Materials & specifications

Technical information on the glass material

Conditions for the use of glass apparatus components

Glass apparatus and glass equipment for chemical and technological processes are used in all branches of industry, in agriculture and in healthcare. The advantage of glass equipment over equipment made of other materials lies in its high resistance to aggressive substances and in the perfectly smooth walls, which allow the highest standards of cleanliness and hygiene in operation; thanks to its transparency, the processes taking place can be observed. Its light transmission also allows the apparatus to be used for biochemical and photosynthesis processes.

Industrial glass equipment can be used for processing chemical substances, with the exception of hydrofluoric acid, fluorosilicic acid and phosphoric acid as well as hot concentrated alkalis. Further limiting factors for its use may be the materials used to seal the connections and the non-glass auxiliary components that come into contact with the process medium.

Other restrictive factors are local occupational safety requirements, which must be observed for toxic or flammable process media, media that form explosive mixtures and the like.

1. Properties of borosilicate glass 3.3

All glass components are made of borosilicate glass 3.3.

This type of borosilicate glass is characterised by high chemical resistance and a low coefficient of thermal expansion, and therefore also by high resistance to temperature changes. The properties of the glass are continuously monitored and have been certified as complying with ISO 3585.

1.1 Chemical resistance

Products made of borosilicate glass 3.3 are characterised by high resistance to water, steam, acids and salt solutions and relatively good resistance to alkalis. For these reasons, borosilicate glass 3.3 is used wherever products are required to have high chemical resistance and to behave neutrally towards the substances stored or processed in them, i.e. in chemistry, laboratories, medicine, pharmaceuticals, the food industry, etc.

Chemical resistance is assessed using the international standard methods defined in the ISO standards.

1.1.1 Hydrolytic resistance at 98 °C

The test is carried out in accordance with CSN ISO 719. For practical purposes, the value refers to the extract from 2 g of glass grains with a grain size between 300 and 500 mm in water of purity grade 2 for 60 min at 98 °C.

1.1.2 Hydrolytic resistance at 121 °C

The test is carried out in accordance with CSN ISO 720. For practical purposes, the value refers to the extract from 10 g of glass grains with a grain size between 300 and 425 mm in water of purity grade 2 for 30 min at 121 °C.

1.1.3 Acid resistance

Like all internationally recognised borosilicate glasses, borosilicate glass 3.3 resists practically all aggressive substances, with the exception of hydrofluoric acid, fluorosilicic acid and phosphoric acid as well as hot concentrated alkalis, which visibly attack the glass surfaces in contact with them. Hydrofluoric acid damages the glass surface even at low concentrations. Phosphoric acid and alkalis cause only minor damage to the glass at low temperatures and concentrations. At high concentrations and temperatures, however, its resistance decreases noticeably. Continuous alternation between acidic and alkaline conditions increases corrosion.

The test is carried out in accordance with ISO 1776. Samples with a surface area of 30–40 cm² are exposed to an aqueous solution of hydrochloric acid at 100 °C for 3 hours.

1.1.4 Alkali resistance

The test is carried out in accordance with CSN ISO 695. Samples with a surface area of 10–15 cm² are immersed for 3 hours in a boiling solution of equal volumes of sodium carbonate and sodium hydroxide.

1.2 Physical properties

1.2.1 Thermal properties

The test is carried out in accordance with CSN ISO 719. For practical purposes, the value refers to the extract from 2 g of glass grains with a grain size between 300 and 500 mm in water of purity grade 2 for 60 min at 98 °C.

The permissible thermal load depends on the temperature gradient in the wall of the glass component. Provided that no sudden thermal shock occurs, this glass can be used at temperatures of up to approx. 300 °C. As a rule, and above all taking into account the sealing and connecting materials, glass pipes and apparatus are recommended for use at temperatures of up to approx. 200 °C.

The limit for rapid temperature changes depends on the thermal load resulting from the operating conditions and from the connection and fixing of the components, and it is also influenced by the different wall thicknesses of these components. For these reasons, no limit value can be given that applies to all technological and operating conditions that may arise.

An essential condition for good resistance to thermal shock is that the glass is not mechanically worked and that no deep scratches or matt spots are made anywhere on the glass surface.

