classic | mobile
 

Search...

SA Instrumentation & Control Buyers' Guide

Technews Industry Guide - IIoT 2018

Technews Industry Guide - Maintenance, Reliability & Asset Optimisation

 

Sliding gate valves in control at PVS
May 2018, Valves, Actuators & Pump Control


Belgium-based PVS Chemicals produces extremely pure chemicals for use in the semiconductor industry. One of the company’s outstanding innovations is the production of ultra-pure sulphuric acid. As the only worldwide producer, PVS is able to supply diluted acid at a consistently high level of purity in which any impurities are measured down in the ppt (parts per trillion) range. The purity of acid enables semiconductors to be manufactured in a way that allows the individual circuit paths to be placed even closer together, allowing electronic devices to be made smaller and lighter. Schubert & Salzer Control Systems’ sliding gate valves have proved to be outstandingly successful in the processing plant producing the sulphuric acid. The valves’ excellent control precision over a very wide control range and their extremely high corrosion resistance are the key to the manufacture of these ultra-pure acids.

The demands on highly pure acids increase continually: nowadays, the end-product has to be produced consistently for many applications in a precisely defined concentration with a tolerance band of less than ±0,05%. The dilution presents a special challenge in this process. One of PVS’s activities centres on the production of highly pure diluted sulphuric acid in which the addition of the sulphuric acid in the dilution process can vary between 0 and 100%.

“Producing such a high-quality product with minimal deviations in a continuous process presents a special challenge,” comments Kristof Spreutels, plant manager at PVS. “Across the world, we are the only one to have found the solution at such a high quality level. However, it has needed a control valve with exceptional characteristics to be able to compensate for the variation range of 100% in the basic medium with absolute accuracy. It is extremely important for us that the control valve can deal with any variations in concentration at the inlet with the minimal delay and the maximum precision for the end-product. Process parameters exist such that the control valve must compensate for variations on the intake side between 0 and 100%, followed by 0 to 80%.”

Outstanding rangeability and excellent control quality

The sliding gate valve handles this challenge with ease. At the heart of this valve are two slotted discs sliding against each other and forming a seal. One of the discs, a seal plate permanently secured in the body at right angles to the direction of flow, has a specific number of transverse slots of the same height. A second non-rotating disc with a similar slotted arrangement is moved vertically against the first, thus changing the flow cross-section. The pressure differential forces the moving disc against the fixed one. Thus the sliding disc valve seals itself without the need for a separate seat.

The sliding gate valves’ very fast response time to signal changes is a key factor in their accurate control quality. Short stroke, low moving masses and low actuation forces are the key parameters that enable fast response and a high resolution of the stroke position. The sliding gate valve offers all of these features in one package. The typical stroke between open and closed is only 6-9 mm.

Positioning of the pneumatically-controlled sliding gate valve is provided by the digital Schubert & Salzer 8049 positioner, twin-lead version, with IP65 protection. Since the positioner rests centrally on the valve actuator, it takes up no additional lateral space, as well as saving weight. As a result of this integrated design system, no moving parts can be accessed thus maximising operational safety and security.

Surrounded by gold and PTFE

The sliding gate valve’s resistance to corrosion is another aspect in which PVS refuses to compromise. “In our process, we provide resistance to corrosion by making exclusive use of high alloyed or even exotic materials like PTFE, glass, platinum or gold. That is why the control valve has to be made from Hastelloy C. Valves made from stainless steel or plastic would corrode away or dissolve in less than a week due to the wide variations in concentrations at the inlet in our process. As a result, the combination of control precision and high resistance to corrossive media is an absolute must for our process,” says Spreutels. “Since we have been using Schubert & Salzers’ valves for over 10 years in steam generation and distribution, for example, it goes without saying that we should also use the same expertise for this special application.”

Furthermore, sliding gate valves in their twin flange version are very compact and light. Therefore, they present no problems in installation, even in PTFE pipelines. At the same time, the stress on the pipes is so small that additional valve supports can be dispensed with.

“We use sliding gate valves wherever we want high availability, good control properties and low maintenance costs. Even in the most challenging acid dilution, the sliding gate valves have required no maintenance or repairs whatsoever up to now. Also, despite the extraordinary stress placed on them by the media, they are showing no signs of degradation. So, thanks to the Schubert & Salzer sliding gate valves, we are the only company in the world able to produce these products to such a high quality and we’ve even been able to reduce the variation range in the concentration of the end product to ±0,02%,” concludes Spreutels.

