ISO 6553:2016

Overview

ISO 6553:2016 - Automatic steam traps - Marking defines the mandatory and optional marking requirements for automatic steam traps. This second edition (2016) replaces ISO 6553:1980 and updates marking requirements to align with ISO 5209 and EN 19. The standard sets basic rules for how information must be displayed on trap bodies or plates to ensure traceability, safe operation, and correct installation.

Key Topics and Requirements

• Scope: Specifies mandatory and optional markings for automatic steam traps; intended to be used alongside any specific contractual requirements.
• General requirements:
  • Markings shall be applied on the body or on plates integral with or securely fixed to the body.
  • Markings must not be hidden by the fixing elements of the steam trap.
• Mandatory marking (each automatic steam trap shall show):
  • Manufacturer’s name and/or trademark
  • Maximum allowable pressure (bar or MPa)
  • Maximum allowable temperature (°C)
  • Flow direction indication (arrow)
  • Shell material designation
  • Nominal size (DN or NPS)
  • Nominal pressure (PN or Class designation)
  • Note: For traps without a defined PN or Class, maximum allowable pressure and temperature are mandatory.
  • For DN/NPS sizes with PN/Class designation, letters “DN” or “NPS” may be omitted if PN/Class follows immediately (e.g., “50 PN 25” or “2 CL 300”).
  • For traps ≤ DN 50 (NPS 2) the shell material marking can be omitted.
• Optional markings:
  • Maximum operating pressure or maximum differential pressure (as relevant)
  • Maximum test pressure (bar or MPa)
• Additional markings:
  • Manufacturers may repeat required markings in more than one place (body and plate).
  • Other information (e.g., catalogue numbers) may be added provided it does not cause confusion with mandatory markings.

Applications and Who Uses ISO 6553:2016

ISO 6553:2016 is used by:

• Steam trap manufacturers for product labeling and compliance.
• Plant engineers and maintenance teams to verify correct trap selection, installation, and safe operating limits.
• Procurement and inspection to confirm traceability, material and pressure/temperature ratings.
• Compliance officers and certification bodies checking conformity with industry marking practices. Practical benefits include improved safety, easier maintenance, reduced installation errors, and clearer product identification in steam systems and industrial plants.

Related Standards

• ISO 5209 - General purpose industrial valves - Marking
• ISO 6552 - Automatic steam traps - Definition of technical terms
• EN 19 - Industrial valves - Marking of metallic valves

Keywords: ISO 6553:2016, automatic steam traps, steam trap marking, marking requirements, manufacturer marking, maximum allowable pressure, nominal size, PN, DN.