SEALS & GASKETS FEATURE CAREFUL CONSIDERATION DURING INSTALLATION
Vulcan Seals explains the methods used for the internal and external groove installation of encapsulated ‘O’-Rings
F
EP/PFA Encapsulated ‘O’-Rings consist of an elastomeric core with a thin FEP
or PFA encapsulation. The encapsulation is a hard material with limited flexibility compared to a fully elastomeric ‘O’-Ring. Encapsulation damage can occur when installing into an internal groove or on to an external groove, where manipulation or stretching of the ring is required. Care must therefore be taken during
installation to prevent encapsulation damage, which would affect sealing capability and performance. Common installation issues: • Kinking of the encapsulation due to
bending, folding, twisting etc. This creates an uneven sealing surface, preventing an effective compression seal. • Physical damage to encapsulation, due
to use of a sharp installation tool, uneven stretching of the 'O'-Ring, or installation over sharp edges/burrs. This results in scratching, thinning or tearing of the encapsulation which will reduce the sealing capability and chemical resistance lifetime. Common installation issues can be
minimised by ensuring the installation process is carefully considered. Key elements include: 1. A carefully selected heating method
for softening the encapsulation to reduce the stretching/bending force needed during installation. 2. Ensuring installation surfaces are free
from sharp edges and have a surface finish of 30 micro-inch on a bore and 15 micro-inch on a shaft, to prevent physical damage. Heating Methods: Hot Water 1. Heat water to 100°C / 212°F (ensure
no excessive temperature fluctuation) 2. Place rings into the heated water (no
limit to submersion time) 3. Heat rings for a minimum of three
minutes 4. Remove ring when required for installation
5. Install ring quickly before
ring/encapsulation cools and hardens again 6. A hot water bath is
recommended for use in production environments where fitting demand is constant Advantages include: • Consistent and even
heating of entire ring to avoid damage to encapsulation during installation • Lower purchase and
operating costs compared to oven heating • No limit to submersion time Oven Heating 1. Fit 2 or more shelves into the oven to
allow cycling of products a. Lowest shelf to be used for rings ready
for installation b. Upper shelves to be used for initial
heating of the rings c. When lowest shelf is empty, replace
with the shelf above and move to top shelf 2. Set oven to 100°C (ensure no
excessive temperature fluctuation) a. Use an additional internal
thermometer to check against the oven’s digital reading 3. Place and spread rings evenly on a
heavy gauge baking sheet 4. Heat rings for a minimum of 15
minutes (no max. time limit) 5. Remove the rings, keeping them on
the baking sheet 6. If possible and safe, removing
individual rings as and when required is ideal (e.g. using heatproof gloves/tools) 7. Install ring quickly before ring/
encapsulation cools and hardens again Advantages include: • Consistent and even heating of entire
ring to avoid damage to encapsulation during installation • No time limit to heating duration Disadvantages • Multiple rings need to be quickly
External Groove (left): Typical Applications • Cartridge filters
• Drum/barrel caps and connectors • Valves • Mechanical Seals
Internal Groove (right): Typical Applications • Mechanical Seals • Valves
Internal Groove (Mechanical Seal), right
External Grooves (Filter Cartridge), above
removed and installed at the same time before the ring/encapsulation hardens again (unless heatproof gloves/tools are used to remove individual rings) • Oven temperature can fluctuate
excessively when oven door is opened/ closed • Oven purchase and running costs Direct Heating (Not Recommended) Use of direct heating methods (e.g. heat
lamps and hot plates) are not recommended due to the uneven and inconsistent heating applied. Installation Method: External Groove – Ensure an even
stretch of the ‘O’-Ring by use of a tapered fitting tool until it drops into the target groove. Heating of the ring prior to installation is recommended to prevent damage. Once installed, and if needed, external
pressure can be applied evenly across the entire circumference of the ring to ensure it returns to its original diameter. To avoid sealing performance issues and failures, the tool used to apply this pressure should be smooth and not cause damage to the ring’s encapsulation. Ensure the ‘O’-Ring groove is free from
sharp edges and burrs before and after installation. Internal Groove - An Encapsulated ‘O’-
Ring must be temporarily collapsed into an oval for it to be installed into an internal groove. Heating of the ring prior to installation is recommended to prevent damage kinking of the encapsulation. Once collapsed, push one side of the ring
into the opening where the internal groove is situated. Push until the leading edge of the ring fits into the groove. Then, ideally using a suitable pushing tool, push the trailing edge of the ring into the opening until the entire ring fits into the groove. Again, ensure the ‘O’-Ring groove is free
from sharp edges and burrs before and after installation.
Vulcan Seals
www.vulcanseals.com
PROCESS & CONTROL | APRIL 2019 23
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