Failsafe Air-intake Shut-off Valve 4″ ISOV N400-FS

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ISOV N400-FS air shut off valve is a swing-gate, spring-operated air shut-off valve mounted in the air intake system. It works on impeding airflow into the cylinders and positively stop the engine. It can be installed pre- or post-turbo.

Control/Actuation: Mechanical Failsafe
Bore size/Flange Size: 4 in – 101.6 mm

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  • Technical Data

In stock



Although diesel engines are generally considered safer than gasoline engines in hydrocarbon-rich environments, they can pose ignition risks in specific scenarios. Diesel engine speed is regulated by an internal speed governor that controls the fuel supply. When flammable vapors are present in the atmosphere, they are drawn into the intake system alongside clean air, causing the engine to accelerate due to the additional fuel.
This acceleration leads to an increase in engine speed, resulting in the intake of more air and vapors, perpetuating the cycle until the engine starts running on unmetered vapors as its primary fuel source. If this cycle is not interrupted, it can result in engine overspeed or runaway, potentially becoming an ignition source for explosive vapors. This situation may lead to various hazards, including:
• Valve bounce
• Flames emanating from intake and exhaust pipes
• Elevated surface temperatures (auto ignition)
• Sparks
• Severe injury or fatality

The ISOV functions as an air shut-off valve integrated into diesel engine air intake systems, effectively halting airflow into the engine cylinders, thereby immobilizing the engine and ensuring the safety of both personnel and equipment. It offers manual or automatic control options, capable of responding to various fault or hazard conditions.
Having gained widespread adoption globally, the ISOV demonstrates exceptional performance in diverse environments, including challenging locations such as the Canadian Arctic, the Gulf of Mexico, the North Sea, African deserts, the Middle East, and the Pacific Rim, both onshore and offshore. Our product consistently meets or exceeds the stringent standards set by our diverse customer base, which includes leading engine OEMs.

Key Features & Benefits:

  • Manual or automatic controls – Electric, Pneumatic
  • Mechanical Failsafe control option available
  • Used on-shore and off-shore
  • Responds to a variety of fault or hazard conditions
  • Available with 2” (51mm) to 8” (204mm) of unrestricted port
  • Operates safely at ambient and induction air temperatures between 350°F – 400°F (176°C – 205°C)

Typical applications include power generation, rig saver, off-shore platforms, bulk fuel loading facilities, marine engine rooms, mining equipment, refineries, and petrochemical plants.


electric-failsafe air intake valves


Note: There are a wide range of sizes and flange adapters available


Generally, ISOV Air Intake shut-off valves can be installed pre-turbo or post-turbo on turbo-charged engines. For further support on installation, please contact our team here.


ISOV Failsafe Valves are found on offshore cranes as well as on Oil and Gas installations whereby the valve must close whenever electric power is lost. This version requires Oil or Air pressure to guarantee its functionality. The Failsafe version is available in sizes from 2″ up to 8″ (50 – 203 mm).

The Failsafe (FS) Series work in the following way:

isov failsafe

ISOV is opened by rotating the Hexagon as shown. While holding the Hexagon in the open position, the push button (2) has to be pressed.

At this stage the rotating Hexagon can be released provided the Push button (2) is pressed.

To hold the open position of the valve the locking switch has to be pressed and release the push button. After this procedure Oil or air pressure will take over the push button function which means that the valve will be latched in open position until pressure is lost through the 2/3-way solenoid valve.

The 2/3 Valve is a normally closed valve (see diagram) which means that whenever electric power is lost, the 2/3 Way will close the port and starve ISOV off the required pressure to remain in the open position.



ISOV Air-intake shut-off valves are designed to work with a wide range of engines used in heavy-duty trucks, exploration, production, mobile, and rental equipment. Here are a few examples where ISOV valves could be installed.

ISOV Failsafe Series can be alternatively used on many installations. You can contact us for support in choosing the best ISOV air-intake valve for your needs.

Heavy Duty Trucks:
Common MakesCommon EnginesActivation MethodBenefits
PeterbiltCummins ISX1512 V electric or


Meet international regulations that require air shutoff valves on vehicles that transport hazardous materials
KenworthPaccar MX Series 11, 13
International TrucksPaccar PX Series 9, 8
Freightliner TrucksCAT C15
Western StarMaxxforce Series 9, 11, 13
VolvoDetroit DD13, DD15, DD16
Mercedes Benz


Exploration & Production Equipment
Common MakesCommon EnginesActivation MethodBenefits
Well servicing equipmentCummins QSK50

Cummins QSK38

Cummins QSK23

Cummins QSK19

Cummins QSK30

24 V electric


These products are designed for high horsepower, heavy duty engines and harsh operating environments.

• High vibration resistant

• IP Rated – Sealed from environment

• Tolerates extreme temperatures

• Corrosion resistant

• Fits a wide range of pipe sizes

Pressure pumpsMTU 4000
Fracturing blendersMTU 2000
Offshore production enginesCaterpillar C18

Caterpillar C15

Caterpillar C13

Cummins QSM 11
Cummins QSL 9
Detroit Series
DD 13, DD15, DD16


Mobile & Rental Equipment
Common EquipmentActivation MethodsBenefits
Portable welders12V electric• Designed to fit small engines

• Compact and lightweight for tight spaces

Light towers
Fork lifts
Boom lifts
Air compressors
Portable generators


Additional information

Weight4 kg

Possible replacements and related products