Which pressure gauge & what's a \"snubber?\"

Brad White_203

meaning, I am not a regular installer, but detail provisions to do just that. Usually instead of elbows, I use tees with plugs at changes of direction. This allows rodding-out and filling.

In actual practice, the first few cycles will fill the gauge with water (in theory) but in doing so, exposes the gauge to steam. I prefer to protect my instrumentation, personally.

Consider too that some gauges are rated for temperatures well below steam temperatures (some in the 140F range maximum). The siphon/pigtail makes all of the difference.

Another thought, open to debate:

Sometimes a single pigtail (or an assembly of tees and nipples in large brass or red brass pipe so configured to do the same thing), is used.

If that large assembly, I sleep better knowing that clogging is minimal and that cleanout is a breeze.

But if one uses a single standard bent pigtails (usually 1/4" or 3/8" brass tube) and on top of that, installs both the gauge and pressure controls and safeties, that is putting all of your eggs in one basket.

I am leaning these days toward individual pigtails for each device. Thus if one clogs (say the gauge mis-reads or the pressure controls over-shoot), you have a point of comparison that one hopes is not also clogged.. Just a thought.

Jason_44

Looking to replace the pigtail and pressure gauge on my pressuretrol.

The attached image (from the State Supply catalog) shows a couple of different low pressure gauges for one-pipe steam.

I'm planning to order the 2psig gauge and a pigtail, but what exactly does a "snubber" do? Do I need both the pigtail and the snubber?

Jason

Brad White_191

Snubber

A snubber is pretty much as illustrated, a form of coupling but with a small bore hole through it's center axis. The orifice slows the rate of pressure change, avoiding shock to the gauge internals (Bourdon tube).

There is a device of similar function called an "impulse dampener" and both terms are used interchangeably. An impulse damper, strictly speaking, is a device with an internal diaphragm filled with liquid on one side. These are used where you want the pressure conducted to the gauge, but none of the fluid. These are handy for steam, sometimes hard to find but more applicable to chemical processes.

The siphon tube ("pigtail") is a must. Use them between the steam chest, gauges and pressure controls.

The only downside of using a snubber is if your water has a lot of fine particulates, it is an easy orifice to clog. I usually use them but be prepared for a change-out if the water is not pristine.

It is perfectly OK not to use them, but at least the siphon tube. Most installations have just that.

Oh, I meant to add- use brass siphon tubing, not steel. And get the 4" gauge if you can. Much easier on the eyes.

Jason_44

Do I need to manually fill the trap with water when replacing the pigtail?

Jason