Graco SaniForce Instruction Manual

Operation
SaniForce® Sanitary Tote
Unloader (STU)3A5416C
EN
For use with food grade bulk supply of medium to high viscosity product. For professional use only. Only
select models are approved for use in explosive atmospheres or hazardous locations. See Configuration
Matrix on page 6 for more information.
Important Safety Instructions
Read all warnings and instructions in this manual and all related
manuals. Save all instructions.
For Maximum Working Air and Fluid
Pressures, see Models on page 8.
PROVEN QUALITY. LEADING TECHNOLOGY.

Contents
Related Manuals ................................................ 2
Warnings ........................................................... 3
Configuration Matrix............................................ 6
Models............................................................... 8
Overview............................................................ 9
System Components.................................... 9
Before Installing.................................................. 11
Uncrating Equipment.................................... 12
Location ...................................................... 13
Moving Frame to Location ............................ 13
Installation.......................................................... 14
General Information ..................................... 14
Grounding ................................................... 14
AC Power.................................................... 15
Fluid Outlet Lines......................................... 15
Safety Latch ....................................................... 16
Install Lockout Extension .............................. 16
Safety Latch Lockout.................................... 16
Engaging Safety Latch ................................. 16
Disengaging safety latch............................... 16
Controls and Connections ................................... 17
Control Panel (Pneumatic)............................ 17
Control Panel (Electro-Pneumatic) ................ 22
Operation........................................................... 24
Pressure Relief Procedure............................ 24
Flush the Pump Before First Use .................. 24
Adjust Tote Guides ...................................... 25
Loading the Tote.......................................... 25
Start and Adjust the Pump............................ 26
Change Tote................................................ 26
Emergency Stop .......................................... 27
Pump Shutdown .......................................... 27
System Shutdown ........................................ 27
Flushing and Storage ................................... 27
Maintenance ...................................................... 28
Lubrication................................................... 28
Cleaning the Ram Plate................................ 28
Cleaning the Pump Lower ............................ 28
Electro-pneumatic Control Panel Display
Screens................................................ 29
Startup Screen............................................. 31
Automatic Screen......................................... 32
Manual Screen ............................................ 34
Recipe Screens ........................................... 36
Event Log.................................................... 44
Job Log ....................................................... 47
System Configuration Screen ....................... 48
Feedback Control Settings Screens .............. 50
About .......................................................... 53
I/O Status Screen......................................... 54
Dimensions ........................................................ 55
Schematic (pneumatic control) ............................ 56
Schematic (electo-pneumatic control) .................. 57
Technical Data ...................................................62
Related Manuals
Manual Number Title
3A5417 SaniForce Sanitary Tote Unloader (STU), Repair
3A5798 SaniForce 5:1 Sanitary Pumps, Instructions and Parts
3A5799 SaniForce 12:1 Sanitary Pumps, Instructions and Parts
3A5999 SaniForce High Sanitation Diaphragm Pumps, Instructions and Parts
3A6781 SaniForce 1590 High Sanitation Diaphragm Pump, Repair and Parts
3A6782 SaniForce High Sanitation Diaphragm Pumps, Models 2150, 3150, 4150, Repair
and Parts
3A1211 SaniForce Air Motors, Instructions and Parts
3A6101 Enclosed Manual Controls, Repair/Parts
3A6102 Electro-pneumatic Controls, Repair/Parts
23A5416C

