STEEL CHAIN FOR HOT-DIP GALVANIZING
BY THOMAS LANGILL, Ph.D.
INTRODUCTION
determine the reaction between steel and the
The purpose of the American Galvanizers
Association’s steel chain study was to determine
the type of chain that will provide the best
performance for overhead lifting use in a
galvanizing facility. The test included load testing
of steel chains at ambient and elevated
temperatures (850 F/454 C). Prior to conducting
the load testing, the different types of chain were
exposed to the chemical cleaning solutions in one
test or the molten zinc of the galvanizing process
in a second test. A load weight was calculated
from these preliminary tests and was verified by
using this weight through the entire galvanizing
process in a verification test. The chain study was
divided into four separate phases to separate the
effects of the process variables on chain
performance in a galvanizing operation.
The chain study evolved after discussions with
two chain manufacturers about the AGA draft on
Galvanizing Guidelines for Chains in Overhead
Lifting. The chain manufacturers stated that the
information cited in the draft from the St. Joe
Mineral Study1 on chains is outdated and should
be updated. The report from St Joe also exposed
the test chains to only the zinc environment and
did not use the acid environment. The chain
manufacturers claim that the steel used in the St.
Joe study was different from the steel they use
today in manufacturing chain. In the St. Joe study,
carbon, alloy, stainless steel, and Monel chains
were immersed in molten zinc for several weeks to
molten zinc. The carbon steel chains had no
significant deteriation when exposed to the molten
zinc. The alloy chains experienced significant
reduction in chain diameter due to the molten zinc
reaction with the higher silicon content of the
alloy steel. Monel and stainless steel chains were
also significantly affected by the immersion in the
molten zinc and did not last very long. Besides
the outdated data on chain reactions to zinc,
another problem with the study by St. Joe’s is the
lack of data for a working load limit for chains
used in a galvanizing environment. Although the
stainless steel chain did not perform well in the St
Joe’s test, this chain has been used very
successfully by some galvanizers. Another study
on chain usage was performed by Valmont
Industries2 in 1985 and the results of this test
indicated that hardness of the chain was important
with regard to chain life in the galvanizing
operation. With the results of these two previous
November 2004
Protecting Steel for Generations
1
tests and with the chain manufacturers support, a
new chain study was developed to update the
information and to determine the correct working
load limit for chains exposed to the galvanizing
process.
Before the chain study began, the types of chains
that would be tested were discussed. After careful
deliberation, it was decided not to test stainless
steel and Monel chain because this chain is not in
common use throughout the North American
galvanizing operations. Carbon steel and alloy
steel chains were included since carbon steel
chains are what galvanizers are most commonly
using and alloy steel chains are the chains that
OSHA recommends for overhead lifting3. Alloy
steel chains were also included to determine
whether the steel in the chain making process for
alloy chain has improved its resistance to the
molten zinc environment since the time period of
the St. Joe’s test, the early 1980s.
The types of chain tested were proof coil (grade
30), high test (grade 43), and alloy grades 63 and
100. The grade number relates to the strength
level of the chain, with the grade number
increasing as the strength increases. The sizes of
the chains were 3/8-inch, 1/2-inch, 5/8-inch, and
3/4-inch. The 1/2 and 5/8-inch chains were only
tested in Phase 1 to find out if the relationship
between the breaking strength at room temperature
and at elevated temperature are the same as the
3/8-inch and3/4-inch. The 3/4-inch size was only
available in the grade of proof coil. Two different
chain manufacturers supplied chain materials for
the test program. The two chain manufacturers
were the ones who recommended that the AGA
pursue updating the St. Joe study. Both chain
manufacturers donated all of the chain for testing
and the chain met the minimum requirements for
chain materials listed in ASTM A 413
“Specification for Carbon Steel Chains”4. The
chain manufacturers will be designated as A and
B. There were four hot-dip galvanizers associated
with this testing program. The galvanizers will be
designated as # 1, # 2, # 3, and # 4.
The following is a brief description of the four
phases of chain testing.
• Phase 1 – Chain samples were load tested at
0% chain link reduction (beginning-of-life,
BOL) and 15% chain link reduction (end-oflife, EOL) at both ambient and elevated
temperatures. The chains were reduced in
diameter by immersing the chains for specific
periods of time in sulfuric acid.
• Phase 2 – Chain samples were reduced in
diameter through the entire chemical
processes. This included the caustic, caustic
rinse, acid, acid rinse, and preflux. The
preflux was removed by immersing the chain
in the acid strip tank and then rinsing in plain
water. The chain samples were immersed in
each process, except the rinses, for 10 minutes.
Two different acids, hydrochloric and sulfuric,
were tested. Chains were load tested when the
chain link’s thinnest point reaches EOL. Load
testing was conducted at ambient temperature
and elevated temperature.
• Phase 3 – Chain samples were reduced in the
molten zinc by immersing the chains for five
minutes in the kettle and then cooling for five
minutes out of the zinc. One cycle was equal
to ten immersions in the kettle. The chains
were then sent to the strip tank (hydrochloric
acid) until all of the zinc was removed. Once
the chains were stripped, the chains were sent
back to the kettle and the cycle started again.
The chains were load tested at elevated
temperature when they reached EOL. Some
chains were load tested at ambient temperature
when the diameters reached 7% reduction to
November 2004
Protecting Steel for Generations
2
•
verify that chain wear related to reduced
strength.
