Design Recommendations_Pump and Pipe Mechanical Installation Guidelines

8/12/2019 Design Recommendations_Pump and Pipe Mechanical Installation Guidelines

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Water & Wastewater

Design recommendationsPUMP AND PIPE MECHANICAL INSTALLATION GUIDELINES


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Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Piping support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Concrete foundations . . . . . . . . . . . . . . . . . . . . . . . . . 6

Anchor recommendations . . . . . . . . . . . . . . . . . . . 6

Pump attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Soft installation alternative . . . . . . . . . . . . . . . . . . . 9

Calculation of critical pipe length . . . . . . . . . 9

Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Explanations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

These design recommendations are intended toassist pump station designers, planners, applica-tion engineers, consulting engineers and users

of pump stations incorporating Flygt pumps fromXylem pumps. Recommendations for both wet pitand dry pit installations are covered to ensure a reli-able installation with a minimal noise. Requirementsfor the fixing of the pump and the connecting pipesare described. Factors affecting sound and noiselevels are also described and recommendations

when special considerations should be taken.

Please see pump sump design recommendationsfor optimal hydraulic conditions. These design rec-

ommendations contains the layout and benchingdetails to avoid air entrainment, vorticity, swirl etc.and all can instigate vibrations and noise.

Please consult our engineers to achieve optimumperformance and life of the installation. If furtheranchor bolt analyses are needed please contactXylem for a Flygt Engineering Tool, FET, Anchor BoltLoad calculation. The design recommendations areonly valid for Xylem equipment. We assume no li-ability for non- Xylem equipment.


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Introduction

Proper installation and anchorage of Flygt pumpsfrom Xylem and installation accessories is criti-cal to limit vibration and achieving reliable,trouble free operation. It is important to remem-ber that all piping, fittings and supports that aremechanically connected to a pump are all partof a single system. Vibrations are unavoidablewhen a mass, such as a rotor assembly, is turn-ing at high speeds. The rotating mass of a Flygtmotor together with forces from the motor andthe hydraulic end, will generate an intrinsic set ofdisturbance or excitation frequencies that are

related to the speed of the motor (unbalance andblade pass are the two most important frequen-cies affecting vibration). When these frequenciescoincide with a natural frequency of the system,vibration levels will increase substantially. The like-lihood of this occurring is increased for variablespeed applications where the pumps can operateover a range of speeds rather than a single con-stant speed. Most variable frequency drives havethe option to exclude certain frequency ranges toavoid regions of high vibrations.

In addition, proper anchorage and support is criti-

cal to minimizing vibration. In vertical installations,the tall unsupported mass of the vertical motorexacerbates vibration levels at the upper bearingcaused by imbalance, poor installation quality orhydraulic disturbances more so than in hori-zontal installations. Therefore, eliminating systemresonances and ensuring high quality installationin vertical Flygt pumps from Xylem is critical toachieving a smoother running installation.

The following recommendations are consistentwith industry standards and generally accepted

good design practices for concrete anchorage ofrotating equipment. These recommendations canbe applied to all Flygt pump installations but spe-cific emphasis is placed on vertical, dry pit instal-lations. Failure to follow these good design andconstruction practices may result in higher levelsof noise and vibration than desired. A licensedCivil Engineer should be consulted for specificconstruction design details for each individualinstallation.


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Flygt pumps will generate disturbances that aretransmitted to the adjoining pipe and structurethrough mechanical connection of the piping andthe installation structure. Pump speed (imbalance)and blade pass (hydraulic forces) typically aretwo frequencies at which disturbances can occur.These frequencies can be used to estimate thecritical pipe length; i.e. the natural bending fre-quency of a pipe filled with liquid.

1. Xylem recommends that the distance betweenpipe supports be set at 70% of the critical

length (see Calculation of critical pipe length)for the first mode.

2a. It is also recommended that pipes should havea support located at a distance of 1/3 of thecritical pipe length from the pump.

2b. Support can be required in deep sumps,check the critical length.

3. Heavy parts of the piping system, such asvalves, must be properly supported. Gatevalve and non return valve (NRV) and pipe uptoNRV should all be supported to allow for the

removal of the NRV without loading the adja-cent pipe work.

