Published in: Das Schwimmbad und sein Personal, edition 02/2022
... or how to double the flow rate.
In the middle of the "Sauerland Rothaargebirge Nature Park"” lies the
Municipality of Herscheid
on beautiful 59 square kilometers.
The object says about itself, of course on their own website: "Lying in a beach chair, the feet in the sand, the view towards the water: what sounds, like a holiday dream by the sea, can be reality every day in Herscheid. This is just one of the many facets of the warm water outdoor pool: Here feel both the little ones, as well as the big ones.
What distinguishes the object, that is its vastness: On the large lawns you can still find a free spot even on busy days.
Who likes it comfortable, you can rent a beach chair or a lounger. Visitors have a good overview of the site from the sun terrace, which is located next to the kiosk, where refreshments and treats are offered. Things get sporty just a few meters away on the soccer field and the beach volleyball field. The four pools form the center of the object. The youngest visitors prefer to have fun in the modern paddling pool with a water mushroom and play equipment. The non-swimmer pool has been redesigned: It features flow channel, wave slide, massage jets, Water bowl and neck shower. But that's not all of the attractions: A diving pool is connected to the swimming pool with its seven lanes. At this there is a diving board, from which the guests can slide more or less artfully into the water from a height of one or three meters.”
The website
... is right but somehow not. Because the website is a bit flimsy, because it is outdated. Updating is necessary, the text was just up 2020 really correct.
A lot has happened in the pool since then. Funding has made “the new” non-swimmer pool obsolete, because since early summer 2021 also grace a new swimming- and a new diving pool (see above) the outdoor pool made of stainless steel. More than 10 Years earlier, the resourceful planner, just like the pool and its staff did not give up hope for this expansion and took some precautions in the first construction phase.
Nobody could guess, that the community up 2021 will have to live with a cracked concrete ceramic basin and its high water losses.
With the first two stainless steel pools, a paddling pool and an attractive non-swimmer pool, a new water treatment system was installed back then.
Illustration 1: A place by the creek, Source: aqua&pools
Platznot
Due to the extreme lack of space in the filter room, the planner had a vacuum precoat filter for more than 750 DIN m³/h filter performance, plus piping plus pumps provided.
The stainless steel- and the ceramic pools were then operated at 400m³/h. The plant was 2020 on the (virtual) test and weighed the measures against each other.
- Repair of the filter and reduction of the pump performance to 400m³/h or
- Modernization of the filter and conversion to energy-efficient(re) Pumps up to 800m³/h.
During the first inspections of the filter, it turned out that the filter fabric on the filter elements had been damaged several times. The Company, who made these items, had long since succumbed to bankruptcy.
Nevertheless, the municipality decided with the new planner, bring more than double the number of new elements to the tender.
Illustration 03: Installation of new filter elements, Source: aqua&pools
Probably the only specialist, who dared to take on this task, was the WTA Vogtland GmbH from Plauen in Saxony. Especially their sense of detail in the fabric was in demand. Finally had the material, the number, the density of the threads are so correct, that the filter aids accumulate.
More information on precoat filtration can also be found in the article in article 05/2020 be read.
One of the precautionary measures taken by the old planner when building the filter was the
"Courage to gap".
The place of 43 Filter elements was through 21 elements and 23 blind plug used. The plant manufacturer from Plauen was therefore commissioned, 43 supply and assemble new identical elements.
The theoretical way to double the volume flow was open.
Illustration 04: 3 from 4 Circulation pumps, Source aqua&pools
Which sounds simple in theory, can pose unsolvable problems in practice. You have to think, that the flow conditions in the filter and especially between the filter elements also change. With the existing fixed frequency control, if you can call it that, there was no alluvial flower basket to be won.
Regulation and control
So it was valid, 4 new pumps and 5 old(!) motor flaps to synchronize in this way, that the holding vacuum never breaks off. The filter cake should remain on the fabric and not be constantly replaced. Here the programmer of the new control played his instrument with virtuosity.
He also had to anticipate air bubbles in the system and prevent the filter from overflowing.
Illustration 05: Idyll in the area, Source aqua&pools
Run over,
... who looked for Herscheid on the map, will surely ask: Isn't there something overflowing??
Yes! But only the creek just before it crosses the outdoor pool in the immediate vicinity of the filter. It is thanks to the local fire brigade and many helpers, that 1 week after the formal acceptance, a new renovation was not due.
Overflow tank
An open point in the (planned) renovation is the unfortunately very small old surge water tank. If the levels are low here, the controller first reduces the volume flow, which drives water from the downhill pipes into the tank and fills it up as a precaution.
Illustration 06: dyeing test, Source aqua&pools
If this measure is not enough, then the precoat filter changes to the circulation, which is also used during the precoating process. So double security against the loss of the filter cake.
For these measures a tailor-made control cabinet was needed, witch the pool and its staff assisted in maintaining water quality.
More efficient circulation pumps are not necessarily smaller circulation pumps!
... and they are not lighter either. For this reason, the new pumps were first assembled by a local manufacturer team. Neither the transport nor the positioning was possible otherwise. Even some pipes had to go - and not every connection could be made with the hydraulic standard.
Illustration 7: The new filter, Source aqua&pools
In the end everything was fine!
The negative pressure did not tear any tissue! The diatomaceous earth has precoated up and filtered! The pool water is clean and has passed the chemical and biological tests! The pool survived the staining test and the first season well.
Well planned! Realized well! Well operated!
Anyone planning something similar, find the link as always:
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