FW Murphy MLS Series User manual

00-02-0730
2019-01-15
Section 15
MLSSeries
LiquidLevelSwitches
Installation and Operations Manual

CAUTION: MLS Series parts are not interchangeable with other
FW Murphy liquid level products. Damage caused by using incorrect
parts is not covered by our Limited Warranty.
Please read the following information before installing. A visual
inspection for damage during shipping is recommended before
mounting.
BEFORE BEGINNING INSTALLATION OF THIS FW 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.
OBSERVE all pressure and electrical ratings and requirements
for the devices and the operating environment.
BE SURE all pressure HAS BEEN REMOVED from the vessel
before opening any pressure connections.
Please contact FW Murphy Production Controls immediately if
you have any questions.

Table of Contents
Product Information...................................................................................................................1
Features.......................................................................................................................1
MLS Series Models and Accessories...........................................................................1
MLS Diagram ..............................................................................................................................2
Pressure Vessel Installation.....................................................................................................3
Direct Installation into the Wall of the Pressure Vessel................................................3
Installation with a Weld Collar......................................................................................4
Installation Using FW Murphy External Float Chamber................................................4
Electrical Wiring ...........................................................................................................5
Testing the MLS at Routine Preventive Maintenance...........................................................6
Test Button –MLS TF Model Only...............................................................................6
Testing MLS Switch Manually –MLS Models ..............................................................7
Replacement Parts.....................................................................................................................9
15000531: MLS Float...................................................................................................9
Accessories ................................................................................................................................9
15050375: Weld Collar................................................................................................9
15051098: External Float Chamber ............................................................................9
15700799: Series 100 External Float Chamber ........................................................10
Specifications...........................................................................................................................11
MLS Series.................................................................................................................11
Approximate Shipping Weights and Dimensions........................................................11

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Product Information
MLS Series Liquid Level Switches with 2 inch NPT and 1-1/2 inch NPT mounting are float activated to
operate an electrical SPDT reed switch for alarm or shutdown of an engine or electric motor. The MLS
Series connects directly into the scrubber wall and can be used with an FW Murphy weld collar or FW
Murphy external float chamber.
Features
Clean magnet design virtually eliminates iron filing accumulation onto the magnet
Seal-free construction
Designed for harsh gas compressor scrubber applications
Optional push button to test functions
CF8 (304) cast stainless steel body and 304 stainless steel float
MLS Series rated for 2000 psi (13.8 MPa) [138 bar] working pressure
Electric model only available
Improved design provides better dependability with reduced number of moving parts
All models screw directly into the scrubber or can be mounted via external float
chamber
CSA C/US Class l, Div. 1, Grp. B, C & D locations
Canadian Registration Number: MLS-020, MLS-015: 0F12013.2 C (all provinces and
territories) CSA approved
MLS Series Models and Accessories
This manual covers the models and accessories listed below.
Part Number
Description
Notes
15700840
MLS-015
1-1/2 in. NPT
15700905
MLS-015-TF , with Test Function
1-1/2 in. NPT
15700839
MLS-020
2 in. NPT
15700904
MLS-020-TF, with Test Function
2 in. NPT
15700799
External Float Chamber
Operating Pressure: 2000 psi (13.8 MPa) [138 bar]
Operating Temperature: 400° F (204° C)
15050375
Weld Collar
15000892
1-inch Float Extension Kit

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MLS Diagram
All models of the MLS Series install the same and share dimensions other than Test Button.
MLS (TF) Models
MLS
NOTE: Refer to Table 2 for clearances.

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Pressure Vessel Installation
Direct Installation into the Wall of the Pressure Vessel
CAUTION: Determine that the float travel is not
obstructed by the coupling in the vessel wall, internal
baffles, etc.
Refer to tables 1 and 2 for application data.
INSTALLATION SHOULD BE ACCOMPLISHED BY
QUALIFIED PERSONNEL ONLY.
 Make certain the float is tightly screwed onto the counter-balance.
 Before installing the level switch, use of a pipe thread sealant is
recommended. Screw the unit directly into the threaded connection in
the wall of the pressure vessel.
 Verify that the electrical connection is positioned at the bottom.
NOTE: The word TOP is cast into the top of the body.
 Make the electrical wiring connections according to appropriate wiring
diagrams for the alarm or shutdown system to be used. The electrical connection is ½ inch-
14 NPT.
 Ensure all electrical connections are insulated and the cover is fully installed before
reconnecting electrical power.
 Verify all pressure connections are tight before pressurizing the system.
Float Clearance Reference Tables
Pipe Data - Table 2
Nom. Size
(inches)
O.D.
(inches)
Schedule
Number
Wall Thickness
(inches)
Inside Diameter
(inches)
2.5
2.875
40STD
0.203
2.469
3
3.5
40STD
0.216
3.068
3
3.5
80XS
0.3
2.9
4
4.5
40STD
0.237
4.026
4
4.5
80XS
0.337
3.826

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Installation with a Weld Collar
 The weld collar, P/N 15050375, must be welded into the wall of the
pressure vessel according to code standards and good welding
practices.
 Follow above instructions for installation directly into the wall of the
pressure vessel.
NOTE: Weld collar 15050375 is not recommended with
a 1-inch float extension.
Installation Using FW Murphy External Float Chamber
 Install the FW Murphy float chamber 15051098 or 15700799 on the outside wall of the
pressure vessel using 1” NPT piping. Position the 2-inch NPT threaded connection at the
height where you want the level switch to operate. The 2-inch NPT threaded connection
must be positioned away from the tank wall.
NOTE: If using Float Chamber 15051098,
best practices recommend a surface mount
installation.
 A tee and bleed valve are typically installed at the
bottom of the lower 1-inch pipe riser to allow draining
of the float chamber for servicing or replacement.
NOTE: A typical installation with blocking
and bleed valves is shown at right.
 Install the MLS-020 in the 2-inch NPT connection of
the float chamber. BE SURE float travel is not
restricted and that the float is tight onto the counter-
balance.
 To complete the installation and wiring, follow the
instructions for mounting directly into wall of the vessel
and for wiring.

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Electrical Wiring
Under Back Cover
Switch Rating: 30VDC/VAC @ 75 mA
Back Cover

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Testing the MLS at Routine Preventive Maintenance
Test Button –MLS TF Model Only
Considerations
The tank level can affect the test results. If the tank level is above the float, the float will already be in
the up position, and the test button won’t have anything to move. If the float is partially floating, you
might not be able to hear the float drop.
NOTE: With a higher tank pressure, the Test Button will be noticeably harder to
push.
Test IMPORTANT: The panel should be in Test Mode if it is operating to avoid unintentional
shutdowns during test.
This procedure tests for float function; the complete mechanism including the magnetic activation of the
reed switch; and the wiring from the switch to the control panel.
1. If operating at time of testing, put the panel in Test Mode to avoid an unintentional shutdown.
2. Push the Test Button in while listening for the float to hit the top of the body.
3. Release the Test Button while listening for the float to hit the bottom of the body.
a. When you hear the float hitting the body as you press and release the button, the float is
attached and working properly.
b. If the float is gone, the counter balance will rotate to the faulted or high level position
causing the switch to trip. The MLS unit will have to be removed and repaired or
replaced.
c. As the test button is being pressed, the motion should be fairly smooth and consistent
through the entire travel of the button and return. If it is not, there is a problem with the
float mechanism, and the MLS unit will have to be removed and repaired or replaced.