4. Because vibrations are independent of grav-ity, horizontal supports should be includedsince they are as essential as vertical supports.Thermal elongation has to be accounted for.

5. The anchorage must be able to safely absorband withstand the pump shut off pressurethrust load. Especially for a long pipe and apossible water hammer loads.

6. Piping should be supported by the surround-ing structure and not by couplings or pump

flanges.

Please see to the structure allows easy mountingand demounting (details omitted for clarity).

Piping support

All the pictures above show examples with Flygt pumps

1/3L

1/3 L

0,7 L


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1. Concrete pedestals should be reinforced.Reinforcement should mesh with the floorrebar when possible.

2. Pedestal overall height (concrete and grout)should be as low as possible but should allowfor proper piping alignment and clearance ofsuction piping with the floor (see Detail E).

3. Pedestal length and width should be sufficientto meet civil engineering design standard andlocal codes.

4. Opening between pedestals should allow forproper clearance of the inlet elbow flange at

the pump suction.

5. Access to suction elbow and pump mountingbolts should be considered.

6. The foundation and concrete must be of ad-equate strength to support the weight of thepump with its accessories plus the weight ofthe liquid passing through it, and the forcesgenerated by the pump.

7. Consult a registered Civil Engineer for specificdesign details.

1. Chemical anchors can be used to anchor Flygtpumps from Xylem but the bond can degradeover time and is more elastic than a mechani-cal anchor. Mechanical cast in place anchorsmeshed with re-bars in concrete are the mostrobust alternative, and are recommended forlarge dry (vertical) pump installation.

2. The anchors length required for pre-stressingshould be well protected to prevent bond-ing (heat shrink, wax or heavy grease) with theconcrete or grout.

3. Finally, apply the specified torque in 3 steps 33%, 66% and 100% of max torque. At eachstep, torque all bolts before starting the nextstep, in an opposing pattern.

4. It is recommended to check the anchor bolttorque for pre-stress relaxation after comple-tion of the initial pump start up test runs. Ifpre-stress relaxation has occurred, the torqueshould be re-applied as above. If correctionwas required after start up test runs, checkagain after 50 hours of pump operation andrepeat this process every 50 hours of opera-tion until pre-stress relaxation stops.

Ensure contact on the entire length of the base tothe concrete foundation. Local leveling devicessuch as washers are not allowed as this can makethe base partly unsupported.

If leveling and grouting is needed:1. Install and level the mounting plate (or base)

only (without the pump) using steel blocks andleveling wedges (see Detail B). Steel blocks,leveling wedges, and anchor bolts should becoated with light oil just prior to leveling andgrouting.

2. Pre-stress all anchors (lightly torque) after lev-eling and prior to grouting. Re-check levelprior to grouting.

3. Leveling nuts on the anchors should NOT beused since the anchor will not be properly pre-stressed into the concrete/grout foundation.

4. Leveling shims and blocks should be as smallas possible and placed as far as possible fromthe anchors such that the voids do not impairthe grout strength after the shims removal.An alternate solution would be the additionof threaded holes for jackscrews in the plate

(not standard) and use the jackscrews for level-ing (see Detail C). Leveling equipment shouldbe removed and the voids filled with grout toallow full support of the mounting plate.

5. Thickness and application of grout should beper the grout suppliers recommendations.

6. The grout around the plate should be pouredto approximately of the plate thickness (t)so that some head is developed and the groutwill contact all areas under the plate withoutvoids (see Detail A).

7. Blockouts shall be provided at all leveling po-

sitions to allow for removal of leveling equip-ment after grout has cured. Voids should befilled with grout after leveling equipment isremoved.

8. A 45 degree chamfer should be located at thefinal elevation of the grout.

See also Installation, Operation and MaintenaceManual and the dimensional drawings.

