a seawater sampling bottle (rli fjarlie)

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FISHERIES RESE RCH  O R D O F C N D A Seawater Sampling  ottle R L I j rlie  95

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Bottle requirement for seawater sampling

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FISHERIES RESEARCH BOARD

OF CANADA

477

A Seawater Sampling Bottle

R.L.I . Fjarl ie

1952

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dl j J )ITt!. '1 1- \ t ,

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PACIFIC OCEANOORAPHIC

Nanaimo, B.C.

A SEAWATER SAMPLING BO'1T.LE

R.L.I. Fjarlle

P.O.G. File: N 7-7

August 15, 1952.

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A SEAWATER SAMPLING BOTTLE

by

R.L.I . Fjarlie1

The ear l ies t seawater sampling bottles such as used by the f i r s t

Challenger expedition consisted of a simple tube, through which the

water flowed more or le ss f re ely (flushed) while i t was lowered to any

desired depth on a sounding l ine. When in position, i t was closed by

striking a t r igger mechanism with a small weight (messenger) sl id down

the l ine. The bott le and the sample were recovered by hau li ng t he l ine

aboard'ship. With the advent of reversing thermometers in 1902, a re-

versing mechanism was added.

The most successful bottles are the Nansen (figure 1) , Knudsen

(figure 2) and Ekman (figure 3) in which the thermometers a re a tt ached to

the tube which r ever se s ( tu rn s over) and closes when the t r igger is

actuated. In the f i r s t two, both ends of the bottles are attached to the

sounding l ine while being lowered into position, but when the messenger

st r ikes the release mechanism the top end fal ls away fran the l ine by

i t s own weight, and so reverses. The main difference between the two is

in the tube closing mechanism. The Nansen bot t le has a stopcock a t each

end closed by the weight of the bottle actuating a lever as it fal ls over.

The Knudsen bottle has rubber gaske tedl ids

which are s pring loaded and

are tripped individually by the messenger, as a separate act ion af te r

the top of the bottle is released from the wire. Both of these bottles

are l ight in weight and easy to handle. They have a cOllllllon objection in

that the end of the sampling tube is not perfect ly seaJ.eU when the

1. Now with the Pacific Naval Laboratory, Defense Research Board.

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o o ~ t l e is r e v e r s e d . As a resul t , contamination o f the sample wh ile i n th e

s e a and l o s s by leakage when it is brought on deck ca n occur. T h e i r

flus hing c h a r a c t e r i s t i c s a r c poor and th e y must be allowed t o remain a t

sampling depth f o r some time t o enable them t o o b t a i n a t r u e sample.

Once the b o t t l e s a re t ri pp ed , they a r e fastened only a t on e end, an d

tend t o gyra te around th e l ine , and t h e r e is a p o s s i b i l i t y o f damage

a g a i n s t the s i d e o f th e s h i p , p a r t i c u l a r l y i n ba d we a th e r.

In th e :El' ~ b o t t l e th e thermometer and sample tube assembly i s

mounted on pivots i n a frame t h a t ca n be a tta c he d to th e sounding wire

a t both ends. The l i d s a re held t o the ends o f th e tu b e by an i n -

t e r n a l spring and a re pushed open by e x t e r n a l cams, as the tub e w ith

thermometers attached is cocked b ef or e l ow er in g. This b o t t l e is

rugged, b u t v ery heavy and t i r ing to h a n d le . I t has r e l a t i v e l y good

f l u s h i n g c h a r a c t e r i s t i c s , and with proper c a r e the l i d s ca n be

maintained leakproof. The method of locking th e tube af te r r e v e r s a l

is p o o r. an d u s u a l l y does n ot f u n c t i o n . I n t h i s case t h e b o t t l e

is f r e e to r o t a t e through 110 degrees and t h e r e is a r e a l p o s s i b i l i t y

t h a t the thermometer readings could be a l t e r e d , an d t h e l ids could be

opened.

The i d e a l water sampler must obta in and preserve a true

sample of th e water a t sampling depth, and b rin g i t on shipboard

intact . This r e q u i r e s good flus hing c h a r a c t e r i s t i c s when open, and

a p o s i t i v e s e a l when c l o s e d . Furthermore, once th e thermometers have

reversed th e y should be locked i n t h i s p o s i t i o n to s a fe g u a rd th e tem-

p e r a t u r e re a dings . The u n i t should be f a s t e n e d to the l ine a t both

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enps to prevent damage aga in st th e side of the ship in rough weather.

The thermometer cases should be readily removable so that the instruments

may be stored properly(3)(5) between observations a t sea. In addition,

it should be l ight in weight, corrosion resis tant , easy to manipulate,

and must be dependable.

