R/€ = 13.71
R/$ = 10.88
Au 1199.05 $/oz
Pt 1245.50 $/oz
May 11, 2007
Self-acting controls offer stabilityBack
System|Systems|Water|External Systems|Food|Maintenance|Oil Outflow Heaters|Systems|Bobbie Brooke-Taylor|Power|Water|Valves
© Reuse this Process temperatures or pressures can be controlled in different ways. Spirax Sarco self-acting controls are fully calibrated, easily adjusted and can be arranged to be completely tamper- proof.
The controls are easily adapted for remote timed on/off modulating and the ‘safeguard’ option protects processes by automatically shutting off heat at the source in the event of temperature overrun or system failure.
“Self-acting control valves require no external power source or instrument signal. It relies on the vari- able process conditions to respond in some predetermined way,” explains Spirax Sarco marketing manager Bobbie Brooke-Taylor.
Self-acting controls give stable, modulating control and are suit- able for steady loads, such as storage tanks, oil outflow heaters and hot water storage.
This type of control responds well to gradual changes in the pro- cess condition, holding the variation in the process very close to the set point and avoiding large swings that can lead to system hunting.
However, for applications with rapidly fluctuating temperatures, self-acting controls may not react quickly enough to provide close control. It is also unsuitable where a temperature ramp-up is needed, as when starting a process. Self-acting controls cannot generally be interfaced with external systems.
These valves are generally used when the process has one set point condition. The self-acting valve is tuned to that set point and, as the process varies, responds in a way to return conditions to the set point. Pressure and temperature are the two most popular process conditions to whicha self-acting valve is applied.
The Spirax Sarco self-acting control valves can be used in a wide variety of environments from the hospitality industry to the food pro- cessing industry. They also enjoy a long maintenance-free life with repeatable performance, as they oper- ate through liquid expansion with friction-free bellows.
Where speed of response is not essential and electricity is the preferred source, electric actuation offers reliable and accurate control.
Electric controls are suitable for applications requiring slower res- ponse times, such as drying, preheating, feed tanks and space heating.
Spirax Sarco electric controls are offered with a sensor, controller, actuator, positioner and valve in one complete system. A plug-in positioner card provides accurate valve movement irrespective of varying forces.
In the majority of applications, temperature or pressure control needs pneumatic actuation to maintain accuracy under rapidly changing load conditions.
Pneumatically actuated controls are ideal for dusty and hazardous conditions and offer powerful actuation for high-pressure applications.
Edited by: Laura Tyrer© Reuse this Comment Guidelines (150 word limit)
Other Valves News
In a move that will ensure valve manufacturer AVK South Africa’s compliance with the Department of Trade and Industry’s (DTI’s) new designation law that requires State-owned companies (SOCs) to buy locally manufactured products with a 70% local content, AVK South...
Specialist alloys and valve supplier Energy Engineered Products reports it has completed its latest contract for State-owned power utility Eskom’s Kusile power station project, in Mpumalanga. The company completed the supply of products, valued at about R2-million,...
Thermal spray service provider Thermaspray is expected to complete a Stellite alloy 6 ball valve, which will be laser-clad to the SAF 225 alloy, allowing for the ball valves to be used in highly corrosive environments at wood and paper pulp and paper-based solutions...
Recent Research Reports
Defence 2014: A review of South Africa's defence industry (PDF Report)
Creamer Media’s Defence 2014 report examines South Africa’s defence industry, with particular focus on the key participants in the sector, the innovations that have come out of the sector, local and export demand, South Africa’s controversial multibillion-rand...
Road and Rail 2014: A review of South Africa's road and rail infrastructure (PDF report)
Creamer Media’s Road and Rail 2014 report examines South Africa’s road and rail transport system, with particular focus on the size and state of the country’s road and rail network, the funding and maintenance of these respective networks, and the push to move road...
Real Economy Year Book 2014 (PDF Report)
This edition drills down into the performance and outlook for a variety of sectors, including automotive, construction, electricity, transport, steel, water, coal, gold, iron-ore and platinum.
Real Economy Insight: Automotive 2014 (PDF Report)
This four-page brief covers key developments in the automotive industry over the past 12 months, including an overview of South Africa’s automotive market, trade figures, production and the policies influencing the sector.
Real Economy Insight: Construction 2014 (PDF Report)
This five-page brief covers key developments in the construction industry over the past 12 months. It provides an overview of the sector and includes details of employment in the sector, infrastructure and municipal spending, as well as insight into companies’...
Real Economy Insight: Electricity 2014 (PDF Report)
This five-page brief covers key developments in the electricity industry over the past 12 months, including details of State-owned power utility Eskom’s generation activities, funding and tariffs, independent power producers and prospects for the sector.
This Week's Magazine
Updated 6 hours ago In the next 20 years, it was expected that, in Africa, more people would live in cities and towns than in rural areas, United Nations Habitat executive director Dr Aisa Kirabo Kacyira said at the Human Settlements Indaba that took place earlier this month in...
Updated 6 hours ago Tough-talking Human Settlements Minister Lindiwe Sisulu has committed government to building 1.5-million low-cost houses over the next five years, telling the Human Settlements Indaba in Johannesburg on Wednesday that the State would achieve this target through the...
Updated 6 hours ago Over the past 20 years there has been persistent concern about deindustrialisation in South Africa, as well as the fact that locally produced manufactured products have been increasingly displaced by imports.
Updated 6 hours ago Financial agreement for Ghanian independent power producer (IPP) Cenpower Generation Company’s $900-million, 350 MW combined-cycle gas-turbine power plant was finalised earlier this month, paving the way for the project’s construction to begin before 2015 in Tema,...
Updated 6 hours ago The revenue implications for South Africa of ‘base erosion and profit shifting’ by corporate taxpayers are firmly in the crosshairs of the Davis Tax Committee (DTC) and Judge Dennis Davis hinted last week that recommendations were being considered to “detect and...