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Recommendations for flat gaskets

Installation
Proper installation is essential to ensure that a gasket will function reliably. Sealing surfaces and bolts must be selected based on the minimum required surface pressure and maximum permissible surface pressure for the gasket.


Please note

• Only use new, undamaged and dry gaskets; observe storage conditions (see below).
  
• Thoroughly clean sealing joints without scratching them, then dry them.
  
• Place gaskets in the center; do not use any aids (such as grease, releasing agents or sealers) on gaskets or sealing joints.
  
• Do not use corroded bolts, nuts or washers. The calculated and actual surface pressure must correspond to one another, so apply lubricant to the bolts and nuts.
  
• Install second sealing joint plane-parallel and tighten the bolts by hand. In order to achieve an even pressure distribution, apply defined screw tightening in a criss-crossed pattern in at least three stages.
  
  Example:
  • Stage 1: 20 % of the required torque.
    
  • Stage 2: 60 % of the required torque.
    
  • Stage 3: 100 % of the required torque.
  
  
• All of the bolts must have the same required torque.
  
• All gaskets will settle, especially after having been installed for long periods of time. Retighten bolts at 100% torque prior to initial commissioning.
  
• Fiber or PTFE-based gaskets which have already undergone high operating temperatures should only be retightened when cold. This should also be done in several stages and great care should be taken, since there is a risk of destroying the gasket (especially with fiber gaskets which have already hardened).

Storage conditions for fiber-based gaskets and gasket plates (FA pursuant to DIN 28091-2)
Maximum shelf life of two to three years under the following conditions:

• Temperature < + 20 °C
  
• Relative air humidity 30 % to 60 %
  
• Away from direct sunlight
  
• No artificial light with high UV content
  
• No ozone
  
• Must not be stored under tension

Major deviations from these conditions will shorten the permissible storage time. If critical (i.e. toxic) gases are involved, the storage time may not exceed one year. Store gaskets or gasket plates in special packages (airtight and light-protected) if necessary.

Fuji films for determining the surface pressures
The Prescale from Fuji Film is a great and easy way of determining the actual mounting surface pressures and their distributions over the pressed area of flat gaskets.

It uses a scale of red hues to depict surface pressures between 0.2 N/mm² and 130 N/mm² (depending on how sensitive the selected film is). The Fuji Film Prescale is available through REINZ-Dichtungs-GmbH.

Call us at: +49 (0) 731 / 70 46 – 777

Special application cases:
In practice, there are applications in which simple punched gaskets will not suffice.

In many cases, only a small amount of surface pressure can be achieved (especially with molded gaskets on covers or casings), meaning that even very soft gaskets cannot be compressed sufficiently. An elastomer bead can be applied to one or both sides of the gasket by way of screen printing. The bolt force is concentrated at these points, thus sufficiently compressing the gasket and keeping it tight. This can also be accomplished with MatriCS/RETALL, an elastomer-coated metal gasket with bead.

Flange gaskets with a metallic inner eyelet (preferably made of stainless steel) can be used to increase blow-out resistance or chemical resistance. AFM 34 CO ME, the new generation of blow-out resistant flange gaskets, boasts maximum sealing integrity even at low surface pressure, thus providing ideal conditions for complying with the leak-tightness class according to VDI 2290 based on TA-Luft.