On 16 Jan 2009, at 10:19, Adrian Stott wrote:
> Why would a more complex (i.e. adjustable) one be needed?
If there is no barrier between the air and the water, the air will
all tiptoe gradually away as it dissolves in the water. Hence there
is usually some sort of diaphragm or bladder to stop that happening.
No matter what the arrangement, the air pressure is bound to reduce
over time from loss one way or another. Thus most accumulators have a
tyre valve in the top so that you can pump it up.
Because the optimum pressure is either half the pump cut out pressure
or a little less than the cut in pressure (depending who you believe,
and often comes to much the same thing), and because pumps vary in
these pressures, you need to be able to adjust the accumulator pressure.
The Cleghorn Wareing ones come pressured to 5 bar, so that you can
bleed off as much as you want when installing. If you don't realise
this, you are wasting your time installing it, as the pump will cut
out long before water starts entering the flask.
As a final ironic note, having started this thread: after installing
the new pump, and having had to wait to get the new accumulator, when
I came to install the latter, I discovered that the old one was now
performing perfectly. Applying the NB=DF rule, I have therefore
retained the new accumulator as a spare.
All the best
Bruce
There are no strangers on the cut, only boaters we've yet to meet.
[Non-text portions of this message have been removed]
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