Concrete foundations

Anchor recommendations

Pump attachment


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Leveling and grouting details

B

Base plate

Levelingwedgesor shims(remove aftergrouting)

Concrete C

Base plate

Jacking screws(not std.)(remove aftergrouting)

Concrete

45 chamfer

Form

Concrete

Base plate Grout

1/2 tt

A

Concrete foundations for T pump installation

D Concrete

Wedgesor shims(removeaftergrouting)

Alt:Jackingscrews


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E FSuction elbow

H*

*

**

* =minimum required for piping/elbow installation

Base

Grout

Concrete

Pin to floor and mesh rebar

* *

G H

Base plate

Sleeve

Grout

Forms

Concrete

d

3d min.sleevelength

Sleeves protect

from bonding togrout

Embedmentlength asspecifiedby adhesivemanufacturer

Base plate

Sleeve

Grout

Forms

Concrete

Rebar

d

Sleeves protect

from bondingto grout

4d min.sleevelength

P or Z pump installation usingchemical/epoxy anchors

T pump installation on a new base(square plate and J anchors)

Concrete foundations for T pump installation


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It may be necessary in some cases to explorealternative methods of installation. For example,natural frequencies may exist that make it diffi-cult or impossible to adequately reduce vibrationlevels. Variable speed applications are far morelikely to experience these problems due to thewide range of pump frequencies. If system reso-nance can not be resolved by adding stiffness ormass to the system or if resonance is predictedthrough system analysis, then it may be necessaryto modify the pump installation in the followingmanner:

1. Provide vibration isolation (bellows or flexiblejoints) at the pump suction and dischargeflanges

2. Provide adequate support of piping immedi-ately adjacent to these joints

3. Provide a concrete base of at least 2x the massof the pump and motor

4. Anchor the Flygt pump firmly to the base

5. Provide machine feet or rubber carpet be-tween the base and the floor of adequatedimensions

6. Please note that the force from the fluidpressure has to be supported.

The piping must be well anchored if flexible jointsare used. Flexible joints between the pump andpipe can transform pressure fluctuations into dis-turbances, causing severe vibrations in the piping.Be aware that new modes of motion may occurthat have to be handled. Soft installation isdifficult to design and proper analyses are vitalin order to have a good result. Because of this,Xylem recommends this typeof installation only be designed by an experi-enced Civil Engineer.

Calculation of criticalpipe length (L)

Soft installation alternative

Critical length distancebetween supports

12

8

4

10

6

2

00.1 0.2 0.3

Pipe diameter [m]

Length[m]

0.4 0.5

750

RPMx no. of vanes

1000

1500

3000

This graph shows an example with critical lengths for different pipe

diameters and RPMs x no. of vanes typical for 50 Hz. The pipe is

assumed to be fixed in one end (x=0.25) and densities are assumedas for water and a steel pipe. The pipe wall thicknesses are 4 mm

(Dy 100 mm), 6,3 mm (Dy 200 mm), 7,1 mm (Dy 300 mm), 8,8 mm (Dy

400 mm), 12 mm (Dy 500 mm).

Where:

L = critical pipe length based

on natural frequency (m)

k = (n + x)2where:

n = mode or order, 1 for

first mode

x = 0 if simply support ends

0.25 if one end fixed

0.50 if both ends fixed

-0.50 if cantilever beam

= frequency (rad/s)

e.g. blade pass, motor

speed, etc.

E = Youngs modulus (N/m2)

Dy = pipe outer diameter (m)

Di = pipe inner diameter (m)

= pipe density (kg/m3)

m= density of added mass,

e.g. water (kg/m3)


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Sound is the result of pressure changes in the air.Undesirable sound is usually referred to as noise.Pressure changes can be transmitted to the airfrom a vibrating structure resulting in noise. Thebetter the transmission from the vibrating sur-faces to the air, the higher the sound levels willbe. Structure borne vibrations can travel somedistances before becoming airborne and audible.Liquid born pressure fluctuations can also travelvery far before causing the structure to vibrateand generate noise. Consequently, the source ofthe vibrations causing the noise are not necessar-

ily in the same location as the noise itself.

Sound pressure (Lp) measured in dBA gives moreweight to frequencies where the human ear ismore sensitive (noted A-weighted). Therefore,dBA is the most appropriate scale of measure-ment when evaluating noise within a pump room.The noise from the pump is normally given as thesound power level (Lw). The sound pressure (Lp)in a certain position is determined by distanceand positioning of the source together with theacoustical properties of the room. When evaluat-ing the source of pump noise, it is important to

remember that disturbances generated from theelectrical motor, cavitation and other flow inducedvibrations make important contributions to thesound level.