Phase 4 – Chain samples transported material
through the entire process with a
predetermined
load
weight
maximum
calculated from the information from the first
three phases. The information gathered in
Phases 1-3 was used to determine a working
load limit. After completing sufficient cycles
to reduce the chain diameter to the EOL
condition, chains were load tested at elevated
temperature. This phase tested and affirmed
the correct working load weight limit that was
developed.
A testing laboratory with facilities in Peoria, IL
and Houston, TX conducted the load testing. The
Peoria testing lab conducted the ambient
temperature load testing. The Houston testing
laboratory conducted the elevated temperature
load testing. The testing laboratory specified that
the chain samples must be a minimum of five feet
in length. The main purpose for this chain length
was to allow chains to be heated sufficiently in the
furnace used in the elevated temperature load
testing. Load testing was conducted by pulling the
chain on two ends until it broke in accordance
with ASTM A 413 and ASTM A
391”Specification for Alloy Chain”5. For elevated
temperature load testing, the chain was heated in a
furnace with a thermocouple attached to the chain.
The chain was heated to 850 F/454 C and the
furnace was then removed prior to pulling the
chain until it broke. The thermocouple was used
to verify that the temperature was 850 F/454 C
when the chain was load tested. The following are
pictures of the set-ups used to perform the
breaking strength test on five-foot sections
of chain.
PHASE TESTING AND RESULTS
Phase 1
Phase 1 was conducted at Galvanizer # 1. The
chains received from Chain Manufacturers A and
B were labeled and divided into two groups. The
November 2004
Protecting Steel for Generations
3
Initial measurements were taken of the chain
samples that would be used to calculate the target
diameter. The target diameter was the calculated
diameter that takes into account the
15% reduction.
To reduce the chains to the target diameter, the
chains were immersed into sulfuric acid for
specific time durations. The chains were removed
from the acid every four hours and then rinsed for
measurements.
Chain measurements were
performed with either a micrometer or caliper
along the entire length of the exposed chain. The
diameters were recorded and compared to the
target diameter. If the chain measurement was
above the target diameter, the chain remained in
service. If the chain measurement was less than
the target diameter, the chain was immediately
removed from further testing and sent to the
testing laboratory. Visual inspections of the
chains were also performed. Visual inspections
involved looking for any excessive wear or pitting
on the chains. If any of the chains showed signs
of pitting or excessive wear on any portion of the
chain link, the chains were removed from the test.
There were four designated chains that were
selected for measurement. Each of the four chains
represented a type of chain. This was done to
avoid having to take measurements on all of the
chains each time. If there were no changes, the
measurements would occur after four hours of
exposure for the one designated chain. After
another four hours the remaining designated
chains would be removed for measurement. Once
the chain’s diameter decreased a significant
amount the measurement frequency increased.
Chain Diameter (in)
Phase 1 High Test Chain
Chain Manufacturer B
0.4
0.38
0.36
Time = 71 hours
0.34
0.32
0.3
0
20
40
60
80
100
Time (hrs)
Chain measurements were graphed to help predict
the amount of time before the chains would reach
the target diameter. A best-fit line was plotted to
help estimate when the chains would be taken out
of testing. This type of graph was used for all
three phases of testing.
Different sizes of proof coil chain from the two
chain manufacturers were also load tested at
ambient and elevated temperature for BOL. The
two additional size of proof coil chains were 1/2
and 5/8-inch.
The purpose of testing the
additional size chains was to affirm that there was
a corresponding relationship between the size of
the chains and the breaking strengths. The
following graphs show the relationship of the
chain sizes to the breaking strengths.
Proof Coil Chain
Size versus Initial Breaking Strength
Room Temperature
Breaking Strength x
1000 (lbs.)
first group of chains was tested at BOL at ambient
and elevated temperature. The second group of
chains was tested at EOL at ambient and elevated
temperature. OSHA requires that chains be
removed from service once the chain’s diameter
reaches a 14% reduction. The 15% reduction in
diameter was chosen since it represented the
worst-case scenario when chain is not removed
from service right away.
70
60
50
40
30
20
10
0
1/4
3/8
1/2
5/8
3/4
7/8
Size of Chain (in)
ASTM
Chain Manufacturer A
Chain Manufacturer B
November 2004
Protecting Steel for Generations
4
manufacturers.
Chain Manufacturer B also
normalized their proof coil chain for testing
purposes; however, normalizing is not a regular
procedure in their manufacturing of proof coil
chain. Chain Manufacturer A does not normalize
their chains.
Proof Coil Chain
Size versus Initial Breaking Strength
Elevated Temperature
50
Breaking Strength x 1000 (lbs.)
45
40
35
30
Phase 1 Results
25
20
15
10
5
0
1/4
3/8
1/2
5/8
3/4
7/8
Size of Chain (in)
ASTM
Chain Manufacturer A
Chain Manufacturer B
Both chain manufacturers had breaking strengths
above the minimum values in ASTM A 413. In
comparing the proof coil and high test chains from
the two chain manufacturers, there were some
physical and metallurgical differences. Chain
Manufacturer B had a thicker diameter than Chain
Manufacturer A for both proof coil and high test
chain. Both chain manufacturers also use different
types of steel in manufacturing their chain. The
different type of steel may be the cause for the
different breaking strengths between the two chain
Chain Type
Proof Coil – A
Proof Coil – B
High Test – A
High Test – B
Alloy 63 – B
Alloy 100 – A
The BOL chain samples were load tested at
ambient and elevated temperature. The average
reduction in breaking strength from exposure to
elevated temperature at BOL was 30%. The
breaking strengths for the chain samples are listed
in Table 1. Specification A 413 lists the breaking
strength minimum for 3/8 – inch Proof Coil chain
to be 10,600 lbs. and the breaking strength
minimum for 3/8 – inch High Test chain to be
16,200 lbs. The values tested for the chains in this
program meet these specification minimums as
seen in the initial breaking strength values at
ambient temperatures. The variation in initial
breaking strength from one manufacturer to
another is due to the type of steel used to make the
chain as well as some differences in initial chain
diameter.
