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Impact Idlers vs. Impact Saddles vs. Elastic Bands

If you’re in an industry that involves using conveyor belts to move lots of potentially-hazardous stuff from one place to another, you’ve probably encountered that horrible moment where some piece of debris being dumped onto the belt hits just right and punctures a hole. If you’re unlucky, you’ve seen that debris, still stuck it its own hole, carried all the way to a pulley or crossbar, where it got stuck and proceeded to slice a long gash right down the middle of your conveyor belt.


There has to be something to keep that from happening, right? Of course there is. In fact, there are three common variations:

  • Impact Idlers: several sets of three large pulleys that sit below the site of impact. Each set has one pulley angled up on either side, with a third pulley flat and lower in the middle. The earliest attempt to reduce conveyor belt damage.
  • Impact Saddle: several sets of U-curved iron bars lined with dense polyurethane squares.
  • Elastic Bands: several sets of thick elastic bands with a few polyurethane pads riveted on.


The Problems with Impact Idlers

Impact idlers don’t sit snug with your conveyor belt; their three flat planes mean that significant gaps occur in the corners, where the belt pulls away from the idlers. A sharp piece of something that lands in that gap can still easily puncture the belt.


The Problems with Elastic Bands

Elastic bands do fit snug with the conveyor belt, so puncture points aren’t a problem. However, elastic bands don’t hold the shape of the belt; they adjust to it. That, in turn, means that in order to use elastic bands, you have to position them between two sets of idlers that force the belt into the desired shape, meaning you can’t use them in situations where space is limited. Also, when the bands do require repair or replacement, you have to shut down the entire operation. Both idler pulleys and saddle pads can be replaced on the fly.


The Problems with Impact Saddles

By and large, we believe impact saddles are the best solution for most situations, but they aren’t entirely without their problems. Unlike idlers and elastic bands, an impact saddle has one shape; it’s not adjustable. They’re available in any given shape, but once they’re installed, any on-the-fly changes you make are going to have to take their existing shape into account.




How The ISO Guide to Hydraulic Filter Performance Works

ISO — the International Organization for Standardization — releases guides for almost every conceivable area of industry on Earth. Some of these are easy to understand, others are packed into language so dense and jargon-filled that it takes an industry expert just to read the introduction. We thought we’d shed a little light on hydraulic filters for everyone by unpacking the ISO codes for cleanliness, which are used for virtually every kind of air and/or liquid filter, including hydraulic ones.


How Small is a Micron?

The core unit by which the ISO measures ‘uncleanliness’ is the micron, which is a measure of distance. Filters are measured by how many particles of what diameter (in microns) they allow through. But before we get into that, let’s talk about what a micron is. Unfortunately, they’re so small, we have to describe them, because simply telling you “one millionth of a meter” doesn’t have any meaning. So here are three quick examples to help you understand:

  • The average human hair is about 70 microns wide.
  • A single grain of standardized table salt is about 120 microns wide.
  • The eye of a standard American sewing needle is a whopping 1,230 microns across.


Particulate in Microns

The ISO standards for particulate break them down into three categories:

  • 4 microns and smaller (about the size of a larger bacterium)
  • 5-6 microns (about the size of a deoxygenated red blood cell)
  • 7-14 microns (about the size of a mold spore)


Presumably, particulate larger than that only gets through a filter if that filter is critically compromised.


The Confusing World of ISO Codes

The ISO tests a filter, and they assign one code for each of those categories, in a string like this: 20/17/14. The ISO code is, unfortunately, not intuitive. In short, an ISO code of ’10’ means ’10 or less of this size of particle per milliliter of volume (after filtration).’  Every number you go up from 10 doubles the “X or less” number; every number you go down from 10 halves it.



So when you see a hydraulic filter with a three-digit rating like 32/12/4, you can look at it and say to yourself “OK, so after the fluid has been filtered, it’s got about 32 bacteria, 12 blood cells, and 4 mold spores in it.” Of course, what those particles actually are is often more important than the size (if they’re aluminum, you’ve got significantly greater problems than if they’re water — but that’s a different post altogether.