Technical Information

Visilume supply a wide range of sight glasses for viewing the contents and/or level of tanks, vessels or pipelines.

• Methods of installation are by welding, bolting or clamping into your equipment.
• Pressure ratings range from high vacuum, through atmospheric to high pressure applications.
• Temperature ratings range for cryogenic to furnace.
• Sizes range from 6 mm through to 600 mm.
• Materials available include aluminium, carbon steels, stainless steels, duplex stainless steels and hastelloy.

Circular sight glass fittings
A sight glass, also called a sight window or view port, comprises two flanges, bolted together, surrounding a glass disc sealed with gaskets and provides a means of viewing the inside of a process vessel or tank. Typically used to visually verify stages of a process, inspect process media, and to observe liquid levels. Common applications include the viewing of internals of pressure vessels, tanks, silos, stirred vessels, separators pipelines etc. In addition to the sight glasses, Visilume can also supply accessories such as a wiper, sight glass Luminaires, cameras and spare glass and gaskets.

Sight flow indicators
A sight flow indicator is used in process pipelines to observe the flow of liquid, powder or gas. It is comprised of a body with one or more viewing windows. It is the most reliable way to verify flow for direction and approximate rate, colour and clarity. We offer standard view and full-view sight flow indicators for industrial, sterile and hygienic applications.
Our range, with a choice of materials including stainless steel, carbon steel and duplex bodies, suit industrial applications with working temperatures up to 250ºC and working pressures up to 16 bar for the standard range and 40 bar for the high pressure range, and up to 250 bar for custom applications.

Metaglas sight glass windows
Metal fused sight glasses “METAGLAS®” consist of a sight glass that is fused into a steel ring. The different expansion coefficients of glass and metal cause a compressive stress inside the glass. The mechanical prestress commands a higher security compared to thermal prestressed glasses. Because of the mechanical treatment of the steel ring, various constructive soultions can be realised.

Glass tube liquid level gauge and Magnetic Level gauges
Magnetic Level Gauge consists of an external chamber mounted byflange or thread to the size of the process vessel. The external chamber is completely sealed and includes only a magnetic float that rises and falls according to the medium level due to buoyancy. Attached externally outside of the chamber is a strip of magnetic flags that are painted either white or red. When the magnetic float passes through the chamber, the magnetic flags are flipped over 180° to indicate level of the medium within the chamber. The flags are made of engineering plastics for general purposes as well as ceramic for high temperature applications. This operation means that the effective medium level could be determined at any point of time by the level of red flags on the chamber without any power source required.

Rectangular sight glass fittings
A sight glass, also called a sight window or view port, comprises two flanges, bolted together, surrounding a glass disc sealed with gaskets and provides a means of viewing the inside of a process vessel or tank. Typically used to visually verify stages of a process, inspect process media, and to observe liquid levels. Common applications include the viewing of internals of pressure vessels, tanks, silos, stirred vessels, separators pipelines etc.

Sanitary and hygienic equipment
Visilume’s Sterile Visual Flow Indicator offers easy cleaning, validation and sterilisation so it is ideal for biotech and pharmaceutical applications. The unique o-ring sealing design offers the smoothest internal bore available with minimal bug traps. Polished stainless steel connections include sanitary clamps, orbital weld & Swagelock TS as standard.

Water Treatment Sight Glass Fittings
Custom Sightports for use on biodigesters and water treatment plants. Suitable for setting into concrete, bolting to a base flange or welding into steel vessels & tanks.

METAGLAS© Improved Safety, Constructive Solutions and Simplified Fitting with Metal Fused Sight Glasses

Introduction
Conventional sight glasses are sensitive to stress, bending and impact and when subject to mechanical overload they may catastrophically fail without warning. This can cause a relatively minor expense and inconvenience if it happens during installation but a major cost and safety implication if it occurs when plant is fully operational.

• METAGLAS® eliminates this mode of sight glass failure, helping to improve safety and avoid the expense and inconvenience of unscheduled plant shut downs. These advantages are due to the unique “glass fused to metal” fabrication of METAGLAS® which gives it unmatched strength and integrity.
• METAGLAS® is made by melting circular glass inside a metal frame. This results in the fusion of glass and metal. Upon cooling, the glass solidifies and the difference in the linear coefficient of thermal expansion between glass and metal then produces forces that create a uniform compressive stress throughout the glass.
• This high degree of mechanically induced compressive stress makes METAGLAS® the strongest and most secure sight glass for sight window or visual flow indicator application.

Special Features
Reliability against total failure – due to the mechanically prestressed glass

• Unsurpassed resistance to pressure, impact and temperature
• Simple, stress free installation – resistant to bending, overtightening and impact
• Reusable – Metaglas can be cleaned and reused in the same or other applications,conventional sightglasses cannot.

Applications 
METAGLAS® can replace conventional glass in many applications including circular flange assemblies for welding into vessels, weld neck & nozzle flanges and sight flow indicators.