Permissible thermal load:

As a rule, the maximum thermal shock is

• 120 °C when heating
• 90 °C when cooling

Thermal shock is a rapid change in temperature between the glass component and its surroundings. It depends on the wall thickness of the glass components and on the heating method. Resistance of glass components to heating according to PN 13 8900 99.

Resistance of the components to sudden temperature changes as a function of the wall thickness of the individual component.

1.2.2 Heat transfer

Guide values for the overall heat transfer coefficient through borosilicate glass walls:

When used as a condenser (steam condensing around the tubes, cooling water inside the tubes): k = 290 – 580 W/m²K (250–500 kcal/m²h °C)

When used as an evaporator (water evaporating around the tubes, steam condensing inside the tubes): k = 465 – 814 W/m²K (400–700 kcal/m²h °C)

When used as a heat exchanger (liquid being heated around the tubes, heating liquid inside the tubes): k = 250 – 400 W/m²K (200–350 kcal/m²h °C)

1.2.3 Change in length as a function of temperature

Borosilicate glass 3.3 stands out for its very low coefficient of thermal expansion.

The change in length of a 100 m pipeline as a function of temperature is shown in the following table:

In longer plants, the change in pipe length due to temperature changes must be taken into account, and fixed pipes must be secured in such a way that a change in length is possible. This is usually achieved by using suitable expansion joints.

1.2.4 Load due to internal overpressure

The permissible internal overpressure in glass pipes and equipment is influenced by the nominal bore, the shape, the operating temperature, the material of the connecting parts and the type of seal used.

For glass apparatus assembled from individual components of different nominal bores and shapes, the permissible internal overpressure is always determined by the component with the lowest permissible load.

Operating values of the liquid overpressure at a temperature difference between the inner and outer wall of t = 5 °C (and temperatures of up to 120 °C) are:

The permissible maximum operating pressures for conveying gases are the values given in the table multiplied by 0.1. Pressure surges caused by the operation of pumps or valves must not exceed the maximum operating pressures of the pipelines. The pipeline must be protected (by safety valves, air vessels, etc.).

1.2.5 Permissible load due to internal vacuum

The permissible vacuum load on the equipment depends on the dimensional stability of the large glass components, the operating temperature, the material of the connecting parts and the type of seal used.

Long-term operating experience shows that the apparatus can be operated safely at a vacuum corresponding to an absolute pressure of 0.0015 – 0.002 MPa.

1.2.6 Optical properties

Borosilicate glass 3.3 shows no significant absorption in the visible spectrum and is clear and colourless. Its transmission of UV radiation in the medium range of the spectrum is higher than that of ordinary window glass, which allows glass apparatus to be used for photochemical reactions, e.g. sulphonation and halogenation processes.

2. Design and engineering of glass apparatus

The documentation for all project preparation stages must include the following documents:

• process flow diagram
• installation diagram
• construction layout
• requirements for building works
• structural stability assessment
• material lists
• technical report
• safety regulations

3. Installation of glass equipment

Correct and safe operation is only guaranteed if installation and commissioning have been carried out professionally in accordance with the accompanying technical documentation and by personnel authorised to work with glass equipment (installers of De Dietrich Germany Leverkusen GmbH or persons who have been tested and authorised by De Dietrich Germany Leverkusen GmbH).

Installation is carried out exclusively in accordance with the project documentation approved by the user. If installation has to be carried out differently from the documentation, the designer must approve every change in advance, or the customer must record the installation in the installation log and amend the relevant documentation accordingly. Inspection of the site prior to installation covers checking that the rooms intended for installing the equipment and the rooms intended for site preparation are ready for construction. At the same time, the construction work is checked with regard to safety during installation. The takeover of the connection points mainly concerns the process pipelines to which the equipment is to be connected and on which the installation depends.

The glass and non-glass components are supplied in single-use packaging. Only undamaged equipment components may be installed. Any contamination must be removed from the glass components immediately before installation. For valves, the seats and plugs must be checked and all parts cleaned.

The supporting structures, mounting brackets, support beds and frames are installed in accordance with the drawings and the approved drawing documentation.

