SANY Crawler Hydraulic Excavator SY215CLC (CUMMINS QSB6.7 engine). Shop Manual - page 15

Structure and Function

SY215C

4-140

4.7.6 Clutch

●

The electromagnetic clutch is used to
transmit moment of torsion. When the en-
gine is operating, the compressor may not
be working. The clutch controls the opera-
tion of the compressor only when the air
conditioner is under refrigerating mode.

●

Operating principle

When the A/C switch is turned on, the
clutch coil with an electromagnet gener-
ates a magnetic

eld and attracts the metal

piece. The stator and rotor of the clutch are
engaged and drives the main shaft of the
compressor into rotation.

1- Rotor
2- Stator coil
3- Snap ring
4- Ball bearing
5- Stator
6- Center piece

ZX215-1002145

3
4

Structure and Function

SY215C

4-141

4.7.7 Condenser

1- Condenser core
2- Bracket
3- Bolt with gasket
4- Refrigerant inlet
5- Refrigerant outlet

Function

●

The condenser changes high-temperature,
high-pressure gas refrigerant (16Kg/cm²,
approx. 80°C) to high-temperature and
high-pressure liquid refrigerant (16Kg/cm²,
below approx. 60°C) through radiating.

ZX215-1002146

Structure and Function

SY215C

4-142

4.7.8 Expansion valve

1- Spring
2- Diaphragm
3- Probe
4- Needle valve

Operating principle

●

Refrigerant from the reservoir spurts out
via the ori

ce, turns into low-temperature,

low-pressure liquid (mist) after expanding,
and enters the evaporator.

4.7.9 Evaporator

1- Expansion valve
2- Evaporator

Operating principle

●

The evaporator is a kind of heat exchanger
that looks like a condenser. Hot air in the
cab is conducted into the evaporator via
the blower motor and undergoes heat ex-
change with the surface of the evaporator.
Heat is absorbed and hot air turns into
cold air, which flows into the cab through
the air ducts. Evaporator surface absorbs
heat

→

Refrigerant in the evaporator ab-

sorbs heat

→

Refrigerant evaporates .

Evaporated refrigerant (gas) is absorbed
by the compressor.

ZX215-1002148

ZX215-1002147

Evaporator

Reservoir

Compressor

Structure and Function

SY215C

4-143

4.7.10 Dehydrator

1- Inlet
2- Outlet
3- Receiver/dehydrator
4- Desiccant

Function

●

Temporary storage of refrigerant

●

Dehydration of refrigerant

●

Dust removal from refrigerant

●

Measure the volume of refrigerant

ZX215-1002149

Structure and Function

SY215C

4-144

4.7.11 Pressure switch

1- O-ring
2- Mobile contact point
3- Hood
4- Plug and

xed contact

5- Spring
6- Chamber
7- Diaphragm

Function

●

The pressure switch is installed between
the reservoir and the expansion valve (hi-
pressure pipe). It is a combination switch
(Hi-Lo pressure combination switch).

●

When pressure is excessively high, the
compressor stops.

●

When pressure and temperature is very
low, the compressor stops.

Operating features

HI pressure
operating value

LO pressure
operating value

MID pressure
operating value

Feature

DIFF

Above 0.02 MPa

OFF

DIFF

0.59±0.2 MPa

0.196±0.02 MPa

0.196~0.250 MPa

2.94~3.19 MPa

OFF

1.23±0.1 MPa

1.52±0.08 MPa

ZX215-1002150

Pressure

Structure and Function

SY215C

4-145

4.7.12 Fresh air sensor

The fresh air sensor is installed beside the
condenser or around the fresh air inlet. It mea-
sures the temperature of outside air and it is
composed of thermistors.

Technical specifi cations

Item

Specifi cation

Service voltage range

4.4~5.6 V

Service temp range

-30~60 °C

Storage temp range

-40~90 °C

Resistance value

1700±85

B constant

3900±195 K

Allowable operating current

1.6 mA (MAX)

ZX215-1002151

-10

Resistance value

Structure and Function

SY215C

4-146

4.7.13 Refrigerant

1. General property of refrigerant

●

High heat absorption and easy liquefaction

●

Non-

ammable, nonexplosive

●

Stable chemical composition

●

Non-toxic

●

Non-corrosive

●

No hazard to clothing

2. Refrigerant cycle

●

After evaporation in the evaporator, re-
frigerant turns from gas into liquid via the
compressor and the condenser, which

ishes a refrigerant cycle.

