petra-pph.pdf

PACKAGEPPH Catalog

Packaged Air Conditioning unitswith Hermetic Compressor

3.0-53.0 T.R. @ 50 Hz3.5-59.0 T.R. @ 60 Hz

R22R22

Abcde abcde

PACKAGEPPH Catalog


3.0-53.0 T.R. @ 50 Hz3.5-59.0 T.R. @ 60 Hz

R22R22

Abcde abcde

PACKAGEPPH Catalog


3.0-53.0 T.R. @ 50 Hz3.5-59.0 T.R. @ 60 Hz

R22R22

Abcde abcde abcdefg50/60 Hz Imperial

www.petra-eng.comwww.petra-eng.com

Petra Products

* For special cases where standard designs do not fulfill the customer’s requirements, custom-made designs can be made available.

Equipment Description Series Equipment Description Series

Air-Cooled Water Chiller (Semi Hermetic Reciprocating Compressors) APX

Air-Cooled Water Chiller (Semi Hermetic Screw Compressor ) APS

Residential Air-Cooled Water Chiller (Hermetic Reciprocating & Scroll Compressor ) RWC

Water Cooled Water Chiller (Semi Hermetic(Semi Hermetic

Reciprocating Compressors) WPX

Water Cooled Water Chiller Screw Compressor ) WPS

Residential Water Cooled Water Chiller (Hermetic Reciprocating & Scroll Compressor ) WRWC

Hot & Cold Residential Water Chiller HRWC

Centrifugal Fans Air-Cooled Water Chiller (Semi Hermetic Reciprocating Compressors) CPX

Centrifugal Fans Air-Cooled Water Chiller (Semi Hermetic Screw Compressors) CPSCentrifugal Fans Residential Air-Cooled Water Chiller (Hermetic Compressors) CRWC

Package Units With Hermetic (Reciprocating & Scroll Compressor) PPH

Package Units With Semi-Hermetic (Reciprocating Compressor) PPS

Water Source Unit PWSPSelf-Contained Wall Mount Air Cooled Package PWM

Split Units Ducted Split Unit (Low, Medium & High Capacity -Hermetic Compressor) DSP

Ducted Split Unit (High Capacity-Semi Hermetic Compressor) DSPS

Ducted Split Unit (Centrifugal Condenser Fans Hermetic Comp.) PECUMini Split Wall Type C/HPWMini Split Universal Type (Floor & Ceiling) C/HPUCassette Type Unit PCU

Free Standing Units FSXClose Control Split Unit (Computer Room) PASCAir Cooled refrigeration Unit RFUAir Cooled refrigeration Unit (Cold Stores) RCUUnit Cooler UCUnit Freezer UF

Fan Coil UnitsLow Static Pressure Fan Coil RAC

Medium Static Pressure Fan Coil DC

High-Wall Plastic Fan Coil PWC

Stack Type Fan Coil RSU

Air Side Control Fan Coil ASC

Free Standing Decorative Units FSW

Air Handlers:

Comfort Maker CM

Air Handling Unit (Modular Type) PAH

Exhaust Fan

Others

Smart Fan PEXT

Full Duty PEXS

HeatersUnit Heater UH

Electric Heater EH

Duct Heater DH

Dry Coolers

Package Unit With Natural Gas HeaterHeat Pump Application For All Dx Units

Note: EMC certification applies to 50 Hz specifications only.

UL & ETL Marks applies on US & Canada markets' products

IndexMain

Introduction 11

Main Description 1Specifications 2Standard Features 3Optional Features 3Microprocessor Controller 5Selection Procedure 6

Series DataGeneral Data 50 Hz 8

Model Layout-standard construction12

Performance Tables 50 Hz 22

Evaporator Coil & Filter PressureDrop Charts 28Petra Fan Series 29Electrical Information

Data Tables 50 Hz 34

Wiring Diagrams 36Refrigeration Schematic Diagram 38

Model Number Nomenclature

General Data 60 Hz 10

Model Layout-optional construction 16

Performance Tables 60 Hz 25

Data Tables 60 Hz 35

Nomenclature

Main Description

1

Introduction

Note:For more technical details, please refer to the nearest Sales Office or to PETRA Factory.

