EQUIPMENT & SUPPLIES: Samplers--P-61 and P-63 Point-Integrating Sediment Samplers

In Reply Refer To:                             November 19, 1979 
EGS-Mail Stop 412  


Subject: EQUIPMENT & SUPPLIES: Samplers--P-61 and P-63 Point-
           Integrating Sediment Samplers

The purpose of this Memorandum is to remind those people who use 
the P-61 and P-63 point-integrating samplers of one of the most 
common causes of malfunction of these samplers. If water gets into 
the head cavity, corrosive damage to the plug and solenoid 
assembly will cause the valve to stick and become inoperable if 
proper maintenance procedures are not taken.

The valve which controls the nozzle and air openings is 
electrically controlled, and has two positions (see Fig. 2). In 
the power-off position the valve is in the pressure-equalizing 
position; the nozzle is closed, and air flows only from the 
compression chamber into the head cavity and from the head cavity 
into the bottle. This equalizes the pressure in the bottle with 
the hydrostatic pressure as the sampler is lowered through the 
water. In the power-on position the valve is in the sampling 
position; the nozzle is open, and the air flows only from the 
bottle into the head cavity and out through the air-exhaust 

Water can get into the head cavity under the following conditions 
if: (References are to the enclosed drawings and parts list)

l) no nozzle is in place. Water will rapidly fill the head cavity 
if a nozzle has not been properly installed.

2) the nozzle gasket is missing. Water will enter between the 
nozzle and nozzle nut.

3) the sampler is submerged without a sample container in the 
sampler. If the sampler is submerged without a container, water 
can enter the head when the valve is in the power-off position. In 
this position water can enter through the air-exhaust opening 
(Section B-B). Solution--never submerge a sampler without a bottle 
properly sealed in place.

4) the sample container is filled to the maximum recommended 
volume and the sampler is allowed to tilt forward more than about 
10 degrees after the valve has closed (power-off position). Some
water can run back through the air exhaust opening into the head 
(Section B-B). If the sample container is overfilled water will 
definitely enter the head cavity when the valve is closed (power 
off). Solution--do not overfill the sample container. Try to keep 
the sampler from tilting head down when retrieving and removing 
the sample container.

5) the nozzle is not tightened into the valve body and the nozzle 
nut is not tightened against the nozzle gasket (O-ring). The 
nozzle (part P61-11) must be hand-tightened into the valve body, 
then the nozzle gasket (P61-13) must be compressed by tightening 
the nozzle nut (P6l-l2) to prevent water from entering the head 
cavity around the nozzle. Solution--Loosen the nozzle nut before 
inserting and tightening the nozzle, and then use an adjustable 
wrench to tighten the nozzle nut gently against the O-ring.

6) the air-line gasket is worn or missing. The air-line gasket 
(P61-29) is seated into the sampler head. When the head is closed 
the gasket is pressed against the air-line opening in the body, 
thus completing the air line from the compression chamber to the 
head cavity and sealing it against leakage. If this gasket becomes 
worn or damaged (or is missing), water can enter the head cavity. 
Solution--The seal should be checked frequently by placing a paper 
strip against the gasket and closing the head. If the paper strip 
can be easily withdrawn, the gasket should be replaced before 
submerging the sampler.

7) rinse water is poured onto the gasket and nozzle area of the 
sampler head when the valve is in the power-off position. When 
these samplers are used to collect samples for chemical analysis, 
that part of the head which is in contact with the sample 
container is supposed to be rinsed with native water at the 
sampling site. If this is done while the sampler head is hanging 
open with the valve in the power-off position (Section B-B), some 
of the water that is poured onto the gasket and nozzle area can go 
directly into the head cavity through the air-exhaust opening. 
Solution--To rinse that part of the head and gasket which is in 
contact with the sample container, l) place a proper container in 
the sampler, 2) close the head, 3) submerge the sampler in the 
stream to be sampled, 4) open the valve (power on), S) leave the 
valve open long enough to fill the container about half full, 6) 
raise the sampler to the point where the tail fin can be grabbed, 
7) open the valve (power on) and tilt the sampler up and down to 
rinse the contact area. Some water will be forced back through the 
nozzle, but will not get into the head cavity as long as the power 
is on. Discard the remainder and begin sampling.