Compressor

Intake

→

Discharge

Evaporator

Absorb heat

→

Emit cold air

Condensor

Via radiating:

Gas refri-

gerant

→

Liquid refrigerant

Expansion valve

Hi pressure

→

Lo pressure

Hi temp

→

Lo temp

Liquid

→

Mist

Compress HI press. side(outlet): HI temp\HI press.\Gas
Pressure/Temperature:

16Kg/cm²

，

approx.

℃

Condensor (outlet)

：

HI temp

HI pressure

Liquid

Compressor LO press. side (inlet): LO temp

LO press.

Gas

Pressure/Temperature:

2Kg/cm² approx. 8

℃

Pressure/Tempterature

：

16Kg/cm²

，

Below

℃

Condensor (outlet): LO temp\LO press.\Mist
Pressure/Temperature:

2Kg/cm²

，

approx.

0~2

℃

CAUTION

Structure and Function

SY215C

4-147

●

Refrigerant cycle principle (pressure - enthalpy diagram)

ZX215-1002152

lgp

h=u+Apv(kJ/kg)

Gas-liquid mixture

Internal energy p

Pressure

Special volume A

Joule equivalent

Expansion throttle

Condensing process

Evaporating process

Compressing
process

Throttling point

Gasification completed

Liquefaction starts

Liquefaction completed

Expansion valve

Liquid

Evaporator

Compressor

Condensor

Refrigerant cyclic curve

Structure and Function

SY215C

4-148

3. Feeding of refrigerant

●

Filling method and volume:

1) Refrigerant: HFC-134a

2) Feeding volume: 900±50 g (for reference)

3) Feeding method: Feeding of liquid refrig-

erant from the low-pressure end is not al-
lowed. If feeding operation fails, discharge
the refrigerant that has been fed before re-
feeding.

●

Inspect the state of the refrigerant in the
A/C circulation system through the sight
glass:

1) Correct feeding: Foam is hardly observed

when the refrigerant is flowing. When en-
gine speed increases from idling to 1500
rpm, foam disappears and the refrigerant
turns clear.

2) Over-feeding: No foam can be observed

when refrigerant is

owing.

3) Under-feeding: Foam is always observed

when refrigerant is

owing.

ZX215-1002153

ZX215-1002154

Proper filling

Inadequate filling

Sight glass

Structure and Function

SY215C

4-149

4. Evacuation

●

Reason for evacuation

No moisture shall be mixed inside the air
conditioning unit. Refrigerant (R134a) is
soluble in water. Very small amount of
moisture in the unit can cause the ori

ce of

the expansion valve to ice up, or cause the
valve of the compressor to rust. To avoid
such problems, moisture in the system
shall be removed before refrigerant is fed.
To reduce the residual moisture in the
system to the minimum, moisture in the
system can evaporate through evacuating.
No better means is available so far.

●

Evacuating steps

1) Connection of manifold pressure gauge:

i) Close the high-pressure valve (HI)

and low-pressure valve (LO) of the
manifold pressure gauge.

ii) Connect the hoses (red, blue) to the

auxiliary valve of the compressor.

Red hose – High pressure side (Mark D)

Blue hose – Low pressure side (Mark S)

★

Connect the end of the hose with a L
to the auxiliary valve of the compressor.
If connected inversely, the valve will
not open. Besides, do not inversely
connect the high-pressure end and the
low-pressure end.

iii) Connect the green hose to the vac-

uum pump.

ZX215-1002155

Lo-pres. valve (ON)

Hi-pres. valve(ON)

Lo-pres.
gauge

Hi-pres. gauge

Vacuum pump (running)

Compressor

Valve

Lo-pres.gauge

above 750mmHg

ON ON

OFF OFF

Blue

Red

Green

Structure and Function

SY215C

4-150

2) Evacuating

i) Open the high-pressure valve (HI)

and low-pressure valve (LO) on the
manifold pressure gauge.

ii) Turn on the vacuum pump and

evacuate for about 15 minutes.

iii) When negative pressure reading

on the gauge (degree of vacuum)
reaches above 750 mmHg, turn off
the vacuum pump and close the Hi-
pressure valve and the Lo-pressure
valve on the gauge.

