Testing the Bitspower BP-EML16 fittings for 16mm hard tubing
I like builds that use all straight tubing with fittings, and I also like builds that use just tubing with bends. I still have not decided if I'm going to use all fittings, or mostly fittings with some bends only where there is an external 90 degree bend.
What I mean by external 90 is like this mock up I did while working on the pump brackets. I want to make sure that the 90 degree fitting hanging out there won't pop off and spray water everywhere (yes I'm slightly paranoid
When I was first looking into these fittings I found a great "mini-guide" on this post
I used this as a starting point while playing around with these fittings.
Here's the Bitspower BP-EML16 fittings.
Let's take one out of the packet. It comes out of the bag with the collar on, and a secondary o-ring already inside. It looks like it comes with an extra o-ring
No there are two different sizes of O-rings.
I couldn't find any information on which one to use. Measuring eight different packets of fittings with a digital caliper the smaller o-ring on the left varied between 2.08mm and 2.12 mm, and the larger O-rings measured between 2.34 and 2.40 mm.
Here's the fitting as it comes out of the packet. Notice the o-ring isn't really pushed all the way into the groove.
Costas used a fat felt pen to push the o-ring all the way into the goove. I used the end of my xacto knive.
Just roll it around a few times.
This picture is from Costa's post, I put a dab of silicon grease on the o-ring with a toothpick. After my testing was completed I decided that I'll be skipping this step.
Then take a small piece of tubing with a nicely sanded edge and push it into the fitting once. Now the o-ring is as far in as possible and will be easier to install the tubing.
Here's with the two sizes of secondary O-rings, smaller one on the left.
With the collars screwed down you can see the left one with the smaller o-ring screws down a little more than the right one with the larger o-ring.
For the testing I decided to put two tubes, with four of the EML16 fittings and a 90 degree fitting under pressure to see how much pressure these fittings can take before a fitting pops off. Now keep in mind this is not a fancy scientific test like you would see from @fast_fate
, just a workbench test for my own peace of mind.
The first test I did was using the smaller secondary O-rings and the O-rings inside the fittings lubed with silicon grease. I slowly pumped pressure in. One of the fittings would always pop off with less than 8 psi. Plus they did not feel very secure.
I swapped out the smaller secondary O-rings for the larger size O-rings, still using the fittings with silicon grease on them. Now I could get to about 8.5 to 9 psi before a fitting would pop off.
Next I opened up four new packets of the EML16 fittings and skipped putting any silicon grease on the O-rings. I still used the xacto knife and pushed a piece of tubing into the fitting first to seat the o-ring.
Using the larger secondary O-rings and pressure it up again. Now this test set-up can hold 11 psi and the fittings feel much better! It would take somewhere between 11 and 12 psi before a fitting would come off.
I finished that testing several weeks back and realized that I did not test the smaller secondary O-rings with the fittings without any silicon grease, so I ran the test again with just a straight tube and two fittings.
Surprisingly I found that both the large and small secondary O-rings would both hold 11 psi and could not hold 12 psi before popping off.
My conclusion is that I will not be putting any silicon grease in the O-rings. I found the tubing went into the fittings just fine without it anyway. If anything just dip the end of your tubing in some water before inserting it into the fittings.
If your tubing run is like this one where there is a fitting on each side that cannot be pushed off then it would be fine to use some silicon grease if you wanted to.
So I will be using the larger size secondary O-rings and no silicon grease.
Coming up next will be the final pictures of the pump set-up. I just have to finish the sleeving... it looks awesome!