Adjustments of Fuel Oil Systems

Diesel After-Sales Service

Service Bulletin

ZAS–22

Technical Information to all the Owners of Sulzer ZA 40S Type Diesel Engines

08.11.96

Adjustments of Fuel Oil Systems

Contents:

FUEL OIL

Page

– INTRODUCTION

1

– 1. GENERAL ENGINE REQUIREMENTS FOR OPERATION ON HEAVY FUEL OIL

1

– 2. FUEL OIL SYSTEM

2

– 3. FUEL OIL PRESSURE AND FLOW DEFINITIONS

4

28.99.07.40 – Printed in Switzerland

– 4. PRESSURE AND FLOW 5 ADJUSTMENT WITH SEPARATELY DRIVEN BOOSTER PUMPS – 5. PRESSURE AND FLOW ADJUSTMENT WITH ENGINE DRIVEN BOOSTER PUMPS

8

– 6. GENERAL REMARKS

9

– 7. SERVICE BULLETINS PUBLISHED FOR ZA 40S TYPE ENGINES New Sulzer Diesel Ltd Phone: (052) 262 80 10 (24hours)

Diesel After-Sales Service Telex: 896 659 NSDL CH

PO Box 414 Telefax: (052) 213 94 83

CH-8401 Winterthur, Switzerland

10

INTRODUCTION Experience gained so far has shown that the design and commissioning of the fuel oil systems are not always optimum, particularly in case of a multiengine plant. When a booster pump supplies fuel oil to several engines, a correct and equal flow distribution of fuel oil to each engine is of great importance. A flow rate through the engine injection pumps which is below the minimum specified value can lead to unsatisfactory injection behaviour and to cavitation conditions in the fuel injection system. This information is herewith supplied as a guide for the description of the fuel oil system for multiengine installations. Its primary task is, however, to give recommendations for the procedure of the adjustment and equalizing of the fuel oil flow rate through the engines of an installation. This Service Bulletin should be kept in a separate file in the control room. The respective pages or tables of the Service Bulletin with modifications to the Operating Manual, Maintenance Manual or Code Book should be copied and filed in the respective Manual or Book. 1.

GENERAL ENGINE REQUIREMENTS FOR OPERATION ON HEAVY FUEL OIL

1.1 ZA40S Engines - General Data Fuel oil viscosity at injection pumps

1317 cSt

Fuel oil service pressure at engine inlet (on engine instrument panel)

810 bar (specification for earlier engines: 68 bar, but aim for upper side)

Fuel oil pressure in the buffer unit

36 bar

Fuel oil differential pressure ∆pe across the engine fuel injection pumps at standstill ( (separately t l driven di high hi h pressure booster b t pumps) 1)

1)

Engine output kW/cyl.

Minimum differential pressure ∆pe

720

1.3 bar

660

1.1 bar

600

0.9 bar

550

0.8 bar

For systems with engine driven booster pumps please refer to paragraph 5.

1 / 10

Service Bulletin ZAS–22

1.2 Engine starting and stopping Continuous operation on HFO is preferable. Changing over to MDO should be considered only if this becomes necessary, for example: to flush the engine before maintenance work if the booster pump(s) or the heating are stopped when in dry dock (or other reasons). due to environmental requirements. Provided the following conditions are met, ZA40S engines can be started on heavy fuel oil: Cylinder cooling water heated to min. 50° C Fuel pumps heated by fuel circulation together with trace heating on the engine, system fuel pipes and components heated Heavy fuel oil viscosity at engine inlet to correspond with the requirements (please refer to enclosure ZAS22/5) The engine is prelubricated When these mentioned conditions are met, the engine can be started, stopped and started again on HFO. Designation: HFO = HEAVY FUEL OIL

MDO = MARINE DIESEL OIL

1.3 Operation at low load When running at low load on HFO it is essential that the cylinder cooling water and lubricating oil temperatures are maintained at their service level and that the LT water temperature at the charge air cooler inlet is not lower than 25° C. 2.

