Sealing of Water Based Paint (again) 2

[Milkboy]

Still getting problems on a water based paint app.

Always getting a high leakage rate. From 6ml/hr upto
40ml/hr

It seems the paint is getting between the faces !

I have read up on Solvent based paints where the solvent
'evaporates' between the faces leaving a residue coated
to the faces.
Here we have water based paint and a flow of barrier water across the faces from the diff pressure.

The App is

Double Mech Cartridge
Barrier 6 BarG on Demin. Water (mandatory Demin Water)
Box pressure approx 0.5 BarG
Plan 53 Barrier Sys. Vessel (no cooler)
Springs outside the product
SiC v SiC inboard
SiC v C outboard
1880 RPM approx

The product is
approx 78% water.
Methoxy propanol less than 0.7% by weight.
Butyl Glycol less than 0.3% by weight.
Hexyl Glycol less than 0.3% by weight.
pH 5.2 - 5.7 @ 25 C.
acid MEq 22 - 30 / 100gms solid.


As I write we even have a Carbon(!) v SiC inboard as one theory was the demin water wasnt lubing the faces enough with SiC v SiC.
Im sure the carbon will fail due to abrasion though but
the leakage rate is still too high >10ml/hr.

The pump has been realigned also.



Any offers - Im stumped as to how the paint can get between the faces


TIA




-
Milkboy

 

[ciddik]

hi milkboy,

this is one of the typical promblem we faced with a paint manufacturing plant, & we design for them seal equi to Burgmann HR Series.

I think you should try one of that with double seal in tandem arrangment, hopefully you will get good result
your face selection is ok, but inbord seal should be nearest to impeller with taper bore stuff at seal end to prevent the slurry accumulation

(do your pump impeller have back vanes?)

ciddik



siddik

 

[Milkboy]

Do you suugest the faces to be near the impeller to be near turbulence of the fluid

I have heard the fluid (paint) is good when it comes
to moving across seal faces by capilliary action.

All I know about cap. action is when water climbs walls in the form of damp !!

Do certain fluid have high 'values' when it comes to their ability to create capiliary action ???

To prevent capiliary action across the seal face I beleive the barrier pressure can be raised to increase leakage rate due to pressure to stop the process of cap.

However, I am maxed out at 6 Bar (shop air)






-
Milkboy

 

[longeron]

Ciddik has a good point. If we're thinking about this like a slurry seal, a dual metal bellows seal with an expeller might be an interesting choice.

Depending upon the amount of water that the process can handle you could use a Plan 32 to flush the paint out of the seal chamber.

I think the last time you posted, I suggested a cousin of the dry gas seal. There is a version that uses the same technology as the gas seal to "pump" fluid across the face. The fluid pumped across would be water held in a small tank, like your current Plan 53, but unpressurized. The as the level dropped, a float valve would open and refil the tank. Depending upon the size of the seal, we're talking a gallon or two a day of water usage. Paint migration across the faces would be stopped. I've heard of this kind of seal refered to as an Upstream Pumping seal. I believe that John Crane offers it.

 

[Milkboy]

Thanks All

Plan 32 is a no go - to much diluting

Site are 'scared' of gas seals

Upstream Pumping seen as 'too expensive' for some reason


I have gotten hold of an Air Amplifier to boost the shop air from 6 to 12 Bar to give the double seal a 12 Bar Barrier pressure to increase flow across the face that we


We'll see how it goes


Merry Xmas



-
Milkboy

 

[longeron]

Another quick note: you generally want the barrier fluid to be 1.8 to 2 bar over the seal chamber pressure. It can be higher of course, the idea is to make sure that the barrier fluid pressure is high enough to deal with changes in process conditions.