Gate valves installed on Mains?

Jack M

What's the rationale for installing gate valves on these pipes (main takeoffs)?

Jamie Hall

One frequently -- and properly -- sees valves on the main takeoffs from a boiler header. However... I would much rather have seen ball or plug valves than gates. Whatever. There should also be corresponding valves on the wet return to the boiler. The objective of the exercise is to allow raising the boiler pressure to 5 to 10 psi from time to time for maintenance, or to check pressure controls, without overpressuring the rest of the system.

JUGHNE

Does anyone make a full flow plug valve?

pecmsg

On steam i prefer gate valves, no chance of accidentally opening to fast.

Jack M

Would gate valves be as reliable as a ball valve on a wet return?
I run into old gate valves with bad seals at the stem.

Jamie Hall

Jack M said:

Would gate valves be as reliable as a ball valve on a wet return?
I run into old gate valves with bad seals at the stem.

I suspect you may find differences of opinion on this. I have no great fondness for gate valves, as I have found that sediment and crud tend to get into the guts and keep them from shutting off completely. This won't happen to a ball valve. On the other hand, full port ball valves don't come in the larger sizes (although I have 4 3 inch ball valves in my system on the takeoffs from the header) or are alarmingly expensive. That is less of a consideration on wet returns, where a reduced port valve isn't a catastrophe. Also, gate valves must never be used for throttling -- either full open or full closed (when one gets into very large sizes -- say 24 inch on up -- they can be designed to throttle) -- but again this isn't a problem here. Ball valves can throttled without trouble. Not that you'd want to on a wet return.

I'd use ball valves or plug valves (which are very similar from an operational standpoint).

Just a few thoughts...

Jack M

Do the valves on the mains need to be carbon steel or can I go with brass?

ChrisJ

Jamie Hall said:

Jack M said:

Would gate valves be as reliable as a ball valve on a wet return?
I run into old gate valves with bad seals at the stem.

I suspect you may find differences of opinion on this. I have no great fondness for gate valves, as I have found that sediment and crud tend to get into the guts and keep them from shutting off completely. This won't happen to a ball valve. On the other hand, full port ball valves don't come in the larger sizes (although I have 4 3 inch ball valves in my system on the takeoffs from the header) or are alarmingly expensive. That is less of a consideration on wet returns, where a reduced port valve isn't a catastrophe. Also, gate valves must never be used for throttling -- either full open or full closed (when one gets into very large sizes -- say 24 inch on up -- they can be designed to throttle) -- but again this isn't a problem here. Ball valves can throttled without trouble. Not that you'd want to on a wet return.

I'd use ball valves or plug valves (which are very similar from an operational standpoint).

Just a few thoughts...

Sediment and crud in a steam main?
Where does this sediment and crud come from when supplied with nothing other than distilled water?

I second the use of gate valves, however try and avoid the cheap Matco Norca ones I used. I've had endless issues with them. Nothing I haven't been able to fix, but constantly tweaking the packing nuts and then this year the bonnet nut leaked and soaked my header insulation. I was not impressed.

Personally, I'd probably leave them out if I had to do it over again. I've never had a need for the king valves. Oddly enough I have a Matco Norca valve on a radiator and I've had no issues with it.


Brass valves are fine.

Jack M

In shopping for these I come across valves that are listed with
" Standard Port Threaded Ball Valve w/ Steam Trim (108 Cv)" that include "special high-temperature (500 degree) MTFE seats and stem packing." 150 swp.
supplyhouse.com/Apollo-Valves-7014864-2-FNPT-Standard-Port-Threaded-Ball-Valve-w-Steam-Trim-108-Cv
Are standard domestic Watts ball valves (400 degrees F /150 wsp) satisfactory?

pecmsg

Another advantage of a Gate Valve is the ability to rebuild in the field.
As far as sediment the stem should be horizontal, Never mount vertical with the gate traveling down. Crap will settle in the bottom.

Remember Never Seize is your friend!

gerry gill

Steve my business associate likes valves on the takeoffs and return so he can raise boiler pressure to do a serious blow down.

ChrisJ

gerry gill said:

Steve my business associate likes valves on the takeoffs and return so he can raise boiler pressure to do a serious blow down.

This is why I installed them but I don't see the point after building a wand like yours.

Why build 5-10 PSI to do a cheesy blowdown when you can wash the boiler out with 40-60 PSI of hot water?

Just doesn't make sense to me anymore.