Installation and Operation of the
DF Series Hydrostatic Head Level Switches
DF-94063N
Revised 09-03
Section 15
(00-02-0170)
Please read the following information before installing. A visual inspection of this product for damage during shipping is recommended before mounting. It is your responsibility to have a qualified person install this unit and make sure it conforms to NEC and local codes.
GENERAL INFORMATION
WARNING
BEFORE BEGINNING INSTALLATION OF THIS MURPHY PRODUCT
✔
Disconnect all electrical power to the machine.
✔
Make sure the machine cannot operate during installation.
✔
Follow all safety warnings of the machine manufacturer.
✔
Read and follow all installation instructions.
*
**
CAUTION: Certain dangers to human safety and to equipment may occur if some equipment is stopped without pre-warning. It is recommended that monitored functions be limited to alarm only or to alarm before shutdown.
Description
The DF series are diaphragm operated “hydrostatic head pressure” level switches. A pressure sensitive diaphragm operates a snap-switch that can be wired directly to electric pilot circuits to control pumps at predetermined levels. Typical application is to start and stop electric driven pump(s) to maintain tank levels. It is also applicable to engine driven pumps.
The Nitrile sensing diaphragm is impervious to most liquids and is sensitive enough to control levels with 1/4 in. (6 mm) repeatability.
See model descriptions for limits of switch trip point adjustability.
Materials include aluminum body, nylon bottom plate and a special alloy leaf snap-switch as standard.
This simple level switch is highly reliable and can be worked into most new or existing system without major modification or special tools.
DF755 and DF757 are suitable for atmospheric tanks in a non-hazardous location.
The SPDT snap-switch for the DF755 is preset for a 4 in. (102 mm) differential in liquid level, operating at approx. 6 inches (152 mm) rising, and resetting at approx. 2 inches (51 mm) falling level.
The DF757 trip point is adjustable over a 108 inches (2743 mm) differential.
Specifications
Snap-switch Ratings
SPDT (standard–all models)
• 5 A @ 125, 250, or 480 VAC
• 1/2 A @ 125 VDC, 1/4 A @ 250 VDC
Case/Lid: Aluminum (standard); all non-explosion proof models.
Bottom Plate: Glass-filled nylon.
Process Connection: 1 NPT (standard)
Maximum Pressure Rating: 25 psi (172 kPa) [1.72 Bar].
Conduit Connection (electrical): 1/2 NPT.
Warranty
A limited warranty on materials and workmanship is given with this FW
Murphy product. A copy of the warranty may be viewed or printed by going to www.fwmurphy.com/support/warranty.htm
DF-94063N page 1 of 4
DIMENSIONS
DF755EX
DF755 and DF757
5-1/2 in.
(140 mm)
7-21/32 in.
(194 mm)
6-5/32 in.
(156 mm)
1/2 NPT
Plug
Supply
Pump
1 NPT
(standard)
Raw Water Tank
DF#1
DF#2
DF#3
DF#4
1/2 NPT
For Electrical
Connection
1/4 in. (6 mm)
Tube Fitting
(DF756 only)
1 NPT
(standard)
5-5/8 in.
(143 mm)
TYPICAL APPLICATIONS
Transfer
Pump
Filter
Clear Water Tank
DF#5
DF#6
DF#7
DF#8
Injection Pump
OPL Series
SWICHGAGE ®
Typical Water Flood Control System
The diagram above displays eight DF Series switches installed on a
Raw Water tank and a Clear Water tank. When raw water rises to predetermined level, DF#1 stops the supply pump. As tank level falls below the predetermined level, DF#2 starts the supply pump. If the tank level continues to fall, DF#3 initiates shutdown of the supply pump. DF#4 stops transfer pump before raw water tank is completely pumped out.
When clear water reaches the predetermined level, DF#5 stops the transfer pump. As tank level falls to predetermined low level, DF#6 starts the transfer pump. If the tank level continues to fall due to the failure of the filters section, DF#7 initiates shutdown of the transfer pump. (DF755 located at this level will also operate backwash equipment). DF#8 stops injection pump before tank pumps completely out.
An OPL Series pressure SWICHGAGE ® stops injection pump when pressure reaches predetermined high or low pressure.
Tank with Low Pressure
Gas Blanket (DF755EX)
The DF755EX (below) is shown installed on a crude oil tank where a low pressure gas blanket is used to prevent evaporation loss. It is mounted directly to the side of the tank or on riser pipe 4 to 7 in.
