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For the worlds best tank vent check valve there`s only one name you need to know...



JOHN GJERDE Maritime Tank Venting

For almost 40 years John Gjerde AS has designed, manufactured and marketed high quality tank venting equipment for the shipbuilding industry. Ever since John Gjerde AS was founded, the main focus of the company has been to cooperate closely with the shipbuilding industry and shipowners to meet their demands for tank venting equipment. As the years have gone by, the company has expanded and has today has a presence in virtually every part of the world where shipbuilding takes place. The company continues to keep in touch with shipbuilders, shipowners and consultants to continuously develop products for new tank venting needs. The focus on safe and reliable tank venting equipment has led to the development of the Aero 1 series of tank vent check valves. This range of tank vent check valves is a type-approved, thoroughly tested and well documented series of tank vents meeting the demands of almost all general tank venting situations. All the processes needed to manufacture the products are performed at our own workshop, engineering, machining, welding and testing. This ensures that only the highest quality products reach the customer. In addition to the standard tank vent check valves, the company also supplies special valves for different applications: mud tank venting, venting of inerted ballast tanks and venting of tanks on vessels sailing under arctic conditions, to mention a few. If your venting needs are not covered by the above, please contact us, we will be more than happy to help.


The Aero 1 – Tank vent check valves This is the new valve series from John Gjerde As. It consists of six valves, all with the same basic design and therefore the same basic operating principle. Utilizing a flat float, guided on a central pin. Ensuring low noise operation. The valve is a welded steel component, ensuring the necessary strength to withstand severe conditions, with a lifespan equalled by only a few. - The design is optimal for venting purposes - It has uniquely low leakage - It is of a sturdy design - It has uniquely low flow resistance


Aero 1.1

Aero 1.2

Aero 1.3


Aero 1.4

Aero 1.5

Aero 1.6



Basic operation When the valve is in “venting mode”, the float is resting on its support and the vent opening is open. This allows free air flow both in and out of the tank caused by thermal variations and loading/unloading operations. If external water rises and reaches the inner chamber of the valve where the float is positioned, the float will be lifted and come to rest against the gasket. The gasket is of a new design which ensures “no leakage when closed” to the tank. This means that the tank is secured against contamination from seawater penetration.


Aero 1.1 This is the type of valve most commonly used on sailing ships today. It is a valve for mounting on the open deck, venting directly to the atmosphere. It comes with three different connection possibilities: flanged, threaded and with a weldbut. The valve is most commonly supplied in hot-dip galvanized steel, but is also available in stainless steel and aluminium. As a result of the international loadline convention from 1966, all tanks on board ships are to be protected from seawater penetration. This is done by replacing the gooseneck, which was commonly used until then, with automatic closing devices. Today these valves are used on nearly all kinds of service tanks. The valve is used to ventilate all service tanks onboard sailing vessels. Ballast tanks, fresh water tanks, lube oil tanks and fuel tanks are all tanks that you will find on most vessels. This kind of valve is not used to ventilate cargo tanks.

Merits: - Known flow characteristics - Low leakage performance, no leakage when closed - Low cost - Low production times – short delivery time - Easily maintainable

Comes in all dimensions from DN40-



Aero 1.2 This is a valve for mounting through superstructures. This valve is used were it would be uneconomical/impractical to pull the ventline all the way to deck level. In these circumstances it is better to draw the ventline through the ship’s hull and have a vent opening there. It is therefore equipped with an outlet pipe directing the flow. This valve will be mounted through a superstructure and is therefore also available with a flanged end on the outlet for easy mounting. The inlet-outlet measurement can be modified to customer specifications, within reason. This allows for easy mounting and also provides versatility in the design process. Furthermore, our valve can be modified to be fitted as a replacement for almost all other designs. The valve comes in different materials: galvanized, stainless and aluminium.


Aero 1.3 Valve used on non-liquid filled tanks. Manual closing is useful where even the least amount of water penetration is highly undesirable. In bad weather or high seas there might be a need to close the valve manually to stop any water penetration. In case of a fire there might also be a need to shut down the supply of fresh air to the hold and to reduce the escape of flame preventing gasses if these are used.