Breaking Strength at Breaking Strength at
% Reduction in
Ambient
Elevated
Breaking Strength at
Temperature (lbs)
Temperature (lbs)
BOL
13226
8303
37.2
15020
11777
21.6
18409
12650
31.3
16754
12764
23.8
24126
17543
27.3
37993
19797
47.9
The EOL chain samples were immersed in the
sulfuric acid using a spreader bar. The sulfuric
acid was kept at a concentration of 12% and no
inhibitors were used. After 35 hours, the alloy
grade 100 chains began pitting. After 71 hours,
the rest of the chains had developed some pitting
on the links. Only the proof coil by Chain
Manufacturer A and the high test chains from both
chain manufacturers were able to survive until
EOL without any pits. The proof coil chains from
Chain Manufacturer A were removed after 91
hours. The high test chains from both chain
manufacturers were removed after 71 hours. The
chains that reached EOL were sent to the testing
laboratory for load testing at ambient and elevated
temperature. The chains that developed pits were
November 2004
Protecting Steel for Generations
5
not sent to the testing laboratory since pitting
causes an unknown reduction on the chain
diameter. This unknown reduction can affect the
breaking strength of the chain. In normal work
practice, once a chain begins to develop pits, the
chain should be removed from service.
The results from Phase 1 were surprising since the
original plan was to measure straight reductions in
diameter. The development of pits and weld
deterioration were both unexpected.
Some
examples of the pits and weld deterioration are
shown in the above and below photographs.
The breaking strengths at ambient and elevated
temperature for Proof Coil chain were graphed in
the following chart for 0% and 15% reduction.
The BOL and EOL points are marked on the chart.
This graph will be used to help determine the
working load limit to be used in Phase 4. Before
the present AGA chain study, elevated
temperature load testing at EOL was not
performed.
Proof Coil - Chain Manufacturer A
14000
Breaking Strength (lbs)
12000
10000
8000
6000
4000
2000 BOL
EOL
0
0
5
10
15
20
% Reduction in Diameter
Room Temperature
Elevated Temperature
Phase 2
November 2004
Protecting Steel for Generations
6
Phase 2 was divided into hydrochloric and sulfuric
acid pickling since galvanizers use both types of
acids in their cleaning processes. Galvanizer # 2
uses hydrochloric acid and Galvanizer # 1 uses
sulfuric acid.
Chains were properly identified and initial
measurements were taken to calculate the target
diameter that represents the EOL condition. The
chains were placed on a spreader bar without a
load with four chains at the end. The four chains
represented each of the different types of chains.
The chains were then immersed into the caustic,
caustic rinse, acid, acid rinse, preflux, stripping
tank, and finally rinsed off. This was considered
to be one cycle. The chains were immersed in the
chemicals for a time of 10 minutes per tank except
for the rinse tanks. Chain measurements were
taken after the chains had been cycled through the
cleaning solutions four times. The same chain
measurement methodology used in Phase 1 was
applied to this phase. The measured chain
diameters were compared to the target diameter
and the same procedure for removal of the chains
in Phase 1 was used. Once the chains reached the
target diameter and were removed, the chains were
sent to the testing laboratory to be load tested at
ambient temperature.
The Phase 2 testing plan was revised due to the
rapid reduction of the chain diameter when
immersed in the sulfuric acid during Phase 1. The
purpose of Phase 1 was to reduce the chains
diameter by using sulfuric acid. During Phase 1,
several types of chain had severe pitting and weld
deterioration before the EOL. Phase 2 testing was
changed to include both sulfuric, as originally
planned, and hydrochloric, to get some non-pitted
results for elevated temperature testing. Since the
desired results are for the chains to be load tested
at elevated temperature, the testing plan was
revised so that all hydrochloric acid samples were
load tested at elevated temperature.
Hydrochloric Acid Testing
Galvanizer # 2 Operating Conditions
Caustic Bath
Not being used
Pickling Bath
Hydrochloric
Acid
concentration of 12%
No inhibitor used
No separate strip tank
Low 20 Baumé
Zinc Chloride 17.8
Ammonium Chloride 21.44
Preflux
The chains completed 142 cycles before all of the
chains were removed from testing. Several of the
chains had started to develop pits earlier but were
not taken out of testing. In actual practice, chains
should be taken out of service and not be used
once pitting occurs. The pits on these chains were
very small and concentrated around the weld. The
types of chains that developed pits were high test
and alloy from both chain manufacturers and the
proof coil chains from Chain Manufacturer B.
The proof coil chain from Chain Manufacturer A
did not develop pits and was tested until the target
diameter was reached. Chain Manufacturer A’s
proof coil sample was the only type of chain load
tested at elevated temperature. Testing the pitted
chains would not have provided the true breaking
strength at elevated temperature since pitting
causes an unknown reduction in chain strength.
The chemical environment is very harsh on chain
performance due to the attack on steel from all of
the chemicals.
