Application Report PVS Chemicals - Producing dilutions with a tolerance of only ± 0.02 %0 pages

Technical article

Ingolstadt, April 2012
PVS Chemicals Belgium relies on the control precision and media resistance of the sliding gate valve

Producing dilutions with a tolerance of only ± 0.02 %
PVS Chemicals in addition to many other products,

can vary between 0 and 100 %.

produces extremely pure chemicals which are
used in the semiconductor industry, for manu-

"Producing such a high-quality product with minimal

facturing printed circuit boards. One of the com-

deviations in a continuous process presents a special

pany's outstanding innovations is the production

challenge," comments Kristof Spreutels, Plant Manager

of ultra-pure sulphuric acid. As the only worldwide

at PVS. "Across the world, we are the only ones to

producer, PVS is able to supply diluted acid at

have found the solution at such a high quality level.

a consistently high level of purity in which any

However, it has needed a control valve with exceptional

impurities are measured down in the ppt (parts

control characteristics to be able to compensate for

per trillion) range. The purity of acid enables PCBs

the variation range of 100 % in the basic medium with

to be manufactured in a way, so the individual

absolute accuracy. It is extremely important for us that

circuit paths can be placed even closer together.

the control valve can deal with any variations in

This allows electronic devices such as smartphones

concentration at the inlet with the minimal delay and

to be made smaller and lighter. Schubert & Salzer

the maximum precision for the end product. Process

Control Systems' sliding gate valves have proved

parameters exist such that the control valve must

to be outstandingly successful in the processing

compensate for variations on the intake side between

plant producing the diluted Sulphuric Acid. The

0 and 100%, followed by 0 to 80 %."

valves excellent control precision over a very wide
control range and their extremely high corrosion

Outstanding rangeability and excellent control

resistance are the key to the manufacture of these

quality

ultra-pure acids.
The sliding gate valve handles this challenge with ease.
The demands on highly pure acids increase continually:

At the heart of this valve are two slotted discs sliding

nowadays, the end product has to be produced con-

against each other and forming a seal. One of the

sistently for many applications in a precisely defined

discs, a seal plate permanently secured in the body at

concentration with a tolerance band of less than

right angles to the direction of flow, has a specific

± 0.05 %. The dilution presents a special challenge in

number of transverse slots of the same height. A

this process. One of PVS's activities centres on the

second non-rotating disc with a similar slotted

production of highly pure diluted sulphuric acid in which

arrangement is moved vertically against the first, thus

the addition of the sulphuric acid in the dilution process

changing the flow cross-section. The pressure

Technical article: Producing dilutions with a tolerance of only ± 0.02 %

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