Maintenance
68
PKG-SVX027A-EN
Sequence of Operations
Start
1. Shut off relevant pumps.
2. Shut off the primary side valves.
3. Shut off the secondary side valves.
4. Empty the BPHE.
5. Backflush it with water to remove loose contamination.
6. Connect the machine via inlet/outlet at front or
backside if possible.
7. Mix chemical and water according to instructions for
cleaning fluid.
8. Heat the solution to 120°F - 140°F, make use of primary
side heat if possible.
9. Pump the solution in the BPHE using the lower opening
to ventilate air. A flow rate corresponding to 1.5 times
the normal flow rate is suitable. Reverse the flow
direction every 30 minutes if possible. Monitor dP.
The dP equal to design criteria indicates a clean BPHE.
Alternatively, monitor pH. Constant pH value for 0.5 h
indicates a clean BPHE. Then empty the BPHE and
restart at point 5. The cleaning time varies, but is
estimated at 4-8 hours.
Stop
10. Flush from the lower opening for 5 minutes before
changing direction. Repeat this operation until no
more dirt is flushed out.
11. Empty the BPHE and the machine, handle the used
solution properly.
12. Flush the BPHE with water starting from the lower
opening until pH 7.
13. To pickle and passivate steel use 2% phosphoric acid at
50°C (120°F) for 4-6 h.
14. Flush the BPHE with water starting from the lower
opening until pH of 7 is reached.
Useful Information on CIP (Clean In Place)
CIP Fluids and Pumps
CIP Fluids
Mineral/Organic Acids
Mineral acids have a strong ability to dissolve scale. They
include hydrochloric acid, sulfamic acid, nitric acid,
phosphoric acid and sulfuric acid.
Under certain conditions, hydrochloric acid corrodes
stainless steel, and nitric acid corrodes copper just like
products containing ammonia. This is why corrosion
inhibitors can be necessary.
All mineral acids are extremely hazardous. Organic acids
are much weaker than mineral acids, both regarding scale
dissolving ability and ability to corrode the base material
of the BPHE. This makes these acids more useful when
attempting to clean the BPHE, as they are less dangerous.
They include formic, acetic and citric acid among others.
Phosphoric Acid
Phosphoric acid does not remove iron oxide scale as
effectively as HCl, but is preferred for cleaning stainless
steels. Begin with a weak acid such as 5% phosphoric acid
or 5% oxalic acid if the BPHE is frequently cleaned. To
pickle and passivate steel, use 2% phosphoric acid at 50°C
(120°F) for 4-6 h.
Formic Acid
Formic acid alone is unable to remove iron oxide, which is
why it is used as a mixture with citric acid or HCl. Formic
acid can be used on stainless steels, as it is relatively
inexpensive and can be disposed of by incineration.
Acetic Acid
Acetic acid dissolves lime scale, but does not remove iron
oxide deposits. Since it is weaker than formic acid, it is
preferred where long contact times are necessary.
Citric Acid
Mild iron contamination can be removed by using a
mixture of 1% each of citric acid and HNO
3
. For more
persistent contaminations, stronger solutions must be
used.