Sulfuric Acid Testing
Galvanizer # 1 Operating Conditions
Caustic
Concentration of 10%
Pickling
Sulfuric Acid concentration
12%
No inhibitors are used
Preflux
Concentration of 16 Baumé
The sulfuric acid testing was stopped midway
through testing since the hydrochloric acid
samples behaved similar to the Phase 1 samples.
These sulfuric acid samples had only completed
33 cycles when testing was stopped. There was no
sign of pitting on any of the chains. After
evaluating the results from the hydrochloric acid
testing, it was determined that proceeding with the
sulfuric acid tests was unnecessary. Continuing
November 2004
Protecting Steel for Generations
7
with the sulfuric acid tests would not have
produced any useful information since the chains
had previously shown that the pickling acids were
aggressive.
There are two conclusions from Phases 1 and 2.
1. When chains are only used in the chemical
cleaning solutions, pits may develop. Pits give an
unknown reduction of the chain breaking strength.
The photo shows a high test chain with a pit that
penetrates the steel to an unknown depth changing
the breaking strength of this link.
2. During a meeting with a chain manufacturer
about the pitting of the alloy chains, the hidden
potential development of hydrogen embrittlement
during the lifting of steel parts was discussed. The
chain manufacturer did not recommend alloy
chains for high temperature use especially when
going through acid prior to the galvanizing kettle.
Alloy chains should not be used since there is a
problem
with
determining
where
the
embrittlement may occur.
The potential
development of hydrogen embrittlement on alloy
chains creates an unknown factor of when and
where the chains would actually break. This
unknown makes this type of chain unsafe for use
in lifting steel loads.
This photomicrograph of a Grade 100 alloy chain
shows the very thin cracks that can be the
initiation sites for chain link failure under stress
conditions. These thin cracks are caused by the
hydrogen embrittlement during pickling of the
higher strength alloy steel chains.
Phase 3
Phase 3 was conducted at Galvanizer # 2.
Galvanizer # 2 uses special high grade zinc with
nickel additions. The operating temperature of the
galvanizing kettle is 830 F. The chains were
divided into two groups for different target
diameters. Two target diameters were chosen to
investigate the chain sample. The first target
diameter was when the chain was reduced by 7%
in diameter. The 7% reduction samples were
removed to see if there was any significant effect
on the breaking strength of the chains at this point
in testing. The second target diameter was when
the chain was reduced by 15% in diameter.
The chains were hung on the bottom of the basket
and immersed into the molten zinc ten times, each
time consisted of five minutes in the zinc and then
five minutes out of the zinc. The chains were then
stripped in hydrochloric acid and rinsed. This was
equal to one cycle. Chains were dipped five times
in the morning and five times during the lunch
period. One cycle was completed each day. The
average time for stripping the chains was two
hours. The chains were measured using the same
methodology used in the previous phases and the
diameters were compared to the target diameters.
The same procedure for removal of the chains was
used as was done in Phase 1 and 2. Chains were
removed based on the reduction in chain diameter.
The first set of chains was removed when the
chain diameter was approximately 7% reduced
from its original thickness. These chains were
sent to the testing laboratory to be load tested at
ambient temperature. The breaking strengths at
this stage were not that different from the original
breaking strengths of the chains. This indicates
that the wear has some effect on the mechanical
strength but the molten zinc environment is not a
November 2004
Protecting Steel for Generations
8
completely destructive environment. The zinc
coating on the surface of the chains is giving some
protection from acid etching and, therefore,
prolongs the life of the chain materials. The
remaining chains were cycled until they reached
EOL. These chains were cycled in the zinc until
their EOL condition without developing any pits.
There was one High Test sample from chain
manufacturer A that did have some minor pitting,
however this was the only sample from the group
of High Test chains. The chains were then sent to
the testing laboratory to be load tested at elevated
temperature since exposure to elevated
temperature is when the chains would be the
weakest. The breaking strengths of the chains at
elevated temperature at EOL are listed in the
following table along with the breaking strength at
elevated temperatures and BOL condition. All of
the breaking strengths were reduced since the
Chain Type
Proof Coil – A
Proof Coil – B
High Test – A
High Test – B
Alloy 63 – B
Alloy 100 – A
diameter is reduced. This is normal behavior for
chains.
The breaking strengths at elevated temperature
and EOL were used to calculate the weight limit
that would be used for Phase 4. These breaking
strengths are at the chains weakest points. If chain
is loaded above these breaking strengths, the chain
will break. Therefore, a safety factor from the
breaking strength values needs to be taken into
account. Using the breaking strengths at EOL is
conservative but the calculated weights could be
verified in Phase 4. If using the chains at the
calculated weights through the entire galvanizing
process does not have any effect on the chain’s
strength, then the working load limit can be
calculated from the elevated temperature breaking
strengths at BOL.
Breaking Strength at
Elevated Temperature at
0% reduction (lbs)
8303
12764
12650
11777
17543
19797
Conclusions of Phases 1-3
Phase 1
The purpose of Phase 1 was to determine the EOL
breaking strength of the chains at ambient and
elevated temperature. The chains reached EOL by
being immersed in sulfuric acid. During testing,
the sulfuric acid was very aggressive to the chains.
As a result of the aggressive nature of the acid
attack on the steel in the chain, the chain samples
developed pits near the weld areas on each link.
These pits reduced the diameter of the chain an
unknown amount so the chain samples could not
be tested at EOL to give the reduction in breaking
strength that goes along with the reduction in
diameter. The results from Phase 1 were
surprising.
