Deposit control

1. Check for slime build-up in the stock system and treat with a biocide.

2. It may be beneficial to try a different biocide treatment after complete boil-out.

3. Check condition of untreated water.

4. Eliminate “dead” sections of pipe.

5. Eliminate all bypasses that are not essential.

6. Design essential bypasses with a minimum “dead” area.

7. Anionic trash (detrimental dissolved substances coming from many sources in paper machine or approach systems) can collect in system or machine clothing.

Sources include:
— fresh water – (humic acids, biocides, surfactants).
— pulps – (residual lignin compounds, hemicelluloses, fatty and rosin acids, latex, starch, and biocides).
— fillers – (dispersing agents, biocides).
— additives – (starch, CMC, organic acids, dyes, biocides, dispersing agents, wet and dry strength agents, retention aids, etc.).

8. Contamination from pitch, slime, etc.
— ensure correct furnish for system hydraulics, piping, etc.
— check for correct pipe size and velocities.
— avoid long horizontal pipe runs that are bound to collect fines and fillers.
— eliminate any dead ends in piping system.
— avoid excessive air entrainment in system.
— check condition and cleanliness of dryer ropes as potential source of deposits or lumps
— maintain uniform temperature and PH.

Note: Pitch and slime usually accumulate gradually throughout the stock system where they cling to surfaces of pipes, chests, etc. Being somewhat sticky, fibers, fillers, pitch and other materials in the system are often found along with the biological or pitch build-up. Over time, the build-up reaches a condition where it has more cohesive (self-bonding) strength than adhesion to the surfaces to which it is attached so it sloughs off and gets distributed throughout the entire stock system. The proper approach is to have a sound, ongoing control program in place to prevent excess accumulation anywhere in the system. Boil-outs or other localized environmental changes, e.g., temperature or PH shocks, can loosen scale, pitch and slime and precipitate an avalanche of breaks, holes or other defects.