Watson-Marlow 501RL - Manual (Page 5)

Recommended operating procedures
Do keep delivery and suction lines as short as possible.
Do use the minimum number of bends in rigid pipe runs. If there must be a
bend, use a swept bend and not a tight elbow.
Do use suction and delivery pipelines with a bore equal to or larger than the
bore of the tube fitted in the pumphead. When pumping viscous fluids, the
losses caused by increased friction can be overcome by using pipe runs with
a cross sectional area several times greater than the pumping element.
Do run at a slow speed when pumping viscous fluids. When using the 501RL
pumphead, a 4.8 or 6.4mm bore tube with a 1.6mm wall will give best results.
Tube smaller than this will generate a high friction pressure loss, so reducing
the flow. Tube with a larger bore will not have sufficient strength to restitute.
Flooded suction will enhance pumping performance in all cases, particularly
for materials of a viscous nature. Silicone and Marprene tubing is available
with a 2.4mm wall thickness for speeds up to 220rpm. (The rotor will require
re-setting to a roller/track gap of 3.8mm.)
Do use the largest possible bore tube running at slow speed for the longest
tube life.
Do fit an extra length of pump tube in the system so that you can move the
tube through the pumphead occasionally, without needing to break the
pumping circuit. This is particularly useful for extending tube life in long
running sterile applications.
Do keep the track and rollers clean, and ensure that the rollers are free.
Do not fit valves in the suction or delivery lines without considering that
peristaltic pumps are self priming and will hold their prime up to several
metres, so there may be no need for non-return or foot valves, nor for the
loading valves required on many other kinds of pumps.
Any valves fitted must cause no restriction. If electrically actuated valves are
fitted, they should be interlocked so that the pump will only run when the
valves are open. Fit an automatic by-pass if manual valves are installed.
When using Marprene or Bioprene tubing, after about 30 minutes of
running, re-tension the tube in the pumphead by releasing the tube clamp on
the delivery side a little and pulling the tube tight. This is to counteract the
normal stretching that occurs with Marprene or Bioprene, which can go
unnoticed, and result in poor tube life.
Tube selection The chemical compatibility list published in the Watson-
Marlow catalogue is only a guide. If in doubt request a tube sample card for
immersion trials. Remember the sample will be fully immersed, but the fluid
when in use will only be in contact with the inside of the tube. If the material
swells but does not lose its strength it could be worth considering.
Viscous dispensing To overcome the common problems, of reduced
accuracy and dripping delivery pipes, the suction and delivery lines should be
kept as short as possible. Use larger bore transmission tubes than in the
pumphead to keep the friction losses to a minimum. Improvement will be
noticed if rigid or semi-rigid pipe is used on the delivery side. The rigid tube is
effective in reducing over-run because it does not expand during pumping.
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