Valve choice key to efficiency

The importance of correct valve selection for pharmaceutical production processes is evidenced by the benefits it provides, as Ian Webster,hygienic processing field segment manager at Burkert Fluid Control Systems, explains

As well as delivering equipment and installation savings, optimised valve selection can eliminate all dead legs, meaning that sterility is easier to ensure and maintain. It can also mean faster flow shifts and reduced risk of cross-contamination.

The compact design of the latest single diaphragm valves, combined with manifold blocks, ensures minimal hold-up volumes, increased product yields and less media waste.

Traditional solutions are generally based around diaphragm valve technologies. These make use of closely welded cluster arrangements, with the shortest possible tangents and optimised positioning according to draining/cleaning requirements. However, even with optimised design, the requirement for minimised hold-up volumes can often be compromised by complex valve clusters - the more valves needed, the more welds, pipe lengths, T-pieces that are required, and the more hold-up volume generated.

In addition, valve clusters can militate against fast and accurate flow shift. If the accuracy of the flow shift is higher and more reliable, then the relationship between concentrated product and the separation step can be controlled more closely. This will reduce product loss and have a positive impact on the ROI of the installation.

Another challenge with the clustering approach is that in larger systems the complex arrangement of valves, and their individual size, can result in large and heavy clusters that have to be supported, and be easily accessible for maintenance. The larger the valves needed, the more space is required, and when considering the need for fully drainable, cleanable systems, this is not ideal.

New technology and manufacturing advances have resulted in new designs based, for example upon Robolux valves and custom-manufactured stainless steel valve blocks.With this design, hold-up volume is eliminated by reducing - by half or more - the number of valves, diaphragms, pipe fittings and welds required in a system.

Based on diaphragm valve technology, the new generation of valves combines independent dual process switching functions or '2 seats' in a single body with a single diaphragm and single actuator. The actuator has independent pistons - one for each seat, offering a compactly-designed multi-port valve requiring about 40% less space than traditional valve manifolds using conventional diaphragm valves. Since less material is used in the valve bodies, they can be heated more quickly to sterilisation temperature. A low internal volume, and elimination of dead space supports faster cleaning and boosts process efficiency and higher product yield from the process.

Continuing the benefit of minimum space requirement, the overall number of valves, Tpiece, weld joints and pipe runs are greatly reduced. The result is an optimised footprint that reduces installation and maintenance costs and minimises downtime.

The cleanability of a pipe system is influenced by dead space volumes and the application of the 3D rule. Currently, the industry is satisfied with the 3D rule. Its consistent application ensures sufficient flushing for many processes. Dead legs will be completely flushed and cleaned only if the length of the dead legs is less than three times the diameter of the main pipe.

It is usually not possible to consistently implement the 3D rule when arranging complex configurations with conventional valves; the goal of any plant operator and planning engineer is to remain well below the requirements of this rule. One solution is to achieve the 1D rule now, and the Robolux valve solutions are capable of this. The internal volume of the valves and/or valve manifolds is smaller than with conventional valve solutions and there is no dead volume inside them.

If four conventional DN25 diaphragm valves are welded in a typical steam cross configuration, this results in an internal volume of 90ml held in the pipe section between the 4 valve seats. If this solution is enhanced by using a standard valve block, the internal volume can be reduced to 50ml.

Finally, if the standard valve block is replaced with a Robolux valve, the total inner space volume is only 22ml. These valves minimise installation space, the amount of flushing agent needed, and time. The cleanability of the pipes and valve manifolds is important for another reason: Improper flow through the body may result in corrosion. Robolux valve interfaces can help prevent corrosion.

Valve interfaces must meet high standards to guarantee reliable processes and yet remain flexible for different applications.

Robolux valves can provide a 'double block and bleed function' to prevent steam used for sterilisation of the parallel line from contaminating the product and vice versa; it is achieved by using a relief valve in between the two seats.Multi-port valve bodies enable the effective implementation of many complex applications. For example, parallel operation is possible with the use of a Robolux DFP (Double Flow Path) interface which increases overall availability of the plant and saves production time.

Multi-port valves can act as a sterile barrier; a solution using two actuators and 2 diaphragms provides the function of a steam barrier with 4 connections and 4 seats that replaces four conventional valves with their single actuators, and the corresponding piping and connecting elements.

Robolux valves come with either manual or pneumatic actuators in sizes from 1/4 to 2in (DN4 - 50). They are made with a choice of body types: 316-L stainless steel, ultra-pure polypropylene, polypropylene USP V1 and PVDF. The valves also offer a range of diaphragm materials to suit all types of media, including EPDM, FKM, PFA/ EPDM, PTFE, Silicone and PFR91. Robolux valves hold all major certifications.