The LV-Directive (2006/95/EEC)As all ce-related directives this is a new-approach directive, which means that only main requirements (essential requirements) are required. The LV-directive shows the way of showing compliance to the main requirements. Using a list of harmonized standards a manufacturer may assess the safety of it's product or apparatus.
Manufacturers declarationThe manufacturers declaration consists mainly of a liability statement from the manufacturer or importing agent in which he accepts the legal consequences (liability) for conformity of it's equipment to the LVD-essential requirements. The manufacturer is granted permission to do the testing himself, or let the testing be executed by any test-house. Using this route the manufacturer is strongly suggested to use the so-called Harmonized Standards for type testing, although in absence of these any other safety standard or no standard at all may be applied.
Purchase a model ce declaration of conformity Technical Construction File (TCF).In order to prove compliance to the essential requirements of the LVD one has to make up a Technical Construction File. This includes all safety related topics, such as precautions, instructions, test reports and everything necessary to identify the apparatus, such as circuit diagrams, mechanical drawings and detailed part lists. The LVD is not just limited to electrical shock and insulation only. Once an apparatus falls into the scope of it, many other aspects of safety like fire hazards, mechanical hazards, radiation and chemical hazards are part of the approval procedure. Future developments will bring more and more apparatuses within the scope of safety directives. |
Basic Safety ConceptsProtection against electrical shockElectrical safety is implemented using the concept of double safety layers:
Any part at hazardous voltage should be separated from the operator by 2 layers of safety like specified under 1. or 2.In addition to this the failure of one layer may not affect the sessential safety of the equipment. Full safety must be achieved with one layer only. The testing of one layer of safety failure is called SINGLE FAULT TESTING; evulated are the effects of (among others) :
Misuse (foreseeable abuse) of an equipment is considered as a single fault.The LVD approval procedure is based on the utilization of safe and approved parts in all applicable circuits (most important in the mains circuit). This implies that all parts having a safety function need an examination to their specifications and (if applicable) need a ce-declaration of conformity available, before they are allowed in the construction of an apparatus.Component manufacturers in generally are not very cooperative in producing accurate declarations, as a ce-declaration of conformity involves direct liability of the manufacturer for the safety of it's components . A UL, CSA or VDE declaration -although very valuable- is a testimonial declaration and not a manufacturers declaration: less liability for the manufacturer is involved. Most US originated equipment lack sufficient component safety due to the difference in mains voltage. Although manufacturers may specify a product as being suitable for 250 Vac, this does not imply that the same component is safe at 250 Vac. In order of relevance we require safety certificates from (for your applied components with a safety function)
Safety Function What components do have a essential safety function ?In general, all components carrying mains voltage and all components carrying a hazardous voltage to the operator have a safety function. Eevne more general, all components carrying any hazard in them may qualify as such. Other requirements Many more requirements exist considering hazards associated with heat, fire propagation, radiation, mechanical hazards (sharp edges), short circuits, leakage current (touch current) and more. The electrical safety test procedures are not to be underestimated ! Harmonized standardsThis list of standards is an ever increasing subset of world-wide existing standards, that due to their way of defining test-methods, limits and susceptibility criteria, are very well suited for testing by the manufacturer himself, or by any test house using the right equipmentThis list of standards is published approximately once a year.
Routine testingThe Declaration of Conformity is most often based on a one sample of a "type tested product" that ideally should be identically reproduced in series. In order to maintain safety in real life production, some quality control is imperative. The LVD specifies the requirement of such a scheme. Therefore each and every produced apparatus must be numbered and verified for a list of essential parameters -composed by your test house- such as functionality, dielectric strength , the grounding qualities and potential pitfalls created by foreseeable mistakes in production.This focuses the attention on those faults that are easily made without being detected in functionality tests, and that may create a potential hazard to the operator. Examples are grounding clips, insulation barriers, warning labels, insulation (rubber) rings below ring core transformers etc.In general, safety measures should be applied exclusively for the safety purpose, and should not share any task with functionality , unless the safety measure is very obvious. Safety features must be visible and easy distinguishable from fnctional features.Safety measures should not be compromised during normal operation and service.Routine test must be logged, therefore serial numbering your equipment is required.Standards exist for setting up these so-called routine tests::
Your test house will be helpful in selecting a routine type test protocol. Most popular failures....
Although exceptions exist, the insulation between metal (accessible) parts and hazardous voltages (mains) must be no less of 4 mm and up to 8 mm in medical equipment.
Not only equipment but also components must be tested for safety. Most components comply to international IEC or EN standards. Equipment brought to Europe often uses UL or CSA approved components. IYou definitely have to make sure that your components are suitable for European voltages and make sure they are sold to you with written proof of compliance. Just a catalogue page showing the ce mark in the corner won't do ! If it's writing "designed for (to) comply with .[standard].. ' or "tested for [standard]...." , then you can be sure the part is not compliant. Look for the phrase: "Compliant with [standard] " and then don't forget to check it's the correct standard and not an obsolete one.........!Correct part number and applied standard are best be mentioned on a signed document.
You must have seen that in your product's Bill of Materials: many parts have no specified type or manufacturers name behind them. How can you be sure that this part performs the required function, and how can you declare liability for the safety of those parts ?
All equipment should ideally be accompanied by the following documents:
Of all these parts the safety part MUST be translated in the language of the country you are selling to. Many countries require other parts to be translated too. Several parts may be contained in one volume however, but we recommend a separate sheet for those safety aspects that require immediate attention when opening the box... should we mention why ?? Let us quote you for your product and get all this and more taken care of.... |
