Modification in Pump Piping to Comply with Nozzle Allowable

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 4, Issue 6, June 2014)

784

Modification in Pump Piping to Comply with Nozzle Allowable

Harshal M Ghule

1

, S. B. Belkar

2

1_{PG Student PREC Loni, India.} 2_{HOD Mechanical dept. PREC Loni India.}

Abstract— The load and stress imposed from a connecting piping system can greatly affect the reliability of an equipment; these loads either from expansion of a pipe or from other source can cause shaft misalignment as well as shell deformation interfering with the internal moving parts. Therefore it is important to design the piping system to impose a little stress as possible on the equipment, ideally, it is not possible.

This project work is focused on to stress analysis of a pump piping system as per process piping codes B31.3 by CAESAR-II and rethinking the nozzle allowable loads provided by the pump manufacture, to optimize the design and reduced the design, material as well as manufacturing cost. To achieve this, implement various methods. The loads which are imposed on the pump nozzle can be reduced by possible routing the piping system with less modification. But this re-routing of a piping has its practical & layout limitation, so as to overcome this difficulty, explores the methods for setting a higher allowable loads without changing pump manufacturer design consideration and size of pump. A more realistic allowable should be established as per API 610 standard to better balance equipment cost against piping engineering.

I. INTRODUCTION

It is common practice worldwide for piping designers to route pump piping by considering mainly space, process and flow constraints (such as pressure drop) and other requirements arising from constructability, operability and

reparability. Unfortunately, pipe stress analysis

requirements are often not sufficiently considered while routing and supporting piping systems, especially in providing adequate flexibility to absorb expansion contraction of pipes due to thermal loads. So, when “as designed” piping systems are handed-off to pipe stress engineers for detailed analysis, they soon realize that the systems are “stiff” and loads on nozzles is to high to comply with manufactures allowable so as suggest routing changes to make the systems more flexible and to reduced the nozzle loads. The piping designers, in turn, make changes to routing and send the revised layout to the pipe stress engineers to check for compliance again. Such “back and forth” design iterations between layout and stress departments continue until a suitable layout and support scheme is arrived.

But this resulting in significant increase in project execution time, which, in turn, increases project costs. This delay in project execution is further worsened in recent years by increased operating pressures and temperatures in order to increase plant output; increased operating pressures increase pipe wall thicknesses, which, in turn, increase piping stiffness's further. Such increased operating temperatures applied on “stiffer” systems increase pipe thermal stresses and support loads. So, it is all the more important to make the piping layout flexible at the time of routing.

Many researchers were worked on modification of pump

piping. Peng et.al. [1] Identified that the current allowable

for piping loads on rotating equipment nozzle imposed by

the equipment manufacturers are too low. William et.al.

[2] studied the pump reliability problem which is

responsible for the large amount of maintainence budget and lost opportunitycost at chemical plants, refinaryies, and

many electric utilities. James et.al. [3] had studies the

Horizontal process Pump modification to comply with

API-610.sixth edition forces and moments. James et.al. [4]

Worked on the API 610 Base plate and Nozzle loading criteria. The base plate and nozzle loading criteria in the December 1985 draft version of API610 7th Edition is substantially different from the criteria found in the 6th

Edition. Takio Simizu et.al. [5] senior research engineer

in Ebara research company studied "The analysis of nozzle load for process pump." Also discussed shaft end displacement of centerlines mounted pump under nozzle

loads. L.C. Peng et.al.[6]had studied the "Equipment

reliability improvement through reduced pipe stress ". The loads and stress imposed from a connecting piping system

can greatly affect the reliability of equipment. Charles

et.al. [7] Proposed various aspects for pump piping. They studied "Design and Operation of Pump for Hot standby

service.”Peng et.al. [8] Found piping system is designed

based on the piping code created for each individual

industry. Peng,et.al. [9] Studied the "Treatment of support

friction in piping stress analysis".

It is always studied that how to overcome with this low nozzle allowable provided by manufactures. So in this research they have focused the various methods and approach to comply this low allowable, without increasing

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 4, April 2013)

785 Literature of past work does not adequately clarify the proper innovative design of pump system and routine modification in pump piping and Latest edition requirement of API 610. So there is a need to modification in piping as well as support friction factor consideration to reduce the loads on piping nozzles.

II. DESIGN BASIS FOR STRESS ANALYSIS.

The applicable edition of the codes and standards shall be that in effect on the contract date.

