BRONZE vs STAINLESS STEEL

Positive Solution

My supplier started giving me stainless steel circulators. He told me they are the same as bronze circulators. I suspect this is not true. For domestic water, can I use a stainless steel circulator?

EricAune

Stainless is fine for domestic

Most of the major manufacturers are switching to an all cast iron or stainless casting product line.  This may be in line to comply with the "no lead" requirements but also streamlines their inventory.  

markwilo1

markwilo1

Just remember though many manufacuturers would have you believe differently, not all Stainlesss Steels are created equally and it is not indestrctable.  Many independant studies have proven bronze volutes to have better flow and wear charecteristics vs SS. 

Radiohead

Which metal for hydronic heat?

What metal pump should be used for circulation pumps in a oxygen barrier hydronic floor system..  Mine are currently cast iron....

archibald tuttle

bumping this thread. radiohead never got an answer and i'm kind of wondering the same thing. on the one hand, i'm getting maybe 7 or 8 years usually out of cast iron. but i still get my share of calls for circulators that are frozen after summer, or quit during winter.

I would think using stainless or bronze when going to a single variable circ would be a no brainer. but i'm maintaining a lot of systems that were piped with a circulator per zone. while i could still buy the lead full bronze circs for a buck fifty while they were getting cleaned out, that was doin it for me. i'm just not quite ready to go flangeless although that would be one way to go bronze and keep the cost down.

but now i have to buckle down and decide where i'm looking for long reliable service would i use stainless or bronze body. as pointed out above, i may not have the choice much longer. my instinct is that bronze is probably even better than stainless in this application because stainless is really a relative measure not an absolute and bronze always seemed forever to me. But the galvanic scale slightly favors stainless. It just seems to me that isn't how it works out over time. Of course it depends on the number stainless as well but even the teens fair pretty well on the scale compare to bronze.

guess i'm just jaded after replacing the 'stainless' components in my grill every year. that's an extreme environment to be sure but maybe its kind of like being in heating service for 10 or 20 years. i don know. that's why i'm askin'

brian

Gordy

For hydronic heat with proper O2 barrier tubing I see no reason not to stick with iron circs.

icesailor

Bronze is valuable as scrap and it is a commodity. Most old bronze has lead/zinc in it. Stainless Steel may actually be a bad substitute. Put a magnet on the Stainless Steel. The higher the nickel content, the less the magnetic attraction. The Stainless Steel on your outdoor grill might have just enough nickel in it to keep it from rusting. 304 Stainless it isn't.

Good stainless is hard to machine. If you can drill it with a standard Jobbers drill, it doesn't have a lot of nickel in it. If you need a true Cobalt containing bit to drill it and be able to use it after drilling the hole, it has more nickel in it.

archibald tuttle

gordy,

there certainly isn't anything wrong with that advice. the old timers used to give me what they called 'water mixable oil' to throw in the system as well. i've got one closed floor job where there is no make up water and i pumped the system full with antifreeze and little of that go-go juice 20 years ago and the only iron in the entire circuit is the circulator and it still starts every year.

but i've seen the insides of some iron circulator bodies that get pretty ugly after 5 or 6 years in and these systems have iron in the boilers and near boiler piping but no pex whatsoever . . .

I always use bronze when i'm circulating out of a steam boiler also.

i've got this big old cast iron set up and a manifold of circulators and i've got to open up for a bunch of maintenance and some of these are still red barons. you can still get 006 and equivalent bronze circulators for half the price of new stainless of LF bronze and i'm thinking why not. although one reason is i'm pretty much only finding the sweat versions. i wouldn't mind union standard as on fill valves and backflow preventers but these are straight sweat. i suppose if they are going to last forever and i'm just going change a cartridge anyway maybe i should get over it but . . .

SWEI

When copper tops $3 per pound, stainless starts to look like a pretty good deal. As mentioned above, the devil is in the details for specific alloys.

It's generally less expensive to keep the oxygen out than to build a completely non-ferrous system. Given the number of 30+ year old 3-piece iron circulators I've pulled out and the condition of some of them, I'd have to say it works.

archibald tuttle

icesailor,

yeah, i'm sure the 'stainless' for my grill is well into the teens. sounds to me like they are molding these stainless bodies. guess they have to do a little machine work on the finished product so they are balancing anti-corrosive properties with workability. i don't see a quick reference to what grade stainless they are using and of course that could vary by company although probably not a lot unless we're talking no-name stainless circs from china - even then they might be OK , who knows.

brian

hot_rod

You will start to see more and more stainless and composites used in hydronic devices. The cost of copper based alloys, like brass and low lead brass is one reason. The low lead brass alloys are not so easy to machine and manufacture, is another.

The stainless body circ may be the same as the bronze, far as the curve or performance, if that is what you asked.

