Engineering Design Standards: HEI, ASME, TEMA, API 660

February, 2020

Greetings!  Our topic this month discusses the different design standards and construction codes used for the different types of equipment in relation to vacuum systems. Understanding design standards and codes is important when determining the best choice when specifying equipment. This is also important when equipment out in the field may be modified or repaired.

HEI Standards

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.

ASME Standards

The American Society of Mechanical Engineers code and standards are broken down by different categories. One of the main ASME codes used by Graham is the ASME Boiler and Pressure Vessel Codes (BPVC). This code is broken down further into sections and divisions. More specifically Graham uses ASME Section VIII Div. 1 rules for construction of pressure vessels to mechanically design the equipment we manufacture. Other codes used are ASME Section IX regarding welding qualifications, Section II for material specifications, Section V for nondestructive examination (NDE), and Section III for nuclear service. ASME also covers piping standards B31.3 for process piping and B31.1 for power piping along with pipe flanges and flanged fittings, B16.5 standards. ASME has many other codes and standards that are used across industry to establish mechanical design rules to be follow for safety and integrity of the construction of equipment. ASME adds the benefit of having the equipment mechanically designed to a code that is known and accepted worldwide as a benchmark. Graham uses ASME as a standard to design our equipment. ASME provides requirements for standard testing (NDE) of the equipment and certified ASME welders working on the equipment. ASME also requires a third party ASME Authorized Inspector (AI) to inspect the equipment and review the paperwork to insure it meets ASME requirements. ASME also requires the equipment to be registered to the national board, which adds benefits to have your information on file and may have additional benefits with insurance coverage. Once the equipment is in the field, if any work is required to be performed, ASME code would need to be followed. Therefore mechanical calculation will be needed for any welding and welders will need to be certified. An ASME authorized inspector would also be required.

TEMA Standards

TEMA stands for Tubular Exchanger Manufacturers Association. TEMA is a standard used for the design and fabrication of shell and tube heat exchangers above and beyond HEI and ASME standards. The TEMA standard is broken down into three classes. TEMA class “R” is the most severe requirements and is generally used for petroleum and associated processing applications. TEMA class “B” has less severe requirements then TEMA “R” and is used for chemical process services. TEMA class “C” has the least severe requirements of the three, and is typically used for commercial and general process applications. Graham can use any of the three standards as required by the customer. TEMA is traditionally used in addition to HEI and ASME standards. Depending on the class of TEMA being used, it will determine what additional standards are required for the design and fabrication of the equipment. To give an example, TEMA “C” and “B” require additional corrosion allowance when compared to HEI. TEMA “R” requires additional corrosion allowances beyond this. Other examples of additional requirements involves gasket material restrictions, confined gaskets joints, connection requirements, and tube hole and pass partition grooving to name some more of many requirements for TEMA standards. TEMA requires an increase in cost due to the additional requirements.

API 660 Standards

The American Petroleum Institute standard API 660 is typically followed for the fabrication of shell and tube type heat exchangers and condensers in Refinery service. The API 660 requirements include following TEMA but with more stringent mechanical design, closer machining tolerances and adding design features to the equipment. Added NDE is also specified when following the API standard.

In summary, construction of the equipment should be dictated by your facility. Most refineries will require ASME construction for steam ejectors, API 660 construction for shell and tube intercondensers, and ASME/HEI construction for steam surface condensers. On top of these requirements, a site specific specification overlay is often followed. For Chemical Plants, TEMA / ASME / HEI are often followed with added site specifications. In all cases, it is prudent to have your equipment supplier understand the specification needs when getting budget prices for project approvals. This will help you avoid surprise costs during equipment procurement.

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Graham Gulf Coast Office P.O. Box 3940 Covington, LA 70434 Eric Johnson 585-815-9432 Alicia Johnson 585-815-9463

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