Aeb Two Pump Two Loop 90.35

ApplicationEngineeringBulletin

Subject This AEB is for the following applications:Two Pump Two LoopLow Temperature Aftercooling ForHigh Horsepower G-DriveApplications

Automotive Industrial Power Generation

Date: December 12, 2002 Page 1 of 12 AEB Number 90.35

Engine Models included: QST30, KTA38, QSK45, KTA50, QSK60, QSK78

Fuel Systems included: All

Author: Curtis Kwasniewski

Introduction:

Many of Cummins Inc. new G-Drive engine models require the use of Separate CircuitLow Temperature Aftercooling (SCLTA). This method of cooling uses a secondary loop (LTALoop) for cooling the aftercoolers and is referred to as Two-Pump, Two-Loop cooling (2P/2L).The purpose of this document is to provide a system description and Cummins, Inc.requirements and recommendations for selection and installation, of a 2P/2L system.Requirements are labeled ‘must’ while recommendations are labeled ‘should’.

Two-pump two-loop (2P/2L) cooling differs from one-pump two-loop (1P/2L) and jacketwater aftercooling (JWAC) in that it uses its own dedicated coolant pump, plumbing, and heatexchanger. The coolant in the LTA loop does not cool the engine (as in JWAC) or mix with theengine coolant (as in 1P/2L). Because of this, 2P/2L cooling can reach lower intake manifoldtemperatures than with jacket water or one-pump two-loop aftercooling. This lower intakemanifold temperature makes it possible to reach higher power densities and certain emissionslevels.

The performance of the 2P/2L system is critical to the durability, performance, andemissions compliance of the engine. Failure of the system could cause power loss, increasedemissions, and possible engine damage. The equipment manufacturer is responsible for theselection, design, and installation per these requirements.

Scope:

This document addresses aftercooling system requirements for High Horsepower G-Drive engines that utilize the Two-Pump Two-Loop method of aftercooling. This currentlyincludes specific ratings of the QST30, KTA38, QSK45, KTA50, QSK60, and QSK78 enginemodels.

Cummins Confidential 2

Requirements

In order to obtain the concurrence of Cummins Inc. the following requirements must be met:

•The System must have a high temperature shutdown that monitors aftercooler watertemperature.•The System must meet the heat rejection and intake restriction requirements publishedon the Engine Data Sheet.• A Fill Line must be provided for both the Jacket and LTA cooling systems and will runbetween the head tank and the pump inlet respective for that system. •The aftercooler loop coolant must be a 50/50 blend of Fully Formulated Coolant andwater. The coolant should contain Supplemental Coolant Additive (SCA).•The LTA radiator must provide 6% expansion space, 11% draw down capacity, ameans for venting the LTA Loop to the top tank, a means for filling the LTA Loop, andbe mounted so that it receives the coolest possible airflow.• The thermostat must be located between the outlet of the aftercooler and inlet of theLTA radiator. If a customer supplied electrically controlled LTA thermostat is used then itmust fail to the open position (See Table 1 for engine models that require thermostats).•The LTA plumbing must meet the same requirements as piping for the engine coolantloop, steel tubing or five-ply hose, rated for temperatures and pressures experienced inthe aftercooling system, and use T-bolt or constant torque type clamps for all coolanthose connections.•The pressure at the coolant pump must be greater than atmospheric when the engineis operated at rated speed with the pressure cap removed and the coolant temperaturesabove the modulating ranges (refer to engine data sheet).•The cooling system must use either a pressure cap or a pressure relief valve in thedeaerating tank.

System Description, Requirements, and Recommendations:

System Flow:

The 2P/2L aftercooling system consists of a dedicated coolant pump, heat exchanger,engine aftercoolers, filters, and plumbing (including a thermostat device and a bypass loop).

For engines with a thermostat, the flow path is from the outlet of the aftercoolers to thethermostat valve housing. The thermostat bypasses the LTA radiator when the LTA coolant iscold. Coolant flow that is bypassed is recirculated through the aftercoolers by the LTA waterpump until the temperature is high enough to actuate the thermostat (Figure 1).

As the LTA coolant warms the LTA thermostat opens and blocks off the bypass loop.The thermostat will direct the coolant flow to the LTA radiator. Once cooled in the radiator, thecoolant is directed to the LTA pump suction (Figure 2).

