Ammonia Reciprocating Feed Pump

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Ammonia Feed Pump operation & maintenance detail

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AMMONIA RECIPROCATING FEED PUMP Prem Baboo Sr. ManagerProd FIE Institution of Engineers India Technical Advisor an Expert for www.ureaknowhow.com

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CLASSIFICATION PURPOSE OF PUMP MAIN COMPENENTS OF PUMP FUNCTION AND ITS MATERIAL OF CONSTRUCTION MAJOR PROBLEM MODIFICATION LUBRICATION CIRCUIT MAINTENANCE SCHEDULE TRIP CONDITIONS

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The Ammonia feed pump P-1 A/B TYPE-TRIPLEX HORIZONAL RECIPROCATING PUMP MAKE- a M/S URACA Pumpenfabrik GmbHGermany. bM/S BPCL INDIA MODEL-KD 827 DESIGN ST ANDARD:API 674

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• The ammonia feed pump P-1 is used to raise the pressure of the liquid ammonia upto 240 kg/cm2 before feeding it to reactor. • Pump P-5 is used as a booster pump forP-1 so as to maintain required NPSH at the suction of the pump P-1.

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• MEDIUM HANDLED LIQUID AMMONIA • FLOW TEMPERATURE : NORMAL 12⁰ TO 35⁰C DESIGN -32⁰ TO 160 ⁰C • SUCTION PRESSURE:Kg/cm2 MINIMUM 20 NORMAL 21 DESIGN 29 • DISCHARGE PRESSURE :Kg/cm2 240 • NPSHREQUIRED 14m • NPSHAVAILABLE 123m • VISCOCITY AT FLOW TEMPERATURE 0.15 TO 0.19 cp • VAPOUR PRESSURE 13.76 abs

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• The triplex plunger pump in general consist of the following components POWER END 3 STUFFING BOXES VALVE BLOCK AND VALVES SUCTION SIDE PULSATION DAMPER DISCHARGE SIDE PULSATION DAMPER GEAR REDUCER WITH COUPLING TOURQUE CONVERTER WITH COUPLING DRIVING MOTOR

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• PLUNGER DIAMETER 150 mm • STROKE 270 mm • PUMP SPEED :RPM MINIMUM NORMAL DESIGN 32 100 115 • CAPACITY:L/MIN MINIMUM NORMAL DESIGN 450 1421 1642 • POWER REQUIRED AT 680 KW PUMP SHAFT • REQUIRED MOTOR POWER 855 KW • MOTOR SPEED 1480 RPM

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Gear type single helical Design Standard- AGMA 420.04 Rating 680 kw Output speed 75 – 150 min ¯1 Gear ratio 1:13.825 Oil viscosity 220 cst at 40º c Coupling Design Standard API 671 Guide vane adjustment 135 mm From 0 to 100 Set to 45 mm Rated power 872 KW Rated speed n1 1480 / min. Raising speed n2 2800 / min. at 100 guide vane position Guide vane adjustment via pneumatic actuator

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• Crank shaft gives rotating force to connecting rod and is connected to motor through torque convert and gear box. • Material of construction: 42 CrMo 4 1.7225. AISI 4140B • Crankshaft have refill hole drilled in between its webs to furnish lubrication to big end bearing.

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• The connecting rod transfer the rotating force of crank shaft to a oscillating force on the plunger. Connecting rods are split perpendicular to their centerline at the big end for assembly of the rod onto the crank shaft. • MATERIAL OF CONSTRUCTION: ASTM A536 Gr100-70.09 • The connecting rod either drilled or have cast passages for transferring oil from main end to small end.

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BEARINGS • IN THE POWER END FOLLOWING TYPE OF BEARING ARE USED • BIG END BEARING:WHITE METAL LINEDTIN BASED JOURNAL BEARING.SPLITTED TYPE • SMALL END BEARING: BRONZE STEEL BACKED JORNAL BEARING • MAIN BEARING :DOUBLE ROW SPHERICAL BALL BEARING:23256

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• TYPE OF LUBRICATION- I. FOR POWER END-FORCED LUBRICATION II. FOR GEAR DRIVE-FORCED LUBRICATION DESCRIPTION OF OIL CIRCUIT • CRANK CASE serves as oil reservoir. • For supplying oil there are two gear pump installedone running and one standby. • The oil flow through pump oil cooler duplex filter to crank shaft bearings. • There is a center refill drilled in crank shaft through which oil flow to the big end bearing • In the connecting rod there is a hole drilled through which the oil flow to small end bearing.

