Chemical Composition

The borosilicate glass used in the manufacture of our range of process plant and pipe line components  has the following approximate composition.  

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Chemical Resistance

Borosilicate glass is resistant to almost all substances except hydrofluoric acid, phosphoric acid and hot strong caustic solutions. Of these, hydrofluoric acid has the most serious effect and, even when a solution contains a few parts per million, corrosion will occur. 

Phosphoric acid and caustic solution cause no problem when cold but at elevated temperatures corrosion occurs. Caustic solution up to 30% concentration can be handled safely at ambient temperature. Under actual service conditions, the effect of turbulence and traces of other chemical is the solution may increase or decrease the rate of attack. Therefore, it is not possible to give precise figure for corrosion by caustic solutions, but Figure 1 shows typical rates.

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Physical Properties

Coefficient of mean linear thermal expansion

(20°C to 300°C)                     a = (3.3 ± 0.1) x 10-6 k –1

Mean thermal conductivity

(20°C to 200°C)                     l = 1.3 W/mK

Mean specific heat capacity

(20°C to 200°C)                     Cr = 910 j/kgk

Density  at 20°C                   u = 2.23 g/cm³

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Optical Properties

With borosilicate glass, the transmission of ultra-violet light – which is the great importance for photo-chemical reaction- is somewhat greater in the middle spectrum that with normal window glass.

If photosensitive substances are being processed, the glass can be amber stained to special order. This permanent coating reduces the ultra violet light transmission to a minimum. Figure 2 shows a comparison of the light transmission for plain and amber glass.  

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Mechanical Properties

The mechanical properties of the glass differ from those of metals. The lack of ductility of the glass prevent the equalization of stresses at local  irregularities or flaws and the breaking strength varies considerably.

Whilst the average breaking tensile stress of borosilicate  glass with flawless fire polished surface is approximately 70N/mm² the allowable design stress is considerably lower. AD-N4 specifies the allowable design stress in tension, bending and compression taking into account the likely glass surface condition in service

In addition the thermal stresses resulting from differential expansion of the inner and outer glass surface must be considered.  

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Permissible Operating Conditions

Thermal Shock  

The permissible values for working temperature and    pressure must always be considered together as thermal stresses  resulting from high temperature differences between the inner and outer glass surfaces reduce the permissible working pressure (see Figures 3 to 8).

If  the  internal temperature is less than the external - For example: in low temperature applications or for vessels with external heating – the thermal stresses require detailed consideration and we recommend that our Technical Department is consulted.  

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Permissible Operating Temperature

Borosilicate glass retains its mechanical strength and will deform only at temperature which approach its strain point, approximately 510°C. The permissible operating temperature is, however, considerably lower – normally at about 200°C – for glass components, provided that there is no temperature shock.

In exceptional circumstances, higher temperatures can be achieved possibly up to 300°C  (see AD-N4). However, additional precautions are required and we recommend that our technical department is again consulted.

At sub-zero temperatures, the tensile strength of borosilicate glass tends to increase and equipment can be used at temperatures as low as -50°C.

These temperature limits should be regarded only as a guideline and must always be modified in accordance with the actual operating conditions in any given application. The individual operating condition of some of the components detailed in this catalogue must also be considered. Where such operating limits apply, they are detailed in the individual catalogue section and component description

Under normal operating conditions, rapid changes in temperature should be avoided as this will result in increased stress in the glass. Experience has shown however that under exceptional conditions, a degree of thermal shock can be tolerated.

It is undesirable to give an overall figure but, as a general guide, sudden temperature change of up to around 120°C can be accommodated.  

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Permissible Operating Pressure

The maximum permissible operating pressure and the reduction in permissible pressure with increasing temperature difference between the process and ambient (Du) are shown in figure 3 to 8. Figure 3 and 4 are valid for all glass components with the exception of valves and filters (see figure 5 and 6), spherical vessels (see figure 7 and 8) and heat exchanger internal (see section 5 - Heat Exchangers).

Depending on the shape and working conditions, glass components can be used, under certain circumstance, at higher internal pressure. In these cases, the component will be marked in accordance with AD-N4.

Unless otherwise stated all standard glass components are suitable for operating at full vacuum subject to the temperature limits shown in Figure 3 to 8

In cases where glass in operated under a gas pressure or vacuum we are recommend that our technical department is consulted for further information on suitable external protection.  

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Permissible Operating Conditions

Typical External Heat Transfer Co-efficient.

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Working Temperatures

Borosilicate glass retains its mechanical strength and will deform only at temperatures which approach its strain point. The practical upper limit for operating temperatures Is much lower and is controlled by the temperature differentials in the glass, which depend on the relative temperatures of the contents of the equipment and the external surroundings.

provided borosilicate glass is not subjected to rapid change in temperature, creating undue thermal shock, it can be operated safely at temperatures up to 450⁰F (232⁰C). The normal limiting factor is actually the gasket material. The degree of thermal shock (usually defined as sudden chilling) which it can withstand depends on many factors, for example: stresses due to operating conditions; stresses imposed in supporting the equipment; the wall thickness of the glass, etc. It is therefore undesirable to give an overall figure but, as a general guide, sudden temperature changes of up to about 216⁰F (120⁰C) can be accommodated

At sub-zero temperatures, the tensile strength of borosilicate glass tends to increase and equipment can be used with safety at cryogenic temperatures It is always advisable to discuss any difficult applications with our engineers.

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English Metric Conversions

Length:  

• millimeters / 25.4 = inches  

• inches x 25.4 = Millimeters

B. Volume

• Gallons * 3.785 = liters

• liters / 3.785 = gallons

C. Pressure: 1 bar = 14.5 lb/in² = 1.02 kg/cm² = 0.98692 atmosphere  

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Jacketed components are designed to complement the standard range of glass process plant and pipeline equipment's detailed in this catalogue by extending the range of applications for which glass can be used. Jacketed components, as their name implies, are standard glass components with a glass jacket around them. The jacket is sealed onto the glass component with silicone rubber.

Jacketed components are not only used to avoid heat loss for the purpose of saving energy, but also where the product characteristics have to be maintained to prevent crystallizing or unwanted reactions from occurring. A further area of application is thermal insulation where the ability to still monitor the process visually is a major advantage.

Jacketed versions of all the major glass components detailed in this catalogue are available. The range therefore includes pipeline components, valves and vessels as well as a wide variety of column components and heat exchangers.

Permissible Operating Conditions

For the inner part of jacketed components, the permissible operating pressure are identical to those for their non-jacketed counterparts. These pressures are detailed in the previous pages of this section.

However, deviations will arise in the permissible operating temperature for the inner component and the permissible operating conditions in the jacket itself. These are due to permanently flexible silicone seal, which absorbs the different expansion levels of the inner component and jacket.

Permissible Operating Temperature  

The permissible operating temperature for the inner component is -40°C to +_150°C. For  the jacket it is -40°C to +130°C.

In special circumstances, the operating temperature can be increased to +170°C for the inner component and +150°C in the jacket.

Permissible Operating Pressure

The  permissible  operating  pressure in the jacket is –0.2bar.g to + 0.1bar.g, unless lower values are derived from Figure 3 to 8 on the previous pages.

Please Note:

If there is a vacuum in the jacket, care must be taken to ensure that the pressure difference between the inner component and the jacket does not exceed the permissible operating pressure for given Figure 3 to 8 on the previous pages.

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