The components are installed using suitable mechanical equipment in accordance with the safety regulations. When fixing vertical sections of the glass equipment, the condition of a single fixed support must be observed in order to avoid stress in the glass components. If the entire weight of the equipment cannot be held by one support, one fixed support and additional sliding supports must be used. The main (fixed) support must be arranged on a glass component of adequate strength so that the greatest possible part of the equipment’s weight is held. None of the moving parts of the support may rub or jam. Care must be taken that the installed position of the moving support parts allows for the extent of thermal expansion movement during operation. The equipment must be secured with sufficient installation elements to ensure its stability, in such a way that forced installation does not cause stress in the glass components. The PTFE expansion joints are installed so that they not only compensate for expansion along the axis of the pipeline but also prevent the transmission of vibration.

4. Testing of glass equipment

After assembly, reconstruction or repair, the installed equipment must be inspected before it is put into operation. The individual types of test are specified in the project documentation as follows:

• Inspection of the installed equipment (construction inspection) establishes whether the entire design and the materials used correspond to the project documentation and the agreed requirements of the client, and checks readiness for the pressure test,
• pressure tests – to check the pressure resistance of the pipes
• temperature change test – to check the behaviour of the pipes under temperature fluctuations
• leak test – to check the tightness of the glass pipes
• wall thickness measurement

A report must be drawn up on the tests carried out.

5. Operation and maintenance of glass apparatus

5.1 Technical requirements

The operating conditions of each glass installation must be specified in the project. If the user has designed the operation using glass components specified in the supplier’s projects, brochures and documentation, the limits of the working conditions must not exceed the conditions laid down by the manufacturer for the individual components.

Written operating instructions must be available that describe the operating phases in detail, including start-up, production and shutdown of the equipment. The critical factors that lead to an interruption of production must also be specified. Where operations may exceed the limits of the working pressures, the glass equipment must be protected at the relevant points by pressure relief valves, safety devices, alarm systems, etc.

In chemical plants where static electricity poses a risk of fire or explosion, particularly when processing and conveying liquids in glass pipelines, the safety measures must include point earthing in accordance with TRBS 2153 on the outer surface of each glass component.

Glass equipment intended for processing chemical substances whose release could harm the health of operating personnel must be protected by a suitable enclosure or by placing the entire apparatus separately in a room that is closed during operation.

5.2 Commissioning

Before commissioning, all glass components must be thoroughly inspected for any mechanical damage (chips and cracks) that may have occurred during installation. Chips and cracks could make it impossible to carry out the tests on the glass apparatus and could cause material damage.

When filling, heating and commissioning the equipment, the glass must not be subjected to a higher load than that considered by the designer in accordance with the applicable regulations and standards or than the maximum values specified by the manufacturer.

5.3 Operation and maintenance of glass apparatus

5.3.1 Cleaning the glass

To care for the surfaces of the glass components and to preserve all their required properties, the components must be cleaned immediately after shutdown. All abrasive cleaning agents must be avoided, and chemical dissolution of contamination is preferred. Because of the risk of gradually reducing the gloss and transparency of the glass, neutral cleaning agents should be preferred to strongly alkaline ones.

5.3.2 Occupational safety

During maintenance work on the equipment, it is not permitted:

• to work on the equipment and valves while they are in operation and under pressure,
• to use glass equipment components as load-bearing parts,
• to hang auxiliary installation equipment on glass equipment,
• to carry out a pressure test with a faulty, uncalibrated or unchecked pressure gauge or at a higher pressure than specified;
• dismantled components must be cleaned, inspected and checked for damage,
• after a repair, the flange connections and the entire equipment must be checked in operation for 24 hours,
• every repair to the equipment and every test carried out must be recorded in the inspection log.

6. Warranty

The manufacturer of the glass apparatus confirms that the product is made of borosilicate glass 3.3 and meets the requirements of CSN ISO 3585. The dimensions and workmanship of the glass products comply with the standards CSN EN 1595 and CSN EN 12 585 as well as the company standards.

The manufacturer guarantees for a period of one year that the glass components will not fail spontaneously. The manufacturer is only liable for correct and safe operation if installation and commissioning have been carried out professionally in accordance with the technical documentation and by personnel trained to work with the glass equipment supplied by De Dietrich Germany Leverkusen GmbH (installers of De Dietrich Germany Leverkusen GmbH or tested and authorised personnel of De Dietrich Germany Leverkusen GmbH).

The manufacturer does not provide any warranty in the event of mechanical damage or other defects resulting from improper storage, transport, incorrect installation and cleaning, or operation outside the data specified in the accompanying technical documentation.

The products listed in the documentation do not represent a binding production programme; the manufacturer reserves the right to make technical changes.