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WTF … the question?

What’s the Flow?

WTF…We Take Filtration to the next level

Most often the flow (Q) of a system will be either provided in gallons per minute (GPM) or liters per minute (LPM). The flow of a system will be an effective means of determining the size of filter to be used. There are a few other factors (micron rating, space limitations and viscosity) that will influence the size of the filter but will be discussed separately.

The equipment manufacturer or pump manufacturer will have specifications for the fluid system, the flow being one such specification. Build in a safety factor by always sizing the filter liberally or size to the maximum flow that will be seen in the system. This will take into consideration normal operating conditions as well as flow surges or spikes in flow. Trying to save money by sizing to normal operating conditions may result in flow restrictions and eventually component failure, associated component replacement costs as well as cost of non-productive equipment down time.

A Suction Strainer is located in the inlet of the pump. The strainer removes contamination from the reservoir fluid before it reaches the pump and the system components. These filters should be set up with an internal bypass valve to prevent starving the pump.
  • Advantages
    • Last chance protection for pump
  • Disadvantages
    • Must use relatively course media and/or large housing size, to keep pressure drop low due to pump inlet conditions
    • Cost is moderate
    • Does not protect downstream components from pump wear
A Pressure Filter is located downstream of the pump. It is exposed to full system pressure. The filter removes contamination generated or passed by the pump. A particularly contamination sensitive component may be protected by a “point of use filter” located immediately upstream of it.
  • Advantages
    • specific component protection
    • Contributes to overall system cleanliness
    • Catches wear debris from pump
  • Disadvantages
    • Housing is relatively expensive because it must handle full system pressure
    • Does not catch wear debris from downstream working components
A Return Line Filter is located downstream of the pump and system components and upstream of the system reservoir. The return filter removes contamination generated or ingested by the pump and components, before the fluid returns to the reservoir.
  • Advantages
    • Catches wear debris from components before it enters the reservoir
    • Lower pressure ratings result in lower cost
    • May be in-line or in-tank for easier installations
  • Disadvantages
    • No protection from pump generated contamination
    • Return line flow surges may reduce filter performance
    • No direct component protection

An Off-Line Filter is located in a separate loop connected to the reservoir and has its own source of power. The Off-Line Filter operates independently of the main hydraulic system. Cleaning the fluid in the reservoir only.