Air Vessel for piston feed pump

[froya66]

Dear fellow steamboaters

I want to install an air vessel at the pressure pipe from my piston feed pump.

To get an idea of a possible design, I am looking at the drawings for a Stuart 5A feed pump.

The vessel has a bore of 5/16" and a length of approx 1". It has a drilled 1/32" hole connection to the pump outlet.

I do not understand that this can really work. I would have imagined a much larger connection.

Any comments on this?

How is the vessel run? Does it need a drain valve somewhere at the mid of its height, to be operated frequently in order to adjust the air volume?

Best regards
Jørgen

[mcandrew1894]

Hi,

The design guide that I have read regarding pressure bells is five times the swept volume of the plunger. So if the plunger is 1 cubic in, the bell should be 5 cubic inches.
I used that guideline on my pump and it seems to work well....Its not pounding anyway.

I have an appoximately .09" ( 2mm) hole in the base of the bell. My bell is about 4" long by about .3125 ID or about .300 cubic inches It may be a bit small for my new .3125 pump rod...we will see.

The top of the bell has a plug to let air in when needed. I haven't had to yet. I think there are other cushions in the system...like the feedwater heater that may be helping.

Additionally, you plumbing nees to be fairly large...like an ID not less than the pump rod diameter.




Dave

[mcandrew1894]

Here are some photo's of my surge suppressor








The rib in the middle limits the check valve lift, air enters around either side of it.

The last photo shows the plumbing with the bypass valve

Dave

[Edward]

An observation in a fairly early Funnel magazine was that after a relatively short time the air was dissolved ( I'm sure that's not the right scientific term , but you get the idea ) into the water so that the vessel was full of water and was not fulfilling its purpose .
The sugested cure , which apparently worked , was to put a hard rubber ball into the vessel .

Regards Edward .

[mcandrew1894]

Hi Edward,

I too have heard of the hard rubber ball....I suppose some closed cell foam would work too. So far I have not had any pounding what so ever. My new ram is larger now ( .3125 diameter) so we will see soon enough...If I get pounding after a while indicating that the bell has filled with water, I will put some cut up pieces of a rubber ball in the bell. Simple enough.

Dave

[froya66]

Hi

I ended up installing an empty 16 g CO2 bottle (used for example for soft guns)

The hole in the throat is approx 2.5 mm (after breaking the membrane with a nail)

Inside volume approx 12 cm3. Pump volume approx 4 cm3

It works perfectly. Whether the return valve to the hot well is nearly closed or fully open, the flow back to the hot well it completely even, without any sign of pulsating.

All sounds of water hammer in the pressure pipe to the boiler is gone





Best regards
Jørgen

[mcandrew1894]

Outstanding!. Glad it worked itself out.

Good bit of recycling there!

Have you also mounted yours on top of a check valve?, or is that a TEE?


Dave

[froya66]

Hi Dave

It is a TEE. The check valve is upstream of the returnvalve (or should I call it by-pass valve).

And unfortunately the bottle was not re-cycled. I had to buy two new (they come in pairs) as I could find no re-cycled with a threaded neck.

As it is now it resembles brass, but actually it is some sort of yellowish zink treatment.

Jørgen

[mcandrew1894]

"...And unfortunately the bottle was not re-cycled. I had to buy two new (they come in pairs) as I could find no re-cycled with a threaded .."

Well letting th contents out must have been exciting! ....good bit of pressure in those.

Dave