Some engine models do not require the use of a LTA thermostat. In those enginemodels, the coolant flows from pump discharge to aftercooler to heat exchanger and back tothe pump suction (Figure 3).


Figure 1Coolant Flow with LTA Thermostat Closed

EngineCoolantPump

LTA Bypass

LTA

Rad

iato

r

Air Flow

Intake Airflow

Shut DownTemperature

Sensor

Engi

ne R

adia

tor

Jacket Water

LTA Piping (No Flow)

LTA WaterPump

Aftercooler

Aftercooler

LTA Flow Warm

LTAThermostat

EngineCoolantPump

LTA BypassLT

A R

adia

tor

Air Flow

Intake Airflow


Sensor

Engi

ne R

adia

tor

Jacket Water

Cooled LTA Coolant

LTA WaterPump

Aftercooler

Aftercooler

Hot LTA Coolant

LTAThermostat


Figure 2Coolant Flow with LTA Thermostat Open

Figure 3Coolant Flow with No LTA Thermostat

System Requirements:

The LTA loop MUST:

• Use a high-temperature shutdown.

This is accomplished by monitoring aftercooler water temperature with either a sensoror temperature switch. The set point of the shutdown will depend on the monitoringlocation (see Table 1 for set points). LTA Coolant temperature can be monitored ineither the aftercooler outlet or inlet plumbing. A temperature sensor comes supplied insome models (see Table 1 for details).

• Meet the system heat rejection and intake restriction requirements listed on the Engine DataSheet

EngineCoolantPump

LTA

Rad

iato

r

Air Flow

Intake Airflow


Sensor

Engi

ne R

adia

tor

Jacket Water

Cooled LTA Coolant

LTA WaterPump

Aftercooler

Aftercooler

Hot LTA Coolant


LTA WaterPump LTA Return

PipingInstalled ConnectionBoss

Customer SuppliedConnection Boss

Kit Supplied Filter-Head

Figure 4Filter Installation for KTA38 & 50

LTA

Rad

iato

r

Filter

Engine Connections:

The engine connections for the LTA loop come supplied with the engine. Theseconnections are in addition to the jacket water connections. For specific engine connectionsizes and locations consult the Installation Drawing or Sales Handbook.

LTA Water Pump:

The LTA water pump comes as an installed component and is a gear pump driventhrough an accessory drive located in the front gear cover. Flow rates for specific engines aregiven in Table 1 and the engine data sheet. For the LTA water pump location on a specificengine consult the Installation Drawing.

LTA Coolant Filters for KTA38 and KTA50:

The use of bypass coolant filters for the LTA loop is required for KTA38 and KTA50 G-Drive engines. The bypass filters and the coolant filter head are supplied as a kitted option.The customer must plumb the filter head into the LTA loop. A connection is provided in theLTA water pump outlet plumbing for this purpose. The radiator supplier must supply anadditional connection in the LTA pump inlet plumbing to complete the installation (Figure 4).Service filters with supplemental coolant additive (SCA) should be replaced at the normalservice interval. The use of aftercooler filters is not required for the Quantum series engines(QST30, QSK45, QSK60).


LTA Coolant:

The LTA loop coolant MUST:

• Be a 50/50 mix of Fully Formulated Coolant (Ethylene Glycol or Propylene Glycol) and water.

The LTA loop coolant SHOULD:

• Contain supplemental coolant additive (SCA)

In systems that do not have a coolant filter for the aftercooler loop the concentration ofSCA in the aftercooler loop coolant must be monitored. The concentration should bemaintained at the same level as the jacket water side. Refer to Service Bulletin 3666132for additional information.

Aftercooler Radiator:

The LTA loop radiator MUST

• Be sized to not exceed the Maximum Aftercooler Inlet Water Temperature requirement of theengine.

The heat rejected to the LTA coolant, coolant flow, maximum aftercooler inlet watertemperature, and maximum allowable system restriction are listed on the Engine DataSheet. From this information, an adequately sized core can be designed for the needsof the system.

• Provide 6% expansion space to allow heated coolant to expand without overflowing the toptank.

• Provide for 11% draw down capacity in addition to the expansion space (Figure 5).

• Provide a means for venting entrained air to the LTA Radiator top tank (Figure 5).