FUEL OIL SYSTEM

2.1 General Information The standard HFO system consists of the following three main groups: The storage system: bunker, settling and daily service tanks with transfer pumps The HFO treatment or cleaning system The pressurized supply system The principle design of the first two groups for multiengine installation remains the same, except for capacity, whether one considers a fuel system for several engines or for one engine only. We must once more, however, stress the extreme importance of correct fuel oil treatment for the successful operation of engines running on HFO. Proper fuel treatment must be carried out to remove seawater and abrasive particles including catalytic fines. The key to correct fuel treatment lies in good centrifugal separation, the centrifugal separators being the most important part of the fuel treatment system.

2 / 10


The use of separators without gravity disc, meeting the requirements for future HFO separation up to 700 cSt at 50°C and making the continuous operation of the separator units easier, is advisable. As it is usual to have a spare separator, it is of advantage to use it continuously to improve the separation results. For the arrangement of separators, refer to the manufacturer's instructions. The effective separator throughput must be in accordance with the maximum fuel oil consumption of the diesel engine plant plus a margin of about 20%. The separators are in continuous operation 24 hours per day, from port to port. For the sake of simplicity, the third group including the low and high pressure side downstream of the daily tank(s), i. e. from the daily tank(s) to the engine injection equipment, will henceforth be referred to as the "supply" system. 2.2 Supply system description The supply shown in enclosure ZAS22/1 is of the so called pressurized fuel oil system type. Pressurized systems are now common for all installations intended for use with lower quality HFO. It avoids problems with "gassing" at the high supply temperature required by high viscosity fuels in order to achieve the required viscosity for injection into the engines. This supply system is mainly characterized by: A common low and high pressure system for several engines. The low pressure feed pump (7) delivers the fuel oil from the HFO daily tank (3) through the automatic selfcleaning filter (8) into the closed high pressure circuit. To prevent boiling at the high temperatures it is necessary to maintain the required viscosity, the pressure in the buffer unit (11) is 3 to 6 bar. This pressure is controlled by the pressureregulating valve (9) which returns excess fuel oil back to the feed pump suction side or to the daily tank (3). From the common booster line, downstream of the endheater (13) and viscosimeter (14), the fuel is then delivered to one or in parallel to several engines. When several engines are connected in parallel, the correct setting of the fuel flow rate to each engine can be difficult. The recommended maximum number of main engines connected in parallel downstream of the booster pumps is therefore four (4). For the safety of the vessel, separated fuel oil systems are recommended for vessels with more than one engine. On vessels with four main engines coupled to two propellers, the separate fuel oil systems should be connected with the engines in such a way that in case one fuel oil system fails, each propeller shaft has at least one engine which receives fuel oil from the system still in operation.

3 / 10


3.

FUEL OIL PRESSURE AND FLOW DEFINITIONS

3.1 Fuel oil flow rate across the engines When a booster pump supplies fuel oil to several engines as shown on enclosure ZAS22/1, it is necessary to measure and adjust the flow distribution of fuel oil in such a way that each engine is supplied with the same specified fuel oil quantity. For this purpose, the differential pressure measured at each engine serves as reference for the flow distribution. The differential pressure at the engine is to be measured and adjusted with the engines at standstill during commissioning of the fuel oil system in an installation with separately driven high pressure booster pumps. Engines equipped with builton booster pumps have to be run at nominal speed without load. After maintenance work on the fuel oil system a check on the fuel oil supply to each engine is required. 3.2 Measuring the differential pressure The differential pressure is measured between the inlet and outlet of the injection pumps. More recent engines have now a switchingover connection with two cutoff valves to the pressure gauge in the instrument panel allowing the pressure before and after the injection pumps to be measured. The difference between these two pressures gives the differential pressure across the injection system, see enclosure ZAS22/3. Earlier supplied engines require a small modification for measuring as per enclosure ZAS22/4. The fuel flow is only correct when the differential pressure (∆pe) is the same for all engines connected to the same fuel oil system and amounts to: Engine output kW/cyl.

Minimum differential pressure ∆pe .

720

1.3 bar

660

1.1 bar

600

0.9 bar

550

0.8 bar

The differential pressure is measured at standstill with electricmotor driven booster pump (no pressure pulsations).

