Water Gauge Blow Down with Safety Valves in Place

[JonRiley56]

All,

I am thinking about changing out my water gauge. I remain concerned about the possibility of getting poached if a glass breaks, so I am looking at a set up that has safety valves in it that close off if there is a sudden high flow.

My question is how that type of unit reacts when you blow down the gauge. Here is the type of gauge I was considering: http://www.boilersupplies.com/trycocks/index.html

I am looking at the Type A set up.

jon

[87gn@tahoe]

You have to open the blow down valve more slowly than with a regular gauge valve set to prevent the ball from being carried over and closing the gap. That is the only difference I've experienced.

[fredrosse]

There is a previous thread titled "Gauge Glass Safety Issue" that you may want to look at, especially the cutaway drawings of how the top and bottom automatic safety checks work. The top gauge assembly has a "rolling ball check", and that valve actually has three positions: 1. With the handwheel screwed in, the valve is hard against a metal seat, and the valve is shut. 2. With the valve opened fully, the stem seat allows flow, and the "rolling ball" is ready to protect in case of glass breakage. 3. An intermediate position of the valve also allows flow, and at the same time does not allow the "rolling ball" to stop flow. The intermediate position is what you use to blowdown the glass from the steam end of the glass.

[fredrosse]

Jon, also be sure to review a thread you started back in Nov 2012, "Blow Down Pressure"

[JonRiley56]

Thanks Fred ! I will take a look at them. I dont really have a problem with the Reflex Gauge I have now, I was just thinking that it would be nice to have an automatic off on the valve if there was a problem. Do you know if you can buy those valves separate from the water gauge set up anywhere ? I wouldnt mind having one on my pressure gauge too. That way if it gets knocked off or something I dont blow steam.

Still musing, the $400 price tag on the sight glass is intimidating. My kids college is wreaking havoc with my steam boating budget.....

jon

[Lopez Mike]

I can't find it now but there was a post showing how it is possible to end up with one of the two balls out of place thus rendering it inoperative. I believe it involves taking the valve apart and letting one of the balls get trapped in the wrong place.

If anyone remembers where that post resides, I'd love to read it again.

Mike

[DetroiTug]

My sight glass does not have the excess flow checks in it. I just crack the valves enough to maintain flow in and out of the glass. That way if it breaks the discharge will be minimal.

-Ron

[JonRiley56]

Sadly.............I did not think of that............ You are so bright I bet your mother calls you Son.............

[DetroiTug]

Yes, that and many other things

I just went through the sight-glass crash course. As I understand it; Handwheel valves with a lead screw and packing should really only be in two positions; fully closed or fully open (back seated). With good packing, partially open is Okay. Especially if weighed against what would happen if the glass blows out - I'll take the leaking stem.

Another thing I plan to do is put a guard around the glass made of clear polycarbonate tube. Large enough to fit the packing gland nuts for the glass, then just cut a slot down the backside to install it.

On the glasses with excess flow checks, I'm guessing they are intended for systems with a good water quality control program. Pulling out of the lake after two years, I pulled my glass, it's pretty silty in there. Not sure how well a small ball would roll back and forth very freely in that crud. Will start running TSP (TriSodiumPhosphate)in there this year and see if I can get rid of some of that.

Also the sight glass internal passages are all small from what I've seen, I'm thinking that is to increase velocity/cleaning at blow down.

-Ron

[fredrosse]

Mike, the thread you are looking for: "Gauge Glass Safety Issue"

I was the one who disabled the safety ball check on my lower sight glass connection by lubricating the valve stem threads, and the safety ball moved into a wrong place.

Blowing down the sight glass (or reflex glass) cleans out all the crud very well, and should be done on every outing. That process is also well documented within the "Blowdown" thread.