Aero 1.4 Valve with a sounding cap. All tanks have ventlines. Some tanks also have sounding lines. For these tanks there are two separate lines to the tanks were, in principle, one is enough. John Gjerde AS has introduced a vent check valve with a sounding cap built in. The idea is that instead of having separate lines for venting and sounding, one can also use the ventline for sounding.

Aero 1.5 Vent check valve with directed overflow. This valve is similar to Aero 1.2, but instead of a straight pipe at the end, this valve has an elbow. It can also have a customer defined end. This is useful when you cannot mount the valve straight onto the vent exhaust. It is also useful when you are venting to a specified destination, like a buffer tank. You might want to do this if overflow liquid can contain oil residue or other contaminants. Harbour authorities are more and more restrictive about pollution, and this valve could hinder a potentially expensive mistake.

Aero 1.6 Vent check valve for venting through superstructures, inverted mounting. On large passenger ships and cruise liners there are special problems relating to the venting of tanks, this is due to the sheer height of the vessels. They have to vent through the ships side, but there might not always be room for the valves. If the ventline is pulled up to the minimum height, the line can come back down again and through the ships side.



Aero 1.3 inert modified Special tank vent check valve for inerted tanks. On some inerted tanks, for example ballast tanks located around special cargo tanks, a combined tank vent check valve/pressure vacuum relief valve must be used. The tank vent check valve functions as a normal tank vent check valve when the tank is ballasted, and as a pressure vacuum relief valve when the tank is inerted. The common way to do this prior to the introduction of this valve was to have two separate valves, switching between them as the tank was either to be ballasted or inerted. The tanks are not normally pressurised when inerted, but contain inert gas that should not be allowed to escape freely. Our Aero 1.3 valve is a manually closable tank vent check valve. In open mode it functions as a normal tank vent. When it is closed, no venting is possible. In the Aero 1.3 inert modified, a pressure relief and a vacuum relief have been added to the valve body, which makes the valve function as a pressure vacuum valve when it is closed. The set pressures are very low, as the pressure in the tank is normally atmospheric. In reality the valve is there only to keep the inert gas in place. Offshore supply vessels have started using this valve on the cofferdams surrounding methanol tanks. They have a choice of using ballast or inert gas in these cofferdams, and the preference is to use the latter. These tanks are pressurised, hence the set pressures are for these valves adjusted by a set screw on the pressure/vacuum relief valves.



Mud 1 Our tank vent check valve for tanks carrying liquid mud is a valve used on most offshore supply vessels currently being built with mud tanks in Norway. The valve is type approved by DNV for use on liquid mud tanks, and it replaces more complicated arrangements for ventilation of these tanks. The valve is a double vent check valve, with a lower and an upper chamber. The problem with mud overflow is that it might clog and shut off the valve if deposits builds up in the vent chamber of the valve (upper part). To prevent this we introduced a lower chamber so that the overflowing mud is effectively shut off from the upper chamber. If mud rises up inside the valve, the lower float rises, shutting the valve off. The overflow release in the side of the valve will then open and allow mud to overflow through it. The valve is available in hotdip galvanized and stainless steel. Type approved by major classification societies.



Spares and add-ons The Aero valves contain only one moving part, the float. The common design of all the valves in the Aero 1 series makes the number of different spare parts for the whole series quite small. Floats, gaskets and guiding pins are common for all the valves, only the dimension is different. Spares are available at short notice from our stock. In addition to the normal spares, we can also supply electrical heating kits for the valves, for arctic operation. A high flow cup, that almost doubles the capacity of backflow for the valve, is also availiable.


w w w. g j e rd e . c o m John Gjerde AS - Bryggjebakken - 6083 Gjerdsvika - Norway Tel.: +47 70 02 65 00 - Fax: +47 70 02 65 01 -


John Gjerde AS  


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