P Petra

P Packaged Air Conditioner

H Hermetic Compressors

60 Unit Size (Nominal Capacity MBH)

Quiet Operation Capacities to Fit Requirements

Low Cost Installation

PPH series are basically constructed and engineered with There is a large product range of packaged units, with noise reduction as a main consideration with low noise fan capacities ranging from 3.0 to 53.0 tons @ 50Hz and 3.5 to mounting, fiber glass insulation for the evaporator section 59.0 tons @ 60Hz refrigeration tons at nominal conditions.and compressors mounted on vibration isolators.

Units are factory assembled, pre-charged, tasted and provided with a single electrical connection point. On arrival to the job site they are ready to be lifted to their operating position through the lifting supports available on the units.

PPH units are single packaged units which are factory assembled, tested and shipped fully charge complete with compressor, evaporator and condenser coils, fans and controls. These packages are designed for outdoor installation, and they used for cooling only or cooling and heat pump application (optional).

PPH units are ideal for residential, commercial and industrial applications and are available in nominal range 3.0 to 53.0 tons @ 50Hz and 3.5 to 59.0 tons @ 60Hz.

Quality design and construction make PETRA's air-cooled package units with hermetic compressors the preferred choice for applications utilizing DX cooling systems. PETRA's PPH series is designed for flexible capacity applications and easy installation and maintenance.

Easy Installation

PPH units are compact in design, supplied in a complete package ready for operation, with no extra controls or additional items for installation. The PPH units have a single power point entry with simple connections. All units are designed to ensure maximum compliance with European standards CE-Mark and EMC through TUV.Quick start-up is assured once installation is complete, as each PPH unit is manufactured in an ISO 9001 listed facility to guarantee quality. In addition, all units are tested at the factory to provide reliable start up.

Specifications

Casing Belt Drive Evaporator Fan (for models PPH 85 and Heavy gauge galvanized steel casing with oven baked above)polyester-epoxy electrostatic powder coating, designed for Models PPH85 and higher are provided with forward curved outdoor installation. Fiber glass insulation for the evaporator centrifugal DWDI [Double Width Double Inlet] type that are section only. designed for maximum efficiency and uniform air distribution. All fans are V-belt driven with variable pitch

pulley (for fan motors with 5.5 kW and less only). All fans Compressorare statically and dynamically balanced to ensure quiet The compressor(s) used is hermetic refrigerant gas cooled, operation and optimal performance. with internal thermal protection . Starting is direct -on- line

with high efficiency and low sound levels, to match all other Petra products' reliability and efficiency. Evaporator Fan Motors (for models PPH 85 and Models PPH 40 up to PPH 105 are with reciprocating type above)compressors while models PPH 115 and higher are with Motors are of the totally enclosed induction type, with scroll compressors. fan/motor assembly placed on a floating base with a flexible

connection at the fan/casing interface. The base itself is Evaporator and Condenser Coils mounted on rubber in sheer vibration isolators to eliminate The evaporator and condenser coils are designed to deliver noise and vibration transmission to buildings. All fans their respective duties at optimum performance at all design motors are of the single- speed type, four pole and highly conditions. Coils are manufactured from seamless copper efficient, induction type motors, totally enclosed air-over, tubes mechanically- expanded into aluminum fins. All coils squirrel-cage type, internal thermal current protected, IP55 are tested at 450 Psi, air pressure, under water to avoid protection and with class "F" insulation.leakage. They also undergo dry chemical cleaning after manufacturing for optimum system cleanness. Filters

All Models are provided with 1.0 inch thick aluminum flat Direct Driven, Condenser Propeller Fans filter (as standard features). Other filters are available upon All condenser fans are of the propeller axial type, which are request. directly mounted on the motor shaft. All fans are selected for optimum efficiency and for maximum sound power Drain Panreduction. Fan blades are made for maximum corrosion All units are provided with a drain pan having a drain resistance, and are statically and dynamically balanced connection from one side. The drain pan is insulated on the before installation. PETRA also provides its "Patented sides and underside to prevent condensation. Design" for condenser fans mounting. This new design offers low noise operation with high efficiency. All Insulationcondenser fans are equipped with wire guards. All units are internally lined with 1.0 inch thick fiberglass

insulation for the coil and fan section (evaporator side only).Condenser Fan MotorAll fans motors are of the six poles, induction type motors, totally enclosed air-cooled, squirrel-cage type, internal thermal current protected, IP55 protection, with class "F" insulation.