For more information contact Kamil Maharaj, Macsteel Fluid Control, +27 (0)31 581 7800, kamil.maharaj@macfluid.co.za, www.macsteel.co.za


Credit(s)
Supplied By: Macsteel Fluid Control
Tel: +27 11 383 4000
Fax: 086 644 1320
Email: rowan.blomquist@macfluid.co.za
www: www.macsteel.co.za
Share via email     Share via LinkedIn   Print this page

Further reading:

  • Control of abrasive slurries
    October 2018, Bearing Man Group t/a BMG, Valves, Actuators & Pump Control
    BMG’s range of industrial slurry valves, which are designed to cope efficiently in harsh mining conditions, includes robust butterfly and knife gate valves, as well as diaphragm and pinch valves. “These ...
  • Schubert & Salzer stabilises paper production
    October 2018, Macsteel Fluid Control, Valves, Actuators & Pump Control
    The Austrian company, Grünewald Paper, recently modernised its process control to improve profitability. Thanks to a new control system and a grammage-weight control valve, the company’s throughput and ...
  • Quarter-turn actuator for dosing ­applications
    August 2018, Festo, Valves, Actuators & Pump Control
    Thanks to its versatility and flexibility, Festo’s quarter-turn actuator DFPD can be used in a variety of applications. Its modern, simple and compact design impresses whether it is used with ball valves, ...
  • Arca’s new approach to severe-duty microflow valves
    August 2018, Valve & Automation, Valves, Actuators & Pump Control
    Control valves are used in a wide range of capacity, from butterfly valves with a rated flow coefficient (KVs) of more than 50 000 m³/h, enough capacity to fill an Olympic swimming pool within three minutes, ...
  • Advanced slurry valves promote ­efficiency and productivity
    August 2018, Metso South Africa, Valves, Actuators & Pump Control
    There is sound reasoning for using advanced slurry valves in a number of industries where targeted efficiency and productivity require process parameters that may seem totally intolerable for materials ...
  • Richter launches largest PFA lined ball valve
    August 2018, Valve & Automation, Valves, Actuators & Pump Control
    Richter, a leader in PFA lined pump and valve solutions, has introduced a new size control ball for its KNR and KNAR control valve series. Increasing production quantities require a larger diameter of ...
  • The benefit of head-guided plugs on slurry valves
    August 2018, eDART Group, Valves, Actuators & Pump Control
    “Good guiding of the plug head with three or more guide bars offers better benefits to valve performance than otherwise offered by the conventional method of fitting guides around the shaft,” commented ...
  • Blowdown applications using multi-stage trim
    July 2018, Valve & Automation, Valves, Actuators & Pump Control
    The Arca angle style control valves series 350 and 380 are proven under critical process conditions. If used in steam or other process gas applications at high pressure and temperature, in cavitation-free ...
  • Test unit for control valves
    May 2018, AT Technical Services & Supplies, Valves, Actuators & Pump Control
    Although plant designers tend to treat them as ‘necessary evils’, it is obvious that control valves play a key role in process quality and reliability. Extreme care must be taken to avoid costly premature ...
  • Optimised pump ­performance
    May 2018, SKF South Africa, Valves, Actuators & Pump Control
    Ignoring pumps is a risk because when these components break down, or run below optimum efficiency, the whole process suffers. Manufacturing and process companies are always under cost pressure, making ...
  • Sealed bearings eliminate common failures in triple offset valves
    April 2018, Valve & Automation, Valves, Actuators & Pump Control
    Bearing failures are among the highest root causes of failure in triple offset valves (TOV) for tight shutoff applications. This issue is directly attributed to the need to have metal bearings with very ...
  • Proportional regulators optimise the use of compressed air
    April 2018, ASCO, Valves, Actuators & Pump Control
    Precise and reliable dosage of compressed air is needed in the manufacture of container glass to ensure an optimal distribution of the molten glass within the mould. ASCO Numatics has developed a valve ...

 
 
         
Contact:
Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronic Buyers Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Other
Terms & conditions of use, including privacy policy
PAIA Manual





 

         
    classic | mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.