I'm a fool to do your dirty work
Oh yeah
I don't wanna do your dirty work
No more
I'm a fool to do your dirty work
Oh yeah

("Dirty Work," by Steely Dan, 1972)

 

SPECIAL-TASK PIPE FITTINGS
REMOVE IMPURITIES FROM THE FLOWING STREAM

Brilliant PTOA Readers and Students ... meaning those who are reading the PTOA Segments in the intended, sequential order ... already learned about the most common Pipe Fittings in PTOA Segment #251.

PTOA Readers and Students learned that the tasks of common Pipe Fittings include connecting pipes together, increasing or decreasing the diameter of the piping, branching or consolidating the process stream flow, changing the direction of the total stream flow, and capping/stopping the flowrate at the end of a pipe.

The tasks performed by Special-Task Pipe Fittings concern removing impurities from the flowing process stream.

Special-Task Fittings include:

• Strainers.
• Filters.

The common task of Strainers and Filters is to remove impurities from the flowing process stream.

These impurities can scrape against and slowly erode the interior of Piping, Valves, Seals, and Rotating Equipment ... specifically Centrifugal Pumps.

For example:

Particles that flow freely within the process stream could clog up any of the Valves featured in PTOA Segments #254 through #259.

Once the seating area of the Valve is clogged up, the Valve will not be able to close completely.  These particles will eventually wear out the precisely machined Valve components.

Other impurities that are suspended within the flowing fluid are removed by filtration.  The final product will not be desirable to customers unless the particles are removed by Filters.

Just like the more common Pipe Fittings, Special-Task Pipe Fittings must be incorporated into The Piping Network via one of the pipe connection technologies featured in PTOA Segments #249 and #250.

 

FORM AND FUNCTION OF STRAINERS

Strainers are installed in liquid process streams upstream of Valves, Pumps, Pressure Regulators, and Steam Traps for the purpose of removing suspended solids that would otherwise damage these hardware components.

Strainers remove particles that are large enough to see with the naked eye.

These particles are too big to flow through the holes in the Strainer's mesh screens.

Once their flow is blocked by a mesh screen, these particles collect on the interior surface of the mesh and eventually slide to the bottom area of the Strainer.

All Strainer designs use some type of metal mesh screen to remove flowing debris from the process stream.

T-Strainers use mesh baskets to remove large particles. Conical Strainers use a cone-shaped Strainer.

All Strainers have another essential, common feature:

The design of the Strainer will allow easy removal and cleaning of the collected debris.

The debris might be blown out using line pressure. Otherwise, the line pressure may be reduced at intervals to allow safe removal of the debris that has collected on the screens and at the bottom of the Strainer.

Process Operators and the facility's Mechanics should closely examine the debris that is removed from the Strainer. The composition of the debris is a hint of ongoing upstream pipe corrosion and erosion that could result in catastrophic mechanical failure.

 

THE TYPICAL Y-STRAINER

Form of the Typical Y-Strainer

The nearby graphic of a Y-Strainer Cross Section indicates the flow path of the process stream liquid as it flows through the Y-Strainer.

The piping that encases the Y-Strainer is angled and looks somewhat like the capital letter "Y," if the "Y" were lying down on its side.

The supporting leg of the "Y" is on the left. The two extended arms of the "Y" are angled, respectively, downward and upward on the right side of the graphic.

The "downward extended arm of the "Y" contains the metal mesh Strainer.

A different nearby graphic labels the Inlet port, Outlet port, and other hardware components of a Y-Strainer.

Note the cylindrically shaped Strainer (labeled "Strainer Screen"). The Strainer is supported by a Screen Retainer.

The metal mesh Strainer is constructed from two cylindrical-shaped screens, one inserted inside the other.

The inner cylinder screen is a fine-mesh screen. The outer mesh screen is a coarser mesh screen and looks like a sturdy container for the inner, cylindrical-shaped fine mesh screen. 

 

Function of the Typical Y-Strainer

Glance again at the nearby cross-section graphic of a Y-Strainer and once again focus on the flow path of the liquid process stream.

Since the flowing liquid enters the center of the Strainer, the full volume of the process stream initially comes in contact with the fine mesh screen. 

The fine mesh screen barrier prohibits particles from passing through it.  These particles collect on interior surface of the fine mesh.

Other small, dense particles will stop their flowing journey simply because they cannot negotiate the sharp turn that is required to flow up and into the "upper" extended leg of the "Y." These particles will fall to the Screen Retainer that supports the Y-Strainer.

The cleaned fluid is not impeded by the fine mesh screen and thus flows through to the coarse mesh screen and thence into the "upper" extended arm of the Y-Strainer. Finally, the clean process stream exits the Y-Strainer via the Outlet flow port hole.

The cleaned fluid flows happily downstream, perhaps into the suction line of a Centrifugal Pump.

 

FILTERS

Like Strainers, Filters protect downstream equipment from suspended particles in the flowing fluid that could damage equipment.

Generally speaking, ...

Strainers remove large particles and Filters can remove contaminants that are not visible to the naked eye

Furthermore ...

Filters are used to remove contaminants from liquids AND gases. Strainers are used to remove contaminants from just liquid process streams.

Like Strainers, the filtration media used in a Filter can be designed to be regenerable.

Regenerating Filter media prolongs the usable life of the media.

Typically, a filtration process operation will incorporate two Filters.

One Filter is actively operating while the offline Filter is undergoing the regeneration process or on standby ready to be put into service.

"Breakthrough" is evident when the filtered stream still contains contaminants even after flowing through a freshly regenerated Filter.

"Breakthrough" indicates that the filtration media in the Filter must be replaced with new media.

The most brilliant Outside Process Operators will pick up the hint that Filter media needs to be changed out before Breakthrough occurs.

A gas or liquid flowing through a Filter will indicate a growing increase in Pressure Drop (aka, ΔP) as the "filtration cake" builds up on the filtration media.

While the process is operating at similar conditions, Outside Process Operators record the upstream PI Pressure and the Downstream PI Pressure to determine if the ΔP caused by the filtration process is attaining known limits.

Uh-oh!

Fred doesn't remember that Pressure Drop (aka, ΔP) is caused just by a fluid flowing through each type of Pipe Fitting and Valve.

Stress not, Fred!

The subject of predicting Pressure Drop as a fluid flows through The Piping Network is featured in an upcoming PTOA Segment.

Brilliant PTOA Readers and Students already learned in PTOA Segment #165 that losses in the PV Pressure of a flowing fluid result in an increase of utility expenses that are needed to power a Pump or Compressor.

Guess what, Fred?

The liquid process stream that flows through a Strainer will not create a significant Pressure Drop.

Therefore ...

A Filter will only be installed where a Strainer cannot perform the decontamination task successfully.

Otherwise stated, a Filter will be installed to remove impurities when the process stream is a gas, or when the contaminate is too small to be successfully removed by a straining.

 

©2025 PTOA Segment 0260

PTOA PV FLOWRATE FOCUS STUDY AREA
PIPING NETWORK HARDWARE

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