INTRODUCTION

In process operations, fluids and their movement and transfer from place to place, plays a large part in the process. Fluids are contained in various types of vessels and are transported in pipelines. In order to Start or Stop fluid flow, to Control flow and to Prevent Back-flow, various types of valves are installed in the piping. To prevent over-pressure in piping and vessels, we use Safety Relief valves and, to isolate equipment for maintenance etc, Block valves are installed.

Where fluids contain suspended solids - scale, dirt etc…, which must be removed, Filters and Strainers of various types are installed.

In steam systems, steam condensate (water), is a particular problem which can cause 'Water-Hammer' in piping and equipment. (This will be explained later).

To minimize this problem, the water must be drained from the steam lines. This is sometimes accomplished by regularly 'Blowing Down' - (draining the water manually), - from the system. Generally, steam systems are fitted with automatic drainage mechanisms called 'Steam-Traps'.

As previously stated, valves are used for the following purposes :

1. To start and stop flow of fluids
2. To regulate, throttle and control fluid flow or pressure
3. To prevent back-flow
4. To relieve excess pressure / vacuum