Direct Drive Evaporator FansModels PPH40, PPH50 and PPH60 are provided with forward curved centrifugal fans of the DWDI [Double Width Double Inlet] Type that are designed for maximum efficiency and uniform air distribution. The fans are statically and dynamically balanced to ensure quiet operation and optimal performance Fans are 3-speed and driven by permanent split capacitor electric motors, with internal thermal protection.

2

Standard Features

Optional Features

3

b- Through the external timer for Petra Mark III A) Construction standard:controller.

5. Crank case heater for each compressor.1. Easily accessible system components.6. Control circuit breaker.2. Ample space for easy access to power and control panels.7. 220 volt as control voltage.3. Heavy duty mounting chassis for the whole unit with 8. Microprocessor controller for model PPH 85 and above, lifting lugs.

with the following main functions:4. Rubber anti-vibration mounting for the compressors.a- Compressor lead-lag operation to ensure longer 5. Weather proof, polyester-epoxy powder electrostatic paint

life for the compressors and equal running hours oven-baked finish for sheet metal and multi polyester-between compressors.epoxy coating for base frame.

b- External remote ON/OFF button for remote 6. All units are shipped out from factory tested with safety operation of the unit using external ON/OFF and control devices set against client requirement.switch or connection to building management 7. Variable pitch pulley for evaporator motor (for motors of system.5.5 kW and less).

9. One power supply input.8. Single skin evaporator side with 1 inch thick fiberglass 10. High (manual reset) and low (automatic reset) pressure insulation.

safety switches (Capsule type; factory pre-set).9. All suction lines are covered with rubber insulation, and 11. For models PPH 105 and above, voltage monitor for further protection, the lines that extends in the

controller (phase failure relay) for monitoring the main condenser side are wrapped-in cheese cloth and epoxy incoming power supply for the unit, which provides painted with the same compressor color.protection from single phasing, under voltage, phase-voltage imbalance and phase- consequence.B) Electrical features:

C) Refrigeration features:1. Control and power panels include the direct on line 1. Hermetic suction gas cooled compressor motor.starting contactors for the compressors and condenser 2. Filter drier (disposable type).fans' motor.3. Charging ports.2. Internal thermal motor protector for condenser and 4. Service valve on liquid line.evaporator fan motor.5. Thermostatic expansion valve.3. Compressor electronic internal thermal protection.6. Fully charged unit with Freon R-22.4. Anti-recycling protection for compressors (time delay):7. Solenoid Valve.a- Through microprocessor for Petra Mark IV

controller.

14. Economizer option with fresh, return and exhaust air A) Construction options:dampers with actuators.1. Plastic mesh around condenser section perimeter.

15. Gas Heater.2. Mixing box with manually operated fresh and return air dampers.

If this option is installed, the unit has the ability to work 3. Roof top arrangement (bottom air supply and return unit).with free cooling or free heating mode allowing it to exploit 4. Roof curb mounting.the external environmental condition as much as possible, 5. Bag filter.since it avoids turning on the heaters and the compressors. 6. Anti corrosion protection for coils fins (for copper / This function can be achieved by controlling the aluminum coils only).opening/closing of the external air damper. With reference to 7. Copper/copper coils.the difference between the outdoor air temperature 8. Hot water coil (built inside unit)(STD)/enthalpy and the indoor air temperature/(STD) 9. Synthetic fiber media for flat filter.enthalpy. 10. 2.0" or 4.0" thick flat filter or V-type filter.

11. Double skin evaporator side.12. Different evaporator side insulation material.13. 2.0" thick insulation for evaporator side only.

B) Electrical options: C) Refrigeration options:

1. Power circuit breaker for each motor. 1. Heat pump package unit with 4-way reversing valve, 2. Main power molded case circuit breaker for the whole suction accumulator is a standard feature in heat pump

unit (can also be with external handle as an option). option.3. Low ambient control. 2. Pressure gauges for each refrigeration circuit (high/low

The refrigeration systems in all units are inherently pressure gauges).designed to operate efficiently, without extra controls or 3. Other refrigerant application (R-134a and R-407c).modifications. To permit the unit to operate in low 4. Hot gas bypass (where it is necessary to avoid low suction ambient conditions, head pressure control can be installed pressure and "compressor cycling").either by: 5. Extra refrigerant accessories such as suction accumulators

- ON/OFF Condenser fans sequencing (for models (for cooling units only), refrigerant liquid receivers, oil with 2 condenser fans). separators, etc.

