The growing world population has driven scientists to come up with innovative methods of producing potable water from seawater to compliment the available small fraction of freshwater. This potable water production is done using a process called desalination. Today, there are several plants with a very big capital outlay in countries such as Saudi Arabia, Israel and many others that produce potable water from a feed of seawater.
Such plants require state of the art operation to ensure consistent potable water quality and process safety. Often, the operation of such plants is done from a centralised control room in which various commands are initiated to control a series of equipment. These include actuated valves that direct the flow of water and other fluids in different directions during the varying cycles of operation. The valves may be operated by pneumatic actuator or electric actuators. In this article, we discuss the various aspects of the application of actuators in the desalination of water.
Where Can One Apply Actuators In The Desalination Industry
In the desalination of water, it may be common to find reverse osmosis modules in use for the treatment of the salty water. The untreated water is pumped at high pressure through the different stages of membranes at a certain flow rate that can be set by an operator. Actuators can then be used in the following cases:
- Flow control valves – Pneumatic actuators can be used in the control of flow rates of various fluids including water to control the quality of the overall process.
- On/Off valves – These may be utilised to close or open the flow of various fluids into the RO membranes during the various cycles of operation. Various configurations of valves occur due to different cycles such as the production cycle or CIP cycle. These may include electric or pneumatically operated on/off valve actuators.
Why Select COVNA Valve Actuators in Desalination?
Desalination processes may use a vast array of actuated valves, which in some contexts may be over 250 for each plant. COVNA offers customers a choice of two valve actuators for different applications – pneumatic and electric actuators. The choice of each actuator depends on the actual use. The benefits of selecting COVNA actuators in desalination are as follows:
- Reliability– Both COVNA Pneumatic Valve Actuators and Electric Valve Actuators are made of strong materials that resist abrasion and ensures a longer life of the actuators. The IP67 rating on the COVNA electric actuator is very essential in the desalination industry where there is water.
- Corrosion-resistant– The desalination environment consists of very humid air and corrosive water – these generally reduce the lifespan of any equipment. COVNA actuators are well designed with optimum running and maintenance costs. Special care is taken to select the most resistant material in the manufacture of the valves that ensures these valve actuators have a prolonged lifespan
- Flexibility-Both COVNA electric and pneumatically operated actuators come with the provision of manual operation in the event of electricity or compressed air failure. This increases the flexibility of operations.
The COVNA AT series pneumatic valve actuator has a lot of features that make it suitable for application in the desalination industry. The following features are associated with this actuator:
- Stainless Steel fasteners- very suitable for the corrosive environment in the desalination environment.
- Bi-directional stroke adjustment.
- Versa view continuous indictor for physically establishing the actual position of the valve opening.
- Bottom mounting that that is designed to conform with the latest standards under ISO 5211 and DIN3337 standards. This ensures the actuators can be applied to all types of valves
- The actuator body made of aluminium can be treated with hard anodized powder polyester which is resistant to corrosion.
The general operating temperatures range from -20 o C to 150 o C which should meet most of the requirements for operating in the plant.
The second choice of the actuator is the Electric-type which comes with the following features:
- The body is made of hard aluminum alloy treated by hard anodic oxidisation and coated with polyester powder. This makes it very abrasive and corrosion-resistant and therefore fit for use in the corrosive desalination industry.
- Fully enclosed cage motor with class F insulation that makes it suitable to avoid overheating and consequent fires.
- IP67 rating which makes the actuators suitable for the desalination processes. It is not however recommended to install the actuator in the open, and it would be best to cover it
- Conforms to ISO 5211 and DIN3337 for connection with the valve which makes COVNA electric actuators suitable for universal application with any type of valve made according to these standards.
- An Indicator is available for checking and monitoring the position of the valve when the electric valve actuator is in operation.
- Limit switches – some available limit switches prevent the actuator from operation beyond defined limits.
- The electric valve actuators have a ±0.5 % tolerance, with a 0% mechanical repeatability error and a 0 damping
The electric valve actuators are designed to work in an environment with a temperature range of -30 to 60 o C, which should meet most of the needs of the desalination industry.