It would appear that it is almost impossible to use these samplers 
without allowing some water to get into the head cavity. It 
definitely is difficult to prevent leakage; however, if care is 
taken most problems associated with leakage can be minimized. If 
the operator removes the nozzle and the nozzle nut after sampling 
and opens the head while the sampler is in the suspended position, 
excess water in the head will immediately drain through the 
threaded nozzle-nut opening. Since air is free to flow through the 
pressure-equalization hole near the hinge, if the sampler is 
stored with the head open and the nozzle and nozzle nut removed, 
the head cavity should dry within a few hours. A tire pump or 
other compressed air source could be used to accelerate the drying 

Other points to remember are:

1, Disassemble the head and clean all parts frequently. If the 
sampler is only infrequently used it should be cleaned following 
each trip.

2. Be sure that the power supply is fully charged.

3. Make sure that there is direct contact between the hanger bar 
and the Type B connector. Do not use a Type B connector with a 
nylon bushing (See WRD Equipment Catalog, stock number 434003), 
but do use the Type B connector with brass bushing (stock number 

4. Do not use damaged nozzles.

5. The head gasket is seldom a source of leaks. Do not use gasket 
cement. If the head gasket must be replaced, order a replacement 
from the Sedimentation Project. Use of a gasket having improper 
thickness will cause misalignment between the nozzle nut and valve 

6. Never submerge a sampler beyond its rated depth (180 feet with 
pint container or 120 feet with quart container).

A copy of the Instructions for US P-61-Al Suspended Sediment 
Sampler is attached. All operators using point-integrating 
samplers should be entirely familiar with these instructions.

                                 R. J. Pickering


WRD Distribution: A, FO

St Anthony Falls Hydraulic Laboratory
Hennepin Island & Third Ave S E.
Minneapolis, Minnesota 55414


These instructions describe the sampler, present detailed 
maintenance procedures, and outline general operating techniques 
They are not intended as a comprehensive field guide For details 
that pertain to sampling theory and sample analysis, refer to 
Report No 14(1), Techniques of Water-Resources Investigations of 
the U S. Geological Survey(2), and the ASCE Sedimentation 
Engineering Manual(3).


The US P-61-Al was designed to collect special samples required to 
determine the suspended-sediment discharge of a river or stream. 
The sampler may be used to collect either depth-integrated samples 
or point-integrated samples. Before shipment each sampler is 
checked and, if necessary, adjusted to sample at, or very near, 
stream velocity. To maintain the adjustment and thereby insure 
samples of high quality, operators are urged to review and follow 
these instructions.

Physical Characteristics

The sampler is cast of bronze, weighs 105 pounds, has an overall 
length of 28 inches and an overall height slightly less than 13 
inches (fig 1). It will hold either a quart (Owens ~ Illinois 
#6762) or pint (round glass milk bottle) sample container The 
sampler consists of two major parts; the head and the body. The 
head supports both the sampling nozzle and the electrically-
operated, two-position rotary valve Also, it contains several 
passageways that convey air and water The body supports the sample 
container, and the tail vanes which align the nozzle with the 
approaching stream flow The body has a hollow interior which 
serves as a compression chamber that forces air into both the head 
cavity and the sample container. A latch and hinge hold the head 
and body together. The head pivots on the hinge and swings away 
from the mouth of the sample container