Warnings
Warnings
The following warnings are for the setup, use, grounding, maintenance, and repair of this equipment. The
exclamation point symbol alerts you to a general warning and the hazard symbols refer to procedure-specific
risks. When these symbols appear in the body of this manual or on warning labels, refer backtothese
Warnings. Product-specific hazard symbols and warnings not covered in this section may appear throughout
the body of this manual where applicable.
WARNING
ELECTRIC SHOCK HAZARD
This equipment must be grounded. Improper grounding, setup, or usage of the system can
cause electric shock.
• Turn off and remove power before disconnecting any cables and before servicing or installing
equipment. For cart-mounted models, unplug the power cord. For all other units, disconnect
power at the main switch.
• Connect only to grounded power source.
• All electrical wiring must be done by a qualified electrician and comply with all local codes
and regulations.
FIRE AND EXPLOSION HAZARD
Flammable fumes, such as solvent and paint fumes, in work area can ignite or explode. Paint
or solvent flowing through the equipment can cause static sparking. To help prevent fire and
explosion:
• Use equipment only in well ventilated area.
• Eliminate all ignition sources; such as pilot lights, cigarettes, portable electric lamps, and
plastic drop cloths (potential static sparking).
• Ground all equipment in the work area. See Grounding instructions.
• Keep work area free of debris, including solvent, rags and gasoline.
• Do not plug or unplug power cords, or turn power or light switches on or off when flammable
fumes are present.
• Use only grounded hoses.
•Stop operation immediately if static sparking occurs or you feel a shock. Do not use
equipment until you identify and correct the problem.
• Keep a working fire extinguisher in the work area.
Static charge may build up on plastic parts during cleaning and could discharge and ignite
flammable vapors. To help prevent fire and explosion:
•Cle
an plastic parts only in well ventilated area.
•Don
ot clean with a dry cloth.
3A5416C 3

Warnings
WARNING
SKIN INJECTION HAZARD
High-pressure fluid from dispensing device, hose leaks, or ruptured components will pierce
skin. This may look like just a cut, but it is a serious injury that can result in amputation. Get
immediate surgical treatment.
• Do not point dispensing device at anyone or at any part of the body.
• Do not put your hand over the fluid outlet.
• Do not stop or deflect leaks with your hand, body, glove, or rag.
• Follow the Pressure Relief Procedure when you stop spraying/dispensing and before
cleaning, checking, or servicing equipment.
• Tighten all fluid connections before operating the equipment.
• Check hoses and couplings daily. Replace worn or damaged parts immediately.
MOVING PARTS HAZARD
Moving parts can pinch or amputate fingers and other body parts.
• Keep clear of moving parts.
• Do not operate equipment with protective guards or covers removed.
•Pressu
rized equipment can start without warning. Before checking, moving, or servicing
equipment, follow the Pressure Relief Procedure and disconnect all power sources.
43A5416C

Warnings
WARNING
EQUIPMENT MISUSE HAZARD
Misuse can cause death or serious injury.
• Do not operate the unit when fatigued or under the influence of drugs or alcohol.
• Do not exceed the maximum working pressure or temperature rating of the lowest rated
system component. See Technical Data in all equipment manuals.
• Use fluids and solvents that are compatible with equipment wetted parts. See Technical Data
in all equipment manuals. Read fluid and solvent manufacturer’s warnings. For complete
information about your material, request Safety Data Sheet (SDS) from distributor or retailer.
• Turn off all equipment and follow the Pressure Relief Procedure when equipment is not in use.
• Check equipment daily. Repair or replace worn or damaged parts immediately with genuine
manufacturer’s replacement parts only.
• Do not alter or modify equipment. Alterations or modifications may void agency approvals
and create safety hazards.
• Make sure all equipment is rated and approved for the environment in which youareusingit.
• Use equipment only for its intended purpose. Call your distributor for information.
• Route hoses and cables away from traffic areas, sharp edges, moving parts, and hot surfaces.
• Do not kink or over bend hoses or use hoses to pull equipment.
• Keep children and animals away from work area.
• Comply with all applicable safety regulations.
TOXIC FLUID OR FUMES HAZARD
Toxic fluids or fumes can cause serious injury or death if splashed in the eyes or on skin,
inhaled, or swallowed.
• Read Safety Data Sheets (SDSs) to know the specific hazards of the fluids you are using.
•Storeh
azardous fluid in approved containers, and dispose of it according to applicable
guidelines.
PERSONAL PROTECTIVE EQUIPMENT
Wear appropriate protective equipment when in the work area to help prevent serious injury,
including eye injury, hearing loss, inhalation of toxic fumes, and burns. Protective equipment
includes but is not limited to:
• Protective eyewear, and hearing protection.
•Resp
irators, protective clothing, and gloves as recommended by the fluid and solvent
manufacturer.
3A5416C 5

