classic | mobile
 

Search...

SA Instrumentation & Control Buyers' Guide

Technews Industry Guide - IIoT 2018

Technews Industry Guide - Maintenance, Reliability & Asset Optimisation

 

The benefit of head-guided plugs on slurry valves
August 2018, 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 Richard Rule, eDART Slurry Valve director. “Benefits include protection of the actuator, vibration control, prevention of rotation of the plug head, and keeping the seat alignment intact, all of which play an important role in valve longevity and operation.

“The conventional method of fitting guides around the shaft of the plug head has shown that there are constantly reoccurring problems reported from this method. eDART utilises an alternative method throughout its range of valves that embraces three or more guide bars to guide the plug heads, which are polyurethane coated to provide wear resistance.”

The problems associated with fitting guides around the shaft

Five main problems have been established with the conventional method of guiding plugged heads:

1. The guiding is a fair distance from the seat, which is where it is best served to prevent the plug rubbing on one side of the seat ring bore, making any clearance between the shaft and guide magnified at the point of seating.

2. In the case of dart valves installed inside a tank the guides are generally attached to the side of the tank. This makes for a more difficult installation and puts accurate alignment in jeopardy, which can prove costly when the site is remote.

3. The small clearance between the guide bush and the shaft makes this arrangement vulnerable to a deposit of solid material between the two components. Scale build up on the shaft can result in the valve sticking and not moving smoothly.

4. There are forces on the plug head from the fluid flow that can cause the shaft to rotate which is extremely difficult to prevent on a shaft with a relatively small diameter.

5. Shaft guides, wear quickly, leaving the shaft poorly guided.

The advantages of fitting the guides to the plug head (or head guiding)

Guide bars are an interference fit directly on the diameter of the plug. Installation and commissioning is a lot easier when the guiding is attached to the seat assembly, thereby eliminating the need for alignment from guide to seat. It also eliminates material build up that can result in seizure due to the fact that guiding takes place between two circles touching on the outside.

Rule elaborated: “The plug head will be pushed against two bars by the line forces and the friction between the components will prevent all but the most severe rotational forces from twisting the shaft. For larger valves, it is standard to fit an anti-rotation plate, or crown guide, on the back of the plug head, which eliminates all rotation.

“The fact that our guide bars are polyurethane coated means that they are capable of handling fluid flow, and the velocity of this flow is much lower around the bars than between the plug and seat, substantially reducing the potential of erosion.

“Answering the industry question of what plug shape is good for the job at hand, we at eDART use computer modelled fluid dynamics to compare plug and seat type valves using different shapes. We have established that the inverted plug shape has a quick opening valve characteristic, while the cone plug provides a more linear response. The cone plug is well suited to control due to the linearity, unlike the quick opening plug which is better for on/off applications. The linear characteristic shape of the eDART cone plug can easily be controlled by standard PID controllers and is therefore a popular choice for eDART’s range of slurry control valves.”

For more information contact Afrivalve, +27 11 791 1411, sales@afrivalve.co.za, www.afrivalve.co.za


Credit(s)
Supplied By: eDART Group
Tel: +27 11 791 1411
Fax:
Email: sales@edart.group
www: www.edart.group
Share via email     Share via LinkedIn   Print this page

Further reading:

  • Innovative vertical gravity samplers delivered by eDART
    December 2018, eDART Group, News
    To meet the requirement of an international customer, eDART Slurry Valves designed, tested and manufactured a vertical gravity sampler assembly (VGSA) for application within the minerals processing sector. Duane ...
  • 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 ...
  • Slurry control valves for level control
    July 2018, eDART Group, Level Measurement & Control
    In order to improve the froth level control at a flotation concentrator in Rustenburg, eDART was recently commissioned to replace the froth level control valves on the secondary cleaner. Froth level ...
  • 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 ...
  • Sliding gate valves in control at PVS
    May 2018, Macsteel Fluid Control, 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 ...
  • 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 ...

 
 
         
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.