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Frequently Asked Questions

General
  • What is the difference between a strainer and a filter?
  • Strainers and filters are both products that filer solids from fluids. However, when the solid to be filtered is visible to the naked eye (greater than 40 μm) then the term “strainer” is used and when filtration is smaller than or equal to 40 μm, the term “filter” is used.
  • What is the difference between a filter and a separator?
  • Filters are products that are generally used for separation of suspended solids from fluids i.e. liquids or gases. An example of a filter would be a product that separates minute metal shavings of hydraulic pistons in a hydraulic oil power pack. Separators are products that are generally used for separation of phases of emulsified fluids i.e. liquids from gases and/or liquids from liquids. An example of a separator would be a product that separates emulsified liquid water particles in a compressed gas pipeline.
  • Why should I use a strainer?
  • There are two reasons to use a strainer or filter:
    • Safety requirement
      A strainer is to be used before any expensive capital equipment like pump, valve, heat exchanger, flow meters, compressors, etc to protect them damage from foreign particles like dirt, scales, seeds, salt, un-dissolved resins, lumps of pulp, pigments, etc. This guarantees a long service life for the expensive equipment and reduced operational costs in the long run.
    • Process requirement
      If the process requires that the fluid be free from particles above a certain size, then a strainer (or filter) can be used to meet that requirement. For example if an ethylene glycol process line requires that it be free from particles above 25 μm for further processing, then a strainer with a 25 μm opening filter media can be used to eliminate particles above that size.
  • What is flash steam recovery?
  • Flash steam recovery or blowdown steam recovery is the process of recovering the steam that is formed when high pressure and high temperature condensate is transmitted to a low pressure vessel. Flash steam is low pressure steam which may be used in other areas where applicable thereby reducing the need/amount (cost) of low pressure steam generation. Our FR-V Series Flash Vessels are designed for efficient recovery of this flash steam.
  • What is the difference between strainer screen, filter element, inner element, or basket?
  • They are all one and the same. It refers to the filter element inside the strainer body.

    Selection of Filtration & Separation Products
  • What type of strainer should I use?
  • Please refer our Comparative Study of Strainer Types, which provides a general understanding of the different types of strainer and their different applications.
  • What are the different fluids that can be filtered?
  • Sungov strainers are designed to be used for practically any fluid be it liquid or gas. Most of our standard offerings would suit common applications like water, fuel/furnace oil, liquor, diesel, steam, air, nitrogen and the like. In case our standard product does not suit your requirements, we can custom design a strainer for you.
  • What are the major factors in the selection of strainer?
  • There are two aspects to strainer design:
    • Material selection
      This is done based on the fluid and service conditions (atm. pressure/temperature/humidity). Based on chemical resistance charts we decide the recommended material for strainer. Cast steel is the most common material used. Stainless steel or other alloy materials are used where corrosion is a concern.
    • Strainer sizing
      This is done based on fluid characteristics. We optimally design the strainer for you based on your flow data utilizing our extensive filtration know-how.
  • What are the basic features to look for in a good strainer?
  • Some key features to look for in a good strainer are:
    • Adequate filtration area
    • Low rated pressure drop
    • Machined seating for NIL bypass
    • Adequate mechanical strength of body & screen
  • What are micron filters? How are they selected?
  • Micron filters are manufactured using depth filter media. These filter media are called so because of their ability to hold particles in their depth i.e. cross section which have various layers of micro fibers held together in a “Brownian Movement” type pattern. This zig zag pattern helps in greatly improving filter efficiency as both volumetric and linear particles are held in the depth. This is unlike surface filter media (woven wire mesh) which can retain particles only on the surface and are susceptible to let through linear impurities, but have relatively very low pressure drop.
  • A good micron filter has the following features:

    • Good dust holding capacity
    • Low rated pressure drop
    • High terminal pressure drop

    Please see our micron filters range PFS Series.

    Maintenance

    What are the maintenance requirements of strainers?
    Depending on the type of the strainers, the maintenance requirements of strainers vary. Generally basket strainers are the easiest to maintain as the cleaning is from the top and they are designed to hold the dirt in a closed basket design. The easiest of all strainers to maintain are the quick open strainers, which do not require much effort to clean. Please refer our QF Series strainers for more information. Strainers need to be cleaned periodically (at a frequency dependant on volume of impurities).

    Can I clean the strainers without shutting down the operations?
    Certainly yes! if your operation requires continuous running, we can offer the DBX Series strainers which allows for the use of two individual strainer vessels. When one strainer is being serviced, the other is in use and vice versa. This way the operation is online all the time.

    What happens if I don’t clean the strainer screens regularly?
    Strainers need to be cleaned regularly failing which, dire consequences (flow will stop) will occur running in to millions in restoration/repurchasing of expensive capital equipment. They need to be cleaned before clogging to ensure smooth operation. Hence, we recommend that you always have one spare screen on hand to reduce downtime to minimum.

    How do I know it is time to clean the strainer screen?
    The simple way to know when to clean a strainer screen is to install a differential pressure indicator (between inlet and outlet). When the differential pressure reaches a threshold point, it can be ascertained that it is time for cleaning. These differential pressure indicators can even have electronic control equipment fitted to them to enable remote access. Alternatively, one can also use independent inlet and outlet pressure gauges to denote inlet and outlet pressure. The difference between the two would give the differential pressure. Any of these can be provided with our strainers as optional accessories. Please indicate your requirements in your enquiry.

    How do I know when to change out a micron filter element?
    The indication that it is time to change out a micron filter element is provided by either a visual or electrical differential pressure indicator mounted on the filter. Micron filters are strongly recommended to be fitted with differential pressure indicators. Our PFS and PFF Series come with a visual indicator as standard. The pressure differential at which the indicator informs you to change out the filter is called terminal pressure drop – a key parameter in filter design.

  • Functionality
  • How do I know if the strainer is fitted correctly?
    It is essential that the strainer be fitted in the right direction of flow to ensure its functionality. To facilitate this, the direction of flow is marked on every one of our strainers. Please click here to view a pictorial representation of correct fitment of strainers.

    My fluid has 50% impurities by volume. Can I use a strainer for this application?
    As a thumb rule, strainers are best effective when impurities are, at most, less than 0.5% by volume. If the impurities are more than this, specially designed strainers are to be used mostly in a multi-stage set up. Alternatively, once can also use other methods of filtration. Kindly contact us for a thorough discussion of your requirements.