Johnson Pump TG GS2-25 - Piping

32
A.0500.501 – IM-TGGS/05.01 EN (03/2013)
3.18.6.2 Piping
• Use piping with an equal diameter than the connection ports of the pump and shortest possible.
• Thepipediameterhastobecalculatedinfunctionoftheliquidparametersandtheinstallation
parameters. If necessary use larger diameters to limit pressure losses.
• Iftheuidtobepumpedisviscous,pressurelossesinthesuctionanddischargelinesmay
increase considerably. Other piping components like valves, elbows, strainers, filters and foot
valve also cause pressure losses.
• Diameters,lengthofpipingandothercomponentsshouldbeselectedinsuchawaythatthe
pump will operate without causing mechanical damage to the pump/pump unit, taking into
account the minimum required inlet pressure, the maximum allowable working pressure and the
installed motor power and torque.
• Checkthetightnessofthepipesafterconnection.
Suction piping
• Liquidsshouldpreferablyenterthepumpfromalevelhigherthanthepumplevel.Incasethe
liquid should be sucked from a level lower than the pump level, the inclining suction pipe should
rise upwards towards the pump without any air pockets.
• Atoosmalldiameteroratoolongsuctionpipe,atoosmallorblockedstrainerwillincrease
pressure losses so that the NPSHa (NPSH available) becomes smaller than the NPSH
(NPSH required).
Cavitation will occur, causing noise and vibrations. Mechanical damage to pump and pump unit
is not excluded.
• Whenasuctionstrainerorlterisinstalledpressurelossesinthesuctionlinemustbechecked
constantly. Also check if the inlet pressure at the suction flange of the pump is still sufficiently
high.
• Whenthepumpworksinbothdirections,pressurelossesmustbecalculatedforbothdirections.
Self-priming operation
At the start sufficient liquid must be available in the pump filling up the internal clearance volume and
the dead spaces, allowing the pump to build up a pressure difference.
Therefore, for pumping low viscosity fluids, a foot valve with the same or larger diameter than the
suction pipe must be installed or the pump can be installed without foot-valve but in U-line.
Note! A foot valve is not recommended when pumping high viscous liquids.
• Toremoveairandgasesfromsuctionlineandpump,counterpressureatthedischargeside
must be reduced. In case of self-priming operation, start-up of the pump should be performed
with open and empty discharge line allowing air or gases to escape at low backpressure.
• Anotherpossibilityincaseoflonglinesorwhenanon-returnvalveisinstalledinthedischarge
line, is to install a by-pass with isolating valve close to the discharge side of the pump. This valve
will be opened in case of priming and allows air or gas evacuation at low backpressure.
The bypass should be lead back to the supply tank – not to the suction port.