(NW)
Material
BODY: CF8M(316) / SEAL: FKM
TEMP RATE
-5°C~100°C
LEAK RATE
1x10⁻⁸ mBAR L/SEC
PRESSURE RANGE
1x10⁻⁸ mBAR
RELIEF MINIMUM PRESSURE Δ P
7mBAR
PEA PUMPING SPEED
10000(L/MIN)
INSTALLATION POSITION
ANY
Frequently Asked Questions
Can the check valve be installed horizontally instead of vertically?
KF40CV80S has an internal spring, so it does not rely on gravity and can be installed in any direction, vertical or horizontal. While typical gravity-dependent check valves only allow vertical installation, this product allows free orientation matched to the piping layout, making it useful in compact equipment or sections with complex piping.
What does the minimum opening differential pressure of 7 mbar mean?
For a check valve to pass fluid in the forward direction, a minimum differential pressure sufficient to overcome the spring force is required. The KF40CV80S spring is set to open at approximately 7 mbar of differential pressure, which is easily achieved under normal pumping conditions, so the valve operates without flow restriction. In lines that must operate at very low differential-pressure levels, this opening pressure can become an important design parameter.
What happens if the operating temperature range is exceeded?
The standard specification supports the -5 to 100°C range. In high-temperature environments exceeding this range, the FKM (Viton) seal can harden and lose elasticity, reducing sealing performance. For high-temperature lines, heat-resistant seal materials (such as Kalrez) or metal-sealing structures must be considered. Tell us your operating temperature and we will advise on suitability and alternatives.
How much does it affect pumping speed?
KF40CV80S is designed for use even in large-volume pumping lines around 10,000 L/min, and because the minimum opening differential pressure is as low as approximately 7 mbar, its impact on pumping speed under normal operation is limited. However, actual loss varies depending on pump type and piping configuration, so for applications with strict pumping-speed requirements, share the configuration of the applied line and we will review it together.