ZX215-1002156

Tighten pipe joint

Lo-press. gauge
returns to 0

Wait 5 min. or more

Lo-press. gauge

Pointer returns
to 0

Valve

OFF OFF

3) Air - proof check

i) Keep the Hi- and Lo-pressure valve

of the manifold pressure gauge
under closed state for more than 5
minutes, and make sure the pointer
on the gauge does not return to
zero.

ii) If the pointer returns to near zero,

a leakage is available somewhere.
Check and adjust the pipe joint.
Tighten the joint and conduct an-
other evacuating operation until no
leakage is detected.

Structure and Function

SY215C

4-151

4) Leak check

i) Connect the green hose that is pre-

viously connected to the vacuum
pump to the

uorine cylinder.

ii) Connect the other end of the green

hose to the pressure gauge. Open
the valve of the cylinder and press
the vent valve of the pressure
gauge. (Do not press the valve
with naked hand to avoid frostbite
caused by refrigerant). Release the
air in the hose with the pressure of
the refrigerant. (Release the vent
valve when you hear a squeezing
sound).

iii) Add refrigerant until pressure read-

ing on the Lo-pressure gauge is
1kgf/cm2 . Hi-pressure valve of the
gauge is open at this time. Close
the Hi-pressure valve when feeding
is

nished.

iv) Use a leak detector to check if leak-

age is available in the cooling sys-
tem.

v) Make necessary repairs (tightening)

if leakage is observed.

ZX215-1002157

Lo Hi

R134a

Vent valve

Release air

Blue

Red

Green

To compressor

Fluorine cylinder

Open

Valve

OFF OFF

ZX215-1002158

R134a

OFF ON

Lo Hi

OFF OFF

Lo Hi

Lo-press gauge

at 1kgf/cm

Fluorine cylinder

Compressor

Open Hi-pres.valve

Lo-pres.valve (OFF)

Cylinder valve (ON)

Lo-pres. gauge
reads

1kgf/cm

Valve

Structure and Function

SY215C

4-152

5. Refrigerant charging operation

●

When evacuation is

nished, add refriger-

ant into the cooling system as per the fol-
lowing instruction:

●

Charge at hi-pressure side

1) Remove the air green hose of the manifold

pressure gauge from the vacuum pump
and connect it to the

uorine cylinder.

2) Open the valve of the cylinder and press

the vent valve on the pressure gauge. Use
the pressure of the refrigerant to release
the air in the hose.

Release the vent valve when you hear

a hissing sound. Do not press the vent
valve with naked hand to avoid frost-
bite.

Evacuation starts

Evacuation ends

Air-proofness check

Add refrigerant kgf/cm

Air leak check

Add refrigerant

Air leak check

Performance testing

Wait 5 min

More than 15 min.

Pres. gauge

normal

75cm-Hg or more

Tighten pipe joint

Pres. gauge

abnormal

Check leak point

(1) Compressor stopped, charge at hi-press end

(2)Compressor running, add at lo-press end

ZX215-1002159

Lo Hi

R134a

Loosen
this nut

OFF OFF

Vent valve

Blue

Red

Green

To compressor

Fluorine cylinder

Open

Valve

ZX215-1002160

R134a

Lo Hi

Open Hi-press. valve

Lo-press.
valve (OFF)

Fluorine cylinder
valve (ON)

A cylinder
(about 600g)

Valve

Do not operate compressor

Do not open Lo-pressure valve

OFF

OFF OFF

3) Open the hi-pressure valve of the manifold

pressure gauge and the valve of the cylin-
der and

ll the cylinder with refrigerant (ap-

prox.600 g)

At this time, do not operate the com-

pressor when refrigerant charging is
in progress. Otherwise, refrigerant will
counter

ow and cause the cylinder and

hoses to explode.

Do not operate the compressor when

there is no refrigerant. Otherwise, it will
be damaged.