A] Codes:-Comply with all applicable Codes including, ASME, B31.3, Section VII, B16.5.

B] Standards:-Comply with the following applicable Standards: API, API 610, WRC, WRC 107, WRC 297, ASCE-7-05, EJMA

C] Basic Data for Analysis:-For analysis of stress it is required to find out pressure,wight and temperature of the fluid ,along with this loading type is important factor which is to be consider while analysis.

Project Specification And Pump Piping Design Parameters:-Lines which are connected to the deethaniser centrifugal pump in propylene recovery unit has below listed properties.

Suction Line No- 14"-1630-P-400-31174XR

Discharge Line No- 8"-1630-P-013-31174XR Equipment - 1630-D-007

(Reflux Drum )

Equipment-1630-G-004A/B (Reflux Pump)

Density of Fluid - .0004270 kg./cu.cm.

Pressure Rating 300

Operating Temperature - 49 Operating Pressure -18.2 bars

Design Temperature - 87 Design Pressure -32.65 bars

Mill Tolerance-12.5 Test Pressure = 48.98 bars

Corrosion Allowance-3.00mm Piping Material- A333 6

Piping Code-B 31.3 Equipment Standard-API610

Process layout of system

Piping designer and Layout engineer route piping as per design requirement by considering various access ways, maintenance requirement and process requirement as shown in below fig

Caesar model formation is based on the initial routine and possible support location shared by Piping Dept. Design parameters is as per project design basis.

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International Journal of Emerging Technology and Advanced Engineering

786 Nozzle check with Initial Piping.

It is found that the nozzles are not qualified in the existing routine as the initial system is very stiff. Even if the nozzle is not passed in two times of allowable in API 610 then we will suggest possible route modification in existing routine at clouded potion.

NODE Fa N. Fb N. Fc N. Forces Check

Ma N.m.

Mb N.m.

Mc N.m.

Moments Check Remark 70

Limits 24299 23401 13998 20899 13799 19599 2(OPE) 5297 921 2609 0.218 -530 -547 1760 0.09 Qualify 3(OPE) 5366 921 2879 0.221 -612 -831 1856 0.095 Qualify 4(OPE) 5204 1138 2528 0.214 -376 -392 2056 0.105 Qualify 11(SUS) 9347 -1094 -846 0.385 -323 -498 20 0.036 Qualify 500

Limits 4893 3781 3114 2576 3525 1762 2(OPE) -4480 2188 -1139 0.916 -499 -1041 -3258 1.849 Qualify 3(OPE) 38 311 -1154 0.371 -845 -764 -1091 0.619 Qualify 4(OPE) -4075 1995 -1262 0.833 -123 -1491 -2890 1.64 Qualify 11(SUS) 34 -363 -446 0.143 -411 -104 337 0.191 Qualify 750

Limits 4893 3781 3114 2576 3525 1762 2(OPE) -5298 3095 1938 1.083 1360 2854 -5094 2.89 Fail 3(OPE) -4998 2911 1719 1.021 937 2496 -4735 2.687 Fail 4(OPE) -1221 1721 1450 0.466 1613 1440 -3947 2.24 Fail 11(SUS) 39 -330 283 0.091 361 -275 266 0.151 Qualify 2130

Limits 3114 2491 2046 1762 2305 1180 2(OPE) 223 1402 1321 0.645 -188 510 -291 0.247 Qualify 3(OPE) 955 65 301 0.307 -194 108 108 0.11 Qualify 4(OPE) 223 1429 1350 0.66 -195 522 -293 0.249 Qualify 11(SUS) 962 -184 7 0.309 -112 -16 126 0.107 Qualify 2530

Limits 3114 2491 2046 1762 2305 1180 2(OPE) 98 716 743 0.363 147 150 -443 0.375 Qualify 3(OPE) 96 809 820 0.401 120 193 -443 0.376 Qualify 4(OPE) 968 -426 -405 0.311 60 -202 111 0.094 Qualify 11(SUS) 962 -202 -32 0.309 -99 -31 127 0.107 Qualify

In piping routine change some loop will apply to increase flexibility and piping 3D model is as shown in Fig.

Piping Caesar-II model with route modification :-

As the Piping has rerouted the piping needs to be again update the Caesar model as per latest routine which is as shown in Fig.

In Stress analysis to reduced the nozzle loads due to friction effect of support use 0.1 as a friction factor.