4 / 10


3.3 Delivery pressure In order to prevent any water (which may be present), from boiling at the high temperature (necessary to maintain the required viscosity), the lowest pressure in the closed booster circuit must be above the vapour pressure at which this water could flashoff to steam.

min. required pressure [bar] on booster pump suction side (28)

Therefore the min. required pressure p at the booster pump suction side (28) has to be at least 1 bar above the corresponding vapour pressure but not lower than 3 bar (please refer to the following diagram). 7 6 5 4 3 2 1 100

110

120

130

140

150

160

fuel oil temperature [°C] in buffer unit (11) 3.4 Maximum permissible operating pressure It must be ensured that the max. working pressure of all system components are not exceeded. Therefore the max. pressures of these components have to be verified and the relevant safety valves to be checked accordingly. 4.

PRESSURE AND FLOW ADJUSTMENT OF THE FUEL OIL SYSTEM WITH ELECTRIC MOTOR DRIVEN BOOSTER PUMPS ACCORDING TO ENCLOSURE ZAS22/1

4.1 Preliminary conditions before adjustment: All engines at standstill Whole plant on MDO or HFO. For the latter case, heavy fuel is heated to obtain the required viscosity at the injection pumps according to enclosure ZAS22/5 Feed and booster pumps in operation Fuel oil circulates through all engines

5 / 10


4.2 Checks and adjustments 4.2.1 Safety valves Check and set the safety valves (24 and 25) of the feed and booster pumps (7 and 12, also on standby pumps) to their max. admissible operating pressure or ∆p between discharge and suction side respectively. It has to be made sure that these valves are completely closed under normal service conditions in order to avoid any internal bypass possibility. 4.2.2 Pressure at the booster pump Check the pressure at the booster pump suction (28) side which has to be within the following limits: Minimum as described under paragraph 3.3 Maximum (about 6 bar), depending on -Max. admissible operating pressure of the feed pump -Max. admissible operating pressure of the buffer tank including an adequate margin to the setting of its safety valve If necessary, the pressure level at the booster pump suction side can be adjusted with the pressure regulating valve (9). Please note: Especially simpler types of pressure regulating valves do not hold the pressure absolutely constant. Slow pressure fluctuations up to ± 0.5 bar in the low pressure circuit, which also influences the pressure level in the booster system, can be tolerated. Furthermore the pressure difference across simple, springloaded regulating valves is flow dependent i. e. the pressure in the buffer unit decreases with increasing fuel consumption. 4.2.3 Fuel oil pressure before engines For earlier engines the nominal range of the fuel oil pressure before engine amounts to 6 8 bar (aim at upper side). Later engines are specified for a fuel inlet pressure of 810 bar. Important: The design pressure (normally 16 bar, but to be verified) of the various system components must not be exceeded. If the design pressure does not allow such a high pressure level, the pressure before the engines has to be set at the lower limit or even below the specified range for the time being. At this stage the overflow valve (18) must not yet limit the fuel oil pressure (to be set temporarily higher). All pressure retaining valves (17) have to be set to the same position i. e. the distance "x" on enclosure ZAS22/2 should be about the same on all engines (as a preadjustment). If necessary the fuel oil pressure before the engines can be adjusted as follows: The pressure level of the whole high pressure system can be varied by means of the pressure regulating valve (9) within the limits as specified. If this procedure is not sufficient the pressure level can be further adjusted with the pressure retaining valves (17) on the engines which have to be shifted equally for the time being i.e. same amount of turns (please refer to enclosure ZAS22/2) and note down the final pressure after booster pump(s) (29). Attention: The retaining valve KS 87085 must be of the present design or has to be modified accordingly to avoid fuel oil gushing out from the valve by unscrewing the spindle completely (please refer to Service Bulletin ZAS12). 6 / 10