The recommendations made previously to reducevibrations are also helpful with respect to noise.The recommendations given below also apply.Xylem provides guidelines for item 1, 2, 3 and 4in the Design recommendations for pump sta-tions with large centrifugal wastewater pumpsbrochure.

1. A duty point close to the best efficiency pointof the pump is always good.

2. Net positive suction head requirements mustbe met, preferably with a substantial margin.

3. Inlet conditions from the sump and/or suctionpiping should be well designed from a hydrau-lic point of view.

4. Fluid induced vibrations in pipes can be heldat low levels by avoiding sharp bends, espe-cially if they are located close to valves.

5. Mechanically transmitted vibrations can bediminished by a soft installation as earlierdescribed.

6. Liquid borne pressure fluctuations in the pipecan occur at high head conditions with impel-lers having a low number of vanes (pulsationsdue to blade pass). This can be a nuisancein residential areas. It can be decreased byadding pressure pulsation dampers. Pleasediscuss adequate measures with a vibrationconsultant.

In addition to the above, to reduce the noise inthe pump room you may need to implementseveral of the following measures, all involving

recommendations from a vibration consultant:1. Add acoustic absorption material on the roof

and walls to lower the reverberant soundwhich, apart from very close to the pump,normally dominates.

2. Add acoustic dampening material to the pipesand other sound emitting surfaces to lower thesound pressure level.

3. Add a sound cover or shield around or in frontof the pump. Be careful not to inhibit theeffectiveness of the motor cooling surfaces.

To reduce the noise transmitted to the environ-ment outside of the pump room you may alsoneed to:1. Avoid transmittance to the weak parts of the

building structure via rigid connections ofpiping, valves etc. Use rubber bushings orsimilar device between piping or supports andweak walls.

2. Avoid open channels, such as ventilationducts, out of the room with the source of noise.

Noise can never be totally avoided and is also a

matter of perception although well designedstations may keep the noise to acceptable levels.

Noise increases with deviation from best efficien-cy point particularly at run out flows.

Noise


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Xylem offers in-depth expertise in the design andexecution of comprehensive solutions for waterand wastewater transport and treatment.Our know-how and experience are combined witha broad range of suitable products for deliveringcustomized solutions that ensure trouble-freeoperations for customers. To do this our engi-neers utilize our own specially developed com-puter programs, as well as commercial, for designand development projects.

Scope of assistance includes a thoroughgoinganalysis of the situation and proposed solutions together with selection of products andaccessories.We also provide hydraulic guidance and as-sistance for flow-related or rheological issues.Customers turn to us, as well, for analysis of com-plex systems for network pumping, including cal-culations for hydraulic transients, pump starts andflow variations.

Additional services: Optimization of pump sump design for our

products and specific sites

Assistance with mixing and aeration specica-tions and design of appropriate systems

System simulation utilizing computational uiddynamics (CFD)

Guidance for model testing and organizing it

Guidance for achieving the lowest costs in

operations, service and installation Specially developed engineering software to

facilitate designing

The range of services is comprehensive, but ourphilosophy is very simple: There is no substitutefor excellence.

Blade pass frequency The number of the impeller vanes multipled

by the speed frequency of the pump (the fre-quency of blades passing the outlet).

Harmonics Harmonics is an integer multiple of the funda-

mental frequency of a signal. For example, ifthe fundamental frequency is f, the harmonicshave frequency 2f, 3f, 4f, etc.

Youngs modulus

A measure of the stiffness of a material.

Natural frequency All structures have frequencies that are easily

excited, their natural frequencies or reso-nant frequencies. When you hit a structurewith a short pulse, that contains all frequen-cies, the structure will vibrate with its naturalfrequencies.

System resonance A small force of a frequency close to the natu-

ral frequency of a structure cause very high,often hazardous, vibrations. This phenomena is

called resonance.

System engineering

Explanations

Material

Steel

Cast iron (ASTM A-48)

Nodular iron

HDPE (High density Polyethylen)

Youngs modulus [GPa]

210

110

170

0,8


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Flygt is a brand of Xylem. For the latest

version of this document and moreinformation about Flygt products visit

www.flygt.com

845

.Designrecommendation

Pump

andPipe

.1.Master.20111027

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Design Recommendations_Pump and Pipe Mechanical Installation Guidelines