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Process Plant Pipelines

ATR offers Schott Duran borosilicate glass pipeline having many advantages to the end-user, two of which can be singled out as having made a particular contribution to the growing use of these products in the chemical, pharmaceutical and nuclear industries:

  1. Excellent corrosion –resistance and temperature-resistance at a comparatively low price.
  2. High level of operational safety resulting from a coupling system design which is matched to the material of construction.

A number of additional advantages, such as :-

  1. Smooth pore-free surface.
  2. Catalytic inertness.
  3. Dimensional stability over the entire temperature range.
  4. Non-flammability.
  5. Transparency
  6. Physiological acceptability
  7. No effect on odour and taste.

Having opened the way for the use of borosilicate glass piping in the many other branches of industry, such as dyestuffs, foodstuffs, beverages and electroplating.

Taking as a common basis the advantages of DURAN borosilicate glass as a material of construction and the use of the modular construction system, ATR has developed pipeline systems from which user can select the components providing the best technical and most economical solution for their particular applications.

ATR pipelines are predominantly used for drain lines and ventilation lines in chemical and pharmaceutical plants, universities and polytechnics, commercial kitchens, airports, hospitals and nuclear installations.

Operating Range

All components in the pipeline system are corrosion resistant to all organic and inorganic process fluids, the only exception being hydrofluoric acid and fluorides, glacial boiling phosphoric acid and alkalies at high temperature and concentrations.

The maximum operating temperature is 200 deg C.

The maximum rapid change in temperature of the process fluids is 120 K .

All components are suitable for full vacuum.

Maximum working pressure depends upon the diameter.

Diameter (mm) 15 25 40 50 80 100 150 200 300 Pipelines
Pressure (bar gauge) 4 4* 4* 4* 3* 2 2 1 1 * with glass ball valves

For systems fitted with glass valves having PTFE bellows and which are operating above 150 deg C the pressure is reduced to 3 bar gauge for 50 mm and 2 bar gauge for 80 mm diameter. Use the glass ball valves if higher pressure rating is required.

For the systems fitted with a range of components of various diameters, the pressure rating for the whole system is set by lowest rated component. The material of construction of the couplings and gaskets must also be taken into account when designing a system.

Interchangeable Standardization

The most important glass pipeline components over the range 15mm to 150mm are specified in DIN ISO 3587 (BS 2598 part 3). This gives the user a guarantee that components are interchangeable and compatible when a consistent glass flange system is used.

The modular construction system is based on a unit grid measurement of 25 mm. ATR have used this grid system as a basis for all components in their product range for many years.

Modular Construction System in the Metric Grid

Our pipeline use modular construction system for diameter range 15 mm to 300 mm and includes a wide range of fittings, for example :

  1. Pipe lengths up to 3000 mm.
  2. Fittings such as ties, bends, reducers
  3. Glandless valves from 15 mm to 100 mm in the material combination borosilicate glass/PTFE.

The dimensions of all components of the modular construction system are based on a single unit of measurement. This “metric grid system” ensures problem-free construction using standard components. The basic dimension in the grid system is 25 mm and all component dimensions are divisible by this number.

Valves and fittings of the same diameter always have the same arm length. This means that bends can be replaced by tee pieces, tees by valves etc. thus permitting rapid and simple modification to existing plants.


Freedom from maintenance and high operational reliability are hallmarks of the highly corrosion resistant fittings in the piping range. Accordingly the only materials used in combination with Schott Duran are the other highly corrosion-resistant materials such as PTFE, tantalum, and alumina ceramics.

The design principle of all valves, including glandless bellow seal valves, is that the free cross section corresponds to the full bore of the pipework connection. This prevents process problems caused by a reduction in cross-sectional area.

The design of PTFE bellows in glandless valves has proved itself over many years of operation. Our product range includes highly corrosion-resistant valves for almost all possible duties. These include non-return valves, hand control valves, actuated on/off and control valves, vent valves, flush sealing bottom outlet valves, safety relief valves, twin bellow valves.

The Coupling System

The coupling system has been designed to complement glass as a material of construction. It is a decisive factor in the high operational reliability of pipeline.