- Varying the speed of the condenser fan motor 6. Solenoid valve for heat pump mode.using speed controller. 7. Liquid line sight glass.

4. Disconnect service switch, a unit mounted non-fused disconnect service switch with an external handle to isolate the unit from the power supply for servicing.

5. Ampere meter and voltmeter installed on the electric control panel door.

6. Earth leakage relay for each compressor.7. Earth leakage relay for the whole unit.8. External overload relay for each motor.9. Power factor correction capacitors.10. Auto or manual provision for pump down operation of

each compressor stop.11. Building automation system interface. Interfacing with

other building management system can be achieved by an optional card, which can communicate with other devices using the serial communication port.

12. Electric heater for heating purposes (built inside unit for cooling units only).

13. Electric heater (built inside unit) to supplement unit operation in case of heat pump mode operation.

14. Special microprocessor controller with additional feature, such as:

a- Economizer operation and control with free cooling function.

b- Display of additional function (condenser pressure, ambient temperature, return temperature, defrost control, low ambient control, buzzer alarm etc.).

c- Time schedule and zone control.15. Motor actuator for fresh, return and exhaust air dampers.16. Voltage monitor controller (phase failure relay) for

monitoring the main incoming power supply for the unit, which provides protection from single-phasing, under-voltage and over voltage, phase voltage imbalance and phase nonsequence (for models PPH 40 up to PPH 85).

17. Variable Air Volume (VAV) control.18. Winter start relay.19. General alarm out put relay.20. Auto-manual evaporator fan operation for airflow

balancing.

4

Microprocessor Controller (Main Controller)Microprocessor controller is a standard feature on all models.

PETRA's microprocessor controller is engineered to meet allowing service technicians to inspect and maintain such

the most demanding requirements of all control and data devices in the conventional manner.

monitoring applications. It could be activated to perform

different functions for cooling and heat pump applications. For external communication, RS-485 (Industrial

Communication Protocol) interface is provided (optional).

However, in order to render the microprocessor control and An optional special communication adapter could be

peripherals easy to use by all skill levels of service teams, provided to communicate directly with RS-232 serial

only necessary functions for safety sequence of operation interface to provide complete supervision for all functions,

and alarm function are activated as standard. In standard setting (configuration) and alarm condition. A special

execution, while using the microprocessor for packaged unit software can communicate with a remote control room

control, it communicates with the standard conventional through modems for monitor and controlling the unit.

control such as high pressure , low pressure etc, thus

Petra Mark III Controller Optional Advanced Controller (Petra Mark IV)

The Standard Petra Controller (Petra Mark III) provides The Advanced Petra Controller provides the following the following features: features, in addition to all the standard features mentioned in 1- Ease of use with a large LED display of a highly the Petra Mark III controller. This controller has the

attractive user friendly interface. following extra functions:2- Ability to control units in cooling and heat pump modes. 1- L.C.D display (4 lines *20 characters).3- Temperature readings °C or °F. 2- Complete message display.4- Controls activation of three heaters (optional). 3- Automatic pump down at each compressor stop. 5- Remote (ON/OFF) system selection. (optional)6- Controlling activation of humidification and 4- External analogue signal for remote modification of the

dehumidification system (optional). set point which also can be used for power demand limit 7- Extended wall mounted display for remote control and for the unit. (optional)

monitoring of the package unit up to 150 meters using a 5- Historical alarm option which can save the last 1600 bipolar cable. (optional) alarms.

8- Safety and control time delays:- 6- Ability to be connected to a serial printer directly without A-Time delay between two subsequent starts of the using a P.C. (optional)

same compressor. 7- Optional graphical display.st nd 8- Super heat controlling. (optional)B- Time delay between activation of 1 and 2

9- Discharge or/and suction pressure readings. (optional)compressor. 10- Full alarm management with alarm message and an C- Time delay between heaters activation and of

audible alarm. (optional)supply fan speed variation. 11- Ability to be connected to a building management D- Time delay for supply fan in start-up and shut

system using an optional card. (optional)down. 12- Supervisory and maintaining function with hardware

and software provided by Petra. (optional)13- User-friendly interface display.14- Time schedule by using an additional clock board.

