- Primary & Secondary Hydrocarbon Storage Tank Seals

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API 650 advises that all tanks storing hydrocarbon liquids should be fitted with a seal system comprising a primary seal and a secondary seal. Ateco manufacture a range of primary and secondary seals. All Ateco Primary and Secondary Seals are fitted to the rim angle on the floating roof and are designed for a rim gap of 200 mm to 250 mm +/- 100 mm, however most can be modified to accommodate varying gaps provided we are aware of the requirements before seal manufacture begins.

The essential details that operators should take into consideration and provide to Ateco when purchasing a “seal system” are; compatibility of the stored product with all component parts of the seals, rim gap tolerance for the total travel of the floating roof, overall condition of the tank. Ateco has expert engineers available and willing to help – you only have to ask us.

The most popular seals are mechanical seals and this simply means that most of the seal parts are made from metal.

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Weighted Pantograph Primary Seal is the industry standard and oldest seal still in use. The Ateco Mechanical Weighted Pantograph Primary Seal comprises 1.6 mm thick compression plates which can be either stainless or galvanized steel held against the tank shell by a system of levers and heavy weights. The pushing force is gravity and since this is always present this type of seal has proved to me robust and very reliable. However, installation, maintenance and repair is relatively difficult and for this reason Ateco has introduced the Ateco Pusher Plate Primary Seal which is commonly referred to as a “top mounted seal” meaning that this seal can be accessed from the top of the floating roof.

Pusher Plate Primary Seal comprises 1.6 mm thick compression plates which can be either stainless or galvanized steel held against the tank shell by spring steel plates. Installation, maintenance and repair is relatively straight forward since all parts of the seal can be access from the top of the floating roof and even with the tank in service.

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Double Compression Plate Seal is a very efficient and most cost effective seal system since it comprises a primary and secondary seal in the same unit. The Ateco Double Compression Plate Seal features 1.6 mm thick independent and overlapping galvanized or 1.2 mm stainless spring steel plates, a continuous vapour barrier membrane can be included or, in the gasket version, with no vapour barrier, the compression plates are bolted together using shoulder bolts and a gasket is fitted between the plates to form the seal.

Mechanical seals can be fitted with a wax scraper and where highly volatile products are stored a drip curtain can be attached and this has the effect of enhancing the sealing efficiency in areas where seal tip to shell contact is less than perfect due to protruding welds, severe corrosion of shell plates.

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The main Ateco seals in the non- mechanical category are:-

  • Ateco Foam Log Seal
  • Ateco Liquid Filled Seal.

Both of these seal types comprise a tough polymer coated envelope surrounding compressible polyurethane foam or in the case of the liquid filled seals they are simply filled with a liquid such as kerosene.

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Ateco supply a foam dam that bolts on the rim angle and has the same hole spacing as the primary and secondary seals, with either 1.6 mm Galvanized or 1.2 mm Stainless Steel Plates the Ateco Foam Dam meets the intent of API 650 and NFPA10 but to fully comply we also offer 3.5 mm thick plates for bolting or welding to the tank roof.

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Compression Plate Secondary Seal with 1.6 mm thick independent and overlapping galvanized or 1.2 mm stainless spring steel plates is the most popular secondary seal and can be used with all the Ateco primary seals to provide a very effective seal system. The Ateco Compression Plate Secondary Seal can be supplied with a continuous vapour barrier membrane or, in the gasket version, with no vapour barrier; the compression plates are bolted together using shoulder bolts and a gasket is fitted between the plates to form the seal.

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Low Profile Secondary Seal has been designed to reduce the overall height of the secondary seal tip above the rim angle and gives the potential for increased tank storage capacity.

Ateco have a range of seal tips and this ensures that the material used to manufacture them is fully compatible with the stored product and the profile used suits the condition of the tank shell.

To prepare our most competive quotation it is important that the correct information is sent to us; this should include the following:

  • Nominal diameter of the tank
  • Stored product
  • Type of Primary Seal required i.e. Mechanical - Foam - Liquid
  • For Mechanical Primary Seal; specify type i.e. Weighted Pantograph - Pusher Plate - Double Compression Plate
  • For Mechanical Seal; specify shoe plate material i.e. stainless or galvanized Steel
  • If Secondary Seal required, specify stainless or galvanized compression plates
  • Confirm rim gap dimensions for complete travel of the roof are within tolerances of API 650    
  • Additional accessories - such as Wax Scraper and Drip Curtain 

We recommend that you read carefully the Standard Terms and Conditions for Quotation (Item 14.1002) and of course look at the Technical Details included in the Download Section of the Ateco Web Site where full details of the Ateco Primary and Secondary Seal Systems are included.

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