Herrmidifier Load Calculator User Manual

Page 9

L o a d C a l c u l a t i o n G u i d e

w w w. h e r r m i d i f i e r- h v a c . c o m

This brittleness contributes to cracking when the paper or

cardboard is folded, stretched or deformed. Weight and

strength are also reduced by this loss of moisture. Glues

sometimes will not hold, (for the same reasons as discussed

in woodworking) and printing of cardboard boxes dulls or

misregisters.

The recommended Regain of cardboard is 5% to 7%. This

corresponds to the EMC with air in the range of 40%-50%

R.H., depending on the composition of the paper. (Refer to

Table I -C.) Maintaining a proper level of R.H. will result in

less scrap, less rejects and increased production efficiency

Printing And Humidification

The problems suffered in the printing industry are basically

the same as those found in the paper products industries.

The specific problems of the printing industry would include:

brittle paper, curling edges, smeared ink and electrostatic at-

traction between papers and rolls. These problems are, once

again, caused by dry air pulling moisture from the fibers in

the paper.

Paper curling is caused because, as in paper products, mois-

ture loss causes uneven shrinkage of the paper and causes

it to curl with the grain. This leads to difficult handling and

web breakage as paper is fed through the press.

An additional problem encountered in the printing industry

is that of electrostatic charge accumulation. As paper is un-

wound off a roll, or papers are shuffled against each other,

they build up electrostatic charges which cause attraction

between sheets and rolls. The result is to cause the pa-

per unwinding off a roll to pull taut. This also occurs as the

charged paper is attracted to the rollers in the press. These

attractions put undue stress on the paper and, since paper

under these conditions would be dry and brittle, web break-

age, misregistration of colors, smeared ink and folding-jog-

ging problems result. These problems are best eliminated by

maintaining a R.H. above 45%.

The recommended level of R.H. needed in the printing indus-

try is roughly the same as that needed for paper products,

again depending on the composition of the paper. Newsprint,

which is generally about 24% Ash, would require 50%-65%

R.H. Writing paper, generally about 3% Ash, requires 40%-

50% R.H. (Refer to Table 1 -C.)

Textiles And Humidification

Humidification is vital to the textile industry, both for mate-

rial value and operation efficiency. When the R.H. is too low,

the fibers become brittle and will break causing shutdown of

machinery and excessive “fly” in the air.

Huge electrostatic charges can be built up as textiles are

spun and wound. These charges also slow down equipment.

Losses from production problems caused, by dry air can

amount to more than $7,000 per week!

There are also economic reasons to humidify in the textile

industry. The fibers used in textiles are hygroscopic and as

such can increase or decrease in weight as they take on or

give up moisture. For example, a cotton yarn shipment of

1,000 pounds that is a 2% Regain will contain 20 pounds of

water. Another shipment at 8% Regain contains 80 pounds

of water. Both shipments weigh 1,000 pounds, including the

water, but the one with 2% Regain has 60 more pounds of

cotton. If the selling price of this cotton is $.40 per pound

it costs the manufacturer of the 2% Regain yarn 60 x $.40

= $24.00 to provide cotton in place of water to match the

weight of his competitor’s shipment. You can see where sell-

ing a hygroscopic material by weight at less than the proper

Regain not only is detrimental to the material but also eco-

nomically unsound.

The Regain of textile fibers should be between 6%-15% de-

pending on the type of fiber and its use. This Regain cor-

responds to an EMC Regain with 50%-70% air. Care should

be taken in choosing the proper humidification system for a

textile plant, because of the dirty atmosphere in these areas.

Since humidification must be used all year round in textile

plants, steam is not always the best answer. It is best to con-

sult a humidification expert.

Food Storage, Processing And Humidification

Almost all foods are hygroscopic and will be affected by hu-

midity, or lack of it, with regards to quality, texture, freshness

and taste. Potatoes stored in special humidified and cooled

areas stay meatier and resist sprouting and spoiling for lon-

ger periods of time. Apples stored in a proper humidity con-

trolled environment will last longer in a fresh saleable state.

Meats processed in controlled humidity retain their quality

and bright moist color.

Many ripening fruits and vegetables can be enhanced by

proper humidity control. The level of R.H. in food storage and

processing areas is often high-as high as 95% R.H. while

temperature must be kept low. Because of this low tempera-

ture and high humidity the best humidification equipment for

this application is usually atomizing equipment, since it will

add some evaporative cooling. (As we shall see later

on.) For the proper humidification level of R.H. needed for a

particular food, consult Table 1 -D.