Configuration Matrix
Configuration Matrix
Check the identification plate (ID) for the Configuration Number of your system. Use the following matrix to
define the components of your system.
Sample Configuration Number: STU A01AAA1AA1C21
STU A01 AAA 1AA 0C21
Sanitary
Tote
Unloader
Frame Pump Plate Size
(Bin Type)
Seal
Type
Seal
Material
Controls Accessories Wash Kit Certification
NOTE: Some combinations are not possible. Please check with your local supplier.
Sanitary
Tote
Unloader
Frame Pump Plate Size
(Bin Type)
Seal Type
STU AStainless
Steel, Footed 01 5:1 DoubleBall 2pumps A44.375 x 40.375
(plywood) AInflatable
BStainless
Steel,
Extended Legs 02 5:1 Priming Piston
2pumps
B43.9 x 39.9
(Buckhorn 315)
03 12:1 Priming Piston, 2
pumps C55.5 x 42 (Goodpack)
04 5:1 Double Ball, 4 pumps D43.375 x 35.625
(TNT)
05 5:1 Priming Piston, 4 pumps E43.5 x 40.375
(Arena)
06 12:1 Priming Piston, 4
pumps F41.32 x 38.9 (Ceva/Pallecon)
07 2150 HS Ball Check, 2
pumps G43.125 x 36.375
(SpaceKraft)
08 3150 HS Flapper Check,
EO, AODD, 2 pumps
09 3150 HS Flapper Check,
PO, AODD, 2 pumps
10 3150 HS Flapper Check,
PS, AODD, 2 pumps
11 3150 HS Flapper Check,
SP, AODD, 2 pumps
63A5416C

Configuration Matrix
Seal Material Controls Accessories Wash Kit Certification
APolychloro-
prene (White) 1Enclosed Pneumatic AA Bag Clamp Kit 0None C21 EN 10204 type 2.1
BEPDM
(Black) 2*Electro-
pneumatic AB Aceptic Liner
Clamp Kit 1Poly Tank Kit C31 EN 10204 type 3.1
* Not ATEX. Not intended for use in explosive or hazardous environments.
All models are rated and are FDA compliant.
ATEX models with piston pumps are
rated II 2 GD
Ex h IIA T4 Gb X
Ex h IIIB T100°CDbX
ATEX models with diaphragm pumps
are rated II 2 GD
Ex h IIA 82°C...160°CGbX
Ex h IIIB T135°CDb
Electro-pneumatic control panel
component approval
Conforms to UL STD 508A
Certified to CSA STD C22.2 No. 14
3A5416C 7

Models
Models
Pump
Option
Max Pump Air Inlet
Pressure PSI (MPa,
bar)
Max Working Fluid
Pressure PSI (MPa, bar)
Max System Air
Consumption scfm (m3/min)
Max Control Air Inlet
Pressure PSI (MPa,
bar)
01
02
80 (0.55, 5.5)410 (2.83, 28.3) 140 (3.9)
03 100 (0.69, 6.9) 1450 (10.0, 100) 240 (6.8)
04
05
80 (0.55, 5.5) 410 (2.83, 28.3) 140 (3.9)
06 100 (0.69, 6.9) 1450 (10.0, 100) 240 (6.8)
07
08
120 (0.84,8.4) 120 (0.84,8.4) 150 (4.2)
100 (0.69, 6.9)
09
10
11
83A5416C

Overview
Overview
System Components
Fig. 1 Typical components
1–A Stainless Steel Frame: supports all of the system components.
1–B Sanitary Pumps: pump material from the tote to the target application.
3A5416C 9

Overview
1–C Air Cylinders: raises and lowers the pumps and the ram plate in and out of the material container.
1–D Ram Plate: applies an even amount of pressure to the material in the tote. When the ram plate
seal is inflated, it creates a seal. The ram plate presses down on the material in the tote to assist
the pumps in delivering the material.
1–E Control Panel: contains pneumatic controls to regulate the air pressure to pump air motors, ram,
and ram plate seal in order to:
• control pump air motor pressure
• control pump speed control
• control ram up and down pressure and speed
• control seal pressure
• turn the pumps on or off
• inflate or deflate the ram plate seal
• raise or lower the ram plate
• control ram plate blowoff air
1–F Pump Output Lines: delivers product output from pump.
1–G Support Plate: provides support for pump outlet tubes.
1–H Rear Gate: provides tote positioning and access.
1–J Pilot Check Valve: prevents unexpected cylinder movement.
1–K Tote Guides: provides alignment for tote.
1–M Seal Retainer Plate: keeps inflatable seal in place.
1–N Inflatable Seal: inflates to create a seal between the ram plate and inside surface of tote.
1–P Corner Seal: seals corners between ram plate and inside corner of tote.
1–R Crossbar: main structural support for cylinder/ram plate assemblies.
1–S Safety Latch: Engage to prevent accidental lowering of ram plate.
10 3A5416C

