UL 551:2018-01 Transformer-Type Arc-Welding Machines.
1.1 These requirements cover limited duty welding and cutting power sources, wire feeders, torches, and electrode holders that are intended for use by a layperson in a nonindustrial setting in accordance with the National Electrical Code, NFPA 70. Products covered by these requirements include only those welding products rated 600 volts or less, and are commonly known as hobby welders.
1.1 effective July 15, 2009
1.2 These requirements do not cover motor-generator sets or rectifier- or resistance-type welding machines. These requirements do not cover industrial or professional use welders.
1.2 effective July 15, 2009
2.1 Except as indicated in this clause, a component of a product covered by this standard shall comply with the requirements for that component. See the Standards for Components appendix for a list of standards covering components generally used in the products covered by this standard.
2.2 A component is not required to comply with a specific requirement that:
a) Involves a feature or characteristic not required in the application of the component in the product covered by this standard, or
b) Is superseded by a requirement in this standard.
2.3 A component shall be used in accordance with its rating established for the intended conditions of use.
2.4 Specific components are incomplete in construction features or restricted in performance capabilities. Such components are intended for use only under limited conditions, such as certain temperatures not exceeding specified limits, and shall be used only under those specific conditions.
3 Units of Measurement
3.1 Values stated without parentheses are the requirement. Values in parentheses are explanatory or approximate information.
4.1 Any undated reference to a code or standard appearing in the requirements of this standard shall be
interpreted as referring to the latest edition of that code or standard.
5.1 In the following text, a requirement that applies only to a particular type of product is so identified by
a specific reference in that requirement to the type or types of products involved. Absence of such specific
reference or use of the term product indicates that the requirement applies to all types of products unless
the context indicates otherwise.
6.1 An enclosure, an opening, a frame, a guard, a knob, a handle, or the like shall not be sufficiently sharp to cause a risk of injury to persons during normal maintenance or use.
Exception: A sharp edge that must be exposed to enable the product to perform its intended function.
6.2 A welding lead or electrode holder that is attached to a product shall be acceptable for the purpose.
7 Frame and Enclosure
7.1 A product shall be formed and assembled so that it will have the strength and rigidity necessary to resist the abuses to which it may be subjected, without increasing the risk of fire, electric shock, or injury to persons due to total or partial collapse with resulting reduction of spacings, loosening or displacement of parts, or other serious defects.
7.2 A product shall be provided with a case or cabinet that encloses all live parts.UL 551 pdf download.