Industries require flow control for automation purposes in hazardous environments. A valve monitor is the component used to control actuators that open and close gates. Uses of a valve monitor is found in industries for storage of water, gas, oil and other fluids. An example is waste water management, refineries or gas depots. Any other factory environment that uses cold storage or boilers normally has use for a valve monitor and a valve limit switch box. Some of the fluids produce harzardous fumes so the valve limit switch fasteners should be airtight by use of o-rings. The components should be made of stainless steel for corrosion resistance.

Durability of valve monitor is further enhanced by powder coating finish. The closed box should be appealing and the design of the fasteners should be easy to use. There are various types of actuators. They are either hydraulic or pneumatic depending on the scale and pressure of the system. A valve limit switch can be specified to be explosion proof. An alternative to a valve limit switch is a proximity limit switch.

The parts of the valve monitor like the stainless steel enclosure and attachments are standardized. ISO 5211 is the European standard that has also been declared as a national standard by several countries. It defines the part turn actuators which are use in valve limit switch boxes. It includes description of keys like square and flat drives.

Other dimensions specified are for flanges. Any modifications to valve monitor standards should be under written agreement between a supplier and a purchaser. Torque values are essential in valve limit switch and should be indicated. Fasteners bore sizes are also specified proportional to the different flange types. The supplier should be able to manufacture valve monitor consistent to the standards, dimensions and positioning of all units. This means that the manufacturer is ISO certified. Any additional designs may be added for ease of use and to make the valve monitor to be state of the art. Any patents are at the discretion of the valve monitor manufacturer.

The different standard sizes cover from large industrial to miniature domestic use. Depending with the type of valve limit switch, the switching may be frequent or may take months before use. The durability and accuracy of a frequently used valve limit switch is determined by the duty of its motor and materials of its mechanics. The climatic conditions where the valve monitor will be installed must take into account the tolerance to humidity, pressure and temperature.

Safety standards of the valve limit switch must be high in order to avoid leaks. This prevents accidents from high pressure explosions or toxic substance leakage. Standards like IP67 define submersion of the valve monitor into water. This is the case in many applications and it should not cause any stalling of the valve monitor. For extreme climates, the temperature may solidify or liquefy grease. Therefore the correct grease type should be used or it may damage the valve limit switch. Under tedious operation, the valve monitor may tend to heat up. The surface may act as an ignition point of ambient flammables. Valve limit switch boxes are therefore specified to be flame proof.

Nick Guan is the author of this article on Valve Monitor.
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