Herrmidifier Load Calculator User Manual
Page 7
L o a d C a l c u l a t i o n G u i d e
L o a d C a l c u l a t i o n G u i d e
7
w w w. h e r r m i d i f i e r- h v a c . c o m
“Dry Air” And Hygroscopic Materials
HYGROSCOPIC materials (those able to take on or give
up moisture) are particularly sensitive to humidity changes
in their environment. Materials so classified would include
wood and wood products, paper and paper products, tex-
tiles, leather, ceramics, food and a long list of others.
These materials respond to their environment by taking on or
giving up moisture, thereby changing their REGAIN. When
these materials finally reach a balance, where they are sta-
ble and no longer take on or give off moisture, they are said
to have reached their EQUILIBRIUM MOISTURE CONTENT
(EMC).
When a hygroscopic material is stabilized at is EMC for a
particular temperature and R.H., there is little effect on the
material. The problems begin when the R.H. begins to drop
and the air pulls moisture from the material, upsetting its
EMC. When the material loses moisture it will shrink, warp,
crack, check, become thirsty for solvents, etc. This causes
problems not only with the material, but also with the ma-
chinery, finishing processes, coatings and so on. Weight and
texture are also affected.
When the EMC is upset to the point of damaging a prod-
uct (cracking, splitting, warping) and rendering it unsaleable,
economic loss results. This includes the loss of any and all
energy required to make that product, (from the raw mate-
rial refining to the finished product) if the product must be
scrapped, the additional energy input and labor expense
if the product is reworked, down time when machinery is
jammed or damaged and higher per piece costs if machin-
ery must be run slower than normal to prevent electrostatic
buildup. For example, one woodworking plant reported sav-
ings of $900 a week after introducing controlled humidity to
the plant. One investment castings company reported sav-
ings of $4,800 per week and the textile industry was even
more dramatic with $6,700 per week! These savings are re-
alized from better product workability, faster machine opera-
tion and production of less non-saleable units. Following is
a charge listing the Regain for several materials, after which
we shall take a look at some industries in depth.
Industry Materials
Relative Humidity %
10
20
30
40
50
60
70
80
90
Baking:
Crackers
2.1
2.8
3.3
3.9
5.0
6.5
8.3
10.9
14.9
Flour
2.6
4.1
5.3
6.5
8.0
9.9
12.4
15.4
19.1
White Bread
0.5
1.7
3.1
4.5
6.2
8.5
11.1
14.5
19.0
Leather:
Sole Oak, Tanned
5.0
8.5
11.2
13.6
16.0
18.3
20.6
24.0
29.2
Printing:
Paper-Com. Ledger - 75% Rag., 1% Ash
3.2
4.2
5.0
5.6
6.2
6.9
8.1
10.3
13.9
Paper-M.F. Newsprint - 24% Ash
2.1
3.2
4.0
4.7
5.3
6.1
7.2
8.7
10.6
Paper-White Bond Rag - 1% Ash
2.4
3.7
4.7
5.5
6.5
7.5
8.8
10.8
13.2
Paper-Writing - 3% Ash
3.0
4.2
5.2
6.2
7.2
8.3
9.9
11.9
14.2
Textile:
Cotton - Absorbent
4.8
9.0
12.5
15.7
18.5
20.8
22.8
24.3
25.8
Cotton - American-cloth
2.6
3.7
4.4
5.2
5.9
6.8
8.1
10.0
14.3
Cotton - Sea Isle-roving
2.5
3.7
4.6
5.5
6.6
7.9
9.5
11.5
14.1
Hemp - Manila & Sisal
2.7
4.7
6.0
7.2
8.5
9.9
11.6
13.6
15.7
Jute - Average grade
3.1
5.2
6.9
8.5
10.2
12.2
14.4
17.1
20.2
Linen - Dry Spun - yarn
3.6
5.4
6.5
7.3
8.1
8.9
9.8
11.2
13.8
Rayon - Cellulose - Acetate-fiber
0.8
1.1
1.4
1.9
2.4
3.0
3.6
4.3
5.3
Rayon - Cupromonium - Average Skein
4.0
5.7
6.8
7.9
9.2
10.8
12.4
14.2
16.0
Rayon - Vicose Nitrocel
4.0
5.7
6.8
7.9
9.2
10.8
12.4
14.2
16.0
Silk - Raw Cheyennes - Skein
3.2
5.5
6.9
8.0
8.9
10.2
11.9
14.3
18.8
Wool - Australian - Marino - Skein
4.7
7.0
8.9
10.8
12.8
14.9
17.2
19.9
23.4
Cigarette
5.4
8.6
11.0
13.3
16.0
19.5
25.0
33.5
50.0
Wood:
Timber - Average
3.0
404
5.9
7.6
9.3
11.3
14.0
17.5
22.0
Glue - Hide
3.4
4.8
5.8
6.6
7.6
9.0
10.7
11.8
12.5
Misc.:
Charcoal - Steam Activated
7.1
14.3
22.8
26.2
28.3
29.2
30.0
31.1
32.7
Gelatin
0.7
1.6
2.8
3.8
4.9
6.1
7.6
9.3
11.4
Silica Gel
5.7
9.8
12.7
15.2
17.2
18.8
20.2
21.5
22.6
Soap
1.9
3.8
5.7
7.6
10.0
12.9
16.1
19.8
23.8
Starch
2.2
3.8
5.2
6.4
7.4
8.3
9.2
10.6
12.7
Table 1-C
Hygroscopic materials lose moisture to dry air... pick up moisture from humidified air. This can materially affect your profit!
REGAIN OF HYGROSCOPIC MATERIALS
Moisture Content expressed in Percent of Dry Weight of the Substance at Various Relative Humidities - Temperature 75 °F