Article on Pumps

[meow2222]

Somehow I doubt he will :)

NT

[Aidan]

Like the summarize Proust contest..........

rate. Flow claims are normally based on there being no pipe connected to th= e pump outlet.

No, they don't. A pump will produce a specific flow rate at a specific differential pressure (assuming constant speed). A flow rate is meaningless unless the associated dP is quoted. Manufacturers usually supply pump curves for each model. The only pump/fan manufacturers who are given to claiming flow rates without the relevant dP are shower pump/ bathroom fan manufacturers, selling to a (largely) clueless DIY market (3 bar shower pumps? 1,000 lpm fans?). They will produce the curves, if asked.

Not necessarily. You can pump water uphill, downhill & on the level. Circulators (CH) have no static head 'cos the ascending flow is balanced by the descending return (or v v) , so they only operate against pressure loss due to pipe resistance at the specifed flow rate.

Yes. The point is that the resistance is a loss of energy which manifest itself as a loss of pressure due to resistance. See Bernouilli.

rate on x,y axes, and drawing a straight line from max flow to max head. T= his enables flow rates to be read off for any given head.

No. Really, no. It's a curve, which you get from the manufacturers. You estimate the system resistance at the design flow.

No. See above. You estimate system resistance etc..

Plumbing 2 pumps in series gives a total head of the 2 pumps added together. Yes, but only in theory. In reality the system operating point is at the intersection of the pump and system curves, so changing the flow in a given system alters the system pressure loss and so the pumps' flow rate. l [edit]Pump Power [edit]Pump Materials Brass: used for potable water

Bronze usually, SS more recently ISTR. The relevant question is, why? 'Cos potable/mains water is oxygenated and will corrode the steel impeller on ordinary CH circulators. CH systems should be treated with inhibitors, potable isn't. Dodgy plumbers use CH circulators on DHWS circulating system, but they only last a year or two, at most .

Plastics: some are approved for potable water. [edit]Connections [edit]Pump Types Add spiel about cavitation & NPSH here; essential to limit DHWS flow temperature on shower pumps to 60 degC, as per manufacturers' recommendations 'cos it increases likelihood of cavitation. Cavitation will chew lumps out of the impeller, be it bronze or plastic.

[edit]Central Heating circulator Very quiet operation Long service life Speed adjustable. too fast can cause pumping over & noise too slow can cause boiler kettling Standardised pipe fittings. 1 1/4" BSP unions ISTR, but Yanks use 2-bolt flanges on similar/same pumps. They are canned rotor/glandless circulators, which are what really made domestic CH possible in late 50s/early 60s. Pumps formerly used stuffing boxes which had to just drip (or else they were piped to the inlet/suction flange) or the gland packing would burn out. Packed glands have largely been replaced by carbon/ ceramic seals on commercial pumps. There's a web-site somewhere with several hundred pages just on carbon seals.

The pump is glandless because the motor rotor is in the water stream (in the 'can') , so there's no shaft from motor to pump which needs to be sealed on the pump scroll/casing. The relevant point is that there's very little clearance between rotor and stator to get the magnetic flux (electronics geeks please provide correct terminology) to turn the rotor. This narrow waterway will get blocked easily if there's any corrosion debris in the heating system. The jammed rotor can usually be cleared by spinning it manually or you can dismantle the pump and clean it. Dodgy plumbers charge for a new pump ( "It's yer pump, darlin' etc.",) and flog the cleaned-up old pump to their next victim. If the pump blocks regularly, you have a corrosion problem, probably the result of employing incompetent, dodgy plumbers. You could fit a glanded pump with a separate motor which won't block, but these cost lots (=A3200ish, ISTR). I only fitted that to a centralised heating system because there was no propect of being able to clean up the system water quality.

[edit]Shower Boost shower pressure and thus flow Boosts bills too. [edit]Sump pump For draining cellars prone to flooding. USually automatically operated by a water sensor [edit]Drill Pump Small minimal cost pump for occasional clear-up use [edit]Foul Water Pump Able to handle debris in the water

Borehole, multi-stage, end-suction, belt drive, inverters, variable speed pumps, etc..

The thing is this Wiki is under the control of NT who thinks he knows something about pumps (and everything else) and can write a useful article in 100 words. Truth is he knows sod-all about pumps and his efforts are misleading. I work with/specify pumps, it would take me several hours to construct a useful article and I KNOW that I know sod all about pumps because I occasionally come into contact with pump specialists. I also work with/specify heat transfer equipment. The last time I had a disagreement with NT about this (he thinks he knows about heat transfer, too) he suggested I consider a uniform resistive block. I have yet to find out what a uniform resistive block is; if anyone can help, please advise me.

I'm not spending my time producing anything for the benefit of NT. See Wikipedia.

[John Rumm]

No its not! You can go and make changes to any article you like. You don't even have to create an account first (although it helps if you do).

You can't fault NT for the shear quantity of stuff he has added to the wiki, even if much of it represents a "good starting point" rather than a polished result!

On pumps I would have to agree. Not being an expert on the subject I have refrained from fiddling even though a number of statements have struck me as improbable.

Well much of what you posted already could be used to good effect in the article, so why not have a bash?

How would adding / correcting useful material be for the benefit of NT? Surely it would be for the benefit of the rest of us?

[John Stumbles]

I think there's a point to be considered here. I also know a little about pumps but have not contributed to this article because I'd rather concentrate on trying to do a few articles as well as I possibly can than adding a bit to an article which - it seems to me - requires a lot of work to bring to a good standard. I'm not saying NT/meow shouldn't have written what he did but I've been wondering about somehow separating articles that are seriously 'under construction' from more complete and accurate ones. I'm raising this in a separate thread called "DIY Wiki - articles Under Construction"