EN ISO 16812 and API STD 660, both standards specifies requirements and gives recommendations for the mechanical design, material selection, fabrication, inspection, testing, and preparation for shipment of shell-and-tube heat exchangers for the petroleum, petrochemical, and natural gas industries and is applicable to the following types of shell-and-tube heat exchangers: heaters, condensers, coolers, and reboilers.
Since the 9th edition (2015), API STD 660 contains the SI units and additional requirements, so that the technical requirements are identical to API STD 660 with the exceptions specified table below
Note 1: ISO 16812: contain the follow normative references:
- API STD 660 9th edition (2015): Shell-and-tube heat exchangers
- ISO 15156 (all parts): Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production
- ISO 17945: Petroleum, petrochemical and natural gas industries — Metallic materials resistant to sulfide stress cracking in corrosive petroleum refining environments
- ISO 23251: Petroleum, petrochemical and natural gas industries — Pressure-relieving and de-pressuring systems
Note 2: EN ISO 16812 is not a harmonised standard in the sense of the PED and therefore does not contain an Annex Z. which refers to conformity (presumption of conformity) with the essential safety requirements (ESR) of Annex I of the PED.
Table with specified supplements of EN ISO 16812
| API STD 660 clause | API STD 660 requirement | ISO 16812 supplement |
|---|---|---|
| 4.10 | The purchaser shall specify if the service is designated as sour in accordance with NACE MR0175 (all parts) for oil and gas production facilities and natural gas processing plants or is designated as wet hydrogen sulfide service in accordance with NACE MR0103 for other applications (e.g. petroleum refineries, LNG plants, and chemical plants), in which case all materials in contact with the process fluid shall meet the requirements of the applicable standard to mitigate potential for sulfide stress cracking (SSC). Identification of the complete set of materials, qualification, fabrication, and testing specifications to prevent in-service environmental cracking is the responsibility of the user (purchaser). See A.2.2 for guidance on sour or wet hydrogen sulfide service. | The requirements specified in API Std 660, 9th edition (2015), 4.10, apply with the following exceptions: For the purpose of this provision, ISO 15156 (all parts) shall be used in place of NACE MR0175 (all parts). For the purpose of this provision, ISO 17945 shall be used in place of NACE MR0103. |
| 8.2.2 | Pressure-retaining components shall be supplied with a Certified Material Test Report (CMTR). The CMTR shall include the unspecified elements chromium (Cr), columbium (Cb) [also known as niobium (Nb)]), nickel (Ni), vanadium (V), molybdenum (Mo), and copper (Cu) that are used in the formula to calculate the carbon equivalent (CE) as defined by NACE MR0175 (all parts) or NACE MR0103. | The requirements specified in API Std 660, 9th edition (2015), 8.2.2, apply with the following exceptions: For the purpose of this provision, ISO 15156 (all parts) shall be used in place of NACE MR0175 (all parts). For the purpose of this provision, ISO 17945 shall be used in place of NACE MR0103. |
| 9.5.11 | The purchaser shall specify whether weld procedure qualifications for carbon steel in sour or wet hydrogen sulfide service, including tube-to-tubesheet welds, shall include a micro-hardness survey performed on a weld cross-section, including the heat affected zone (HAZ), and transverse to the weld centerline. The micro-hardness testing and acceptance criteria shall be in accordance with NACE SP0472 or NACE MR0175 (all parts), as applicable. Any additional restrictions on residual elements or micro-alloying elements for the qualification test material shall be specified by the purchaser. | The requirements specified in API Std 660, 9th edition (2015), 9.5.11, apply with the following exceptions: For the purpose of this provision, ISO 15156 (all parts) shall be used in place of NACE MR0175 (all parts) |
| sub-clause A.2.2.1 | NACE MR0103 establishes material requirements for resistance to sulfide stress cracking (SSC) in sour petroleum refining and related process environments which contain hydrogen sulfide either as a gas or dissolved in an aqueous (liquid-water) phase, with or without the presence of hydrocarbon. SSC is defined as cracking of a metal under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide. Other forms of wet hydrogen sulfide cracking, environmental cracking, and severely corrosive and/or hydrogen charging conditions that can lead to failures by mechanisms other than SSC are outside the scope of NACE MR0103. | The requirements specified in API Std 660, 9th edition (2015), A.2.2.1, apply with the following exception: For the purpose of this provision, ISO 17945 shall be used in place of NACE MR0103. |
| sub-clause A.2.2.2 | Compared to the high pH environments of refinery sour service, oil and gas production sour environments are covered by NACE MR0175 (all parts). This is because many wet sour streams in oil and gas production facilities also contain carbon dioxide and hence exhibit a lower pH. In addition, chloride ion concentrations tend to be significantly lower in refinery sour services than in oil and gas production sour services. | The requirements specified in API Std 660, 9th edition (2015), A.2.2.2, apply with the following exception: For the purpose of these provisions, ISO 15156 (all parts) shall be used in place of NACE MR0175 (all parts). |
| sub-clause A.2.2.3 | NACE MR0175 (all parts) provides requirements and recommendations for the selection and qualification of metallic materials for service in equipment used in oil and gas production and natural gas processing plants in hydrogen sulfide containing environments. Mechanisms of cracking that can be caused by hydrogen sulfide include sulfide stress cracking, stress corrosion cracking (SCC), hydrogen-induced cracking (HIC), step-wise cracking (SWC), stress-oriented hydrogen-induced cracking (SOHIC), soft zone cracking (SZC), and galvanically induced hydrogen stress cracking (GHSC). | The requirements specified in API Std 660, 9th edition (2015), A.2.2.3, apply with the following exception: For the purpose of these provisions, ISO 15156 (all parts) shall be used in place of NACE MR0175 (all parts). |
| sub-clause A.4.1 | The effects of potential overpressure on the low pressure side of the heat exchanger caused by tube rupture should be considered. In certain extreme circumstances, the large volume of vapor that will be released during a tube failure scenario may lead to excessive size of the relief valve or rupture disk. An option in such a case is to consider using smaller diameter tubes (e.g. 16 mm [5/8 in.]). | The requirements specified in API Std 660, 9th edition (2015), A.4.1, apply with the following exception: For the purpose of this provision, ISO 23251 shall be used in place of API Std 521. |
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Shell-and-tube heat exchangers: Applicable Codes and Standards
