pressuretrol question

Brad White_184

must remain by code. (A gauge reading twice the relief valve pressure is a code requirement, but is useless from an instrumentation standpoint.) Just leave it there or re-install it if you need to use that tapping for new instrumentation.

The second gauge should read from zero to 2 lbs. or 0-32 ounces (same thing, different scales) if you are running off a vapor-stat of 0-16 ounces.

If you cannot find gauges that low and are using a pressure-trol, a 0-5 PSI gauge should work fine. Personally, if you go with a larger scale gauge (such as 0-5 PSI), buy the largest face gauge you can afford, say 4 or 4.5 inches. This does effect cost but gives a better reading.

I got mine from McMaster-Carr and they shipped in a couple of days.

Use brass or red brass siphon loops to protect the gauge and petcocks.

ron5

pressuretrol question

If the pressuretrol is set low and the guage very rarely moves, how can I tell the pressuretrol is operating the boiler at the settings I have selected??

David Nadle

You have to add a second gauge with a lower pressure range.

ron6

pressuretrol

You mean replace the current guage on the boiler?
I should get one which is 1-5 lbs?

Jon Held

I replaced my stock gauge with this one:
http://www.gaugestore.com/prodinfo.asp?number=33041

Brad White_184

I like yours

better... Good to know that there are other intermediate ranges commonly available and at reasonable prices.

Captain Who

The gauge is rated for a maximum of 140 F. I guess the pigtail is enough to to keep gauge below this (especially if you prefill it with water)?

Also, what happens when or if the pressure exceeds the 3 psi.? Will the gauge be damaged or destroyed?

I am trying to diagnose my malfunctioning or out of calibration pressuretrol and I need something like this. I am actually setting up a U-tube manometer with water in clear vinyl tubing to check it out.

Jon Held

If you suspect the pressuretrol then why not simply replace it with a vaporstat? Pressuretrols on a good day have very poor accuracy and zero repeatability, at least from what I've seen.
I would be more concerned with accurately controlling the pressure than spending time and energy and money diagnosing what you already suspect as faulty and has poor track record.

Brad White_184

Temperature Limitations

Good catch. Yes, the temperature and pressure limitations must be observed. I agree that if you instrument to that lower pressure you ought to control it to that level of detail.

A pigtail/siphon loop is step one, regardless of T/P rating and it should be filled with water first. If not, the steam will make the gauge read the pressure accurately but once... A pressure snubber or diaphragm seal is another helpful device but again, applied to the correctly rated gauge.

Gordo2

Mr. Held

You say you replaced your 30 psi gauge with a 3 psi gauge?

You might want to re-install your 30 psi gauge while keeping your 3 psi gauge installed. The 30 psi gauge needs to be there by code.

Here's hoping you never see your pressure above 2 psi!



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Captain Who

Thanks, I'm seriously considering doing this. I'm still learning at this point. The "inner engineer" in me wanted to see how BAD the Honeywell pressuretrol is before I shelled out the $180 or so for the vaporstat. Only cost about $20 for the parts to make the manometer and I will use it to check/calibrate the vaporstat as well when I purchase it (probably inevitable).

Captain Who

Thanks,

Just a few questions:

What would be an acceptable temperature rating for the gauge in this application?

Where could I get the snubber or diaphragm from? Somewhere like McMaster Carr?

Is it true that exceeding the max. dial capacity would destroy the expensive low pressure gauge and, if so, would the snubber or diaphragm be necessary to protect it?

Thanks again.

Brad White_184

Gauge ratings

A steam gauge should have a 212F rating at least. The siphon tube forms a water seal which will protect it from direct steam contact. A snubber is really just an orifice which mitigates shock and sudden jumps, the force of which will damage the gauge. Think of hydraulic shock, higher bursts of pressure from otherwise static pressure systems. It is also known as an "impulse dampener".

A diaphragm seal is similar but different- there is a positive seal of a flexible metal or rubber membrane which indirectly transmits the pressure between the fluid and the gauge. McMaster-Carr does carry both I believe. See on-line catalog page 567.

Neither is designed to "add rating" to a gauge, but can mitigate damage from unforeseen or sporadic surges. It also slows "spikes" which affect control.

Jon Held

If by replaced you mean sitting in my pile of spare parts, then yes it has been replaced. I will take it under advisement.

As far as temperature goes, while the boiler is at full steam ahead, I can rest my hand on the gauge/pressuretrol end of the pigtail. It stays warm to the touch and no where near hot.