(102 to 178 mm) below level to be controlled. Pump automatically stops or starts when liquid reaches predetermined high or low level.
Typical Tank Mounting Methods (DF755)
Bull Plug Installation Tank Wall Mounting With
Drain Cock
Fuel Tank
Gas Blanket
Gas Liquid
1/2 NPT
For Electrical
Connection
Directly
On Tank
DF-94063N page 2 of 4
Riser Pipe
Method
Tank Wall Mounting
BASIC OPERATION
DF755EX
DF755 DF757
C
C
B
B
B
D
C
A
Vent (DF755EX) or Tube Fitting
(DF756)
A
A
Hydrostatic Head
Pressure
Hydrostatic Head
Pressure
Hydrostatic Head
Pressure
As the liquid level rises, hydrostatic head pressure is applied to the diaphragm
A
. The diaphragm is forced upward forcing the actuator arm
B
to activate the snap-switch
C
.
Models DF755 and DF755EX are factory set and operate at approximately
2 in. (51 mm) and 6 in. (152 mm) rising above the level at which the diaphragm is mounted. The switch resets back to normal condition at approx. 2 inches (51 mm) falling level. The trip point(s) for Model DF757 are adjustable between 2 in. (51 mm) and 110 in. (2794 mm) for high and low (make/break) operation by knobs,
D
.
For sealed tanks, model DF755EX can be fitted with a tube fitting to balance the top of the diaphragm chamber to a tank gas blanket (see Typical
Applications). The DF755EX is supplied with an atmospheric vent fitting.
Setpoint Adjustment (DF757)
1. Locate threaded adjustment shaft and adjustment knobs (see drawing above).
2. To increase low level setpoint, rotate lower knob counterclockwise.
NOTE: If adjustment shaft turns when rotating adjustment knobs, grasp the adjustment shaft with a pair of needle nose pliers–then rotate knob.
Adjustment
Shaft
USING THE DF755 WITH MAC1 VOLUME CELL ACCESSORY
The MAC1 Volume Air Cell when attached to the DF755 can monitor water levels on a sump. Activate alarms or start a pump directly. The
MAC1 Volume Air Cell is non-corrosive and provides 1/4-20 stainless steel mounting studs.
The MACT1 Tubing Kit provides 4 ft. (1.2 m) flexible, non-corrosive
1/4 in. (6 mm) tubing (cut to fit). The kit includes necessary fittings to attach tubing.
Both the MAC1 air cell and MACT1 tubing kit are available from
Murphy.
Volume Cell Operation
As liquid rises around the volume cell, it compresses air inside the cell and forces it up in the sensor line. As air pressure increases due to the water level continuing to rise, sufficient pressure will be applied to activate the internal snap-switch, which in turn starts the pump. As the liquid level is pumped down, pressure decreases and the above procedure is reversed. The pump is stopped and held in a standby condition. An air purge may be required in the sensor line. Consult factory.
Choosing a Volume Cell
The volume cell should be constructed of material which will be unaffected by the liquid being measured. For proper “pressure-to-level” ratio, the minimum dimensions of the volume cell should be 6 in. (152 mm) inside diameter and 3 in. (76 mm) inside depth. The sensor line can be of any diameter or material either flexible, or solid, as long as it is of sufficient length to reach from the volume cell to the desired location for the DF755. All fittings and connections should be air-tight to avoid loss of “charge”. Tube lengths longer than 4 ft. (1.2 m) should have provision for periodic air purging.
Installation of the Volume Cell
Install the volume cell according to the level you wish the pump to start and stop. Secured the volume cell with a substantial bracket which will not allow the cell to be “floated” or tilted when the water level rises. The DF755 should be installed well above the highest
DF755 water level and in a position that will allow access for adjustment or repair.
NOTE: Periodically operate pump manually until water level reaches a point approximately 1/2 in. (13 mm) below bottom of the volume cell. This will automatically re-charge the unit and compensate for normal absorption of air into water.
Small electric air pumps are available to automatically charge system at all times.
Sensor Line
(MACT1 Tube Kit)
Volume Cell
(MAC1)
DF-94063N page 3 of 4
Starts at Low Level, Stops at High
Start motor when predetermined low level is reached and stop when high level is reached. Keeps tank level within selected limits. Motor starter equipped with H.O.A.
HIGH
N.O.
C
N.C.
