Watson-Marlow 504U/RL - Manual (Page 9)

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Fit the other end of the tubing into the second spring loaded clamp, ensuring that the tubing is not slack in the
pumphead, since this can reduce tube life.
Close the crank handle and shut and lock the guard.
After the pump has been started, open the downstream clamp for a short time, so that the tube can find its natural
length.
The 501RL pumphead is fitted with four-position tube clamps, to accommodate various tube diameters, which can
be adjusted by pushing in or pulling out the bars at the top of the upper clamp and the bottom of the lower clamp.
Set the clamps so that the minimum necessary pressure is applied to the tubing.
R R R R Roller adjustment oller adjustment oller adjustment oller adjustment oller adjustment
The 501RL has a factory set gap of 2.6mm between the rollers and the track and is suitable for tubing having wall
thicknesses of between 1.6 and 2.0mm. Adjustment of the gap will be required if tubing having a wall thickness of
less than 1.6mm is required. There is an adjusting screw on each of the two roller arms, and each of these screws
will require adjustment. The correct gap is twice the wall thickness less twenty percent. Correct adjustment is
important: over occlusion will reduce tube life; under occlusion will reduce pumping efficiency.
To change the gap setting, turn each adjusting screw clockwise to increase the gap, or anticlockwise to decrease
the gap. A full turn changes the gap by 0.8mm.
To restore the original settings of 2.6mm, turn the adjusting screws until both rollers are just touching the track,
then tighten each screw by three and a quarter turns. The 501RL2 has a factory set gap of 3.8mm between the
wall and the track and is suitable for tubing having wall thickness of between 2.1 and 2.5mm.
Check moving parts of the rotor from time to time for freedom of movement. Lubricate pivot points and rollers
occasionally with a light machine oil with Teflon additives. For scheduled maintenance, remove the rotor from the
pumphead, clean thoroughly and apply light machine oil with Teflon additives to the roller spindles.