4.2.4 Overflow valve To adjust the overflow valve (18) proceed as follows: Adjust the overflow valve (18) to its lower set value. Shut off the supply inlet lines of all engines by closing the valves (23). Adjust the overflow valve until the pressure at the outlet of the booster pumps (29) is 23 bar higher than the pressure noted down before (the design pressure of the components between buffer unit and engines must not be exceeded). Reopen all the valves (23) in the supply lines to the engines. 4.2.5 Fuel oil flow / quantity To adjust or equalise the differential pressures (∆pe) proceed as follow: Measure the differential pressure (∆pe) at each engine at standstill as mentioned under paragraph 3.2. Equalize then, only if it is necessary, the differential pressure (∆pe) by means of the pressure retaining valve (17) only in such a way that it will be the same on each engine of a system. Important: Dirty or clogged fuel oil indicator filters (15) do influence the fuel oil distribution, therefore the fuel filters have to be checked for cleanliness prior to the measurements. Note: At the engines with higher differential pressure (∆pe), the pressureretaining valve (17) should slightly throttle the fuel flow and vice versa. Please refer to enclosure ZAS22/2 for the valve opening characteristic. If the values mentioned under paragraph 3.2 are not achieved, the following items have to be checked: Dimension of the booster pumps: The capacity q of the fuel oil booster pumps should amount to q 0.65 * Ptot [m3/h] Ptot = total engine power installed at MCR [MW] Are all bypass possibilities in systems and components eliminated? Condition of the booster pumps: Are there any additional losses inside the pump (e. g. worn internals, defective safety valve etc.)?

7 / 10


4.3 Final conditions after adjustment 4.3.1 Engines at standstill Engine output kW/cyl.

Minimum differential pressure ∆pe

720

1.3 bar

660

1.1 bar

600

0.9 bar

550

0.8 bar

The fuel flow is only correct when the differential pressure (∆pe) is the same for all engines connected to the same booster system. 4.3.2 Engines in operation Fuel oil pressure at each engine inlet : within within

8 10

bar, normal 9 bar

68

bar for earlier engines, but aim for upper side

If necessary an additional fine adjustment by means of the pressure regulating valve (9) in the feed system within the limits as described in paragraph 4.2.2 can be carried out at service load. Note down the final pressures before and after feed and booster pumps (26, 27, 28, 29). 5.

PRESSURE AND FLOW ADJUSTMENT OF A FUEL OIL SYSTEM WITH ENGINE DRIVEN BOOSTER PUMPS (CONCERNS A FEW PLANTS ONLY) 1. Check and set all bypass and relief valves on: Feed pumps Buffer unit

Engine driven booster pumps, the builtin overpressure safety valve is factory adjusted to ∆p discharge/suction = 10 bar

Fuel oil end heater 2. Whole plant preferably on MDO than on HFO. For the latter case, heavy fuel is heated to obtain the required viscosity at the injection pumps according to enclosure ZAS22/5. 3. Engine running at nominal speed without load. 4. The feed pressure at the engine driven pump suction side is not lower than described under paragraph 3.3. 5. If necessary increase by means of the pressure regulating valve (9). 6. Measure the heavy fuel oil pressure at the engine inlet and adjust to 810 bar by increasing the pressure level of the whole high pressure side by means of the pressure regulating valve (9) and / or adjust the pressure at the engine by means of the pressure retaining valve (17). See also enclosure ZAS22/2. 7. Measure the differential pressure (∆pe) as mentioned under paragraph 3.2. Note: Sufficient damping of the pressure gauges is required. 8 / 10


6.

GENERAL REMARKS

6.1 Recheck After any possible corrections of the engine inlet pressure as described under paragraph 4.3.2 or manipulations in the systems etc., the differential pressures (∆pe) have to be checked once more and compared to the values mentioned under paragraph 4.3.1 6.2 Pressure regulating valve (9) With a pneumatically controlled pressure regulating valve (9), the delivery pressures after the feeder and booster pump can increase above limits if the control air pressure fails. Note: Do not decrease pressure by means of safety valve (25) but rather temporarily by means of safety valve (24) at the feeder pump or preferably by mechanical adjustment of regulating valve (9) until air supply is restored. 6.3 Standby pumps The measurements under paragraphs 4 and 5 have also to be carried out with any standby pump.

