Understanding Type S and Type S-LD

A complication, in our humble opinion, was created by the specification writers when they added “Type S” as a further description of the Categories. Refer to the chart on GamGram No. 8. The LD designation means that the coalescers are required to hold a smaller amount of particulate (dirt) than the (S) standard amount that was defined for Category M for example. Therefore, an LD coalescer is somewhat less expensive than a “S” standard Category M element. Our point is that “S” causes confusion. However, an LD designated element can save you money, especially if you use a pre-filter which necessarily has a vastly greater dirt holding capacity than a coalescer - and at a much lower cost.

The point made in the above paragraph is really important from the standpoint of saving filtration expenses. It has never ceased to amaze us that more filter users do not take advantage of pre-filters.

Consider this:

You have a 600 gpm filter separator that receives dirt contaminated fuel from time to time, causing
the differential pressure to increase to the 15 psi limit.

The cost for the coalescers is approximately $750.00

If you install a pre-filter to handle the same 600 gpm flow rate, the replacement set of elements costs
about $240.00.

You will now say happily that this is only 1/3 the cost of coalescers but you are absolutely wrong.

Prefilters have far greater dirt holding capacity than coalescers and our experience is that they hold
about 3 times more dirt.

Therefore, the real cost difference, in this case, is a factor of 9. That is one-ninth the cost of
operating with coalescers only.

If you are changing coalescers frequently, it should be obvious that you cannot afford to operate
without a prefilter if you now need to change coalescers frequently.

The last item on our list of 5th Edition subjects is “API APPROVAL”. The original title of GamGram No. 8 was, “Who Ever Heard of API Approval?” In those days, API did not “approve” filter separators or their elements. A filter manufacturer performed the tests that were defined in API-1581 when qualified industry representatives could witness the tests. However, API had no inspectors and no functions.

With the 5th Edition, that has all changed because filter separators, monitors and pre filters now come under the API Monogram Program. Witnesses are certified by API to observe the manufacturing and be present for the laboratory tests. The API Inspector must sign the test report. The manufacturer can then advertize his products as being API approved and can apply the monogram (logo) to each item, filter vessel or element. Therefore, under the 5th Edition, the customer will be able see the API designation that proves to any interested party that he has purchased API approved equipment.