When purchasing industrial valves, API 598 and ISO 5208 are two commonly referenced standards for valve inspection and pressure testing.
Although both cover valve pressure and closure testing, they are not identical or automatically interchangeable.
API 598 – Valve Inspection and Testing is an American Petroleum Institute standard widely used in the oil and gas, petrochemical, pipeline, and industrial valve industries.
It covers inspection and pressure testing for valves such as:
API 598 includes requirements for shell testing, closure testing, backseat testing, and other inspections, depending on the valve type and applicable requirements.
It is commonly used together with API product standards such as API 600, API 602, API 608, and API 6D.
ISO 5208 – Industrial valves — Pressure testing of metallic valves is an international standard for pressure testing metallic industrial valves.
Its main purpose is to verify:
ISO 5208 is intended to be used together with the applicable valve product standard. If the product standard specifies different requirements, those requirements take precedence.
The main difference is their overall scope and standards framework:
| API 598 | ISO 5208 | |
|---|---|---|
| Main focus | Valve inspection & testing | Pressure testing |
| Organization | API | ISO |
| Typical use | Oil & Gas, petrochemical, pipeline | International industrial applications |
| Shell test | Yes | Yes |
| Closure test | Yes | Yes |
| Product standard relationship | Commonly used with API standards | Used with applicable product standards |
Therefore, a requirement for API 598 should not automatically be replaced by ISO 5208, even when the physical testing procedures may appear similar.
The correct choice depends on the valve product standard and project specification.
For example, if a project specifies an API 6D ball valve with testing according to API 598, the manufacturer should follow the specified API requirements rather than substitute another testing standard without approval.
For projects using ISO-based specifications, ISO 5208 may be required instead.
When preparing an RFQ, avoid simply writing “hydro test required.” Clearly state the applicable testing standard, test conditions, and leakage acceptance criteria.
API 598 and ISO 5208 both address valve pressure and closure testing, but they belong to different standards frameworks.
For accurate valve procurement, always confirm the product standard, testing standard, test conditions, and acceptance criteria before quotation and inspection
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