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Nayflex Seals

Secondary Seals

Studies carried out on a wide range of storage installations showed the need for more efficiently in seal performance.

It has been shown that Secondary Seals in combination with Primary Seals are necessary to combat the effect of wind generated suction above the rim. This effect creates a serious loss in product, with associated influence on the environment.

The reduction in vapour loss created by fitting a secondary seal depends on many factors such as the product stored, tank location and climatic conditions, but in every case there are measurable savings in vapour loss.

Double Seals

Nayflex Double seals have been developed to replace and to be used as an alternative to metallic and fabric seals combined with secondary seals.

These seals offer enhanced efficiency and are probably the most cost effective seals produced to date.

Essentially this seal design combines the advantages of long service life, ease of maintenance and safety in use aspects of the Nayflex Secondary Seal with a specially adapted Primary Seal.

In developing these seals, Motherwell Nayler Petroseals have not only taken account of increased efficiency but also the service life, ease of maintenance and safety in use aspects have been taken into consideration.


The Nayflex range of seals consist of a seal tip of composite material attached to a ring of flexible steel compression plates bolted to the top of the roof rim.

The plates are pre-formed and specially shaped in such a way to utilise the elastic strength of the steel to provide positive pressure to the seal tip over a range of rim gap variations. This action produces an extremely effective and flexible seal which can accommodate a degree of local shell deformation.

The compression plates are fixed to the roof rim with bolts and clamping channels, thus ensuring a firm connection to develop the positive pressure exerted on the seal tip. The illustrations on the previous page show the seal attached to a vertical lip on the roof rim, but the connection can be designed for other configurations.

A resilient gasket is used between the overlap in the plates to permit relative movement while maintaining a gas-tight seal. As an alternative option, a continuous flexible vapour barrier can be provided which is attached to the tip and the roof rim.

Depending on particular conditions, these seals can show improvements in sealing efficiency of 95% or more over other sealing systems.

Simple Installation

Since the seal is attached only at the top of the roof rim it is easily installed working from the top of the roof and may be carried out with the tank in service.

Maintenance is simple, and should it be necessary, it is possible to renew the tip without dismantling the seal.

Service Life

The specially compounded tip material is highly resistant to chemical attack and abrasion and, depending on the working environment, should last on average 10 to 12 years.

Galvanised steel is used for the compression plates as standard, but where the atmospheric or service conditions can cause serious corrosion it is recommended that stainless steel is used.

These seals have an excellent service record. Some have been in use for 12 years without the need of any major maintenance or renewal.


To provide electrical continuity, stainless steel grounding shunts are attached to the edge of the compression plates and make sliding contact with the tank shell.

Nayflex seals have been tested in rim fire simulations and have shown excellent performance in not only containing the effects of the fire, but also helping to extinguish the fire by excluding the supply of oxygen to the flames.

As an option, integral foam dams can be provided which will meet NFPA requirements.

Nayflex Seal Tips

Three forms of seal tip have been developed made from polymer materials which are highly resistant to chemical and atmospheric attack.

Special compounds can be produced with anti-static properties.


MN-30 Kingoprene Tip
Specially suitable for butt welded tank shells.
Gives positive contact with the tank shell.



MN-32 Duo-Tip
Specially suitable for butt welded tank shells.
Used where shell is distorted or welds are rough.
Gives double contact with the tank shell.


MN-34 E-Tip
Specially suitable for riveted tank shells.
Gives optimum contact with the tank shell over rivet
heads and plate laps.