The glass flange has been designed with a flange angle of 65 deg. This has the following advantages :-

  1. The bolting force acts predominantly in the axial direction, giving a high, permanent sealing force at the gasket.
  2. The backing flanges are easy to remove from the glass, even after many years of operation.
  3. Frequent re-tightening of the coupling is not required, even with temperature cycling and intermittent operation.

The shoulder flange is the optimum design for a glass joint and due to tis mechanical strength, facilitates the use of spherical ground glass sealing surfaces. In principle, all piping components have a ball, or male, flange at one end and a socket or female, flange at the other end. By convention , the glass flanges on all outlets from the vessels and columns are ball type, this make it easier to prepare the pipework design.

The type of joint makes it possible to articulate components by up to 3 degrees, depending on the diameter. In this way, it is easy to compensate for slight differences in length and pipes can be laid at a gradient without recourse to special components.

Couplings and Gaskets

In pipeline assembly, one piece backing flanges are used with a loose hinged insert. The following couplings are available:-

Couplings with plastic flanges and inserts

This is the most frequently used coupling since it is corrosion-resistant, light weight and does not require electrostatic earthing. The plastic material is solvent and acid resistant glass fibre-loaded phenolic resin.

Couplings to DIN ISO 3587 and DIN ISO 4704 with plastic backing flanges and inserts

This coupling has the above features with the advantage that the flanges ca7005-3, n be connected directly to other materials of construction with flanges to ISO 7005-2, PN 10, ISO 7005-3, PN 10 and DIN 2501, PN 10.

This coupling must be used at fixed points in structures.

Couplings with Silumin backing flanges. These couplings are used for high temperature duties for example where lagging is fitted over the top of the coupling or where certain corrosive substances are being processed.

All the above couplings are suitable for operation at 200 deg C on product side and for the full range of operating pressures. The plastic flanges are not to be used in duties where we shall be using lagging over the coupling. The standard bolts, nuts and washers are bright zinc-plated. Stainless steel bolting is available on request.

When processing the fluids which tend to crystallise or are particularly searching. It is advisable to use longer bolts fitted with compression springs. This provides additional elasticity in the joint and ensures permanent leak tightness and freedom from maintenance under extreme conditions.

PTFE is the normal gasket material due to its universal corrosion-resistance.

Some of the precautions to avoid tensile stress in Glass equipment:-

  1. Locate supports in accordance with data supplied by ATR.
  2. Avoid directly adjacent fixed points.
  3. Eliminate external forces such as those from building movement and machinery vibration by the use of bellows between fixed points at the interface between glass and non-glass pipework. Bellows must not transmit any additional force to the glass.
  4. Take account of thermal expansion and contraction, particularly between borosilicate glass ( α=3.3 X 10-6 K-1) and other material of construction which have greater coefficients of expansio
  5. n.
  6. Fit counterbalances to ensure that the maximum recommended loading at a single fixed point support is not exceeded.
  7. Do not over-tighten glass joints.

Leak Testing

After initial assembly, the following procedure us necessary to ensure a leak-free plant:

  1. Heat the entire plant, as far as possible, to the proposed operating temperature. Allow the plant to cool down.
  2. Re-torque the bolts to the torque loading in the above table.

The aim of the above procedure is to allow initial settling of the PTFE gasket. Any further residual cold flow will be taken up by the elasticity of the coupling.

The glass plant can then be checked for leak tightness by filling with water. This is the method used for the vast majority of new installations. The hydrostatic head of water MUST NOT exceed the maximum allowable operating pressure.

If gas testing is called for, the test pressure should be kept as low as possible. A further option for tightness testing is to apply a vacuum. A halogen leak probe can be used to detect leaks or the rise in pressure over a period of time can be measured and compared to the calculated figure. The figure for joints with a ground face and PTFE gaskets is 1 X 10-2 mbar l/s per meter length of gasket. For example a DN100 joint will have a leakage rate of 5 X 10-4 mbar l/s.

In case of couplings fitted with compression springs, it is essential to use a torque spanner to tighten the bolts. Do not exceed the maximum torque loading. It is not necessary to heat the entire plant and re-torque the bolts when springs have been fitted because the springs will take up any initial relaxation of the PTFE gasket.

Process Commissioning

Process commissioning, as with design and installation, is a key component in the range of service offered by ATR. ATR can provide fitters and engineers for commissioning as well as for installation and leak testing.

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