Subject: RE: Accum Size
Date: Tue, 27 Jul 1999 16:39:31 -0500
From: "Kusner, Dave" <Dave.Kusner@mts.com>
To: "Larson, Rod" <Rod.Larson@mts.com>

Rod,  Close coupled accumulators are mainly sized to reduce  inertial
pressure fluctuations.   Inertial pressure is a function of frequency,
flow rate, hose length and inversly to hose cross section.  It doesn't
take much accumulator capacity to kill these fluctuationg pressures if
you can mount the accumulators quite closely to the ports.  We don't
typically use CC accumulators for pilot valves since the flows are so
small and the hoses are relatively large.

Field measurements from ENEA did not show much benefit to mounting close
coupled pilot accumulators.  (maybe the hose compliance helps to soften
the pressure spikes)   But in the case of MOC I did decide to have Pilot
CC accumulators mounted on manifolds near each actuator.  These also
served to make sure we had a stable pilot pressure supply irregardless
to what was happening to the main oil pressure.

Each actuator had one manifold feeding both valves.  The manifold had a
10 liter accumulator pressure and a 10 liter return accumulator.  We
used large hoses (-12) and had the manifold within 10 hose feet of the
pilot valves.  We also located 3 micron filters at each manifold.  At
maximum frequency I calculated a theoretical pressure spike of 100 psi
with the 10 ft hoses which seemed acceptable to me.

Hope this helps.

Dave

> -----Original Message-----
> From: Rod Larson [SMTP:rod.larson@mts.com]
> Sent: Tuesday, July 27, 1999 1:42 PM
> To:   dave.kusner@mts.com
> Subject:      Accum Size
>
> Dave,
> We are going to use the 800 gpm MOC valve on an actuator for Takenaka.
> I
> am recommending 5 gallon pilot pressure accumulators.  What size did
> you
> have on MOC for 2 800 gpm valves?  Am I in the right ball-park?
> Rod Larson
>
