Control Valves Best Practices for Steam Control Valve Installation
Maximum value and life cycle from steam control valves wanted! But how to achieve it? To find the answer, not only the steam control valve itself has to be viewed closer. Twelve steps lead to proper installation and application of control valves.
The steam control valve is one of the most basic and indispensable components of the steam system, and plays a very important role in the quality of the products that the plant is producing. All steam control valves should have an operational life of at least six years due to available technology and current material standards, and proper installation will greatly prolong the life of the valve. Understanding proper installation and application of the steam control valve is essential to experiencing maximum value and life cycle from the valve.
Steam control valves not only control the pressure, but also the temperature in process applications. The steam control valve can be used simply as an on and off device, or any combination of controlling to include regulation, modulation, mixing, or even isolation. Valves can range in size from a 1/2 inch to as large as 28 inches in diameter.
The control valve is one of the oldest products used in the steam system. Today, there are a variety of valves used in a myriad of different and demanding steam applications. Let’s review some of the most common items to understand regarding the steam control valve.
Step 1: Leak Rates for Valves
All valves including steam control valves are designed to meet a designated internal permissible leak rate standard (FCI/ANSI). There are six permissible leak rates or Classes numbered I through VI. The higher the leak rate number, the lower permissible internal leak rate. Therefore, a Class I valve will have the highest internal leak rate and usually the lowest cost; while a Class VI valve will have the lowest permissible internal leak rate. Identifying the permissible internal leak rate for a valve has to be one of the top priorities when choosing the correct steam control valve. A valve with a high leak rate, will cause excessive wear or “wire drawing.” The valves with a high leak rate will pass more steam internally and can result in premature valve failure. Steam valves should be specified to have a leak rate of no less than Class IV. A Class IV steam control valve will maintain a long operational life.