Breaking Strength at
Elevated Temperature at
15% reduction (lbs)
6787
11047
10332
9977
13853
15720
The reduction in the chain diameter did not occur
in a straightforward fashion. The pitted chains
were not load tested since testing these chains
would not provide any relevant information.
Pitting is another qualification for removal of
chains while in service. Any signs on the chains
of pitting or weld deterioration should be an
instant removal of the chain containing such a
defect from service as a lifting aid. The samples
that were reduced by 15% and had no visible signs
of pitting were load tested at room and elevated
temperature.
The table on the next page
summarizes the results from Phase 1 for the
reduction in breaking strength from initial receipt
of chains through EOL after exposure to sulfuric
acid. The diameter reductions were varied due to
the difference in sulfuric acid attack on the steel in
November 2004
Protecting Steel for Generations
9
the chain. These results did not provide a
complete story on the difference between various
grades of steel chain because of the pitting that
was found with some of the chain samples. The
plans for the next two phases of this chain study
were adjusted to give more information about the
breaking strength change with changing chain
diameter, especially at elevated temperatures.
Phase 2
This phase exposed the chains to the complete set
of steel cleaning solutions normally used in a hotdip galvanizing operation. The chains were
exposed to the caustic, caustic rinse, acid, acid
rinse, preflux solution, and then stripped in the
acid and finally rinsed and dried.
Both
hydrochloric and sulfuric acid baths were used for
this phase. Some of the chains developed pits
during the hydrochloric acid testing at 98 cycles.
From both Phase 1 and 2 results in regards to
pitting, it was concluded that the cleaning
solutions by themselves were very aggressive to
chains. When the chains were only used in the
cleaning solutions, rapid chain wear and pitting
can occur. Phase 2 was terminated when the pits
became evident on a number of chain samples in
the hydrochloric acid plant. These pits developed
well before the chains could reach the EOL
condition. There was no attempt to test these
samples for their breaking strength since the
exposure to the cleaning solutions had caused
unusual wear and pitting. Other type of chain,
such as stainless steel or monel, should be used
when chain is employed in the cleaning
solutions alone.
Phase 1 Chain Testing Results.
BOL
EOL
Breaking
Breaking
Strength at
Strength at
Room
Elevated
Temperature Temperature
(lbs)
(lbs)
Chain
Type
Breaking
Strength at
Room
Temperature
(lbs)
Breaking
Strength at
Elevated
Temperature
(lbs)
Time in
Acid
Proof Coil
A – 3/8inch
Proof Coil
B – 3/8inch
Proof Coil
A – ¾-inch
Proof Coil
B – ¾-inch
High Test
A – 3/8inch
High Test
B – 3/8inch
Alloy
Grade 63 –
B
13226
8303
91 hours
11166
7049
14
16754
12764
NA
NA
25
41293
30400
NA
NA
8
61254
46267
NA
NA
9
18409
12650
71 hours –
weld
deterioration
111 hours –
pitted
53 hours pitted
71 hours
5650
4630
16
15020
11777
71 hours
12587
10190
13
24126
17420
71 hours –
pitted
NA
NA
7
November 2004
Protecting Steel for Generations
Percent
Reduction
in
Diameter
10
3/8-inch
Alloy
Grade 100
– A 3/8inch
37993
19797
35 hours –
pitted
Phase 3
In Phase 3 the purpose of testing the chains in the
zinc was to determine whether the zinc and high
temperature had any effect on the breaking
strengths of the chains. This test is similar to the
environment of the chains during the previous
tests performed by St. Joe’s1 and by Valmont2 in
testing different chain materials in the 1970’s and
1980’s. All of the chains, Proof Coil, High Test
and the Alloy Chains Grade 63 and 100, survived
until the EOL condition. There were no visible
signs of pitting or weld deterioration on the
chains. A random sample at 7% reduction was
tested for all of the chains to verify that there was
not a significant drop in the breaking strengths.
The EOL samples were load tested at elevated
temperature. The average reduction in chain
Type of Chain
Proof Coil – A
3/8-inch
Proof Coil- B
3/8-inch
Proof Coil – A
¾-inch
High Test – A
3/8-inch
High Test – B
3/8-inch
Alloy Grade 63 – B
3/8-inch
Alloy Grade 100 – A
3/8-inch
NA
NA
diameter was just below 15%. If the elevated
temperature test data is compared to the elevated
temperature test data from Phase 1 at the BOL, the
decrease in strength was less than 30% for the
carbon steel chains. The alloy chains experienced
a greater reduction in breaking strength than the
carbon steel chains. The factor of 30% reduction
in strength will be a conservative approach to
calculating a reduced load limit when working
with carbon chains in the galvanizing operations.
The elevated temperature strength values from
Phase 3 represent the EOL strength of the chains.
As long as the Working Load Limit does not
approach these strength values, the chains will be
safe for lifting steel parts in the galvanizing
operation.
Breaking Strength at
Elevated Temperature (lbs)
6787
Percent Reduction in
Diameter
14
9977
14.4
28483
7
10332
14.4
11047
14.4
13853
16
15720
12.4
Development and Set-up of Phase 4
Before Phase 4 began, an analysis of the
information gathered in Phases 1-3 was
performed. The chain manufacturers reviewed the
data from the first three phases and offered
comments.
