Formation improvement
1. Reduce headbox consistency if drainage capacity of forming table permits. 2. If other aspects of paper quality allow it: (a) change furnish to one of shorter fibers. — for coating rawstock or offset bond use more hardwood. — for groundwood papers, lower the groundwood freeness and/or increase amount of groundwood. (b) where appropriate, refine […]
Stock temperature varying
Stock temperature varying in headbox of paper machine 1. Check that primary temperature control is at source instead of at each machine. 2. Control fresh water addition and keep it to a minimum. 3. Make periodic (once yearly) heat balances around machines so that system is fully understood. 4. Ensure that furnish supply is steady. […]
Drainage varying
1. Need to maintain uniform stock temperature. — increasing temperature of stock improves drainage. — higher stock temperatures can adversely affect other properties. 2. Check system for surfactants and foaming. (See Foam control.) — surfactants can improve water removal rate but excess will create its own stable foam. — entrained air greatly reduces drainage rate. […]
Crushing, dandy roll
1. Use more long fiber (reduce refining). 2. Check for puddling ahead of dandy and reduce the excess water. 3. Clean the dandy. 4. Ensure that dandy is: (a) correctly positioned with regard to flatboxes. (b) correctly set with regard to forming fabric (about a 2.5 cm impression as seen from below). (c) driven slightly […]
Crush
1. Maintain uniform stock freeness. — tendency to crush increases as freeness decreases. — reduce refining or change furnish to increase freeness. See Freeness varying. 2. Check couch roll for crown and wear. — couch should be in good operating condition and evenly loaded across the machine. — proper couch vacuum must be maintained. 3. […]
Couch vacuum varying
1. First, it must be determined whether the source vacuum or sheet resistance is changing. 2. Check vacuum pumps and seal water, and check for slipping belts. 3. Check that consistency of mixed stock is steady. 4. Examine the basis weight profile. — is it steady with time? 5. Check total head in headbox for […]
Breaks, wet end
1. Breaks may be due to one or more of the following: — low wet web strength. — low solids off couch. — debris or slivers in stock. — lumps. — slime. — water drops — stock quality varying. — stress/strain variations in web. — wet-end chemistry varying. — temperature or pressure variations. — defective […]