With the requirements of an ideal water sampler in view.

a new bottle has been designed (figure 4) to incorporate as many of

t he se f ea tu re s as possible. The design was commenced in 1949 and

the prototype of th e present bott le was f i r s t used in January 1950.

Since then the design has been modified six t imes. I t is presented

here as a unit which has been proven under trying circumstances a t sea

and has been found dependable, easy to handle, and capable of obtaining

t rue samples and temperatures.

This sea sampling bott le consists of a l ight weight metal tube

with hinged l ids on each end tha t are co-ordinated with a rotat ing frame

holding three reversing thermometers. The tube i s clamped to the

sounding l ine a t the top, and hooked a t the bottom end similar to the

Ekman bot t le . A device for releasing a messenger below the bott le when

it closes allows any number of units to be used in series on the l ine .

The major features which have been designed into the bottle allow unres-

t r ic ted now of water through i t when open, a positive seal when the

l ids are closed, and canplete mechanical re l lab i l i ty .

The free flow of water through the bottle bas been faci l i ta ted

by placing the operating spr ings on the outside am providing large

openings a t the ends of th e tube, in ....hich the only restr ic t ion to

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flow is a 1/4 in::h diameter axle passing transversely across i t .

suppo rts the thermometer reversing frame. The springs which hold the l ids

closed have been coiled around the hinge on which they are mounted, in a

manner s im ila r to screen door hinge eonstruction.

The l id is carried on the hinge b olt (fig ure 5) which is bent in

such a way that the l id comes normal to the axis of the tube in closing.

The hinge bolt passes through the center of a pressed metal l id fi t ted

with a rubber gasket, which is tigh t enough to p revent l eak age , but flexible

enough to allow the l id to move s l ight ly . Consequently, if the hinge

bolt i s ac cid en tly ben t, th e l id can adapt i t se l f to the end of the

bot t le and prevent possible leaks. The metal rim which forms the seal

with the gasket has been recessed sl ight ly inside the ends of the bott le

to protect i t from accidental burrs that would destroy the seal .

The linkage between the l ids and the reversing frame is a f lexible

steel cable pass ing through a small hole in the axle of the frame, and

attached at each end to a pulley on the hinge. When the frame is rotated

to r ever se the thermometers, the cable is wound around the axle and pulls

ehe l ids open against the action of the springs . With this arrange-

ment, the thermometer frame is urged throughout the entire 180 degrees of

reversal and ,;hen the l ids are closed. a spring loaded plunger locks the

frame to prevent oscil lat ion and so safeguards the sample and the

thermometer readings.

The removable thermometer case f i t s in a rack in the rotating

f rame where it is locked with two spring catches. The thermometers are

held within thei r cases by a screwed-on l id , which covers a l l the tub es .

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A hole is provided a t one end of each tube to faci l i ta te pushing the

thermometers out of the cases.

The seawater sample in the bottle i s in contact only with

monel metal, which i s used for the tube, l ids , reversing thermometer

frame, am axle . This minimizes the possibi l i ty of contamination of the

sample with corrosion product's. The castings on both ends of the

bottle are manganese bronze, chosen for durabili ty in service.

'rhe weight of the new bott le (7.3 lbs.) compares favorab13

with that of the Nansen bottle , 7.7 lbs . , and i s the same as the

Knudsen bott le . I t is much l ighter than the 17 pound Elanan bot t le .

In use, the bottle is f i r s t attached to the sounding l ine

by a spi ral hook a t the lower end (figur€ 6A) and then clamped

a t the top (figure6B). The plunger locking the thermometer

fra'lle is released and the l ids are opened by rotating the frame 180

degrees unt i l it engages the t r igger (figure6C). The messenger

is t hen a tt ached to a spring loaded plunger bearing against the

lower hinge bar ( figu re6D) and the messenger is then f i t ted to the

l ine (figure 7 ) .

Every attempt has been made to reduce th e number of motions

required. The hook a t the lower end is positioned so that the

movemsnts used in attaching and detaching from the l ine are those which

would naturall3 be used in moving th e bottle towards or away from

the wire. The bottle i s arranged for holding in the l e f t hand,

while the right hand performs the more complicated motion of screwing

up the clamp, which has an extra large wing nut to ensure that it can

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be securely attached to the l ine, with reasonable effor t .

opened and the thermometers reversed in a single motion. The messenger is

attached after this action i s complet ed , so tha t it is not neces sa ry for

t he ope rato r to try and co-ordinate two moving parts.