Chain Manufacturer A voiced
15
concerns about the low breaking strengths at
elevated temperature and the pitting of the alloy
chain in Phases 1 and 2. The recommendation
from Chain Manufacturer A was that alloy chains
should not be allowed for use in galvanizing
chemical and elevated temperature environments
due to the potential development of
November 2004
Protecting Steel for Generations
11
hydrogen embrittlement during the exposure to
acid solutions and the chain’s high tensile
strength. Hydrogen embrittlement could occur
when the chain was loaded and therefore would
not allow for safe chain usage. For Phase 4 testing,
only the 3/8-inch proof coil and high test chains
that had lower tensile strengths and were not
susceptible to hydrogen embrittlement were used
from both chain manufacturers.
temperature were used for the carbon steel chains.
Working load limits are normally calculated by
taking ¼ of the initial breaking strength at room
temperature. For Phase 4, the working load limit
was calculated by taking ¼ of the final breaking
strength at elevated temperature. This value was
further reduced another 20% to take into account
the estimating of weights by the galvanizer. The
weight loads calculated for Phase 4 are in this
table.
In determining the working load limit to use for
Phase 4, the EOL breaking strengths at elevated
Chain Manufacturer
Type
A
B
A
B
Proof Coil 3/8-inch
Proof Coil 3/8-inch
High Test 3/8-inch
High Test 3/8-inch
These values were very conservative since
working load limits take the BOL breaking
strengths and then de-rate, not the EOL breaking
strengths.
Two galvanizers, Galvanizer # 3 who uses sulfuric
acid and Galvanizer # 4 who uses hydrochloric
acid for pickling, tested chains in Phase 4. The
chains were used as part of the production process.
For both galvanizers, the chains would only be
used in straight lengths.
The sulfuric acid
galvanizer used 10 feet samples and attached a
ring to the end of it. The hydrochloric acid
galvanizer used 20 feet samples. Even though the
calculated weight loads from the above table were
different, for simplification in production, all of
the chain samples were used with the assumption
that 1400 lbs. is the most weight that can be put on
the chain. This is a conservative value for the
high test chains, but the use of one weight made
the chains simpler to use through production.
Sulfuric Acid
Galvanizer # 3 used the following operating
conditions for their cleaning tanks and galvanizing
kettle.
Caustic Bath
10% concentration
Single Leg Weight
(lbs.)
1400
2000
2050
2200
Pickling Bath
Preflux
Galvanizing Kettle
Sulfuric acid at 10-12%
concentration
Rodine 95 inhibitor used
Temperature = 150 F
14-16 Baumé
High Grade Zinc with nickel
and brightener bar additions
Temperature – 830 F
The total number of chains put into testing was 34.
The high number of samples was due to taking
random samples out during testing to verify that
the addition of using a weight did not have an
effect on the performance of the chain. Some of
the chains missed their target diameter and were
not taken out for analysis at the early reduction of
7%. All of the chains were load tested at elevated
temperature regardless of their percent reduction.
The percent reduction of the chains varied.
Hydrochloric Acid
The galvanizer for this facility needed to use 20
feet pieces of chain in order to use it through
production. Since 10 feet pieces were originally
sent, the chain manufacturers had to be contacted
to send some more chain at the longer length. The
amount of chains tested in this facility was
considerably less than the sulfuric plant due to
November 2004
Protecting Steel for Generations
12
receiving chains in a longer length.
The
hydrochloric acid galvanizer only tested 10 chains.
The chains were load tested at EOL at elevated
temperature.
Galvanizer # 4 used the following operating
conditions.
Caustic Bath
Pickling Bath
Preflux
Galvanizing Kettle
10% Concentration
Hydrochloric acid at 3 to
15 % concentration
Inhibitors and Foaming
Agents
> 50 F
12 to 13 Baume
Special High Grade Zinc
with bismuth, nickel,
and
brightener
bar
additions
Temperature – 830 F
Phase 4 Conclusions
Sulfuric Acid
An observation was made that high test chains
were reducing at different rates. In comparing the
two high test chains, Chain Manufacturer A’s high
test chain was reducing at a faster rate than Chain
Manufacturer B.
The reduction occurred
throughout the entire link. The proof coil chains
from the two chain manufacturers also showed
different reactions on the surface of the links. The
proof coil chain from Chain Manufacturer A
showed some lines on the surface of the links.
The proof coil chain from Chain Manufacturer B
experienced pitting over the entire link. Samples
from the proof coil and high test chains from
Chain Manufacturer A were shipped to the
manufacturer for analysis.
The chain
manufacturer reported that the lines on the proof
coil chain were actually the lines from the drawing
of the wire process when manufacturing the chain.
These lines would not have an effect on the
strength of the chain. The high test chain was
undergoing normal corrosion and there was
nothing unusual about the chain.
The majority of the chains were removed at EOL;
however, there were a few chains that were
removed early. The random removal of chains at
7% reduction did not occur, but since there were
some chains removed early, the random percent
reduction was still investigated. The importance
of load testing at the random percent reduction
was to verify that there were no problems with
using the chain with the predetermined weight
through the
entire galvanizing process. Once the chains were
removed from being tested, a final chain
measurement was taken before being shipped to
the testing lab. All of the chains were re-identified
with the numbers 1-34 and were load tested at
elevated temperature.
Chain Type
Average Percent Reduction
Proof Coil A
Proof Coil B
High Test A
High Test B
5.4
9.5
16.1
12.3
The chain sample measurements varied from 7 to
18% reduction in diameter. Proof coil samples
from Chain Manufacturer A did not reach EOL.
The safety factor that was used for the carbon steel
chains was effective. The elevated temperature
breaking strengths were well above the working
Average Breaking Strength
at Elevated Temperature
(lbs)
7564
9161
7929
8876
load limit calculated for testing purposes in
Phase 4.