Stainless is really low carbon steel with a 10% or more chromium content. As Ice mentioned there are all sorts of SS alloys 3 and 400 series are very common for water or food process applications. The alloy is selected depending on the use. It comes down to what the fluid is you plan to circulate. High chloride levels are not always friendly to stainless, again, depending on the alloy. You will see all the stainless indirect tanks note acceptable fluid quality on the labels now.

If you have O2 ingress, from whatever source, either all non ferrous components including radiant style expansion tanks, or use a chemical treatment with O2 scavengers blended. But chemicals need constant monitoring and occasional boost.

The price of old style leaded brass components may be dropping to move them from the shelves? Or else ship them to Canada

Frozen circs are usually the fault of the fluid, use a pump relay with an exercise feature to help eliminate "off season stick up"

Union bodied pumps are the main stay in Europe, most common sized US circs can be ordered with union bodies.

archibald tuttle

got it on the exercise and i agree. if i happen to be in a basement with an old honeywell relay offseason, i usually just pop the cover and pull the relay by hand for 20 seconds - and if i've been in anywhere often there is a panel swith for overriding the thermostat so i don't even have to pull covers. along with built in override/off switching and setback exercise when temps drop below a certain setpoint, the off season exercise is a feature i'd like to see in virtually any relay.

what about sweat style pump connections. as i look at bronze alternatives i'm seeing a lot of those that i never saw before. is that the answer to the problems with lead free brass or is there just new habit of piping or both?

hot_rod

archibald tuttle said:

got it on the exercise and i agree. if i happen to be in a basement with an old honeywell relay offseason, i usually just pop the cover and pull the relay by hand for 20 seconds - and if i've been in anywhere often there is a panel swith for overriding the thermostat so i don't even have to pull covers. along with built in override/off switching and setback exercise when temps drop below a certain setpoint, the off season exercise is a feature i'd like to see in virtually any relay.

what about sweat style pump connections. as i look at bronze alternatives i'm seeing a lot of those that i never saw before. is that the answer to the problems with lead free brass or is there just new habit of piping or both?

I suspect sweat style pump bodies will fade away as the cost of low lead alloys is so un-predictable. Much less material used in stainless pump volutes, notice the weight difference. I believe they stamp, or spin form stainless volutes. So the issue of casting and or forging the bronze pump volutes is eliminated, that is a tough, heavily regulated process due to emissions. Even low lead alloys contain some lead, a % by weight is how the current regs are enforced.

Composites and polymers will be more and more common. The pool and spa industry have used composite pumps for decades, as they handle the use, or mis-use of chemicals well, and temperatures below 120°F.
The operating temperature is the key to composite hydronics. If we could embrace system designs not to exceed 140°F composites and polymers would be the most common material.

I have heard of exhaust manifolds for engines being formed with composites, maybe entire engines some day?

The union connection pump allows you to easily adapt to sweat, thread, press, crimp, groove, grip, you name it. It is also an easily removed and installed pump, no more rusted bolts and finding the correct flange dimension and orientation.

archibald tuttle

look for the union label . . . eer threads.

PS - in your experience, what grade stainless are we talking in these pumps -- how much competition is there over alloy or is there a standard.

on the chloride side, are the trace biproducts of chlorination in larger water systems enough to tip that scale toward accelerated corrosion in stainless pumps and fittings. Is this more a problem on open systems that circulate for DHW whereas the same water not exchanged frequently in a closed loop heating system only has so many ions to exchange?

brian

hot_rod

archibald tuttle said:

look for the union label . . . eer threads.

PS - in your experience, what grade stainless are we talking in these pumps -- how much competition is there over alloy or is there a standard.

on the chloride side, are the trace biproducts of chlorination in larger water systems enough to tip that scale toward accelerated corrosion in stainless pumps and fittings. Is this more a problem on open systems that circulate for DHW whereas the same water not exchanged frequently in a closed loop heating system only has so many ions to exchange?

brian

good questions for Perry, maybe search old posts with his name, he works in the nuclear industry and knows a lot about metallurgy. We've had this stainless discussion before at The Wall

I remember working with an outdoor wood boiler manufacturer years ago. They tried 304, 316, and 409 in their product, all had pros and cons.

I believe Viessmann uses a Ti titanium stabilized stainless, also used in quality cookware. I doubt there is a grade of stainless that covers all the requirements of the unknown hydronic and potable water industry?

I remember in the early days of stainless indirects the biggest obstacle was the welds. Many failed from crevise corrosion around the welds. I visited the HTP factory many, many years ago and Dave Davis explained all the challanges of building tanks and boilers with stainless.


I suspect it is all but impossible to know or control what goes into the potable water at various locations, not to mention operator error.