When the messenger hits the t r igger , it releases the thermometer

frame which is now free to rotate under th e t en sion of the springs on the

hinge bar, towards the reversed posi t ion, where it is locked. At the same

time, both l ids close and the messenger for the next bottle on the l ine i s

The bott le is provided with an eye welded to the tl.\be at each end,

so it can be hllng upright on a hook before the thermometers are read,

and hung upside down af ter the sample is drawn and temperatures recorded.

In this way, th e r ever si ng thermometers can be kept in the approved storage

position (3) (5) when they are s t i l l on the bottles, i f it is not convenient

to transfer them to a separate rack. In pract ice, a wooden case is provided

with hooks, which serves as a bottle rack on deck, as well as a case for

shipping.

The messenger shown in f igure 7 is a "spli t" type, cast on two

pieces of manganese bronze, which are held together under tension by a

heavy piece of rubber. The messenger is pushed onto the l ine , and pulled

off , but has no tendency to fa l l off or to become jammed.

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l lushing Efficiency

A Comparison with Other Seawater Sampling Devices

The speed a t which the various water sampling bott les take

up the water typical a t thei r positions in the sea i s of considerable

in teres t and importance.

The relative efficiency of f ou r ty pe s of bott les currently in use

has been investigated in one experiment in water having a moderate sal ini ty

gradient. Stl'ings of Nansen. Knudsen, Ekman and these bottles were hung side by

side from a bar suspended from ·the main cargo boom of H.M.C.S. Cedarwood.

There were four of each type of bottle on a str ing a t in te rv als of two

meters, and the end of the cargo boom was high enough above the sea to

allow a l l of the bott les to be' in the a ir a t once. With the bott les

open. and messengers attached, they were lowered into the wate r, and at a

measured time from immersion of the uppermost bott le , messengers were

dropped on each l ine simultaneously. The bott les were then hauled uP.

and the samples. were drawn. This procedure was repeated to obtain

samples after 0, 1/2, 1, 1 1/2. 2, 3, 4, 5, 6. 9, 11 and 15 minutes

submersion time, the d if ferent in te rval s being observed in random order

(Table I ) .

With this method of sampling i t is believed possible to estimate

the time required for a b ottle to flush completely, by comparing the

sal ini ty of the samples taken. Ideally, the time required for complete

flushing of a l l bottles is the time which must elapse af ter submersion.

before a l l bottles a t the same depth have identical samples. In th i s ex-

periment an arbitrary reference salini ty for each cast was assumed by

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choosing the maximum sal ini ty a t each depth, regardless o f the type of bott le

from which it was drawn. I t was a ssum3d tha t if the sa l ini ty as shown by

one bottle was less than the reference a t the same depth, it was because

some water of a lower salini ty had been trapped in the bottle , and carried

down with it to the sampling posit ion.

To evaluate the relat ive efficiency of the different bott les , the

area between the reference sa l ini ty curve, and the curve shown by each type

of bottle was measured for the various submersion times. I t was a ssumed

tha t as this area approached zero with longer " soak ing", flushing became

more complete. ThUS, the area between the curves and the time required

for i t to approach zero, i s the measure of efficiency., For d iscussion pur -

poses, the units of area have been cal led "Sal in it y Meters" (S.M.).

The data are shown in Table I . The sal ini ty profi les for a sub-

mersion time of 0 minutes are shown in figure 8" together with the re-

ferenceprofi le .

The relat ive efficiency of the four types of bott les is shown in

f igure 9. The variat ion in the data i s about 0 .25 S.M. and becomes approxi-

mately constant after 9 minutes sul::mersion time. The data for the 6 and

15 minute intervals are not consistent with the remainder of the series

and cannot be explained from th e records of the experiment. Despite these

anomalies the relative efficiencies are clearly indicated. In these waters

where the sal ini ty (and consequently the density) gradient was large, the

sample in the new bottle apparently was in equilibrium with i t s surroUD-

dings immediately, the Ekman bott le samples were in equilibrium after one

half m...nute, the Knudsen samples af ter two minutes, but the Nansen bott le

r " ' ' 1 ~ . . r e d five minutes "soaking" to obtain a true sample.

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When a bottle is being lowered flushing occurs due to the velocity

head i n t he f l u i da t t h eendopen i ng , anda f t e r i t i s i npos i t i on t he

l ighter water entrapped and carried down in the lowering. wil l f loat out

and be replaced by the denser surrounding water. Small end openings and

in ternal obstructions cause a flow resistance which is most effective in

retarding th e flu sh ing while lowering when the velocity is greatest , but

is a lso e ff ec tive in retarding th e hydrostat ic f lushing when the bottle

is in posit ion.

