The Heat Exchange Institute publishes standards for many different types of equipment. The HEI standards Graham mainly uses are for steam surface condensers, direct contact barometric condensers and low level condensers, steam jet vacuum systems, and liquid ring vacuum pumps and compressors. HEI also has standards for air cooled condensers, closed feed water heaters, shell & tube heat exchangers, plate heat exchangers, and deaerators.
HEI is the baseline set of standards for designing equipment, including thermal calculations and some guidelines for mechanical calculations. HEI should be the starting point for all specifications. HEI is Graham’s standard baseline for design whether or not it is specified. However, HEI does not go into great detail in regards to mechanical calculations and is less specific on testing and inspection requirements. HEI also does not require specific welding requirements. For example, there are no required certifications per the standard to weld on the equipment once it's in the field.