Pressure Equipment Dir. PED 97/23/EC


Pressure Equipment Directive 97/23/EC - Legal requirement from May 29th 2002

The Pressure Equipment Directive (PED) 97/23/EC was implemented in the United Kingdom by the Pressure Equipment Regulations 1999 and became a legal requirement on 29th May 2002.

This Directive applies to the design, manufacture and conformity assessment of pressure equipment and assemblies of pressure equipment with a maximum allowable pressure greater than 0.5 bar.


All Visilume products and accompanying documentation are supplied in accordance with the Directive. Further information on each of these ranges is given below:

Sightglass fittings, sightglasses and components of sightports

Under the Directive Sight Glass Fittings with frames, gaskets, flanges and bolts are not pressure accessories but are classed as Components of Pressure Equipment. They therefore fall outside the Directive and should not bear the CE mark.

All Visilume sightglass fittings designed for use over 0.5 bar are supplied with a Letter of Conformity giving a general description of the pressure component and stating the standard which it has been manufactured to or assessed against. They are also supplied with instructions for use and maintenance as required by the Directive.

Where nominal pressures are stated for rectangular sightglass fittings, these refer to the design base. It is the responsibility of the pressure equipment manufacturer to ensure that the welded-in assembly meets the appropriate strength calculations and to provide reinforcement of the vessel wall if necessary.

It is also the responsibility of the pressure equipment manufacturer to ensure that all component parts enable the pressure equipment to meet the Essential Safety Requirements (ESR's) of the Directive (See website).

Materials for Sight Glass Fittings and components

To be incorporated into an item of pressure equipment, components that are manufactured from materials such as plates and bar should meet all the relevant Essential Safety Requirements related to the manufacturing process.

Therefore Sight Glass Fittings and similar items are delivered with the appropriate material certificates for base and cover flanges together with letters of conformity covering the glass, studs and gaskets as necessary.

For more detailed information relating to our products and the PED please contact our technical sale office.

Sight-Flow Indicators

Under the PED regulations 'Sight Flow Indicators' are not piping but 'Pressure Accessories' because they are individual piping components

The requirement for CE marking sight-flow indicators under the Pressure Equipment Directive depends upon size, fluid type and pressure:

Sight-flow indicators with NB1" (DN25) or less do not require CE Marking.

Above this size, the requirement for CE marking depends upon:
1) Whether the fluid is a liquid or gas
2) Whether the fluid is categorised as Group 1 (hazardous) or Group 2 (non hazardous)
3) What the pressure is

Once the above information has been established, graphs given in the Pressure Equipment Directive are used to determine the classification of the sight-flow indicator.

Those sight-flow indicators not requiring a CE mark have to be manufactured to Sound Engineering Practice (SEP). This applies to all units of 1" or below and most units for use with Group 1 & 2 Liquids and Group 2 Gases.

Visilume sight-flow indicators Type P, Type PM and Type F can all be supplied CE Marked for sizes above 1"/DN25.

All other Visilume sight-flow indicators fall within the SEP category for use with Group 1 liquids. These are supplied with a Letter of Conformity stating:

  • Materials of construction
  • Maximum operating conditions for the Group 1 Liquid
  • Standard(s) used in the design and manufacture
  • That the requirements of Sound Engineering Practice have been met.

They are also supplied with a general description of the pressure accessory and instructions for use and maintenance and the components are marked to identify the supplier

Sight-flow Indicators Equipment for use outside the EU can be supplied to other international requirements such as American pressure equipment standard

Level Gauges

The Visilume range of Vaihinger Level Gauges have all been assessed under the Pressure Equipment Directive and are CE marked or classed as 'Sound Engineering Practice' according to the appropriate category.

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