ENCLOSURES: Fuel System Layout

ZAS-22/1

Pressure Retaining Valve KS 87085

ZAS-22/2

ZA40S Control of Fuel Pressure in the Supply and Return Pipe (with Measuring Device on Engine)

ZAS-22/3

ZA 40S Control of Fuel Pressure in the Supply and Return Pipe (Without Measuring Device on Engine)

ZAS-22/4

Viscosity - Temperature Diagram

ZAS-22/5

New Sulzer Diesel Switzerland Ltd has issued this Service Bulletin with their best knowledge and ability. However, New Sulzer Diesel Switzerland Switzerland Ltd can not take any liability for any or all information contained in this or any other Service Bulletin. Changes of any nature to the form and or to the content of this or any other Service Bulletin as published by New Sulzer Diesel Switzerland Switzerland Ltd, are not permitted. 9 / 10


7.

SERVICE BULLETINS PUBLISHED FOR ZA 40S TYPE ENGINES

We have so far published the following Service Bulletins which are valid for ZA 40S type engines: Z-6.2 Z-7 Z-8.1 Z-9.2 ZAS-1.1 ZAS-2

dated dated dated dated dated dated

31.07.92 19.07.85 13.12.91 28.09.93 20.10.93 06.11.92

ZAS-3 ZAS-4.3 ZAS-5 ZAS-6 ZAS-7 ZAS-8

dated dated dated dated dated dated

10.06.93 25.03.97 03.12.93 01.04.94 05.04.94 05.04.94

ZAS-9 ZAS-10 ZAS-11 ZAS-12 ZAS-13 ZAS-14 ZAS-15 ZAS-16 ZAS-17.1 ZAS-18 ZAS-19 ZAS-20 ZAS-21

dated dated dated dated dated dated dated dated dated dated dated dated dated

01.06.94 01.08.94 01.03.95 01.03.95 31.03.95 01.06.95 10.08.95 10.08.95 04.04.97 17.11.95 17.11.95 17.11.95 22.03.96

ZAS-22 ZAS-23 ZAS-24

dated 08.11.96 dated 19.11.96 dated 28.01.97

Assessment of Main and Connecting Rod Bearings Flushing Instructions Undersized Bearings and Reconditioning of Crankshafts Lubricating Oil Treatment and Requirements Cylinder Liner Overhaul Grinding of Inlet / Exhaust Valves and Seats, New Valve Seat and New Relief Valve Design Oil Scraper Rings Top Piston Ring Instruction for Testing of Fuel Injection Nozzles Ring for Rotating Piston for ZA 40S Type Engines Adjustments and Maintenance Requirements on Oil Mist Detector Turnomat for Exhaust Valves and Rotocap for Inlet Valves on ZASType Engines Exhaust Pipe Expansion Bellows High Temperature Cooling Water System Cylinder Liner with a Thread in the Upper Part of the Bore New Spindle Design for Pressure Control Valve KS 87085 New Inlet Valves New High Pressure Fuel Pipe Assembly New Fuel Injection Nozzle Specification Flow Control Valve KS 72126 for Cylinder Lubrication ABBTurbochargers Type VTR ..4 After Sales Service Information Tightening Instructions New Piston Ring Fitting Tool New Spring Cage KS 28042 for Rocker Gear Differences in the Drive for the Cylinder Lubrication between Engines with 660 kW/Cyl. and 720 kW/Cyl. Adjustments of Fuel Oil Systems Modification to the Oil Mist Detector Alphabetical Index of Topics of Service Bulletins

Should you not be in possession of the above mentioned documentation suitable for your plant, kindly contact your local New Sulzer Diesel representative for your copy.