Vent lines must be installed between the highest location in the LTA loop and the LTAradiator top tank. Vent lines must run uphill constantly (See Engine Installation Drawingfor connection points).

•Provide a means for filling the LTA Loop (Figure 5).

The fill line must connect the top tank and a low point in the LTA loop (such as the LTApump inlet plumbing). Fill lines must have a continual rise from coolant piping to the toptank. Fill lines must be sized so that the system is capable of being filled to 90%capacity at a minimum rate of 20 l/min (5 GPM) on initial fill.

• Have seals installed between the LTA radiator and the engine radiator when mounted inseries.

Having an installed seal will force the air to travel through both cores. The seal alsohelps prevent debris from becoming entrapped between the cores.


• Have a pressure cap on the top tank (Figure 5).

The pressure cap must be rated the same as the engine radiator pressure cap.

• Be mounted so that it receives the coolest possible airflow.

This can be accomplished in three ways.

1. Mount the radiators in series (Figure 6). In this arrangement, the aftercooler radiatormust be upstream of the jacket water radiator. Care must be taken in this arrangementto minimize debris entrapment between the two radiators.

LTA Radiator

Engine Radiator

Figure 6Series Mounted Radiators

Radiator Cap

Coolant Inlet

Vent Line Connection(above coolant level)

Top ofTubes

Fill LineConnection

Tank large enough toprovide minimum drawdown

CoolantOutlet

Figure 5LTA Radiator Top Tank(2-Pass Core Shown)


2. Mount the radiators in parallel (Figure 7). In this arrangement the aftercooler radiatorand jacket water radiator should be mounted so that the cooling airflow restriction isbalanced across the fan sweep.

3. Remotely mount the radiators. In this arrangement the radiators are cooled by adedicated fan that is not engine driven. The radiators are typically in a separatecompartment from the engine and can be arranged in series, parallel, or each with aseparate fan. Care must be taken when using this arrangement to ensure that thecooling system restriction requirements are not exceeded (Consult the Engine DataSheet for specific model requirements).

The LTA loop radiator SHOULD:

• Match the engine radiator fin density.

Matching the fin density of the aftercooler radiator to that of the engine radiator will allowdebris to pass through both cores without becoming trapped between the two.

Engine Radiator

LTA Radiator

Figure 7Parallel Mounted Radiators


LTA Thermostat:

Table 1 identifies the engine models that require the use of a LTA loop thermostat. Thisthermostat bypasses the LTA loop heat exchanger when the coolant temperature is low. Asthe temperature of the coolant rises, the thermostat begins to open to block the bypass portand send coolant to the LTA radiator. The thermostat continues to open until the bypass is fullyclosed off. The temperature at which the thermostat begins to open and when it is fully opendefines the modulating range of the thermostat (Table 1 lists suggested modulating ranges).There are two types of thermostats that can be used in the LTA loop.

1. Electrically controlled bypass valve. This customer supplied valve must be used inconjunction with an electronic temperature sensor. This sensor must be located in theaftercooler outlet plumbing (monitoring aftercooler outlet temperature) and may be usedadditionally as the high temperature shut down sensor (Sensor location is shown inFigures 1-3).

2. Three-way wax-filled thermostat (Figure 8). This thermostat does not require anadditional sensor to operate. The aftercooler outlet water temperature controls theposition of the thermostat. As the aftercooler water temperature rises the wax in thethermostat expands causing the valve to close off the bypass loop. This directs the flowto the heat exchanger.

Bypass

Outlet

Inlet

ThermostatAssembly

Figure 8Three Way Wax Filled Thermostat Assembly


The LTA loop thermostat MUST:

• Fail to the open position if it is electrically controlled.

• Be located between the outlet of the aftercooler and the inlet of the aftercooler radiator.

This location provides cooling flow through the aftercoolers in event of a thermostatfailure.

LTA Plumbing:

The LTA loop plumbing MUST:

•Meet the same requirements as piping selected for the engine coolant loop.

• Be of steel tubing and/or five-ply hose conforming to SAE J20R1.

Typically 600 kPa (87 PSIG) and - 40° to 100° C (-40° to 212° F) with intermittenttemperatures reaching 120° C (250° F).

• Use T-bolt or constant torque type clamps for all coolant hose connections.

Clamps must be used to prevent hose blow-off. One clamp at each connection point issufficient.

