Most deaerators (Approx 70 to 85%) built over the past 50 years have not used any of the design requirements called out in the HEI standards. With the exception of a very few deaerators (in paper plants) there have been little or no pressure envelope failures to warrant all the extra costs involved in the HEI standards. Deaerator specifications containing the blanket statement ” build to HEI standards” add costs to a piece of equipment that in most cases does not require it.
If there are concerns about certain situations, it can be more cost effective to address (specify) only the actual concerns, i.e. corrosion allowance, weld xray requirements, stress relief, etc. However, unless the deaerator is located in the harsh environment of a paper plant with the typical lack of inspection and maintenance, and high pressure operation, the HEI standards may be “gold plateing” that is not required by the actual application. Most plants with a deaerator operating at 5 – 10 psig, that perform a yearly plant shutdown for maintenance, will not require all of the extra design requirements invoked by the HEI standards.
The HEI standard was developed by a joint effort of manufactures of counterflow type deaerators, to not only regulate the design of deaerator pressure envelope, but to also regulate internal construction and material requirements, by applying requirements of counterflow design to parrallel design type deaerators. The HEI specification states it is only for “tray” deaerators, not “spray” (atomizer) deaerators. If the contents of this specification are so critical to deaerator saftey and performance, then one must ask why is this specification not written to cover “all” deaerators. Is not any vessel using steam to remove non-condensable gases subject to the same failures that the specification is trying to eliminate?
HEI specifications ADDS COST to deaerator construction, that MAY NOT be required in the majority of installations.