Valve Mechanism

The valve serves two purposes: it starts and stops both liquid 
flow into the sample container and air flow to and from the 
container. The porting diagram for the valve is shown in fig 2 
With no electrical power applied, the valve is in the pressure 
equalizing position As the sampler is lowered through the water, 
hydrostatic pressure forces-water through the holes in the belly 
of the sampler and then into the compression chamber Air inside 
the chamber flows through the tube that leads to the head cavity 
At the head-body junction, the air flows through the air line 
gasket (part 29, fig 1) Air in the head-cavity flows through the 
valve plug (fig 2, section B-B, pressure equalizing position) and 
into the sample container The air flow balances the pressure 
inside the sample bottle with that near the nozzle. ~hen power is 
applied, the solenoid turns the valve into the sampling position, 
fig 2. The connection to the compression chamber closes and the 
passage leading from the nozzle to the sample container opens. 
Without surging, the sample flows into the sample container 
Leading from the sample container to the ambient flow, another 
passage steadily expels air displaced by the sample Sampling 
terminates when power is removed and the valve plug returns to the 
equalizing position

Power Supply

To support the sampler and to transmit power, the sampler must be 
suspended on a sheathed single-conductor cable To minimize drag, 
the cable should have a diameter of 1/8" or smaller. To minimize 
power supply voltage, the resistance should not exceed 100 ohms 
per 1000 feet   An Ellsworth cable is commonly used and may be 
purchased from the U S Geological Survey, Shipping and Receiving 
Section, Mail Stop 231, Reston, Virginia 22092. Connect the 
sheath, exterior load-bearing strands, to a special clamp and pin 
the clamp to the top end of the hangar bar. Connect the insulated 
conductor, located in the center of the cable, to the insulated 
wire on the left side of the head. This completes connections at 
the sampler end of the cable On the reel end, secure the cable to 
the reel then connect the center conductor ~o the slip-ring. When 
power is applied at the reel, current will flow from the supply, 
through the center conductor and then through the solenoid Current 
will return through the sampler body, the hangar bar, the cable 
sheath, and the reel frame

The power supply must be direct-current which, at remote sites, is 
most conveniently obtained from dry or wet cell batteries The 
supply voltage is set by the required current and the total 
resistance in the cable and solenoid. For a 100 foot cable with a 
resistance of 100 ohms/1000 feet, the cable resistance will be 10 
ohms. The rotary solenoid has a resistance of 24 ohms and will 
require one ampere to rotate the valve With this cable, the 
voltage must be no less than 36 volts To provide for a margin of 
reliability and for battery discharge, a 48 volt d c supply is 
recommended. Eight 6-volt "hot shot" batteries or from eight to 
ten 6-volt lantern batteries can be used Other batteries such as 
wet cells can be used, but any battery selected must have capacity 
sufficient to sustain the required voltage while delivering a 
current of one ampere. A special capactive-discharge supply (BP-
76) may be purchased from the Sedimentation Project. Compared to 
batteries, the unit is lighter and smaller but is more expensive.


For field sampling with the P-61, a cable, power supply, switch, 
crane, reel, cable connector, hangar bar, and hangar bar pin are 
required. Most of these items can be obtained from the Geological 
Survey at Reston, Virginia A standard threaded hangar bar pin is 
recommended but a plain 3/8" x 3" diameter steel pin may be 
substituted. If a plain pin is used the hangar bar must have a 
smooth hole rather than a threaded hole. The set screw, (P61-25, 
fig. 1) must be installed to retain the pin. With a battery supply 
a single-pole single-throw toggle switch will be required This 
type of switch is available at local hardware or electronic 
stores. Six to ten feet of 14 AWG stranded, insulated wire and two 
clips will be needed to connect the batteries to the reel. The BP-
76 includes a switch and wire.