• Be equal to or larger than the diameter of the engine connections.

The LTA loop plumbing SHOULD:

• Be mechanically braced on either side of flexible hoses.

Environmental Considerations

Depending upon the environment in which the engine operates there may be additionalconsiderations that need to be taken into account. The LTA cooling system must be designednot to exceed the aftercooler inlet water temperature listed on the Engine Data Sheet underany ambient conditions.

In low temperature ambient conditions the aftercooler loop is not expected to requirethe use of coolant heaters. Using a 50/50 blend of Fully Formulated Coolant and water willprotect the coolant from freezing at temperatures of –40° C (-40° F).


Fill Line (Make-Up Line):

The Fill Line is very important as it routes the coolant from the deaerating tank to the engineand provides one of the key methods for purging air from the system.

The Fill Line must have a continual rise from the engine coolant inlet pipe to the bottom of thetop tank.

The Fill Line size is typically about 19 mm (0.75 in) for coolant pump flows up to 757 liters/min(200 GPM), and 25 to 38 mm (1 to 1.5 in) for coolant pump flows greater then 757 liters/min(200 GPM).

If the Fill Line is too small or improperly routed, the engine will not fill properly and reverseflow up the fill line may cause overflow of the deaerating tank.

A Fill Line must be provided for both the Jacket and LTA cooling systems. Cumminsrecommend that this line be routed directly from the top tank to the respective pump inlet in acontinual slope

Afte

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ler T

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1500

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1800

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l/s (G

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let

Afte

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ler

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t

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lter

Num

ber

Inst

alla

tion

Dra

win

gN

umbe

r

QST

30G

4/G

5N

otR

equi

red

Not

Req

uire

dTB

5717

4.5

(71)

5.4

(85)

No

93 (200

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equi

red

3170

341

QST

30G

6/G

7/G

8N

otR

equi

red

Not

Req

uire

dTB

5717

4.5

(71)

N/A

No

71 (160

)52 (125

)N

otR

equi

red

3170

286

3170

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KTA3

8 G

7N

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(86-

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9(9

3)N

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o55 (130

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2

QSK

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4Ye

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(115

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6723

7.1

(112

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5(1

35)

Yes*

N/A

76 (170

)N

otR

equi

red

3170

275

QSK

45G

6Ye

s46

-57

(115

-135

)TB

6723

7.1

(112

)N

/AYe

s*N

/A76 (170

)N

otR

equi

red

TBD

QSK

45G

8Ye

s46

-57

(115

-135

)TB

6723

N/A

8.5

(135

)Ye

s*N

/A76 (170

)N

otR

equi

red

TBD

KTA5

0 G

7N

o30

-40

(86-

104)

SW60

165.

9(9

3)N

/AN

o55 (130

)38 (100

)W

F207

636

2641

9

KTA5

0G

8/G

9N

o52

-60

(125

-140

)SW

6016

5.9

(93)

7.1

(112

)N

o85 (185

)76 (170

)W

F207

6TB

D

QSK

60G

3Ye

s46

-57

(115

-135

)TB

6723

7.1

(112

)N

/AYe

s*N

/A76 (170

)N

otR

equi

red

3170

381

QSK

60G

5/G

6Ye

s46

-57

(115

-135

)TB

6723

N/A

8.5

(135

)Ye

s*N

/A76 (170

)N

otR

equi

red

3170

292

QSK

78Ye

s46

-57

(115

-135

)TB

6723

N/A

17.6

(279

)Ye

s*N

/A76 (170

)W

F207

631

7054

3

* Tem

pera

ture

sen

sor s

uppl

ied

on th

e en

gine

. The

Hig

h Te

mpe

ratu

re S

hutd

own

set p

oint

is in

tegr

ated

into

the

engi

ne c

ontro

ller.

** In

the

case

of a

n el

ectri

cally

con

trolle

d by

pass

val

ve th

e va

lve

mus

t be

fully

ope

n (n

ot b

ypas

sing

) by

the

high

tem

pera

ture

of

the

mod

ulat

ing

rang

e. T

he v

alve

mus

t als

o fa

il op

en (n

ot b

ypas

sing

) in

the

even

t of a

sen

sor f

ailu

re.

Tabl

e 1

LTA

Syst

em In

form

atio

n

Documents

Aeb Two Pump Two Loop 90.35