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Chris Heal FBHI watchmaker |
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WATER RESISTANCE
A watch is not water resistant unless stated on the dial or case back. Watches which
are not marked water-resistant should always be removed whilst washing etc.
Water resistance
is measured in bars (a bar is a unit of pressure, 1 bar being equivalent to 1
atmosphere), and watches are tested at these pressures in a static laboratory test
for a short period of time. Exceptional pressure, as when diving, or prolonged
and active use in water may exceed those limits. If the watch is to be used for
diving or impact water sports it will need to be able to tolerate that extra
pounding. Thus in all practicality the limits stated on the watch should always
exceed those of its actual use.
Translation of
water resistance varies and the best guide is the supplier or maker of the
watch as it will almost certainly be part of the guarantee. Manufacturers often
measure water resistance to a number of feet, meters or atmospheres (ATM).
Normally, terms of depth imply that a watch will remain resistant at this
(Atmospheric pressure) depth in still conditions. As a general rule, the
minimum could be described as follows:
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3 ATM or 3 BAR (30 m or 100 ft) |
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5 ATM or 5 BAR (50 m or 165 ft) |
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10 ATM or 10 BAR (100 m or 330 ft) Everyday use, poolside diving and snorkelling. Not suitable for high board diving, high impact or water sports. |
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15 ATM or 15 BAR (150 m or 500 ft) Everyday use, poolside diving and snorkelling, most water sports. |
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20 ATM or 20 BAR (200 m or 660 ft) Minimum required for high board diving, high impact water sports or sub aqua diving. The only watches, which are designed to withstand continued use in these conditions, are professional divers watches. Only watches marked "DIVER'S" on the dial should really be used for diving as these fully comply with the international standards for diver's watches. |
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100 ATM or 100 BAR (1000 m or 3300 ft) Minimum required for professional deep sea diving. Only watches marked "DIVER'S" on the dial should really be used for diving as these fully comply with the international standards for diver's watches. |
It
is wise to remember that when mountain climbing, parachuting, sky diving, hang
gliding, or skiing, you may also require a watch that is ATM damage-protected,
as pressures change both above and below sea level. Always ensure that any
screw down crowns or pushers are properly fastened tight as this can compromise
the water resistance of your watch and invalidate any warranty, if water enters
because they where not screwed down.
Re-sealing a watch
We only reseal watches marked 50m or better.
For a watch to still be water resistant the seals and gaskets should be
replaced periodically. This is usually best done when replacing the battery or
when ever any work is carried out on the watch. The rubber gaskets that seal
the case back, crystal, crown or pushers will inevitably deteriorate with time.
Thus water resistance is not a permanent condition. When removing case backs,
the case back gaskets often break or stretch and should always be replaced to
guarantee water resistance. The only safe way to know if a watch is water
resistant is to test it in specially designed vacume
or pressure test equipment.
The price of a
re-seal usually depends on both the type of watch and on the make and brand as
some watches require a new crown to be fitted as the seals inside some crowns
cannot be replaced
Further reading
on water resistance
Water Resistant mark
From Wikipedia, the free encyclopedia
(Redirected from ISO 6425)
Jump to: navigation, search
Water Resistant is a common mark stamped on the
back of wrist watches
to indicate how well a watch is sealed against ingress of water. It is usually
accompanied by an indication of the static test pressure that a sample of newly
manufactured watches was exposed to in a leakage test. The test pressure can be
indicated either directly in bars,
or (more commonly) as an equivalent water depth in meters (in the
An indication of the test pressure in terms of water depth does not mean
that the watch was designed for use in such water depths. For example, a watch
marked at 30 meters depth cannot be expected to withstand activity in a
swimming pool, let alone continue to function at 30 meters under water. This is
because the test is conducted only once using static pressure on newly
manufactured watches. In practical use, a watch is subjected to variations in
pressure which can add pressure to the static pressure of the water. Examples
of this include the movement of a swimmer's arm through the water, or violent
sprays encountered in water skiing. The test for qualifying a diving
watch for repeated usage in a given depth includes safety margins to take
factors in account like aging of the seals, rapidly changing water pressure and
temperature, as well as dynamic mechanical stresses encountered by a watch.
