Y Strainers 1

[1969grad]

When using a y-strainer upstream of control valves or equipment what basket perforations or mesh is typically used to remove mill slag, weld beads and other trash in carbon steel piping.

 

[martindup]

I would say the best would be to choose a perforation that would catch the trash in your fluid that would cause problems for your equipment. Have a look at the typical size of these mills slag and weld beads found in your piping. And then at what size of particles your equipment can handle. If the equipment were nozzles for example you would know that your particles should be considerably smaller than your nozzle size. The suppliers of the different equipment might be able to answer you on this.
Martindup

 

[unclesyd]

We always used a very fine mesh strainer during testing or the initial inservice start. It was then taken out and larger mesh strainer was installed for operation. If you use a small mesh strainer in such a manner make sure it's supported. On new construction there is not telling what will be caught.


Here is website that has a lot of information on strainers and others.

http://www.lesliecontrols.com/Handbooks/Handbooks.html

 

[PeteBennett]

Agreed, would advise a 100mesh on start up. Also some of our clients use a ball valve srewed in to the base plate of the strainer , to blow it down, during start ups. From experience on the larger strainers it is a goods idea as it stops it blocking and thus keeping it efficient. And it means you don't have to keep taking apart.

There is also a theory that they should be fitted on their side which helps, but have to admit, I cannot comment on this though.

 

[1969grad]

Martindup is correct in theory. But how big are the weld beads and mill slag particles and what sizes are significant? Selecting a fine mesh screen would get everything but could also cause pressure drop problems with minimum plugging. Selecting a screen or basket with too large perforations results in having to replace seals in control valves and perhaps damaging starters, etc. Hence, selecting the size of perforations is a compromise based on engineering judgement and past experience which was the point of this question.

Agree with Unclesyd and PeteBennett that after startup and a period of initial operation that the screen can be replaced with one having larger perforations and/or removed depending on the application.

I recently specified a strainer on the inlet to a starter with a 100 mesh screen but then begin second guessing myself. One past application in particular was the fuel gas regulators to a gas turbine located a short distance downstream of a filter-separator in which weld beads caused us to have to pull and repair the regulators several times despite having blown the line "clean" with full line pressure prior to commissioning. (Yes we had a small PECO in-line filter mounted on the inlet flange to the gas turbine.)

I typically use start-up strainers on the inlet to compressors, pumps, separator liquid dump lines to name a few usually using perforated baskets or "witches' hats." Since nothing was damaged then "no news is good news" but others may have a more difinitive take on this issue which is the reason for opening this discussion.

Thanks to anyone for my future education based on their experiences.