DF755
#1
TYPICAL WIRING
Starts at High Level, Stops at Low
Start motor when predetermined high level is reached and stop when low level is reached. Motor starter equipped with H.O.A.
HIGH
N.O.
C
DF755
#1
N.C.
N.O.
C
N.C.
LOW
DF755
#2
MOTOR
Single Magneto Shutdown
Wiring of magneto to N.O. switch terminal will shut down engine at predetermined high level, shown below. Wire to N.C. terminal to shutdown on low level.
MAGNETO
MOTOR
N.O.
C
N.C.
LOW
DF755
#2
Dual Magneto Shutdown
Shutdown dual magneto engines using Murphy MS2120 Magnetic Switch.
Diagram below shows hookup for low level shutdown. Wiring changes and mounting locations are necessary for high level shutdowns.
Model MS2120
N.O.
C
N.C.
DF755
Cover (aluminum)
Case (aluminum)
Cover Screws (3), #6–32 x 5/16 round head
SPDT snap-switch and movement assembly/repair kit (5 amp)
Screws (3) for switch assembly to case, #6–32 x 1/4 round head
Diaphragm repair kit
Bottom Plate (1 NPT connection)
Bracket and movement repair kit
SPDT snap-switch and insulator repair kit (5 amp)
DF755EX
Cover (aluminum)
Case (aluminum)
Gasket
SPDT snap-switch and movement assembly/repair kit (5 amp)
Screws (2) for switch assembly to case, #6–32 x 1/4 round head
Actuator assembly/repair kit
Diaphragm repair kit
Bottom Plate (1 NPT connection)
Screw (1), #8–32 x 1/4 round head
Terminal cup washer
Plug 1/8 plastic pipe hex (DF755EX)
Connector, 1/4 tube x 1/8 pipe male (DF756)
Plug 1/2 NPT hex (brass)
SPDT snap-switch and insulator repair kit (5 amp)
15050154
15050155
15050305
15000118
80040605
15000119
15000123
15050083
80040814
00000827
86060203
85030402
86060801
15000117
Magneto
6 1 2 3 4 5
Magneto
N.O.
C
N.C.
Jumper #2 & #5
SERVICE PARTS
15050081
15050082
80040607
15000122
80040605
15000123
15050083
15000313
15000121
DF757
Case (aluminum)
Cover Screw (3), #6–32 x 5/16 round head
15050081
15050594
80040607
SPDT snap-switch and bracket assembly/repair kit (5 amp) 15000174
Screws (2) for switch bracket and assembly to case (#6–32 x 1/4 round head) 80040605
Spring and piston assembly/repair kit
Diaphragm repair kit
Bottom Plate (1 NPT connection)
SPDT snap-switch and insulator repair kit (5 amp)
15000190
15000123
15050083
15000230
FW Murphy
P.O. Box 470248
Tulsa, Oklahoma 74147 USA
+1 918 317 4100
fax +1 918 317 4266
e-mail [email protected] www.fwmurphy.com
CONTROL SYSTEMS & SERVICES DIVISION
P.O. Box 1819; Rosenberg, Texas 77471; USA
+1 281 633 4500 fax +1 281 633 4588
e-mail [email protected]
MURPHY DE MEXICO, S.A. DE C.V.
Blvd. Antonio Rocha Cordero 300, Fracción del Aguaje
San Luis Potosí, S.L.P.; México 78384
+52 444 8206264 fax +52 444 8206336
Villahermosa Office +52 993 3162117
e-mail [email protected]
www.murphymex.com.mx
FRANK W. MURPHY, LTD.
Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.
+44 1722 410055 fax +44 1722 410088
e-mail [email protected]
www.fwmurphy.co.uk
MURPHY SWITCH OF CALIFORNIA
41343 12th Street West
Palmdale, California 93551-1442; USA
+1 661 272 4700 fax +1 661 947 7570
e-mail [email protected]
www.murphyswitch.com
MACQUARRIE CORPORATION
1620 Hume Highway
Campbellfield, Vic 3061; Australia
+61 3 9358 5555 fax +61 3 9358 5558
e-mail [email protected]
R
E
G ISTERE
D
USA–ISO 9001:2000 FM 28221
UK–ISO 9001:2000 FM 29422
In order to consistently bring you the highest quality, full featured products, we reserve the right to change our specifications and designs at any time.
Printed in U.S.A.
DF-94063N page 4 of 4
