Shutdown, repair, and downtime of steam boiler or power plant should be reduced. This matter can be done by maintain steam and condensate systems in well performance. Plant or boiler damage is often caused by impurities in the pipeline such as scale, corrosion, compounds on the connection, welding metals and other solids, which can enter into piping system . Strainer is device that captures solids in liquids, gases or steam. Strainer protects equipment from harmful influences, thus reducing the time of shutdown and repair. Strainer should be installed at upstream of each steam trap, at flow meter and at control valve.
Strainers in steam and condensate system can be classified into two main types according to shape and composition of body as follow (see Figure 1):
- Y-type Strainer
- Type Basket Strainer.
Figure 1: Y-Type Strainer and Basket Strainer Type
Y-type strainer is common standard and widely used everywhere especially for fluid steam or gas. The body is cylinder and compact-shaped, very strong and can handle high pressure. This device can be grouped as pressure device because the Y-type strainers are capable to handling pressures up to 400 barg. At that pressure, steam usually has high temperature, then to overcome this condition, strainer is made from unusual materials such as chrome-molybdenum steel.
Y-type strainer has capacity to eliminate dirt lower than the type basket strainer. Furthermore the Y-type trainer requires more frequent to cleaning. In steam systems, this is not a problem, except when level of corrosion is high.
If in the steam and condensate system there are a number of significant impurities, then a blowdown valve can be usually installed on the strainer cover. This will create strainer has steam pressure steam to clean without having to shut down the plant.
At Y-type strainer where flow of steam / gas is distributed horizontally, pocket shall be mounted in the horizontal plane. This way to prevent water gathered in the pocket, helping to prevent entrainment of water droplets which can cause erosion and affect the process of heat transfer. Pocket forms must be led down vertically.
Installation sometimes does not always in the horizontal direction, but allows also to be mounted vertically in steam and condensate system which has flow direction of fluid vertically from top to bottom. The dirt will flow naturally down into the pocket. Installation of strainers cannot be done if the fluid flows upwards (from bottom to top) because the existence of pockets in the strainer will be useless.
Figure 2: Horizontal Strainer and Vertical Strainer