Contents
[hide] |
[edit] ISO 2281
water-resistant watches standard
The International
Organization for Standardization issued a standard for water resistant
watches which also prohibits the term waterproof to be used with watches,
which many countries have adopted. The international standard ISO 2281
Horology -- Water-resistant watches defines the water resistance of
watches. This standard was only designed for watches intended for ordinary
daily use during exercises under water for a short period under conditions
where water pressure and temperature vary.
The ISO 2281 standard specifies a detailed testing procedure for each mark
that defines not only pressures but also test duration, water temperature, and
other parameters. Besides this ISO 2859-2 Sampling
plans indexed by limiting quality (LQ) for isolated lot inspection and ISO
2859-3 Sampling procedures for inspection by attributes -- Part 3: Skip-lot
sampling procedures concerning procedures regarding lot sampeling
testing come into play, since not every single watch has to be tested for ISO
2281 approval.
ISO 2281 water resistance testing of a watch consists of:
- Immersion of the watch in
10 cm of water for 1 hour.
- Immersion of the watch in
10 cm of water with a force of 5 N perpendicular
to the crown and pusher buttons (if any) for 10 minutes.
- Immersion of the watch in
10 cm of water at the following temperatures for 5 minutes each, 40°C,
20°C and 40°C again, with the transition between temperatures not to
exceed 5 minutes. No evidence of water intrusion or condensation is
allowed.
- Immersion of the watch in a
suitable pressure vessel and subjecting it to the rated pressure for 1
hour. No evidence of water intrusion or condensation is allowed.
- Exposing the watch to an
overpressure of 2 bar. The watch shall show no
air-flow exceeding 50 μg/min.
- No magnetic or shock resistance properties are
required.
- No negative pressure test
is required.
- No strap attachment test is
required.
- No corrosion test is
required.
Except the thermal shock resistance test all further ISO 2281 testing should
be conducted at 18°C to 25°C temperature. Regarding pressure ISO 2281 defines:
1 bar = 105 Pa = 105 N/m2.
In practice, the survivability of the watch will depend not only on the
water depth, but also on the age of the sealing material, past damage,
temperature, and additional mechanical stresses.
None of the tests defined by ISO 2281 are suitable to qualify a watch for scuba
diving. Such watches are designed for everyday life and must be water
resistant during exercises such as swimming. They can be worn in different
temperature and pressure conditions but are under no circumstances designed for
diving with underwater breathing apparatus.
[edit]
ISO 6425 divers' watches standard
The standards and features for diving
watches are regulated by the ISO 6425 - Divers' watches
international standard. ISO 6425 defines such watches as: A watch designed to
withstand diving in water at depths of at least 100 m and processing a system
to control the time. Diving watches are tested in static or still water under
125% of the rated (water)pressure, thus a watch with a 200 meter rating will be
water resistant if it is stationary and under 250 meters of static water. The
testing of the water resistance is fundamentally different from non-dive watches,
because every watch has to be fully tested.
ISO 6425 water resistance testing of a diver's watch consists of:
- Reliability under water.
The watches under test shall be immersed in water to a depth of 30 cm ± 2
cm for 50 hours at 18°C to 25°C and all the mechanisms shall still
function correctly. The condensation test shall be carried out before and
after this test to ensure that the result is related to the above test.
- Condensation test. The
watch shall be placed on a heated plate at a temperature between 40°C and
45°C until the watch has reached the temperature of the heated plate (in
practice, a heating time of 10 minutes to 20 minutes, depending on the
type of watch, will be sufficient). A drop of water, at a temperature of
18°C to 25°C shall be placed on the glass of the watch. After about 1
minute, the glass shall be wiped with a dry rag. Any watch which has
condensation on the interior surface of the glass shall be eliminated.
- Resistance of crowns and
other setting devices to an external force. The watches under test shall
be subjected to an overpressure in water of 125% of the rated pressure/10
bar for 10 minutes and to an external force of 5 N perpendicular to the
crown and pusher buttons (if any). The condensation test shall be carried
out before and after this test to ensure that the result is related to the
above test.
- Water-tightness and
resistance at a water overpressure. The watches under test shall be
immersed in water contained in a suitable vessel. Then an overpressure of
125% of the rated pressure shall be applied within 1 minute and maintained
for 2 hours. Subsequently the overpressure shall be reduced to 0.3 bar within 1 minute and maintained at this pressure for
1 hour. The watches shall then be removed from the water and dried with a
rag. No evidence of water intrusion or condensation is allowed.
