Positioners with a noncontact Hall Effect sensor, which detects changes in magnetic flux when the control valve stem moves and then feeds it back to the positioner so that it may alter the air signal to the actuator, can assist in valve system maintenance, reports Spirax Sarco. This ensures that the valve is operating in the correct position and can provide a solution for a number of problems.

The company has a range of communicating positioners, the SP300.

Control valves are often located in an environment that makes them challenging to install and maintain, and control processes. It may be difficult to gain access to the control valve, or extreme temperatures might make maintenance an unpleasant job. These problems mean that the control valve can be neglected, leading to sudden breakdowns and loss of production.

Remote access to the control parameters in a positioner can be achieved through communication protocols. Spirax Sarco reports that some plants, however, do not use this technology and access to the positioner is still needed for maintenance.

The SP300 provides a solution for difficult access through the use of the Hall Effect sensor. This has no mechanical linkage to the valve stem and can be mounted directly to the valve or at a more convenient location, up to 20 m away.

The SP300 positioner is compatible with a variety of process measurement and control instrumentation systems and it can connect to all existing network systems. It is suitable for use in all operating environments, including intrinsically safe, explosionproof, heavy vibration, extreme temperature, high-corrosion atmosphere and difficult access areas. The posi- tioner has weatherproof and explosionproof compatibility, with a stainless steel enclosure option for corrosive areas.

The positioners are compatible with all pneumatic actuator types and have a Namur-standard actuator mounting, which is operationally compatible with all rotary, linear, single-acting and double-acting pneumatic actuators. The SP300 can be fitted to new and existing control valves, which means that the SP300 positioner can be a standard unit for all types of control valves.

The SP300 positioner is self-configured in a short space of time, and adjustment of parameters through local display means that no special tools are required. The company reports that engineers are able to quickly understand the operation of the SP300 as they are supplied with remote operation through communication proto- cols.

The challenges associated with process instability that arise as a result of vibrations from the plant have a detrimental effect on the positioner and, therefore, the performance of the control valve. The SP300 also provides a solution for vibrating plants through the Hall Effect sensor. As it has no mechanical linkage to the valve stem, it is, therefore, unaffected by vibration.

Corrosion of the positioner enclosure is another common problem faced by industry, especially in atmospheres con-taining corrosive substances such as salts and chemicals, or environments that require regular hosing down.

Stainless steel enclosures are provided as a solution to this problem. High investment has traditionally been required for a positioner with a stainless steel enclosure. Spirax Sarco says that its integrated manufacturing and global purchasing practices have made stainless steel enclosures a cost-effective, long-term solution to corrosion problems caused by salts, chemicals and cleaning practices.

Heat Exchanger
The company also recently launched a heat exchanger, QuickHeat, for use alongside valves in manufacturing processes.

The company says that the QuickHeat's compact design has a smaller footprint, height and weight than other solutions, providing ease of installation and reducing the size of the required storage space.

Spirax Sarco reports that the product can be used in heat exchange applications ranging from 100 kW to 10 000 kW.

It is designed for applications where steam is the primary medium. The choice of materials of construction which are avail-able for the heat exchanger allows for a wide range of secondary fluids to be scatered for.

The product offers combinations of control methods, secondary piping arrangements and condensate removal options.

The company reports that it is recommended that an independent high-limit safety shut-off system be considered when heating water for personal use, or in process applications where overheating could be dangerous or cause a costly shutdown. It recommends that safety equipment be fitted where local regulations require it.

Spirax Sarco says that all its control valves have characteristics specifically designed for use with steam and they can be matched with either a pneumatic actuator or an electric actuator.

QuickHeat is designed to be integrated into existing control systems and mechanical designs.

Spirax Sarco partner Vahterus provides the heat exchanger at the core of the QuickHeat.

Its compact, fully welded construction provides a durable gasket-free construction, able to withstand high temperatures and pressures. It provides a low cost for each kilowatt with no possibility of energy loss or safety risks through leaks. The gasket-free, low-fouling design reduces maintenance requirements, which contributes to a lower cost of ownership.

The company reports that the QuickHeat units can be easily broken down and reassembled on site. All units are supplied with the certification, approvals and documentation to meet local statutory requirements.