10 / 10


FUEL SYSTEM LAYOUT To air vent manifolds From diesel oil separator From heavy fuel oil separator From transfer pump LAH

2

3

Note: The return pipe may also be led to tank 3 4

LAL

1 DAH

5

DI

16

29

28

PI

PI

22 DAH

VAH

14

1 DI

23

29

28

PI

PI

Air inlet 7 bar

25

Air outlet

15

20

16

Flexible hose quick– coupling connection only in use when filling air

To heavy fuel oil separator

9 PI

27

26

PI

PI

27

26

PI

PI

DAH

DI A

24

17 LAL TI

13 25 19

20

19

24 12

From additional engines

1 2 3 4 5 6 7 8 9 10 11 12 13 14

18

6

15 11 10

8

21

7

Emergency MDO supply line

23 17

To additional engines

Main engine HFO settling tank, heatable and insulated HFO daily tank, heatable and insulated MDO daily tank Threeway valve, manually or remotely operated Suction filter, heatable Low pressure feed pump Automatic selfcleaning filter Pressure regulating valve Flow meter Buffer unit High pressure booster pump Fuel oil end heater Viscosimeter

15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

Duplex filter, heatable Inlet to engine fuel injection pump Pressure retaining valve fitted on engine Overflow valve Fuel oil leakage Fuel oil monitoring Shutoff valve after feed pump Shutoff valve after booster pump Shutoff valve at engine inlet Safety valve on feed pump Safety valve on booster pump Pressure gauge before feed pump Pressure gauge after feed pump Pressure gauge before booster pump Pressure gauge after booster pump

Service Bulletin Enclosure ZAS–22/ 1

Pressure retaining valve KS 87085 Fig. 1

From fuel pumps

1 2 3 4 5 6 7

Valve opening characteristic

8

adjusting range

"X"

Fig. 2

9 10

differential pressure across valve

Engine outlet (to buffer unit) 1 2 3 4

Hexagon for spanner Washer Locking nut Locking plate

5 Nipple 6 Adjusting spindle 7 Oring

8 Housing 9 Sleeve 10 Compression spring

Working principle of the pressure retaining valve: The sleeve (9) is pressed downwards against the compression spring (10) until the fuel entering the valve can pass between the sleeve (9) and the spindle (6) to the outlet. This requires a differential pressure across the valve depending on the position of the spindle (6). The more the spindle is inserted into the valve body the more the fuel oil differential pressure across the valve increases which is necessary to open the valve due to the increased compression of the spring (see Fig. 2). Fig. 1 shows the spindle in its initial position as the sleeve (9) is in its upper end position. If the spindle is screwed upwards beyond this point the valve becomes inoperative because the fuel oil can pass the valve without pressing down the sleeve.

Attention: The retaining valve KS 87085 must be of the present design or has to be modified accordingly to avoid fuel oil gushing out from the valve by unscrewing the spindle completely (please refer to Service Bulletin ZAS12). Service Bulletin Enclosure ZAS–22/ 2

ZA40S Control of fuel pressure in the supply and return pipe (with measuring device on engine)

Instrument panel on the engine

Fuel pressure

Connecting box

Cutoff valves (one is to be closed)

to pressure switch

supply line return line

limiting plate

NORMAL POSITION


ZA40S Control of fuel pressure in the supply and return pipe (without measuring device on engine)

Instrument panel on the engine Fuel pressure

Fuel injection pump

Supply

ÔÔ ÔÔ ÔÔ ÔÔ ÔÔ ÔÔ

Isolating valves

Return Pressure retaining valve

Orifice (3 Stage)

Square flange

Pressure gauge (for temporary use)

Square flange with isolating valve for inlet and outlet

Flange for: supply line:Connection to pressure gauge on engine instrument panel return line: to be blanked off with a plug screw or not drilled through Valve must be fitted as close to the flange as possible Thread size according to the connection used

To be closed by cap nut after use

All fittings used must be of qualified standard and made of steel! Service Bulletin Enclosure ZAS–22/ 4

VISCOSITY TEMPERATURE DIAGRAM (Typical Values of Petroleum Fuel Oils)

Oils can be pumped only with difficulty or not at all

91.7055b

Recommended viscosity before fuel injection pumps

Example: To obtain the recommended viscosity before fuel injection pumps a fuel oil of 150 mm/s (cSt) at 50C must be heated to 108 to 120C.


Adjustments of Fuel Oil Systems

Recommend Documents