Before Installing
Before Installing
Palletized STU
3A5416C 11

Before Installing
Uncrating Equipment
NOTICE
Moving the SaniForce STU off the pallet without
following this uncrating procedure can damage
equipment.
Uncrate the STU as follows:
1. Inspect the crate for shipping damage. Contact
the carrier if damaged.
2. Remove plywood top and sides of crate.
3. Check the contents for loose or damaged parts.
4. Compare the packing slip against items inside
the crate. Immediately call your Graco distributor
about any shortages or damage.
5. Remove all band straps.
6. Remove the clevis pins holding the rear gate and
remove the gate.
7. Remove the bolts holding the frame parts and
move to the installation location.
NOTE: Use sanitary anti-sieze (provided) on all
threaded joints to prevent galling.
NOTE: When installing, the crossbar (1–R) must
be oriented with the safety latch bracket facing
the leg assembly which doesn’t contain the
control panel. This orientation is also necessary
to allow proper installation of the rigid air line from
the pilot check valve (1–J) to the air manifold
located on the crossbar between the air cylinders.
8. InstallaprovidedPTFEgasketontopofeach
frame at the location (FG) where the crossbar
will be mounted. Use a forklift or overhead crane
to move the air cylinder and pump assembly into
place on the top of the frame assembly. Attach
the crossbar to the leg assembly using the bolts
provided.
NOTE: Air pressure must be provided to raise
the air cylinder center shafts enough to allow the
safety latch to be disengaged. Do not force the
safety latch to disengage. It may be necessary
to install this safety latch extension rod at a later
time.
9. Disengage the safety latch (1–S). On the leg
assembly without the control box mounted on it,
insert the end of the safety latch extension rod
through the hole closest to the vertical center
leg and then through the D-shaped hole on the
safety latch. Install the locking nut on the safety
latch extension rod.
10. Install the rear gate and clevis pins on the frame.
11. Attach the rigid air line between the cylinder air
distribution manifold, down air pressure fitting
(EE) and the pilot valve tee (EE1).
12. Install each air motor exhaust hose to the top of
the closest muffler tube.
13. Attach independent air lines to the 2 control box
inlet valves.
NOTE: Separate air inlets are provided to prevent
loss of pneumatic valve control should pumps
consume high volumes of air. Use independent
air supplies.
14. Attach output tubing to the pump output piping.
NOTE: Use only appropriate pressure-rated
components.
123A5416C

Before Installing
Location
When selecting a location, make sure the location:
• Is close to where the fluid is being delivered to
minimize back pressure and maximize flow rate.
• Provides enough room around the equipment for
maintenance.
• Does not interfere with opening the control panel
door or frame door (on one or both sides).
• Provides enough room on the right and/or left side
of the SaniForce STU to easily load and unload
fluid totes with a forklift or pallet jack hand truck.
• Provides easy and safe access to the air supply
shutoff valves and the control panel. Graco
recommends a minimum of 3 ft (0.91 m) of open
space in front of the panel.
• Provides enough overhead clearance (10 ft, 2.7 m
recommended) for installing and servicing the STU.
• Has a flat, level floor, or level pads.
Moving Frame to Location
The frame is shipped with several major
components attached and weighs about 1500 lb.
(680 kg). To avoid injury and equipment damage,
follow instructions below.
The STU must be firmly attached to the floor. The
STU is capable of exerting downward force of 2220
lbf (9.9 kN) which could cause the STU to lift off of
the floor during operation.
• Use a forklift or hand truck and support devices,
such as a hoist, and have an adequate number of
personnel to move the frame to the installation site.
• Avoid jarring or tilting the frame while moving it.
• When the fully assembled unit has been moved to
the installation location:
–Markthel
ocation of the mounting foot holes on
the floor.
–Movethef
rame out of position by rotating it to
the side.
– Drill anchor mounting holes and insert anchors
at all marked foot hole locations.
– Rotate the frame back into position and install
frame mounting bolts through frame feet.
3A5416C 13

