[modeleng] Re: Fwd: Re: Re: Lapping, pumps, etc was

  • From: "kenny" <kenny.macdougall@xxxxxxxxxxxxxx>
  • To: <modeleng@xxxxxxxxxxxxx>
  • Date: Mon, 20 Feb 2006 14:12:53 -0000

Hi just a test can anybody read this
kenny
----- Original Message ----- 
From: "Allen Messer" <al_messer@xxxxxxxxx>
To: "modeleng" <modeleng@xxxxxxxxxxxxx>
Sent: Monday, February 20, 2006 2:08 PM
Subject: [modeleng] Fwd: Re: Re: Lapping, pumps, etc was


>
>
> --- Phill Smith <steam@xxxxxxxxxxxxxx> wrote:
>
>>> Subject: Re: [modeleng] Re: Lapping, pumps, etc was
>
>> Date: Mon, 20 Feb 2006 13:25:25 +0800
>>
>> Gents,
>>
>> Modern fluid flow analysis has shown that the close
>> fitting plunger in a
>> bore causes more problems than it's worth, at other
>> than low piston speeds.
>> Optimal piston speed is below our "normal running
>> speed" of our models. The
>> greatest efficiency was found to be with a plunger
>> operating in a free water
>> space of at least twice the displaced volume of the
>> plunger. The factors
>> against the fitted plunger was due to the following
>> factors;
>>
>> - Insufficient valve area due to limited space. To
>> over come this, the
>> valves had to have a high lift. This in turn
>> resulted in water being pumped
>> back down the suction pipe (and/or into cylinder
>> from the discharge valve)
>> for up to 30% of the compression stroke (this was
>> worst on unsprung ball
>> valves). Vapour pressures were entered into in the
>> worst cases (suction
>> pressures dropped low enough for the water to
>> momentarily turn to steam).
>>
>> - Surge forces, due to rapid water flow in full
>> cylinder, causing high
>> friction losses and extenuating valve opening time.
>>
>>
>> So, summing it all up.........
>>
>> You'd have a 1/2" plunger operating in a minimum
>> 3/4" bore, with the "O"ring
>> gland mounted as close to the water space as
>> practical within the gland.
>> This can be a screw in (replaceable)
>> gland/guide/support. The guide is made
>> from an extension of the gland which is fed with
>> oil. Two small grooves are
>> placed, longitudinally, on the bearing area of the
>> plunger carry oil. One
>> top and bottom. The large cylinder will accommodate
>> larger valves
>> (preferably of the disc type), on the end if
>> possible (with flow axis in
>> line with the plunger) with an area equal to the
>> plunger diameter.
>>
>> This type of pump also allows for 2 different
>> materials to be used for the
>> plunger, and hence compatible bearing materials may
>> be used for the gland
>> and bearing area of the plunger. Especially since
>> oil can be used as the
>> lubricant.
>>
>>
>> Cheers,
>>
>> Phill.
>>
>> PS     Could someone please post this to the
>> "modeleng" discussion group, as
>> I have not yet had time to sort out my "why I can't
>> post anything (after a
>> certain date) but receive fine" problem.
>>
>> ----- Original Message ----- 
>> From: "alan stepney" <alan@xxxxxxxxxxxxxxxx>
>> To: <modeleng@xxxxxxxxxxxxx>
>> Sent: Monday, February 20, 2006 8:07 AM
>> Subject: [modeleng] Re: Lapping, pumps, etc was
>>
>>
>> > I have used stainless, and a reamed bore, and not
>> had any problems so far.
>> >
>> > I leave a reasonable clearance between the bore
>> and ram so that the
>> packing
>> > is the only thing making contact.
>> > That should (??) prevent galling.
>> >
>> > A reamed bore seems to be sufficiently smooth to
>> work OK and wear well.
>> >
>> > Alan
>> >
>> > MODEL ENGINEERING DISCUSSION LIST.
>> >
>> > To UNSUBSCRIBE from this list, send a blank email
>> to,
>> > modeleng-request@xxxxxxxxxxxxx with the word
>> "unsubscribe" in the subject
>> line.
>> >
>> >
>>
>>
>
>
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