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• The valve block is bolted to the power end casing. It contains the suction and discharge valve which are designed as tandem valves. • MATERIAL OF CONSTRUCTION-SS ASTM A182 Gr.F304

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Earlier the material of construction used for valve block was LTCST St E355 .But these valves blocks were more prone to failure due to fatigue phenomenon. The main problems were of erosion at the ‘O’ ring seat due to failure of ‘O’ ring which finally leads to cracking. Therefore the MATERIAL OF CONSTRUCTION of these valve blocks were changed to STAINLESS STEEL ASTM A182 Gr. F304.

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• ORIGINAL VALVE BLOCKS: 4 Nos. in LTCS T St E355 Material of Construction for Urea Line-I During project stage in1987 4 Nos. in LTCS T St E355 Material of Construction for Urea Line-II during expansion project stage in year 1996. • Spare valve block: YEAR 2 Nos. in LTCS T St E355 1990 FROM M/S URACA 1 No. Forging in CS DIN 1.0402 1990 4 Nos. Forging in Carbon Steel DIN 1.0402 1990- 1994 2 Nos. in LTCS T St E355 1997 1 No. in Stainless Steel ASTM A182 Gr. F304 2004 1 No. in Stainless Steel ASTM A182 Gr. F304 2004 1 No. Forging in Stainless Steel ASTM A182 Gr. F304 2005 1 No. Forging in Stainless Steel ASTM A182 Gr. F304 2005 2 Nos. Stainless Steel ASTM A182 Gr. F304 2005

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• The failure of the Valve Blocks of Ammonia Feed Pumps is also encountered in other the Fertilizer Plants in India. To improve the reliability of the Ammonia Feed Pumps many fertilizer plants in India have installed Modified Valve Blocks supplied by O.E.M. of Ammonia Feed Pumps i.e. M/s. URACA Germany with satisfactory performance. M/S URACA have come out with a permanent solution by modifying the valve block fitted with tandem valves and TRAPEZOIDAL GASKETS completely eliminating ‘O’rings which had been the cause of failure in the past.

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The valves used in P-1 pump are called tandem because both the function i.e. suction and discharge has been done by single valve.

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• VALVE SEAT SS 1.4112 90 Cr MoV 180 AISI 440B • VALVE CONE SS 1.4112 90 Cr MoV 180 AISI 440B • VALVE PLATE SS1.4112 90 Cr MoV 180 AISI 440B • GUIDE BUSH SS 1.4112 90Cr MoV 180 AISI 440B • ‘O’ RING NITRO BUTYL RUBBER • SUPPORT RING TEFLON

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PROBLEMS:VALVE BODY CRACK REASONS: Carbamate carry over along with ammonia: As these valves are made up of vanadium steel having high hardness any carry over of carbamate will lead to corrosion and stress corrosion cracking. CAVITATION:The cavitation due to suction condition shall lead to severe impact and hammering during compression stroke will lead to premature valve failure. STRESS CONCENTRATION: Due to sharp edges or corners. Invasion of foreign material along with Ammonia

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• The stuffing boxes are of two gland design consisting each of a high pressure and a low pressure part. Sealing is done by packing rings. The plungers are centered by means of guide bush. • The purpose of the packing is to limit and not to prevent the penetration of the medium. A small amount of leakage is necessary and desirable to reduce the friction.

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The 3 STUFFING BOXES are supported in the power end casing and are flanged to the valve block. They contain the plunger with packing and guide bushings. The plungers are connected to the power end cross head extensions by plunger couplings. Material of construction: STUFFING BOX:ASTM A350 LF2 PLUNGER :IS:2004 CHROME PLATED KASSET RING:SS AISI 316 GUIDE BUSH:MORGANITE STUFFING BOX NUT:FORGED STEEL STUFFING BOX INSERT:ASTM A 350 LF2 PACKING RING:BRAIDED ARAMID RING:DELRIN

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• Earlier the oil sealing was done instead of water sealing. But the oil sealing produced the problem of oil carry over with the ammonia in subsequent stages and consequently cause the oil contamination problem in waste water section. • Therefore the water sealing was adopted and the water leaked is taken to waste water section and produces no harm. • Water sealing is done by injection of cooled condensate at 30⁰C at the rate of 1 to1.5 l/min per stuffing box.