Installation
Installation
All electrical wiring must be done by a qualified
electrician and comply with all local codes and
regulations.
General Information
Reference letters in the text, for example (A), refer to
the callouts in the figures.
The STU System consists of stationary parts and
parts attached to the air cylinder center shafts. The
parts, such as the pumps and plate, attached to
the air cylinder center shafts will raise and lower
(move) during normal operation. These moving parts
comprise the ram.
Installation will involve attaching air lines
between various system components. Refer to
Controls and Connections, page 17 for details
regarding those air line connections from the control
panel.
Grounding
The equipment must be grounded to reduce the
risk of static sparking and electrical shock. Electric
or static sparking can cause fumes to ignite or
explode. Improper grounding can cause electric
shock. Grounding provides an escape wire for the
electric current.
Before operating the pump, ground the system as
explained below.
•Electro-pneumatic control panel: If installed, it is
grounded through the grounding conductor of the
incoming power wiring.
•Pump: The pumps are grounded by the metal
components being attached to the STU.
•Air and fluid hoses: Use only grounded hoses with
a maximum of 500 ft (150 m) combined hose length
to ensure grounding continuity. Check electrical
resistance of hoses. If total resistance to ground
exceeds 29 megohms, replace hose immediately.
•Dispense valve: ground through connection to a
properly grounded fluid hose and pump.
•Fluid supply container: Follow local code.
•Solvent containers used when flushing: Follow
local code. Use only conductive metal containers,
placed on a grounded surface. Do not place the
container on a non-conductive surface, such as
paper or cardboard, which interrupts grounding
continuity.
•STU: If using the electro-pneumatic control panel,
the STU is grounded by the ground wire in the
electrical connection to the panel. If using the
pneumatic control panel, the user must attach a
ground wire between the STU and earth ground.
Ground wire 237686 is available separately.
Check your system electrical continuity after the
initial installation, and then set up a regular schedule
for checking continuity to be sure proper grounding
is maintained. The resistance should not exceed 1
ohm.
143A5416C

Installation
AC Power
AC power is required for an unloader with an
electro-pneumatic control panel.
All electrical wiring must be done by a qualified
electrician and comply with all local codes and
regulations.
1. Route wires to control panel through electrical
conduit. Attach conduit using hole on bottom
right hand side of enclosure with a type 4X rated
conduit hub.
2. Attachthepowersystemgroundwiretothe
chassis ground lug (as shown) with a minimum
14 AWG (2.0 mm2) stranded copper wire. Torque
to 35 in-lbs (3.95 N•m).
3. Connect equipment to 100 – 240 VAC, single
phase, 50/60 Hz, with a maximum 15 A branch
circuit protection and disconnect switch provided
by the installer. Use 14 AWG (2.0 mm2) stranded
copper wire and attach to L1 and L2 on power
switch as shown. Torque to 8 in-lbs (0.9 N•m).
Fluid Outlet Lines
NOTICE
To prevent damage to equipment, be sure all
components are adequately sized and pressure
rated to meet the system’s requirements. Refer to
the pump manual for output pressure.
1. Connect desired pump outlet fittings (not
supplied) to the fluid outlet port (1-F) of each
pump.
2. Connect a grounded, flexible fluid hose (not
supplied) to either the user-supplied fittings or
thefluidoutletport(1-F).
3A5416C 15

Safety Latch
Safety Latch
The overall system weighs about 2400-3400 lb.
(1089-1542 kg). To prevent being trapped under
ram plate, always set manual safety latch to
Engage position when working under the plate.
Install Lockout Extension
A safety latch lockout extension rod has been
provided for use on the safety latch. Installation of
the extension rod requires the safety latch to be
disengaged.
1. Disengage the safety latch. See Disengaging
Safety Latch.
2. Use ram jog to lower the ram plate to its lowest
position.
3. Follow the Pressure Relief Procedure, page 24
4. Insert the safety latch extension rod (W) through
thebracket(X)andattachtheextensionrodto
the safety latch at the D-shaped hole on the latch
with the polymer insert nut provided.
Safety Latch Lockout
Lockout/tagout holes have been provided to lock the
ram in the raised position.
1. Push the safety latch handle all the way in to
align the lockout/tagout holes (Y).
2. Insert a padlock through the hole and lock in
place.
Engaging Safety Latch
1. Using the ram position selector, raise ram until it
stops at the maximum height.
NOTE: Thesafetylatchmustalignwiththe
grooves in the cylinder center rods to move.
2. Push the safety latch handle in the direction
shown to engage with the groove in the cylinder
rod (shown engaged).
Disengaging safety latch
1. Using the ram position selector, make sure plate
is raisedallthewayup(notrestingonsafety
latch).
2. Pull the safety latch handle all the way out to
disengage the groove in the cylinder rod.
16 3A5416C

