Pump question (not a shower pump!)

[T i m]

Hi All,

My mate with a greenhouse (well several ) showed me a small blue metal bodied pump that us used to mix via a 'Computer' (not as we know it) and solenoid valves, varying amounts of acid and alkali into the alto watering mix for his 4,000 tomato plants ;-)

He showed me a sorry looking pump that he said cost 400 pounds new.

It's a 240V single phase jobby and about 140mm long by 80mm diameter and uses an inductive coupling to drive the plastic impeller in the plastic pump body (is that what they do in shower pumps?). From memory the pump flow return had an inner bore of about 10mm.

I was wondering if anyone in an industry that might use such equipment might know of what might make a 'cheap' (but reliable) replacement maybe please?

He recently used up his last 'spare' as one (of the three in use) seized solid. I'll be taking him some Plus Gas as he was trying WD40 on it (when will folk learn ?)

All the best ..

T i m

[aj]

Sounds like a magnetically coupled pump (magpump) with a sealed impellor housing. March May make a range of these pumps. I aven't found a web address but this is their number - 01480) 214444 - they are in St Neots. The most regular failure of these pumps is caused through running them dry, this melts the seating of the impellor bearing.

[John Stumbles]

Central heating circulators (pumps to you & me) will take all sorts of abuse and are free for the skipdiving.

Mind you what sort of 'acid' is he feeding his 'tomato plants' ? ;-)

[T i m]

Do they have an isolated impeller John? I'n not sure how the seals / bearings would cope in this environment?

I'm not exactly sure .. other than whatever it is, it's safe enough to put yer fingers in (apparently)?

The plants need a ph of 5.5 (or summat) and as the water is regularly pumped round to each plant from a tank the size of a swimming pool, it's 'mixed' (on the fly) in a small tank (the size of a domestic water tank) with acid / alkali to try to hit the required ph.

He even buys boxes of bees in to assist with the pollenation .. 1 pound 50 per bee I believe!

All the best ..

T i m

[John]

The last set up I saw was under the trade name VOCOM. IIRC there were storage tanks for about three lots of feedstock and a buffer tank which recirculated via a pump with graduated injector valves which were located on the suction side of the pump so as to draw the stock chemicals into the water. I can recall pH probes, conductivity, and dissolved oxygen probes in the control loop as well as a flow sensor in the pumped output to the greenhouses which gave early indication to the programmable controller handling everything. Out in the greenhouses the header pipe branched off via solenoid valves to subsections of the crop. It was possible to give each section a session of "watering" with appropriate nutrients for that particular crop. The pumps on a Vocom were Grundfos again IIRC

Phosphoric sticks in my mind so probably weak Coca Cola strength

Cucumber growers use biological predators to control aphids and other pests (but don't ask about the Hydroflouric acid used each year to clean the glass or the formaldehyde sprayed about with gay abandon to clean up during the off season)