Hydrochloric Acid
There were a total of 10 chains put into
production. Since there were fewer samples to
November 2004
Protecting Steel for Generations
13
test, only the EOL condition was load tested at
elevated temperature. During testing, two of the
chains were lost and a third chain was damaged
and was no longer usable. Two samples of proof
coil chain, one from Chain Manufacturer A and
the other from Chain Manufacturer B, were
missing. The third chain that was damaged was a
high test chain from Chain Manufacturer A.
reviewing the previous data and examining the
state of the chains, it was decided to remove the
chains after 160 cycles and send them to elevated
temperature testing. The results would give an
answer to the question whether the pull strength
had degraded significantly more than expected
after the 160 cycles that equated
to about 6% reduction in chain diameter. The
results of the high temperature pull testing on the
chains used in the hydrochloric acid process are
listed in next table. The High Test chain from
Chain Manufacturer B was damaged in the
production process and could not be tested after
the completion of the test cycles.
The reduction of the chain diameter did not
proceed as fast as the sulfuric acid galvanizing
facility. Testing proceeded more slowly at
Galvanizer # 4 due to his operation procedures.
Only one cycle per day was performed. This
meant that the test proceeded very slowly and
there were not many cycles per week. After
Chain Type
Average Percent Reduction
Proof Coil A
Proof Coil B
High Test A
High Test B
*Did Not Test
Phase 4 Discussion
5.0
5.2
6.4
DNT*
The verification tests performed in Phase 4 used
chains to hold actual loads of steel throughout the
hot-dip galvanizing process in both a sulfuric acid
plant and a hydrochloric acid plant. The sulfuric
acid is much more aggressive to the steel in the
chain and, therefore, the inspection and removal of
the chains used in a sulfuric plant will occur much
sooner than chains in a hydrochloric plant. The
high temperature testing of chains after being used
through the galvanizing process showed pull
strength numbers that were well above the
working load limit. This indicates that the
working load limit is a good safety limit for steel
chain use in a hot-dip galvanizing operation.
The sulfuric acid plant used the chains for about
two months so the inspection period for this chain
in a sulfuric acid plant should be every two weeks
at the very least. The best inspection practice for a
complete inspection of the chains used in the
sulfuric plant would be once a week.
Average Breaking Strength at
Elevated Temperature (lbs)
8250
12620
11595
DNT*
The hydrochloric plant used the chains for about
six months without taking them out-of-service
because the final degradation percentages were
still in the range of 6% so there was plenty more
life in these chains. Under this type of usage a full
inspection every month would be the best
inspection practice.
Both plants noticed that the chains are susceptible
to damage when dragged across the floor unloaded
or when used harshly during transfers from
pickling to galvanizing. Some care and training
may be appropriate for handling of chain that will
not induce damage that can render the chain
unusable.
Another issue that needs some attention in the
galvanizing industry is the maintaining of chain
identity throughout the plant.
There were
instances during the testing when the chains would
be “lost” in the galvanizing operations. Tags and
identifications should be maintained throughout
the plant to keep track of individual chains.
November 2004
Protecting Steel for Generations
14
PROOF COIL
Nominal Chain Size
(inch)
Minimum Breaking
Force (lbs.)
Working Load
Limit, Max
Room Temperature
(lbs.)
Working Load
Limit, Max
Elevated
Temperature
(lbs.)
3/8
1/2
5/8
3/4
10600
18000
27600
42400
2650
4500
6900
10600
1850
3150
4830
7420
HIGH TEST
Nominal Chain Size
(inch)
Minimum Breaking
Force (lbs.)
Working Load
Limit, Max
Room Temperature
(lbs.)
Working Load
Limit, Max
Elevated
Temperature
(lbs.)
3/8
1/2
5/8
3/4
16200
27600
39000
60600
4050
6900
9750
15150
2830
4830
6820
10600
Working Load Limits to be used for Lifting in
Galvanizing Operations
The working load limits to be used for lifting in
galvanizing operations is calculated by using the
breaking strengths listed in ASTM A 413. The
breaking strengths are reduced by 75% to get the
working load limit at room temperature per the
National Association of Chain Manufacturers
Standard “Welded Steel Chain Specification”6.
To get the working load limits for elevated
temperature, the values need to be further reduced
by 30%. The 30% reduction takes into account
the change in temperature when chains are used to
hold steel loads during the operation of
galvanizing at temperatures of over 800 F. The
above charts are the calculations of working load
limits for proof coil and high test chains based
upon the method described below for calculating a
working load limit for chain use in the specialized
operation used during hot-dip galvanizing
operations. As can be seen in the charts, the
working load limit is higher for high test chain
than for proof coil chain since the pull strength of
high test chain starts at a higher value from the
initial stage.
CALCULATION OF WORKING LOAD LIMITS
1. Working Load Limit at Room Temperature
- Take the specification Minimum Breaking
Force (commonly referred to as breaking
strength) and reduce by 75%.
- This calculated value is the working load
limit for chain use at room temperature
2. Working Load Limit at Elevated Temperature
- Take the specification Minimum Breaking
force and reduce by 75%. Multiply the
breaking strength by 0.25 for the working
load limit at room temperature.
- Elevated temperature reduces the breaking
strength by 30%. Multiply the calculated
value for the working load limit at room
temperature by 0.70 to obtain the working
November 2004
Protecting Steel for Generations
15
-
load limit for chain use at the elevated
temperatures of hot-dip galvanizing
(>800 F).
This calculated value is the working load
limit for hot-dip galvanizing operations.