Controls and Connections
Controls and Connections
Control Panel (Pneumatic)
Part No. 25C578
Control Side View Component Panel
3A5416C 17

Controls and Connections
Connection Side View Bottom View
NOTE: When routing hoses for the air motor air
supply, seal inflation, and air assist (blowoff) through
the hose support bracket on the side of the frame,
most of the lengths of each hose must be able to
move freely above the hose support bracket as
the ram moves up and down. Select which hose
support bracket hole to use for each specified hose
by observing where that hose will travel during
movement.
18 3A5416C

Controls and Connections
Ref. Symbol Description
Ram Position Selector:
Ram Up: Ram moves up. Up speed is regulated by flow control valve FC2. Up pressure
is regulated by R4 (V).
Ram Hold: Holds ram at intermediate position.
A
Ram Down: Ram moves down and maintains force against top of product in tote. Down
pressure is regulated by R3 (J). Down speed is regulated by flow control valveFC1.
BRam Jog: While pressed, the ram will travel downward. Releasing the button will stop
the ram travel.
Pump Speed Selector:
Fast: Maximum air flow will be supplied to all pumps in the system.
Off: Pumps will be turned off and all supply pressure will be dumped to atmosphere.
C
Slow: Air flow to pumps is restricted to allow more effective priming. Pump slow speed
can be adjusted using flow control valve FC5.
Seal Inflate Selector
Inflate: Seal will inflate until the pressure set by regulator R1 (F) is reached. Pressure
will be maintained until Deflate is selected.
Pause: Seal will hold current pressure. Venturi will be turned off.
D
Deflate: Seal will deflate until empty. Venturi will aid deflation and will remain on.
Venturi flow rate can be adjusted using flow control valve FC3.
EAir Assist: While pressed, will force air through check valve (BB) to help unstick the ram
plate from the bottom of the tote or tote liner.
3A5416C 19

Controls and Connections
Ref. Symbol Description
FSeal Regulator: Controls the air pressure supplied to the inflatable seal.
GRam Up Regulator: Controls the air pressure supplied to the cylinder for moving upward.
G5 ——— Seal Pressure Gauge: Indicates actual seal pressure.
HPump Regulator: Controls the air pressure supplied to the pumps.
JRam Down Regulator: Controls the air pressure supplied to the cylinders formoving
downward.
K——— Control Panel Supply Ball Valve: Connect a clean, dry, air supply to this valve for
the control valve. This valve will supply air to control valve pilots, air assist, and the
inflatable seal.
NOTE: It is recommended that the Control Panel Supply be separate from the Pump
Supply to avoid the high air consumption of pumps from starving the control pilots.
Use only clean dry air.
L——— Pump Air Supply Ball Valve: Connect a clean, dry, air supply to this valve forthe
pumps. See specific pump instruction manual for minimum and maximum pressure and
flow requirements. Use only clean dry air.
MAir Assist Port: Route hose through the hose block on the side of the frame and through
holes in the support plate to the check valve (B1) in the center of the ram plate. Use the
provided 172 inch hose.
NPump Air Supply Ports (3 provided): Connect to supply air to pump manifold (FF) ports.
Route hoses through the hose block on the side of the frame. Use the three provided
109 inch hoses. Connect the pump manifold (GG) ports to the pump air motors.
PCylinder Down Port: Connect to the down pressure port (DD) on the cylinder distribution
manifold on the top side of the crossbar.
RCylinder Up Port: Connect 1/2 in. tube to the pilot check valve, V6–IN (R1) located
on the side of the frame.
SPilot Signal Port: Connect 3/8 in. tube to the pilot port (S1) on the pilot check valve (V6)
locatedonthesideoftheframe.
TSeal Inflation Port: Route hose through the hose block on the side of the frameand
through holes in the support plate to the inflation tube (A1) of the inflatable seal. Use
the provided 172 inch hose.
20 3A5416C