Ga oil

[JRM]

With the diferent ga oils offered is there any way to know what is the right one to use.
From what I understand the RED .867 is for 6" in the incline and the BLUE 1.910 is for 13". But what are the others for .
I know there is violet, green, water addative.

[larrycavan]

JRM,

The Green is a wetting agent for use with distilled water. It's rated at 1.0SG.

The Violet is also rated at 1.0SG and is used when a better meniscus is desired.

Larry

[JRM]

Thanks larry,
I talked with the guys who build the sanez benches, they are using the violet in their 600 cfm benches. From what i have found out sofar the red fluid is to thin for 28" using the 246 durablock. I was suggested i switch to the heaver fluid. violet or blue.

[larrycavan]

Can't hurt. Just remember it will affect the scale if you switch to fluid with a different SG.

[gofaster]

I ordered manometers from Dwyer for the bench I'm building. I ordered two 60" Vertical manometers, and a 246 inclined, all spec'ed for .826 sp. gr. red gage fluid.

After seeing your post, I was concerned, so I checked in with the engineer from Dwyer with whom I'm working, and asked:

Should I be using purple gage oil in my manometer for testing flows at depressions greater than 28" ?
Is it correct that .826 sp. gr red oil is too light?

The Dwyer Engineer's reply:

If you are trying to measure the differential pressure accross an orifice, it doesn't matter which fluid you use as long as the pressure range meets your system pressure requirement. This is because the manometer itself is calibrated for that specific fluid to read pressure.

I hope this information is helpful.

[Thomas Vaught]

The manometer engineer is correct.

The 246 manometer normally comes with the .826 red fluid with
the scale and well calibrated for that fluid. The scale is typically a
6 inch (Deltas P) manometer scale The length is about 19.85 inches
long.

The SF 300 used that fluid and the the same 246 manometer.

The SF 1200 bench also used that fluid/ 246 manometer but with larger orifice diameters working together to get the 1200 cfm range.

The manometer/ fluid will work fine.

The orifice calibration is much more important. 86Rocco has an
excellent excel spread sheet for calculating orifice diameters vs flow vs
Delta P. I would use that and assume 6 inches for the delta p in all cases for your calculations.

Tom V.

[larrycavan]

A little explanation should be brought forward regarding the consideration of heavier guage fluid.

First:

There's an overpressure situation that John [JRM] is trying to resolve. The consideration of heavier fluid is not an answer to the problem. He's merely considering it as a tool to aid him in resolving the problem. It could then also be retained to extend the orifice range capacity of the bench once the problem is resolved.

Second:

Dwyer makes excellent instruments. They correctly and accurately design them for use with the proper fluids.

Larry

[JRM]

[quote="larrycavan"][/quote]
Yes I'm chasing down a over pressure problem. What happens is when the vire mano reads over 12" all of the fluid in the incline fills into the main well and bubbles.

[84-1074663779]

There seem to be a few fairly simple cures to blowing all the fluid out of the manometer from overpressure.

The first would be to fit some sort of large area mechanical pressure relief valve to the system, but it would need to be absolutely leak free.

Another way would be to fit an upper reservoir to the manometer, so all the fluid simply drains back after an over pressure accident. Or simply extend the upper manometer tube right up to the ceiling !

A third way that I have never tried, and only just thought of right now, could be a differential air pressure switch that turns off power to the blower. These air pressure switches are commonly fitted to washing machines to control the water level during filling. Often there are two barbed hose fittings and a screw pressure adjustment. That could be connected right across the manometer and set to cut blower power if pressure suddenly rises. It may not be fast enough acting, but is simple enough, and may be worth a try ?