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|Properties Of Borosilicate Glass||Per. Operating Temperature|
|Chemical Composition||Permissible Operating Pressure|
|Chemical Resistance||Per. Operating Conditions|
|Physical Properties||Buttress Ends|
|Optical Properties||Working Temperatures|
|Mechanical Properties||English Metric Conversions|
|Permissible Operating Conditions||Jacketed Components|
glass used in the manufacture of our range of process plant and pipe line components has the following approximate composition.
the following approximate composition.
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.
Coefficient of mean linear thermal expansion
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
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.
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.
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.
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.
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
can be accommodated.
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.
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.
Typical External Heat Transfer Co-efficient.
The glass process plant and pipeline components detailed in this catalogue have either standard flat buttress ends (Type A + B from DN 25 to DN 450)
The following table provides dimensional information on standard flat buttress ends form for the range of glass components detailed in this catalogue.
Maximum Working Pressures
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.
English Metric Conversions
C. Pressure: 1 bar = 14.5 lb/in2 = 1.02
kg/cm2 = 0.98692 atmosphere
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
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.
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.
Copyrights Reserved 2001-2007 by Garg Scientific Glass Industries.