Compresion test with contant pressure in a cylinder packing

Hi everyone!
I'm working on a project where as the title says, I need to apply a constant pressure over a cylinder packing.
In order to simulate friction with the cylinder walls I seted two particle taggs, one for the ones with fixed position (Walls, Tag=12)) with the setParticleNonDynamic(..) command and another to the particles inside(tag=1). I tried the Wall Piston Runnable
http://www.esys-particle.org/wiki/pmwiki.php/Main/WallPistonRunnable
with a third tag (tag=2) but at the step when it start working my wall and particles just "explode" as when you have a big time step size.

Is there any way to make kind of a circular piston or maybe other idea that archive what I need?
Here is my script. And I apologize by my poor English, I hope it's not that bad.

from esys.lsm import *
from esys.lsm.util import *
from esys.lsm.geometry import *
from LHDRun import LHD
from PistonRun import PistonRun

sim = LsmMpi(numWorkerProcesses=4, mpiDimList=[2, 2, 1])

Rmin=0.005
Rmax=0.005
minPoint = Vec3(-2, -2, 0)
maxPoint = Vec3(2, 2, 1.2)
Time=15
TimeBCkP=0.1
TimeStepSize=1e-3

sim.initNeighbourSearch(
    particleType="RotSphere",
    gridSpacing=2.5*Rmax,
    verletDist=0.2*Rmin
)
NumTimeSteps=int(Time/TimeStepSize)
sim.setNumTimeSteps(NumTimeSteps)
sim.setTimeStepSize(TimeStepSize)
sim.setSpatialDomain(
   BoundingBox(minPoint, maxPoint)
)
sim.createInteractionGroup(
   GravityPrms(name="earth-gravity",
               acceleration=Vec3(0, 0, -9.81)
   )
)
sim.readGeometry('particles.geo')
sim.setParticleDensity(
       tag = 1,
       mask = -1,
       Density = 2600
)
sim.setParticleDensity(
       tag = 12,
       mask = -1,
       Density = 2600
)
sim.setParticleDensity(
       tag = 2,
       mask = -1,
       Density = 2600
)
sim.setParticleNonDynamic(tag=12)
sim.setParticleNonRotational(tag=12)
sim.createInteractionGroup(
    FrictionPrms(
      name="friccion",
      youngsModulus=100000,
      poissonsRatio=0.25,
      dynamicMu=0.4,
      staticMu=0.6
   )
)
sim.createWall(
   name='disco',
   posn=Vec3(0,0,0.9),
   normal=Vec3(0,0,-1)
)
sim.createInteractionGroup(
   NRotBondedWallPrms(
      name='prensa',
      wallName='disco',
      normalK=100000,
      particleTag=2
   )
)
sim.createInteractionGroup(
   LinDampingPrms(
      name="linDamping",
      viscosity=0.1,
      maxIterations=100
   )
)
sim.createInteractionGroup(
   RotDampingPrms(
      name="Damping2",
      viscosity=0.002,
      maxIterations=50
   )
)

sim.createCheckPointer(
   CheckPointPrms(
      fileNamePrefix="prensa",
      beginTimeStep=0,
      endTimeStep=NumTimeSteps,
      timeStepIncr=int(float(TimeBCkP/TimeStepSize))
   )
)

sim.createFieldSaver(
 WallVectorFieldSaverPrms(
  wallName='disco',
  fieldName='Force',
  fileName='out_force.dat',
  fileFormat='RAW_SERIES',
  beginTimeStep=0,
  endTimeStep=sim.getNumTimeSteps(),
  timeStepIncr=int(float(TimeBCkP/TimeStepSize))
 )
)
sim.createFieldSaver(
 WallVectorFieldSaverPrms(
  wallName='disco',
  fieldName='Position',
  fileName='Posicion_disco.dat',
  fileFormat='RAW_SERIES',
  beginTimeStep=0,
  endTimeStep=sim.getNumTimeSteps(),
  timeStepIncr=int(float(TimeBCkP/TimeStepSize))
 )
)
#Runnable (this one works perfectly)
lhd=LHD(sim=sim)
sim.addPostTimeStepRunnable(lhd)

#Runnable (here I have some problems)
piston=PistonRun(
   sim=sim,
   wallName='disco',
   wallInteractionName='prensa',
   rampTime=10/sim.getTimeStepSize(),
   pressure=10000,
   startTime=1/sim.getTimeStepSize()
)
sim.addPostTimeStepRunnable(piston)

sim.run()