Fasten one end of the cable to the reel and connect the center 
conductor to the reel slip-ring. ~eel the cable onto the drum, 
mount the reel on the crane, then thread the cable over the crane 
sheaves. Clamp the other end of the cable into the cable-
connector, then suspend the sampler on the hangar bar. Connect the 
center conductor to the sampler lead wire. On the power supply 
connect one wire to the reel slip-ring and connect the other wire 
to the frame of the crane or reel. The P-61 solenoid is not 
sensitive to direction of current so connections can be made 
without regard for polarity. Check for rotation of the valve plug 
by operating the switch several times while sighting through the 
nozzle. If the sampler has been in storage, water-formed deposits 
may cause the valve plug to seize in the valve plug body. If the 
valve will not turn, connect the power supply directly to the 
sampler leat-wire, apply power, and strike the side of the sampler 
head with a rubber or wood mallet. Never strike the nozzle. If a 
few sharp blows will not free the valve, refer to the Maintenance 
Section When the valve is operating properly, insert a sample 
bottle then close the head slowly. Guide the lip of the bottle so 
that it centers and seals against the face of the bottle gasket. 
Insert the aluminum adapter into the sample-container cavity if 
pint bottles are to be used Lower the sampler to the desired 
depth, then close the switch for the desired sampling interval. 
Open the switch, hoist the sampler, ant remove the sample bottle 
Optimum sampling intervals vary

with stream velocity and container size, so some experimentation 
will be necessary The interval must be chosen so that the 
container is approximately 2/3 full Samples that are overfilled 
must be discarded and the process repeated with a shorter interval 
To be valid, a sample must enter the container only through the 
nozzle with a pint container the bronze P-61-Al sampler will 
function properly to a depth of 180 feet but with a quart 
container, the depth is only 120 feet At greater depths,water 
instead of air, will flow from the compression chamber and enter 
the sample container

To collect a point-integrated sample, support the P-61 at a fixed 
depth during the entire sampling interval To collect a depth-
integrated sample first open the valve then depending upon depth 
and velocity, either raise or lower the sampler at a uniform rate. 
If the stream is less than 18 feet deep and the velocity is 
moderate, close the switch to open the valve then lower the 
sampler at a uniform rate from the water surface to the bottom of 
the stream When the sampler touches bottom, instantly reverse reel 
rotation and,at a uniform rate, hoist the sampler through the 
flow. Switch the power off only after the sampler emerges from the 
stream If the stream is between 18 and 30 feet deep, or has a high 
velocity, the sampler may be used to depth-integrate in one 
direction, from the bottom of the stream to the surface With power 
off, lower the sampler to the stream bed. Apply power then, at the 
same instant, start hoisting at a uniform rate Switch power off 
when the nozzle breaks through the surface

Deep, fast streams may be depth-integrated in sections At each 
sampling station, divide the vertical into several segments, then 
depth-integrate each segment individually When depth-integrating, 
never lower or hoist the sampler at a rate that exceeds 0 4 of the 
mean stream velocity For shallow streams transit rates are less 
Report No 14, p. 45 shows rate limits imposed by each of several 
factors Refer to the diagram for the 3/16" nozzle With the quart 
container, maximum rates as limited by air compression must be 
reduced to 1/2 of those shown in Report No 14(4). When handling a 
P-61 filled with a sample, never allow the nose to tilt down more 
than ten degrees. A portion of the sample may escape through the 
tube leading to the compression chamber

Those unfamiliar with sampling theory or program objectives, must 
consult with the hydrologist to clarify details such as the number 
and the location of sampling stations within a particular cross 


If the valve plug fails to turn, disassemble the head. Remove the 
nozzle, then remove the hinge pin to free the head from the body 
To free the head the catch may be left in place, however, if the 
catch mechanism is to be disassembled take precaution to restrain 
the spring under the catch With the head free of the body, remove 
the six cap-screws that hold the head-base to the head-cover 
Separate the two parts and avoid damage to the gasket

To disassemble the valve mechanism, first remove the screw in the 
end of the valve plug, then remove the washer, spring, and spring 
boss Note the shape of the valve arm and its orientation Punch 
marks on the valve plug and valve arm show their correct alignment 
The solenoid must be removed to free the plug from the valve body 
On the band that holds the solenoid, loosen the set-screw and 
remove the exposed screw that anchors the band. Note the 
orientation of the solenoid leads, then slide the solenoid free of 
the band Now slide the valve plug out of the valve body Use fine 
steel wool or fine sandpaper to clean and polish the plug and the 
inside of the valve body Household cleansers should not be used 
because the abrasive may become imbedded in the brass valve body 
and cause the plug to bind To check the solenoid, apply voltage 
directly to the solenoid lead wires. When power is applied, the 
solenoid should rotate 45! then, when power is removed, the 
solenoid spring should return the armature to its rest position If 
the solenoid fails to turn, corrosion may have damaged the winding 
or ball-race Replace the complete solenoid.