- Resistance to thermal
shock. Immersion of the watch in 30 cm ± 2 cm of water at the following
temperatures for 10 minutes each, 40°C, 5°C and 40°C again. The time of
transition from one immersion to the other shall not exceed 1 min. No
evidence of water intrusion or condensation is allowed.
- An optional test
originating from the ISO 2281 tests (but not required for obtaining ISO
6425 approval) is exposing the watch to an overpressure of 2 bar. The
watch shall show no air-flow exceeding 50 μg/min.
Except the thermal shock resistance test all further ISO 6425 testing should
be conducted at 18°C to 25°C temperature. Regarding pressure ISO 6425 defines:
1 bar = 105 Pa = 105 N/m2. The required 125% test pressure provides
a safety margin against dynamic pressure increase events, water density
variations (seawater
is 2 to 5% denser than freshwater) and degradation of the seals.
Movement induced dynamic pressure increase is sometimes the subject of urban
myths and marketing arguments for diver's watches with high water resistance
ratings. When a diver makes a fast swimming movement of 10 m/s (32.8 ft/s) (the
best competitive swimmers and finswimmers can not nearly swim that fast) physics
dictates that the diver generates a dynamic pressure of 0.5 bar
or the equivalent of 5 meters of additional water depth.[1]
Besides water resistance standards to a minimum of 100 meter (330 ft) depth
rating ISO 6425 also provides minimum requirements for mechanical diver's
watches (quartz and digital watches have slightly differing readability
requirements) such as[2]:
- The presence of a time-preselecting device, for example a unidirectional
rotating bezel or a digital display. Such a device shall be protected
against inadvertent rotation or wrong manipulation. If it is a rotating
bezel, it shall have a minute scale going up to 60 min. The markings
indicating every 5 min shall be clearly indicated. The markings on the
dial, if existing, shall be coordinated with those of the preselecting device and shall be clearly visible. If
the preselecting device is a digital display, it
shall be clearly visible.
- The following items of the
watch shall be legible at a distance of 25 cm (9.84 in) in the dark:
- time (the minute hand
shall be clearly distinguishable from the hour hand);
- set time of the time-preselecting device;
- indication
that the watch is running (This is usually indicated by a running second
hand with a luminous tip or tail.);
- in
the case of battery-powered watches, a battery end-of-life indication.
- The presence of an
indication that the watch is running in total darkness. This is usually
indicated by a running second hand with a luminous tip or tail.
- Magnetic resistance. This is tested by 3
expositions to a direct current magnetic field of 4,800 A/m. The watch
must keep its accuracy to +/- 30 seconds/day as measured before the test
despite the magnetic field.
- Shock resistance. This is tested by two
shocks (one on the
- Resistance to salt water.
The watches under test shall be put in a 30 g/l NaCl
(sodium chloride) solution and kept there for 24 hours at 18°C to 25°C.
This test water solution has salinity comparable to normal seawater.
After this test, the case and accessories shall be examined for any
possible changes. Moving parts, particularly the rotating bezel, shall be
checked for correct functioning.
- Resistance of attachments
to an external force (strap/band solidity). This is tested by applying a
force of 200 N
to each springbar (or attaching point) in
opposite directions with no damage to the watch of attachment point. The
bracelet of the watch being tested shall be closed.
- Marking. Watches conforming
to ISO 6425 are marked with the word DIVER’S WATCH L M or DIVER'S
L M to distinguish diving watches from look a like watches that are
not suitable for actual scuba diving. The letter L indicates the diving
depth, in metres, guaranteed by the manufacturer.
[edit]
Diver’s watches for mixed-gas diving
Diving at a great depth and for a long period is done in a diving chamber,
with the diver spending time alternately in the water and in a pressurized
environment, breathing a gas mixture. In this case, the watch is subjected to
the pressure of the gas mixture and its functioning can be disturbed.
Consequently, it is recommended to subject the watch to a special extra test.
ISO 6425 defines a diver’s watch for mixed-gas diving as: A watch required to
be resistant during diving in water to a depth of at least 100 m and to be unaffected
by the overpressure of the mixed gas used for breathing.