The data in figure 9 show that t he e ff ic iency is proportional to

the effective size of end openings and freedom of f low through the

bot t les . The end caps on th e EIanan bott les must retard free flow, but

equilibrium is quickly attained (1/2 minute) because th e openings are

large. and the tube is unobstructed. The end opening of the Knudsen

bottle is of a fa i r s ize. but is part ial ly obstructed by the internal

spring, which also occupies a large proportion of the cross s ec ti on a re a

of this narrow bottle. The stopcocks on the Nansen bo tt le const ri ct the

end openings so much that they require more th an twic e the time of any other

bott le for flushing.

The bottle described here approached the postulated requirements

more closely than any of t hese s tandard des igns . and i t is belieTed to be

an acceptable improvement.

Copies of the plans and specifications may be obtained a t cost

from the Oceanographer in Charge. Pacific Oceanographic Group,

Nanaimo, B.C.

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1. Anonymous. Deutsche Atlantische Exped. 'Meteor ' , Vol. IV, Part I , p 21

f f .1925-27.

2. Knudsen, M. A frameless reversing water bott le . Journal du Conseil ,

Vol. IV, No.2 , P 192, 1929.

3. Ekman, V.W. On the use of insulated water bott les and reversing

the rmomete rs. Pub!. de Circ. No. 23, April , 1905.

4. Knudsen. M. Some oceanographical instruments. Publ. de Circ. No. 77,

April , 1923.

5. Richter, N. Uber die funktion der umkipp thermometer sowle die beseitigung

von storungen. Richter and Wiese. Berlin, Germany, 1951.

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The salinity of samples taken simultaneously in four types of seasampling bottles after various intervals of immersion.

Typesof Bottles

Depth~ ~ ~ ~ !!!!!!a

Salinity (S ·1 •• )o }linutes "Immersion"

23.35 23.39 23.33 23.3123.42 23.33 23.35 23.37

24.43 23.57 ;13.64 24.3024.69 24.78 25.48

1/2 Minutes "Immersion"

23.93 23.90 23.93 23.9024.16 24.00 23.90 23.95

24.36 24.42 24.7825.62 24.90 25.55 25.64

1 Minute "Immersion"

24.40 24.2724.29 24.29

24.29 24.30 24.30 24.2925.30 24.74 25.01 25.2825.68 24.69 25.52 25.68

1 1/2 Minutes "Immersion"

23.98 24.50 23.98 24.0224.20 24.14 24.16 24.1624.81 24.61 24.69 24.8125.81 25.52 25.73 25.80

2 Minutes "Immersion"

24.16 24.38 24.40 24.4024.5:1. 24.45 23.87 24.4725.35 25.16 25.39 25.41

25.59 25.50 25.59 25.57

1 Minutes "Immersion"

24.02 24.00 24.02 24.0024.00 24.04 24.00 24.0424.92 24.61 24.92 24.9425.75 25.53 25.73 25.72

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TABLE I Continued.

Types of Bottles

Depth

~ ~ ~ ~ ~Salinity (8 ·1 ••)

4 Minutes "Immersion"

23.60 23.69 23.71 23.69

23.73 23.71 23.73 23.74

24.34 24.05 24.18 24.34

25.59 25.48 25.57 25.57

5 Minutes "Immersion"

24.14 24.13 24.11 24.05

24.11 24.13 24.11 24.14

24.47 24.38 24.31 24.47

25.73 25.64 25.72 25.72

6 Minutes "Immersion"

24.11 24.18 24.11 24.11

24.22 24.27 24.27

24.76 25.16 24.69 25.10

25.82 25.84 25.82 25.84

9 Minutes "Immersion"

23.59 23.66 23.62 23.57

23.69 23.62 23.71 23.68

24.45 24.54 24.61 24.50

25.55 25.61 25.62 25.62

11 Minutes "Immersion"

24.18 24.07 24.11 24.11

24.22 24.25 24.27 24.27

24.58 24.54 24.52 24.6025.81 25.81 25.80

15 Minutes "Inunersion"

23.48 23.44 23.38 23.44

23.48 23.51 23.50 23.55

24.09 25.10 25.37 25.3925.64 25.72 25.62

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I n pos it io n Reversing

The Nansen deep sea reversing

irater S8JIlpling bot t le .

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In pos ition Reversing

The Knudsen deep sea reversingwater slillpling bottle.

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In position Reversed

The Ekman deep sea reversing

water sampl ing bottle.

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·The seawater sampling bot t le .

Detail of l id construction onthe seawate r sampling bot t le .

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Attaching the new bottleto the Bounding l ine .

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Pushing the sp l i t messenger

onto the sounding l ine .

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The sal ini ty of samples taken simultaneously in the

four types of bottles af te r zero minutes sul:mersion.

Deviation of the sal ini ty in each type of sample bottle from thereferen ce v alu e. E fficien cy varies inversely with the deviation.

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