Structure and Function

SY215C

4-153

ZX215-1002161

1300~1500rpm

H I

Hi-press. valve (OFF)

Manifold pressure
gauge

Start the engine

ZX215-1002162

Lo Hi

Valve

Fluorine cylinder
(never placed upside down)

Compressor
running

Hi-press. valve (OFF)
(Never open it)

Lo-press.
valve (ON)

Fluorine cylinder
valve (ON)

Lo-press. gauge
(1.5~2.5kgf/cm

)

When no foam

is observed

Hi-press. gauge
(13~17kgf/cm

)

ON OFF

OFF OFF

●

Charge at lo-pressure side (additional)

1) Con

rm the hi-pressure valve of the mani-

fold pressure gauge is closed.

2) Start the engine and open the cab door.

3) Turn on the air conditioner, and set Tem-

perature control switch to minimum.

4) Adjust engine speed to 1300 – 1500 rpm.

5) Open the Lo-pressure valve of the mani-

fold pressure gauge and the valve of the
fluorine cylinder, and add refrigerant into
the reservoir until no foam is observed.

Do not open the lo-pressure valve of the

manifold pressure gauge; otherwise,
the compressor will be damaged.

4) Close the hi-pressure valve of the pressure

gauge and the valve of the fluorine cylin-
der.

Remark:

Manifold pressure gauge reading (for refer-
ence):

High pressure 13~17kgf/cm² (outside temper-
ature 30°C)

Low pressure 1.5~2kgf/cm² (outside tempera-
ture 30°C).

6) When refrigerant charging is finished,

close the Lo-pressure valve of the mani-
fold pressure gauge and the valve of the

uorine cylinder.

7) Check carefully for air leaks with a leak

detector.

Structure and Function

SY215C

4-154

8) When outside temperature is low

When refrigerant charging can not be
performed due to low outside tempera-
ture, place the cylinder in water of less
than 40C to increase the pressure of
the refrigerant inside the cylinder.

9) When outside temperature is high

When outside temperature is very high,
cool the compressor with an electrical
fan.

ZX215-1002163

Lo Hi

Water less than 40°C
(Do not use hot water)

Compressor
running

Hi-pressure valve
(OFF)

Lo-pressure
valve (ON)

Cylinder valve
(ON)

ON OFF

When no foam

is seen

Valve

OFF OFF

Never open the Hi-pressure valve of

the manifold pressure gauge. If it is
opened, high-pressure gas will coun-
ter

ow and cause the air hoses and the

uorine cylinder to explode.

Do not position the

uorine cylinder up-

side down (when engine is operating
and charging in progress). Otherwise,
liquid refrigerant will be sucked directly
into the compressor and cause liquid
compression, resulting in damage to
the compressor valve and the gaskets.
Place the cylinder vertically and charge
gas refrigerant.

Structure and Function

SY215C

4-155

●

Replace the

uorine cylinder

When the refrigerant in a cylinder is used
up, replace the cylinder as per the follow-
ing instruction:

1) Close the Hi- and Lo-pressure valves of

the manifold pressure gauge.

2) Raise the needle and disc plate of the cyl-

inder and remove the empty cylinder.

3) Install a new cylinder onto the cylinder

valve.

4) Release the air in the hose as per the fol-

lowing instruction:

i) Tighten the valve of the

uorine cyl-

inder, and then, loosen it a bit.

ii) Open the Lo-pressure valve of the

manifold pressure gauge a bit.

iii) Press the vent valve and allow a

little refrigerant to come out. Im-
mediately close the valve of the cyl-
inder and the Lo-pressure valve of
the manifold pressure gauge.

★

Do not press the vent valve with
naked hand to avoid frostbite by
refrigerant.

5) Turn the handle of the cylinder valve to

pierce the cylinder and continue charging
operation.

ZX215-1002164

Air hose connector

Handle

Gasket

Needle valve

Refrigerant
cylinder

Disc plate

ZX215-1002165

OFF

Lo Hi

R-134a

Loose

Blue

Red

Green

To compressor

Refrigerant cylinder

Loosen the valve a bit

Valve

Lo-pressure
valve

Close the Lo-pressure valve
once you hear the hissing sound

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