Example calculation for working load limit at
elevated temperature for 3/8 proof coil chain
based on the breaking strength from the ASTM A
413 specification value for proof coil (Grade 30)
chain.
W.L.L. = (10,600) x .25 x .7 = 1855 lbs.
This value of working load limit can be used
throughout the life of the chain so there is no need
for plant personnel to calculate any other number
for this particular chain size and type. The chain
EOL diameter can be inspected with a GO/NO GO
gauge that is set to a specific reduction percentage
based upon the initial thickness value from ASTM
A 413 for each nominal chain size. These GO/NO
GO gauges are available from chain
manufacturers.
Chain Test Summary
The study of chain use in the hot-dip galvanizing
operations was undertaken to determine the
correct chain material appropriate for this
application. In the Code of Federal Regulations
(CFR) section 1910.184 OSHA requires that
overhead lifting be done using alloy chains for
slings. The practical experience of the galvanizing
industry and previous tests by St. Joe’s and
Valmont Industries indicated that alloy chain
would not survive the harsh environment of the
galvanizing operation. OSHA states in 1910.184
that if slings are made from other materials the
user
should
follow
the
manufacturers
recommendations. In the case of proof coil and
high test chains there were no specific
manufacturers recommendations so this study
program was initiated to determine the best
material and working parameters for chains used
in the galvanizing process.
The study was divided into four phases to separate
the variables that influence the reduction in chain
diameter during its use. Phase 1 tested the chains
in both room temperature and elevated
temperature pull tests. The chains were then
immersed in sulfuric acid to reduce the chain
diameter and accelerate the chain corrosion to
produce an EOL condition. During the immersion
in sulfuric acid most of the chains developed
pitting that caused the chains to be rejected from
the test matrix. If pits develop in the chain, then
the actual diameter of the chain at its thinnest
point is unknown since there is no way to measure
from the bottom of the pit to the other side of the
chain link. The occurrence of pitting on most of
the chains indicated that this environment, acid
use only, was not appropriate for chains in the
galvanizing operation.
Phase 2 tested the chains in both room temperature
and elevated temperature pull tests. The chains
were immersed in all of the cleaning solutions and
rinsed before chain diameter reductions were
measured. This type of environment also induced
a significant amount of pitting in the chain
materials. There were some chains from Phase 1
and from Phase 2 that experienced no pitting.
These chains were tested at elevated temperatures
after reaching the EOL condition.
The
relationship between the room temperature
breaking strength and the elevated temperature
breaking strength did not change from BOL to
EOL conditions. The reduction in breaking
strength at the galvanizing temperature (>800 F)
was an average of 30%.
Phase 3 performed the same tests as Phase 1 and 2
but used the zinc bath to reduce the diameter of
the chain to its EOL condition. The chains were
immersed in the zinc bath for a number of cycles
and then stripped before chain links were
measured. There was only one chain with any
signs of pitting in the chains during this phase.
The breaking strength change from BOL to EOL
on all of the chains tested in this phase showed a
consistent drop that was correlated to the reduced
November 2004
Protecting Steel for Generations
16
chain diameter. Since the behavior of the chains
in this zinc environment was predictable, there
was confidence that using a working load limit
based on the initial breaking strength of the chain
would allow sufficient safety factor to account for
the change in breaking strength throughout the life
of the chain. The working load limit included a
normal safety factor of 25% of the initial breaking
strength of the chain plus a further reduction of
30% to account for the use of chain at galvanizing
temperatures (>800 F).
Phase 4 was a verification of the working load
limit calculated from the previous phases. The
chains were loaded with a maximum weight of
80% of the calculated working load limit to allow
for some additional weight during lifting and
balancing of loads and to add an extra safety
factor before during the verification. The sulfuric
acid plant used the chains more than once per day
and the chains reached the EOL condition in about
two months. The hydrochloric plant used the
chains once per day and the chains were still not at
the EOL condition after almost six months of use.
The sulfuric acid plant chains were taken out of
service when the EOL was reached. The chains
were then subjected to elevated temperature pull
testing until the breaking strength was reached.
BIBLIOGRAPHY
The numbers for the breaking strength were
compared to the working load limit. The breaking
strength well exceeded the working load limit so,
even at the EOL condition; there was sufficient
safety margin for chain usage. The hydrochloric
acid plant chains were taken out of service after
160 cycles through the process that equates to
about 6% reduction in chain diameter. The chains
were then pull tested at elevated temperature. The
numbers for the breaking strength were compared
to the working load limit. The breaking strength
well exceeded the working load limit.
The rationale for the calculation of the working
load limit was developed in Phase 1, 2, and 3 and
then verified in Phase 4. Using this working load
limit in the galvanizing operations will insure that
the use of chains to lift steel loads during hot-dip
galvanizing is a safe practice.
1. Amistadi, R. L., & Young, C. S., Chain Slings for Galvanizing, (St. Joe’s Minerals Corporation)
2. Valmont’s Galvanizing Chain Evaluation, Valmont Industries, March 1985.
3. Occupation Health & Safety Administration, Code of Federal Regulations, 29CFR1910.184,
Slings, March 1996.
4. American Society of Testing & Materials (ASTM), A 413, Specification for Carbon Steel Chain,
2001.
5. American Society of Testing & Materials (ASTM), A 391, Specification for Grade 80 Alloy
Steel Chain, 2001.
6. National Association of Chain Manufacturers (NACM), Welded Steel Chain Specification, April
2003.
November 2004
Protecting Steel for Generations
17