How to select the right gasket for a piping application? To choose the proper flange gasket, piping engineers should take into consideration the following 4 key factors: fluid type, process temperature/pressure, fugitive emissions Laws, other general considerations. While gaskets are relatively cheap components of the overall piping system, they are critical for its reliability and integrity: saving a few bucks with gaskets may create way larger disasters in the mid-long term, be careful!
Flange gaskets shall be selected based on multiple process factors, such as operating temperature/pressure, type of fluid conveyed by the pipeline, flange type, size, pressure rating, material grade, and specifications. Let’s now dive into each of these factors:
FLUID TYPE
The first criteria to select the right type of gasket is, of course, the type of fluid conveyed by the pipeline – and the fluid temperature and pressure.
Different fluids require different gaskets materials to make sure that the flanged joint performs over a long period of time.
PROCESS TEMPERATURE AND PRESSURE
A second factor to consider to select the right gasket material is the working temperature and pressure of the piping system.
In particular, the gasket material shall be able to withstand the highest temperature and pressures expected for the process (highest expected temperature-pressure for high-temperature applications, and lowest temperatures for low-temperature applications).
The gasket should not creep at the highest temperature and pressure expected for the process, otherwise, the flanged joint would become ineffective generating leaks.
The flange gasket should be able to withstand the maximum pressure expected in the pipeline; this is often the test pressure, which can be at least 2 times the flange rating at ambient temperature.
FUGITIVE EMISSIONS LAWS
The fugitive emission laws in the country of installation shall be also taken into consideration when selecting the right type of gasket for a process.
Indeed, more stringent fugitive emissions laws may drive specific decisions about the flanges and the gaskets to be used for the flanged joints of the process.
OTHER GENERAL ASPECTS
The other key factors to consider to select the type of gasket to use are:
a) Pipeline vibration and oscillation: the gasket shall withstand the oscillations and the vibrations that may affect the pipeline
b) Fluid contamination risk: For some applications, it is important to use gaskets that do not contaminate the fluid conveyed by the pipeline (for example; pharmaceutical and food applications, or gas pipelines)
c) Flanges corrosion: Some flange materials, such as austenitic stainless steel, are subject to stress corrosion cracking. This fact shall be considered when selecting the gasket type and material
d) Integrity: Toxic fluids require totally leak proof seals to prevent soil contamination or threats to human life. As a consequence, tighter and stronger gaskets may be the natural choice for these types of applications (example spiral wound gasket with outer ring vs. non-asbestos gasket)
e) Financial risk incurred in case of gasket failure: Although gaskets have a relatively low-cost impact on total piping materials costs, the selection of wrong gaskets may generate huge financial impact and savings in this respect may be dangerous both for the contractor, which may be subject to penalties, and the end-user.
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