5

Selection Procedure

6

This example illustrates a step by step selection procedure to assist any user of this catalogue to select the appropriate package unit to meet specific requirements.

Total cooling load 530 MBHSensible cooling load 350 MBHAmbient Temperature 95 °FEvaporator entering air temperature (DB/WB) 80 / 67 °FEvaporator air flow 15,000 CFMExternal static pressure 0.5” of WaterAltitude 3000 Ft

Unit Size Selection

Using the correction factor table to correct capacity for altitude, the required capacity will be:Corrected Capacity = Required Capacity / Correction Factor

= 530 / 0.985 = 538.1 MBH

Corrected Sensible Capacity = Required Sensible Capacity / Correction Factor = 350/ 0.985 = 355.3 MBH

Design Condition Requirements

From the cooling capacity tables (Performance Tables on page 24, model PPH530 is the closest selection to the required capacity. So, from the table:

Total Capacity = 542.5 MBHSensible Capacity = 361.9 MBH

Evaporator Fan Selection

1. Determine Evaporator Coil Face Velocity 2From the general data tables on page 9, find the evaporator coil area ft .

2Coil face velocity = Air flow rate [CFM]/Coil Area [Ft ]= 15000/32=468.75 fpm

Filter Face Velocity =468.75 fpm

Now use the coil and filter charts on page 28, using face velocity of fpm to get the coil pressure drop and filter pressure drop which are about 0.33 inch [H O] and 0.125 inch [H O] respectively.2 2

Calculate total pressure dropTotal static pressure drop = External Static pressure drop+Evaporator Coil pressure drop+filter Pressure drop

= 0.5+ 0.33+0.125= 0.955 Inch of [H O]2

Altitude (ft) Capacity

Correction Factor

Sea Level 1

1000 0.995

2000 0.99

3000 0.985

4000 0.98

5000 0.973

6000 0.967

7000 0.96

8000 0.95

7

Now from the general data table on page 9 find the evaporator fan model to be PETRA 9 unit, From the fan curves on pages 30 with air volume of (16000 cfm) find the following:-

A. Dynamic pressure drop [Velocity pressure] at 16000 cfm to be inch of [H O]2

B. Determine total fan pressure drop:

- Total Fan pressure drop = Total static pressure drop + Dynamic pressure drop= 0.955 + 0.48= 1.435 inch of [H O]2

2Now from the fan curve with 7500* cfm and 1.435 H O we get the following:

1) Revolution / miniature impeller : 585 RPM2) Absorbed power : 1.75 KW

*From the above data the following must be done to get the data for the double fans (this unit has 2 fans)

1) RPM should be multiplied by * 1.05, so585 * 1.05 = 614 RPM (approximately)

2) The absorbed power should be multiplied by * 2.15, so1.75 * 2.15 = 3.76 kW (approximately)

3) The motor kW can be obtained by adding power correction , (i.e 20%), so3.76 * 1.20 = 4.512 kW = 5.5 kW ( from the standard motors)

- Sound power level: from the general data tables on page 9, the sound pressure level at10 ft=78.0 dB(A)33 ft=72.0 dB(A)

*note:- when the unit has two evaporator fans, the following should be done:

1) CFM should be divided by 22) RPM should be multiplied by * 1.053) The absorbed power should be multiplied by * 2.15

16

Model Layout - Optional ConstructionWith Bag Filter

17

With Mixing Box

Model Layout - Optional Construction

With Mixing Box & V. Filter

18


19

With Economizer & Return Fan


20

Rooftop


21

Rooftop With Gas Heater


29

Petra Fan SeriesPetra 4

Air Flow Rate [CFM]

Tot

al P

ress

ure

Dro

p [

inch

of

wat

er] 1.20

1.08

0.96

0.84

0.72

0.60

0.48

0.36

0.24

0.12

0

0 235 471 706 942 1177 1413 1648 1884 2119 2354 2590 2825

Note: This curve is for direct drive fan - 3 speed

31

Petra Fan SeriesPetra 8

4.40

4.00

3.60

3.20

2.80

2.40

2.00

1.60

1.20

0.80

0.60

0.40

0.36

0.32

0.00

0.2 0.4

1.47

0.8

8.83

1.2

11.77

1.6

0.90

2.0

1.18

4.0

1.77

8.0

2.35

12.0

3.00

16.0

3.53

20.0

4.124.71 5.30 5.89

To

tal

Pre

ssu

re D

rop

[in

ch o

f w

ate

r]