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• NEED OF PULSATION DAMPENER: During the reciprocating motion of plunger it doesn’t moves with uniform velocity for the entire stroke but it has an acceleration developed for the first half of each stroke and retardation has developed for later half of the stroke. Since the liquid flowing through pump closely follows the plunger its acceleration and retardation effect will correspondingly transmitted to the liquid flowing in the suction and delivery pipe. These pulsation in flow of liquid in the suction and discharge pipe can create vibration problem. Flow-induced piping vibrations create cyclic loading on piping welds and piping supports and can also accelerate the loosening of mechanical joints.

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• The main function of pulsation dampener are: To reduce the pulsation in the line created during the discharge strokes of the ammonia feed pump. To make up the fluid volume reduced during the three suction stroke of ammonia fed pump.

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• Pulsation dampener works according to air chamber principle and can supply and absorb the excess and deficit volume by means of a compressible gas cushion. • The cushion is formed by evaporation of liquid ammonia. The heat of evaporation is provided from outside by a heating coil.

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Pulsation dampener is simple cylindrical vessel with both ends covered by elliptical dished end. Earlier almost three forth of the vessel is steam jacketed from the top. Steam jacketing is provided to heat the liquid ammonia to raise the vapor pressure of ammonia at 40 ⁰C. Once liquid is heated at 40⁰ C it converted into vapour form. During and after heating the level of ammonia in the vessel is to be maintained in such a way that sufficient space at the top of vessel is left to accommodate the required volume of ammonia vapor. This ammonia vapour acts as a level cushion or dampener during the complete suction cycle.

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The DISCHARGE SIDE RESONATOR serves to diminish the pressure variation in the discharge line. The effect is retained with in the pressure range existing in the installation. There is no wear at all because no moving parts are available. Thus no maintenance is required.

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• Earlier the positioning of suction dampener as well as the steam jacketing of the suction damper were faulty. • The suction dampener was installed too away from the suction of the pumpabout 4.5 m. The far off position suction dampener resulted in higher pulsation in the suction line leading to higher line vibration. • The steam jacketing of the suction dampener was resulting in passing of ammonia vapors in the suction of the pump which result into cavitation.

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…… • Considering these two point following changes were made: • The position of suction dampener was shifted to about 1.5m distance from the suction of pump. • The steam jacket was removed and a steam coil was provided at its top.

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• The hydrodynamic torque converter is provided for step less speed/torque transmission. o TURBINE WHEEL o ADJUSTABKE GUIDE BLADES o PUMP IMPELLER o INPUT AND OUT PUT SHAFT o ADJUSTMENT MECHANISM

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• The pump impeller absorbs the mechanical energy of the driving motor converting it into kinetic energy by accelerating the oil. • The turbine wheel converts the kinetic energy existing in fluids mass back to mechanical energy. • The guide wheel absorbs the differential torque between pump impeller and turbine wheel which result in a torque multiplication. • Depending on the guide vane position between 0 and 100 a corresponding torque is transmitted via the turbine wheel as a function of speed.

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• The housing is provided as oil tank. The same oil is used as working oil control oil lube oil. • WORKING OIL CIRCUITTC OPERATION The TC is supplied with working oil by a gear pump installed inside. The gear pump supplies the working oil directly into the working chamber. The working oil pressure is around 5 kg/cm2.

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• Control oil circuit. A gear pump supplies the adjustment mechanism with control oil. The oil pressure of this circuit is provided by A pressure relief valve. The control oil pressure is around 15 kg/cm2. • Lube oil circuit All anti friction bearing are surrounded by the torque converter working oil. A separate lubrication of the bearing is not necessary during operation of the torque converter.

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DESCRIPTION FREQUENCY OF MAINTENANCE Crankcase Inspection Two Year MPI of Crankshaft / Connecting Rod Two Year Main Bearing Replacement 40000 hrs. Tandem Valves it’s ‘O’ Rings Replacement 3000 hrs. Torque Convertor Inspection Two year Valve Block Inspection 3000 hrs Gear Box High Speed Shaft Seal Inboard Two Year Torque Converter Shaft Seal Outboard Two Year

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• For overload protection of crankshaft we have an inductive proximity switch and an isolation switch unit. • The proximity switch is incorporated in rear cover of the power end frame. The isolation switch unit is incorporated in control room. • The distance between switch and crankshaft web is set by adjusting the proximity switch. If due to overload the deflection of the crank shaft is too great the control device stops the pump motor.

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• When Crank Case lube oil pressure low 2.5 kg/cm2 • When Gear box oil pressure low 0.35 kg/cm2 • When torque converter lube pressure low 3.0 kg/cm2 • When discharge pressure is high 265 kg/cm2 • At high speed 114/115 R.P .M • Packing flushing fluid pressure low at 2.5 kg/cm2

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