The most commonly used containers for pulp are the five-gallon can, the No. 10 and the No. 1 can.
The usual method of filling 5–gal. cans is to draw the pulp from the finishing machine by means of a large, heavy wall, single line hose filling one can at a time. Some packers use a manifold by which five cans can be filled at once. This requires a lot of valves and enamel lined pipe fittings, and unless the operator is very expert the manifold will not do the work any faster than a single line hose.
Square Can and Round Can
The square 5–gal. can is preferred by nearly all packers to the round can. The round can is hard to handle, hard to stack, and is very wasteful of space wherever it is stacked. The square can is to be preferred in every way.
Testing for Leaks
When new cans are being used it shouldn’t be taken for granted that they are absolutely free from leaks, as it is sometimes found that a large percentage of a car of cans will run bad, and the packer should test representative samples from the car as soon as it is received, so that he can reject it and secure other cans if the car doesn’t test up right. The best way to do this testing is with a small tank of water, a one-eighth inch air line, giving about four pounds pressure, and a can tester. A simple kind of can tester can be easily constructed in any blacksmith shop, and merely consists of an iron brace to fit around the can and which can be quickly tightened over the can and released, and a soft rubber semi-circle to fit tightly into the cap hole and which is gripped at the top and held in place by one side of the brace. The one-eighth inch brass air pipe passes through the center of the rubber semi-circle and into the can. As soon as the can is tightly clamped and the cap hole sealed by the rubber, the air is turned on and the can is immersed in the water. The leaks show up very quickly under a four-pound pressure, and a dozen cans can be tested in as many minutes.
Washing and Steaming
New cans, as well as old ones, should be thoroughly washed and steamed before filling. There is often a fine, light colored dust in new cans which a good strong spray of water properly directed into the inverted cans will remove. Through the same pipe which directs the spray of water into the cans, the cans can be steamed by means of a simple arrangement of valves on the steam and water pipes. A washing and steaming rack can easily be fitted up which will wash and steam a half dozen cans at once. A single stream of water entering the cap hole of the inverted can is not sufficient to clean it. The pipe which enters the cap hole should be capped, and about three holes drilled into this cap at a slight slant so that the upward spray of water will strike three different spots in the bottom of the inverted can, and make the washing thorough.
If the average packer could see just how little of the inside surface of his 5–gal. cans is actually washed, he would be surprised. About fifteen seconds is sufficient time to spray the inside of the cans, and then the water valve can be closed and the steam valve turned on. The steam should be kept on for a full minute and kept on strong. The idea is not merely to heat the can but to sterilize it, at least to some degree, before the pulp is admitted. The average employee steaming 5–gal. cans leaves the steam on ten seconds at the most, and often not more than three seconds. Such a short steaming does very little good. The space of time between the steaming and filling should be just as short as possible. The employees should not be permitted to keep a half dozen cans steamed ahead all the time so that they are cold by the time the pulp enters them.