Air Flow Rate [CFM] * 1000

Fan Dynamic Head [inch of water] 10¸

32

Petra 9

Petra Fan Series

4.00

3.60

3.20

2.80

2.40

2.00

1.60

1.20

0.80

0.60

0.40

0.36

0.32

0.00

0.2 0.4 0.8

8.83

1.2

11.77 17.66

1.6 2.0 4.0

1.77

8.0

2.35

12.0

3.00

16.0

3.53

20.0 40.0

4.12 4.71 5.30 5.89



To

tal

Pre

ssu

re D

rop

[in

ch o

f w

ate

r]

33

Petra 19

Petra Fan Series

4.00

14.00

12.00

8.00

2.00

1.60

1.20

0.80

0.40

0.32

To

tal

Pre

ssu

re D

rop

[in

ch o

f w

ate

r]

42.37 63.57 95.341.27 2.12 4.24 6.36 8.47 10.60 21.19


0.04 0.2 0.4 2.0 4.0 20.0 40.0


36

Typical Wiring Diagrams

37

Typical Wiring Diagrams

38

Refrigeration Schematic Diagram

International Distribution Offices

Quality Management System ISO 9001;2000 and Environmental Management System ISO 14001;1996 Certification applies to Jordan Office only

Copyright © 2002 By Petra Engineering Industries Co.Design & Layout Copyright © 2002 By Petra Engineering Industries Co.

ALL MODELS SIZES AND DIMENSIONS ARE SUBJECT TO CHANGE WITHOUT PRIOR NOTICE

Kuwait - Nouri Industrial Est.

Tel (965) 4333355 Fax 4344085

Qatar - Ajjaj Trading Co. (W.L.L.)

Tel (974) 4691546 Fax 4687258

California - USA

Air Treatment CorporationTel (909) 8697975 Fax 5985265

Pennsylvania, Maryland, Delaware

and Parts of New Jersey - USA

Peirce - Phelps, Inc.Tel (215) 8795079 Fax (215) 8795141

North New Jersey and New York City - USA

DEBTRA A/C SalesTel (973) 4292828 Fax (973) 4294909

e-mail: [email protected]

Upstate New York and Vermont - USA

Advanced Comfort SystemsTel (518) 8848444 Fax (518) 8848411

United Arab Emirates

Abu Dhabi - Petra Air Conditioning Est.

Tel (9712) 6391308 Fax 6211027

Dubai - Saif International Group

Tel (9714) 2958989 Fax 2958990

Lebanon - Petra Liban Ltd

Tel (9611) 663573 Fax 646209

West Bank - Petra International Export Co. Ltd.

Tel/Fax (9702) 2960701

Tunisia - Tunis Universal Petra

Tel/Fax (216) 71441960

Egypt - Ain Shams Company

Tel/Fax (202) 2754463/72

Saudi Arabia - Peninsular Distribution Company Ltd.

(An Abdul Latif Jameel Group Company)Tel (9662) 6930000 Fax 6283923

Pakistan - Genaire (PVT) Ltd.

Tel (9221) 4534161 Fax 4538162

ENGINEERING INDUSTRIES CO.

Headquarters

Offering You a Different ChoiceOffering You a Different Choice

PP/PPH-R22-50-60 Hz-Imp/2002/rev.0

P.O.Box 141351 Amman, 11814 JORDAN

Factory Tel (962 6) 4051055 Fax 4051228Marketing Tel (962 6) 5531508 Fax 5531513

Local Sales Tel (962 6) 4051425 Fax 4051248

International Sales Tel (962 6) 4051050 Fax 4051087

North/South America Sales Tel (962 6) 4051425 Fax (In the US) (888) 5226610 - (877) 4723010

LOCAL BRANCHESAmman: Tel (962 6) 5531508 Fax 5531509

Mecca Street: Tel/Fax (9626) 5850553Marj Alhamam: Tel (962 6) 5716151 Fax 5712008

Irbid : Tel/Fax (962 2) 7252406Aqaba : Tel (962 3) 2019189 Fax 2019728

e-mail:[email protected] www.petra-eng.com

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