To reassemble, reverse the above procedure The clock-type spring 
should be wound approximately 1/2 revolution and mounted so that 
movement of the valve to the sampling position tightens the 
spring. After all parts are assembled energize the solenoid. The 
valve arm should seat tightly against the stop and the valve plug 
sampling-intake hole should align with the corresponding hole 
through the valve body. If necessary, adjust the solenoid so that 
it does not bind against the valve wheel Clean the surface of the 
head gasket, position the head cover, then insert the six cap 
screws. Seat the screws firmly but do not tighten Face the screw 
heads and rotate the head so that the catch is at the 12 o'clock 
position. At the two o'clock position, label the screw number 1 In 
a clockwise direction label each screw then tighten in the 
sequence 1-4-6-3-5-2 Repeat the tightening sequence two or three 
times, each time increase the torque. Final torque should be 100-
125 pound inches. The exact torque is not critical but all screws 
should be tightened as nearly equal as "feel" permits

Corrosive damage to the plug and solenoid assembly is caused by 
water that collects in the head cavity Even a small quantity will 
cause problems if the sampler is stored before removing the water 
When sampling is complete, remove the head base Drain and, with a 
cloth, dry ~he interior of the head cover then let the assembly 
air-dry before reinstalling the base. Slow leaks around the valve 
plug are unavoidable because the plug must be loose enough to 
rotate freely Parts that are missing or defective will cause 
serious leaks. A missing or defective nozzle gasket (o-ring) will 
allow water to leak into the head A worn or missing air-line 
gasket will allow water to enter the head and will interfere with 
the compression process. To seal, the air-line gasket must be 
pliable To check for seal, open the head, place a paper strip 
against the body where the gasket makes contact, then close the 
head If the paper is loose or can be withdrawn easily, replace the 
gasket. Contrary to expectations, the head gasket is seldom a 
source of leaks. Do not use gasket cement If the head gasket must 
be replaced, order a replacement from the project. In emergencies, 
gaskets may be cut locally, but be sure to use gasket stock of the 
same thickness as the original. Improper gasket thickness will 
cause misalignment between the nozzle ~and valve body. Even with 
good seals, improper operation can cause damage. If the sampler is 
submerged to depths beyond its rating or if the sampler is 
submerged without a proper sample container, the compression 
chamber will fill and water will enter the head through the 
compression line.

A nozzle that is bent or burred around the ends will contribute to 
sampling errors and must be replaced. Replacement parts may be 
ordered from the Federal Inter-Agency Sedimentation Project. Also, 
samplers that require maintenance or recalibration may be shipped 
to the project.

(l) Inter-Agency Committee on Water Resources, "Determination of 
fluvial sediment discharge," Rept 14, A study of methods used in 
measurement and analysis of sediment loads in streams; 
Subcommittee on Sedimentation, Minneapolis, Minnesota, 1963.

(2) Guy, H. P.; Laboratory theory and methods for sediment 
analysis, Techniques of water-resources investigations of the U. 
S. Geological Survey, bk 5, ch Cl, 1969.

(3) American Society of Civil Engineers, "Sedimentation 
Engineering," by Task Committee, V. A Vanoni, ed , ASCE, New York, 
N. Y., 1975.

(4) Inter-Agency Committee on Water Resources, "The design of 
improved types of suspended sediment samplers," Rept. 6, A study 
of methods used in measurement and analysis of sediment loads in 
streams; Subcommittee on Sedimentation, Minneapolis, Minnesota, 
1952, p 22-34