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International Journal of Emerging Technology and Advanced Engineering

787

Fig.Pump Piping Caesar-II Model with Pump B Operating and A stand by

Fig.4.8 Pump Piping Caesar-II Model with Pump A Operating and B stand by

III. CAESAR-II OUTPUT.NODE DISPLACEMENT IN SUS

CASE

In sustain case the displacement in Y direction i.e. in vertical downward, should not be more that the specific value in design basis . In this design basis in sustain case sagging should not be more than 8 mm.As the sagging is more than 8 mm then its shows that restrain which is provided is not sufficient. even if the system is passed in sustain stress. so Piping stress Engineer to check sagging and needs to provide supports accordingly.

By using Caesar-II software, analysis of system is

carried out and result is tabulated below

Maximum Stresses in piping system

11 (SUS) W+P1 Load Case

Code stress Check Passed

Highest Stresses: (N./sq.mm)

Code Stress Ratio (%): 49.7 @Node 20

Code Stress: 67.1 Allowable 134.8

Axial Stress: 66.6 @Node 30

Bending Stress: 36.4 @Node 1720

Torsion Stress: 1.8 @Node 1760

Hoop Stress: 134.7 @Node 30

3D Max Intensity: 139.7 @Node 30

16 (OCC) L16=L12+L11 Load Case

Code Stress Ratio (%): 43 @Node 1720

20 (EXP) L20=L2-L11 Load Case

Axial Stress: 2 @Node 1360

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International Journal of Emerging Technology and Advanced Engineering

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Hoop Stress: 0 @Node 30

PipingNozzleCheck.

Nozzle Check Criteria By API-610.

If we considered nozzle allowable 2times of the API then we have to comply "Annex F".

Annex F (Horizontal pumps):

F.1.1 Acceptable piping configurations should not cause excessive misalignment between the pump and driver. Piping configurations that produce component nozzle loads lying within the ranges specified in Table 4 limit casing distortion to one-half the pump vendor’s design criterion (see 5.3.3) and ensure pump shaft displacement of less than 250 μm (0,010 in). [13 3]

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International Journal of Emerging Technology and Advanced Engineering

789

a)The individual component forces and moments acting

on each pump nozzle flange shall not exceed the range specified in Table 4 (T4) by a factor of more than 2.

b)The resultant applied force (FRSA, FRDA) and the

resultant applied moment (MRSA, MRDA) acting on each pump nozzle flange shall satisfy the appropriate interaction equations below.

[FRSA/(1,5×FRST4)]+[MRSA/(1,5×MRST4)]≤ 2...(F.1)

[FRDA/(1,5×FRDT4)]+[MRDA/(1,5×MRDT4)]≤ 2....(F.2)

c)The applied component forces and moments acting on

each pump nozzle flange shall be translated to the centre of the pump. The magnitude of the resultant

applied force (FRCA), the resultant applied moment

(MRCA), and the applied moment shall be limited by

Equation (F.3), Equation (F.4) and Equation (F.5) (the sign convention shown in Figure 20 through Figure 24 and the right-hand rule should be used in evaluating these equations). [13 3]

FRCA<1.5(FRST4+FRDT4)...(F.3)

|MYCA|<2,0(MYST4+MYDT4)...(F.4)

MRCA<1,5(MRST4+MRDT4)...(F.5)

IV. RESULT AND DISSCUSION

Condition 1- Nozzle Load with initial routine

DESIGN CONDITION : PRESSURE: 33.8 kgf/cm square TEMPRATURE: 87 C

Fx = Fc Fy = Fa Fz = Fb Mx = Mc My-Ma Mz = Mb

750 8" RFFE 300 # / N1/A 1938 3095 5298 5094 1613 2854 Operating Load System Fail 500 8" RFFE 300 # / N1/B 1262 4480 2188 3258 845 1491 Operating Load System Fail 3114 4893 3781 1762 2576 3525 Allowabel Load As Per API 610

2130 6" RFFE 300 # / N2/A 1350 962 1429 293 195 522 Operating Load System Pass 2530 6" RFFE 300 # / N2/B 820 968 809 443 147 202 Operating Load System Pass 2046 3114 2491 1180 1762 2305 Allowabel Load As Per 2 API 610 Node No Nozzel Discription Forces In N Moment N-m Type of Loads Remark

RATING: 300 # OPERATING CONDITION :

NOZZLE SIZE: 219 NB (6") PRESSURE:

SCH THICK : XS (12.7 mm) TEMPRATURE:

Type of Loads Remark

EQUIPMENT NO: 1630-G-004 A/B SPEC : 31174XR

NOZZLE NO: N2 Discharge Nozzle SYSTEM Discription: DEETHANISER REFLUX PUMP

NOZZLE SIZE: 219 NB (8")

SCH THICK : XS (12.7 mm)

Node No Nozzel Discription Forces In N Moment N-m

NOZZLE NO: N1 Suction nozzle SYSTEM DISCRIPTION: DEETHANISER REFLUX PUMP

RATING: 300 #

Condition 2- Nozzle Load After route modification.

