Design of pipelines
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Customer information Customer information DESIGN, LAYOUT AND INSTALLATION OF PIPELINES FOR LEWA METERING PUMPS DESIGN, LAYOUT AND INSTALLATION OF PIPELINES FOR LEWA METERING PUMPS Warning: LEWA metering pumps are reciprocating displacement pumps with pulsating delivery ow. The dimensioning of pipe lines connected to such pumps must Warning: LEWA metering pumps are reciprocating applying therefore be based on criteria different from those displacement pumps with pulsating delivery flow. The the to rotary pumps. If this is not observed, then there is dimensioningserious faults connected such as metering danger that of pipe lines may occur to such pumps must therefore be based on criteria different pump those applying errors, excesive noise and damage to from and plant. to rotary pumps. If this is not observed, then there is the danger that serious faults may occur such as metering ■ Criteria for the design and layout errors, excesive noise of the metered ow, pressure Due to the pulsation and damage to pump and plant. The exact equations for the examination of these layout criteria can be found in LEWA-Information leaet: Principles D 10 - 012 e (available on request). The exact equations for the examination of these As layout criteria can be found in LEWA-Information in most practical cases the viscosity of the metered leaflet: (η 10 mPas), a 012 e (available on request). uid is low Principles D 10 -simplied computation process can be applied as shown overleaf. As in most practical cases the viscosity of the metered fluid is low (η 10 mPas), a simplified computation process can be applied as shown overleaf. uctuations arise which are to be superimposed on to n Criteria for the design andsuction as well as at the the static pressure level at the layout Due to the pulsation of into meteredthis pressure prole discharge side. Taking the account flow, pressure fluctuations arise which are criteria must be examined: versus time, the following to be superimposed on to the static pressure level at the suction as well as at the discharge side. Taking into account this pressure profile I. Cavitation versus time, the following criteria must be examined: Cavitation symptoms appear when the vapour pressure of the metered uid is reached anywhere in the system. I.The consequences of cavitation may be excessive noise, Cavitation Cavitation symptoms appear when the vapour pressure uctuations in metered ow, valve wear and overload of the metered fluid is reached anywhere in the system. damage. Cavitation-free operation is ensured when the The consequences of cavitation may be excessive noise, following condition is fullled (g. 1): fluctuations in metered flow, valve wear and overload pSmin > p (1) damage. tCavitation-free operation is ensured when the following condition is fulfilled (fig. 1): II. Overloading Overloading, which could cause immediate or fatigue pSmin > pt (1) fractures, occurs when the highest pressure peaks exceed II. Overloading permissible operating pressure. The pump the maximum Overloading, whichoverloading if immediate or fatigue will work without could cause (g. 1): fractures, occurs when the highest pressure peaks exceed pperm pDmax (2) the maximum permissible operating pressure. The pump will work without overloading if (fig. 1): Ill. Excess delivery This p pperm means that the pump delivers more than its displace(2) Dmax ment volume. Excess delivery occurs when the pressure at the suction ange Ill. Excess delivery is momentarily higher than that at the discharge ange. Consequences of excess delivery can be This meansthat the pump delivers more than its displaceserious metering errors, severe valve hammering and ment volume. Excess delivery occurs when the pressure at excessive flange is momentarily higher avoided at all the suction valve wear. Excess delivery is than thatifat the times ( flange. dischargeg. 1): Consequences of excess delivery can be serious metering errors, severe valve hammering and pDmin > pSmax (3) excessive valve wear. Excess delivery is avoided if at all times (fig. 1): p So p DF p SF static pressure at pump anges pperm pDmax static pressure at discharge ange pDF pDo pDmin simplex pump duplex pump static pressure at suction ange © D10-010 en • 01.2013 • Subject to change without no

Customer information DESIGN, LAYOUT AND INSTALLATION OF PIPELINES FOR LEWA METERING PUMPS n Simplified pipe line calculations Range of validity: low viscosity media (η 10 mPas). For trouble-free plant operation the following design criteria must be met: Criterion I (cavitation on suction side) The appropriate design equations for this condition can be found in LEWA-Information leaflets D5-200 e and D10-012 e (available on request). n Suction valve pressure drop ΔpE Versus metered flow per pump head Q (=Qtot/i) for various types of valves. PDF Criterion IlI (excess delivery) n Layout of...