• In addition, Metaglas cover flanges can be mounted onto flat face base flanges, these are available for all international flange connections including ANSI & BS. Existing installations can therefore be easly retrofitted to improve safety and extend plant life. The unique pro­perties of METAGLAS®also make it ideal for use with sanitary mounting systems.
• METACLAMP®s are available as sight glass caps for sanitary clamp and In-line systems and sight glasses and Luminaire adaptors for sterile flush mount designs such as the
• NA-Connect system and Triclamp fittings.
• METAGLAS® has been subjected to the most rigorous tests by specific testing facilities in the chemical industry and has subsequently been integrated into their works standards.

Specifications • Pressure Equipment Directive 2014/68/EU

• module H/H1 (DIN/EN/ISO9001)
• Materials to VdTUV specifications & DIN/EN standards
• Sight glass fused to metal to DIN 7079
• AD Standards W0/TRD 100
• 3-A Standard for food processing

Tech Data • Materials: Duplex stainless steel 1.4462

• Carbon steel 1.0570, Hastelloy and others
• Operating Temp.: -30°C to +280°C (300°C)
• Operating Pressure: 64 bar (TUV)
• 1000 bar, depending on material and design

METAGLAS© versus Toughened Glass
The structure of toughened glass is such that any surface damage or stress caused by uneven forces can lead to catastrophic failure. The structure of Metaglas is such that surface damage is limited to local areas and does not affect the overall strength of the glass. Local pitting or cracking may cracking may obscure the view but the glass remains leak tight and secure. Likewise, uneven stresses do not cause Metaglas to fail.

      Tempered Glass                                                                                                                                      METAGLAS^®    

ATEX (ATmospheres EXplosibles) Directive 2014/34/EU

Equipment for potentially explosive atmospheres (ATEX)
A potentially explosive atmosphere exists when a mixture of air gases, vapours, mists, or dusts combine in a way that can ignite under certain operating conditions.

Equipment and protective systems intended for use in potentially explosive atmospheres (ATEX) cover a range of products, including those used on fixed offshore platforms, petrochemical plants, mines, and flour mills, amongst others.

EU Legislation and ATEX
The ATEX Directive 2014/34/EU covers equipment and protective systems intended for use in potentially explosive atmospheres. The Directive defines the essential health and safety requirements and conformity assessment procedures, to be applied before products are placed on the EU market. It is aligned with the New Legislative Framework policy, and it is applicable from 20 April 2016, replacing the previous Directive 94/9/EC.

There are two ATEX directives (one for the manufacturer and one for the user of the equipment):

• ATEX Directive 2014/34/EU, Equipment and protective systems intended for use in potentially explosive atmospheres;
• ATEX 137 workplace directive 99/92/EC, Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.

The ATEX 94/9/EU that is dedicated to the manufacturer has changed. Always applicable up to 19 April 2016 the ATEX 94/9/EC has been removed and replaced by the new directive.

This new ATEX directive was published on Saturday 29 March 2014, under the new reference : Directive 2014/34/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (recast) Text with EEA relevance – Official Journal of the European Union L 96 from 29/03/2014.

This new ATEX directive 2014/34/EU will be mandatory for manufacturer on 20 April 2016 as is stated in article 44 of the directive.

Promised for a long time, this new ATEX directive has been published together with 8 other directives in the frame of NEW LEGISLATIVE FRAMEWORK (NLF) ALIGNMENT PACKAGE (Implementation of the Goods Package). It was the subject of a “COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT AND THE COUNCIL” for the Alignment of ten technical harmonisation directives to Decision No 768/2008/EC of the European Parliament and of the Council of 9 July 2008 on a common framework for the marketing of products, in Brussels, 21.11.2011 under reference COM(2011) 763 final.

Further Information
The European Union website address for ATEX information is here

You can also link to HazardEx for current information and events

End Users/Employers’ Directive 99/92/EC – ATEX 137
Requires employers to protect workers from the risk of explosive atmospheres

This directive applies to most industry sectors but some, such as mines and quarries, are exempt because they already have their own set of stringent regulations.

ATEX 137 (and ‘CAD’, the Chemical Agents Directive) will be implemented in the UK through DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) safety regulations. These will be enforced by the HSE.

Essentially there should be no major changes for End Users who are already working with good practice and to current regulations.

Pressure Equipment Directive 2014/68/EU – Legal requirement from July 20th 2016
The new Directive 2014/68/EU will fully enter into force on 20 July 2016. 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.

Visilume
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 here for more information.

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:

• Whether the fluid is a liquid or gas
• Whether the fluid is categorised as Group 1 (hazardous) or Group 2 (non hazardous)
• 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 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.

If you would like a copy of our ISO 9001 or 14001 certificate, you can download them from the links below.

ISO 14001 Environmental

ISO 9001 Quality