The following specific additional requirements for testing of diver's
watches for mixed-gas diving are provided by ISO 6425:
- Test of operation at a gas
overpressure. The watch is subject to the overpressure of gas which will
actually be used, i.e. 125% of the rated pressure, for 15 days. Then a
rapid reduction in pressure to the atmospheric pressure shall be carried
out in a time not exceeding 3 minutes. After this test, the watch shall function
correctly. An electronic watch shall function normally during and after
the test. A mechanical watch shall function normally after the test (the
power reserve normally being less than 15 days).
- Test by internal pressure
(simulation of decompression). Remove the crown together with the winding
and/or setting stem. In its place, fit a crown of the same type with a
hole. Through this hole, introduce the gas mixture which will actually be
used and create an overpressure of the rated pressure/20 bar in the watch
for a period of 10 hours. Then carry out the test at the rated water
overpressure. In this case, the original crown with the stem shall be
refitted beforehand. After this test, the watch shall function correctly.
- Marking. Watches used for
mix-gas diving which satisfy the test requirements are marked with the
words "DIVER’S WATCH L M FOR MIXED-GAS DIVING". The
letter L indicates the diving depth, in metres, guaranteed by the
manufacturer. The composition of the gas mixture used for the test shall
be given in the operating instructions accompanying the watch.
Most manufacturers recommend divers to have their diving watch pressure
tested by an authorized service and repair facility annually or every two to
three years and have the seals replaced.
[edit]
Water resistance classification
Watches are classified by their degree of water resistance, which roughly
translates to the following (1 metre = 3.2808398950131 feet):[3]
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Water resistance rating |
Suitability |
Remarks |
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Water Resistant 30 m or 50 m |
Suitable for water related work and fishing. |
NOT suitable for swimming or diving. |
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Water Resistant 100 m |
Suitable for recreational surfing, swimming, snorkeling, sailing and water sports. |
NOT suitable for diving. |
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Water Resistant 200 m |
Suitable for professional marine activity and serious
surface water sports. |
NOT suitable for diving. |
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Diver's 100 m |
Minimum ISO standard (ISO 6425) for scuba
diving at depths NOT requiring helium gas. |
Diver's 100 m and 150 m watches are generally old(er) watches. |
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Diver's 200 m or 300 m |
Suitable for scuba diving at depths NOT requiring helium
gas. |
Typical ratings for contemporary diver's watches. |
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Diver's 300+ m for mixed-gas diving |
Suitable for saturation diving (helium enriched
environment). |
Watches designed for mixed-gas diving will have the
DIVER’S WATCH L M FOR MIXED-GAS DIVING additional marking to point this out. |
[edit] See also
[edit] References
- ^
Dynamic pressure is the pressure induced by movement in dense fluids, in
the case of a diver typically the pressure caused by his swimming
movements in water. As a reminder 1 ATM = 1 kg/cm2. A dynamic
pressure of 1 ATM (for example the flow of a river) on the surface of a
hand (assuming the surface of an "average hand" of 150 cm2)
will correspond to a dynamic pressure induced force of 150 kg
(331 lb).
In order to calculate the dynamic pressure caused by a fast underwater swimming movement of a diver this formula can be applied:
P = 0.5*ρ*v2
P = dynamic pressure in Pa (1 atm = 1.01325*105 Pa)
ρ (rho) = density of the fluid in kg/m3
v = speed in meters per second
For a fast swimming movement of 10 m/s this works out as:
ρ (rho) of typical sea water = 1026 kg/m3
v = 10 m/s
P = (0,5 * 1026) * (10 * 10) = 51 300 Pa = 0.5063 ATM
This calculation shows that fast swimming movements will not create dynamic pressure surges exceeding 0.5 ATM (the equivalent of 5 meters of water pressure). - ^
Manual of a 300 m mixed gas diver's watch dealing with many
diving watch characteristics.
- ^
This
water resistance classification guide has been developed by the Jewellers
and Watchmakers of New Zealand (Inc.) in conjunction with the major watch
importers and wholesalers in New Zealand.
[edit] External links
Retrieved from "http://en.wikipedia.org/wiki/Water_Resistant_mark"
Categories: Certification marks | Watches
| Horology