Valves, Actuators & Pump Control


Arca’s new approach to severe-duty microflow valves

August 2018 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, down to microflow valves with rated flow capacity that would take more than 20 hours to fill a glass of water.

Typically, microflow control valves are globe valves with a seat diameter of 2 mm or less, where the plug is either parabolic or a V-notch type. The turndown ratio and control performance of such a valve is mainly dependent on the tolerances between plug and seat ring. Assuming a control ratio of 20:1 and following the rule of thumb that a KV of 1 m³/h corresponds to 28 mm² vena contracta area, on such valve trim the tolerance between plug and seat ring must be less than 3 μm. Besides the challenge to produce such high-precision parts, this kind of trim can only be used on clean process fluids and, due to the thermal expansion, only within a restricted temperature range.

Arca’s new patent-pending approach is based on a rotary sliding gate valve, where two slices with lapped surfaces are installed in the valve pressed together by a spring and differential pressure. This enables zero-tolerance without any limitation due to thermal expansion. Each slice has one or more bores for the flow passage. Normally the flow passage of such sliding gate valve is only open when the bores overlap. Especially with small rated flow coefficient (small bores) this results in the on/off characteristic of the valve. In this new design one of the slices is equipped with a tangential flow channel, which leads and expands into the bore of this slice. This enables a smooth control behaviour with sufficient opening angle (more than 60 degrees).

The slices can be made of any material (even ceramics), which makes the trim resistant to process fluid and pressure drop. Although the valve plug movement is quarter-turn, a standard globe valve housing DN 15–25 rated PN16–PN 250 is used. This makes the design economical and allows changing from a standard valve to the new design, even in existing applications.

First flow characteristic and critical flow factor FL measurements up to 150 bar differential pressure have proven the performance of this approach, even under pressure drops up to 250 bar.

For more information contact Desmond Delport, Valve & Automation, +27 11 397 2833, sales@valve.co.za, www.valve.co.za


Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

The evolution of partial stroke testing
April 2019, Valve & Automation , Valves, Actuators & Pump Control
The failure of these valves in crucial moments can be catastrophic, potentially rendering useless a Safety Instrumented System (SIS), put in place to reduce the possibility of an accident. Though static ...

Read more...
Stafsjö introduces Linak electric actuator
April 2019, Valve & Automation , Valves, Actuators & Pump Control
Linak’s electric actuator is a compact maintenance-free unit for on/off operations with a speed of 7-11 mm/sec. It is available as standard in a 24 V DC version but it can also work on 230 V AC or 120 ...

Read more...
Quarter-turn actuator for harsh conditions
February 2019, 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, ...

Read more...
First Metso valves with 3D printed parts
February 2019, Metso South Africa , Valves, Actuators & Pump Control
Metso’s Helsinki plant has delivered the first valves with 3D printed parts. The units include 3D printed metal components that allow them to perform in a particularly demanding application, where they ...

Read more...
Richter’s PFA-lined ball valves
February 2019, Valve & Automation , Valves, Actuators & Pump Control
Richter, a leading supplier of PFA-lined pump and valve solutions, has a new size control ball for its KNR and KNAR valve series. Increasing production quantities in the chemical and petrochemical industries ...

Read more...
Schubert & Salzer adds GS4 series
February 2019, Macsteel Fluid Control , Valves, Actuators & Pump Control
Sliding gate valves optimised for pressures up to 160 bar.

Read more...
Flow control problems in a pulp mill
January 2019, Valve & Automation , Flow Measurement & Control
NAF’s advanced process valves solve pulp, paper and cellulose applications.

Read more...
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 ...

Read more...
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 ...

Read more...
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, ...

Read more...