DESIGN CONDITION : PRESSURE: 33.8 kgf/cm square TEMPRATURE: 87 C

750 8" RFFE 300 # / N1/A 505 8501 2347 3191 352 2066 Operating Load System PASS 500 8" RFFE 300 # / N1/B 360 9524 2516 3447 342 1666 Operating Load System PASS 6228 9786 7562 3524 5152 7050 Allowabel Load As Per 2 API 610

2130 6" RFFE 300 # / N2/A 1350 962 1429 293 195 522 Operating Load System Pass 2530 6" RFFE 300 # / N2/B 820 968 809 443 147 202 Operating Load System Pass 2046 3114 2491 1180 1762 2305 Allowabel Load As Per API 610

NOZZLE NO: N1 Suction nozzle SYSTEM DISCRIPTION: DEETHANISER REFLUX PUMP

RATING: 300 #

NOZZLE SIZE: 219 NB (8")

SCH THICK : XS (12.7 mm)

Node No Nozzel Discription Forces In N Type of Loads Remark

NOZZLE NO: N2 Discharge Nozzle SYSTEM Discription: DEETHANISER REFLUX PUMP Moment N-m

RATING: 300 # OPERATING CONDITION :

NOZZLE SIZE: 219 NB (6") PRESSURE:

SCH THICK : XS (12.7 mm) TEMPRATURE:

Node No Nozzel Discription Forces In N Moment N-m Type of Loads Remark

V. DISSCUSION

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International Journal of Emerging Technology and Advanced Engineering

790 So to overcome this difficulties we will plan to route modification in existing routine and also increase the nozzle allowable for the same nozzle by complying API 610 Conditions Condition-2. In route modification we increase the flexibility of pump piping by adding extra elbows and loops. which reduced the circumferential movement. In above nozzle loading chart the nozzle allowable loads is considered to be 2 times of API 610 and comply all condition of API 610

VI. CONCLUSION

By following the proper guideline of pump piping & support philosophy, the forces & moments which is on the nozzles are kept within allowable as per API 610.and ASME section VIII DIV-1/2. Also increase the nozzle allowable loads to reduces the design cost by complying with allowable standards,

The low equipment allowable nozzle loads forced piping engineers to use excessive pipe loops coupled with complex restraint arrangement to meet the requirements. This not only increase capital expenditure but also increase potential operational problems. Vibration, cavitations, and loss of net positive suction head (NPSH) are some of the common operating problem resulting from excessive piping loops To overcome the above difficulties, we have increase the Pump allowable loads than the vendor without violating API 610 standard.

REFERENCES

[1 ] L. C. Peng and A.O. Medellin " Rethinking the allowable pipe load on rotating equipment nozzle " pp

[2 ] William D Marscher "Avoiding Failures in centrifugal Pumps"(1999).

[3 ] James E Steiger "Horizontal process pump modifications to comply with API-610 sixth edition force and moments"(1981)

[4 ] James E Steiger "API 610,Baseplate and nozzle loading criteria"(1981).

[5 ] Tokio Shimizu and Hironori Teshiba "Analysis of nozzle load for process pump".

[6 ] L.C.Peng "Equipment Reliability Improvement through Reduced Pipe Stress"(1993).

[7 ] Charles C.Head & David G.Penry ."Design and operation of pumps for hot standby services".

[8 ] L.C Peng "Understanding piping Code stress evaluation paradoxes and ASME B31.3 Appendix P".(2013). pp 6-13.

[9 ] L.C. Peng "Treatment of support friction in Piping stress analysis". [10 ] L.C. Peng "The Art of designing Piping Support System". [11 ] "Code Piping Stress Analysis Seminar Notes". pp 8-50 [12 ] Code ASME B31.3 2004 .pp 1-38.