Indicator diagram for a reciprocating pump?

Answer 1

It is a diagram which shows the pressure head in the cylinder corresponding to any position during the suction and delivery strokes. the effects if inertia pressure and friction on the performance of the pump can conveniently be shown by plotting this diagram.

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Steam indicators are more often used on engines than pumps, because most pumps retain full admission of steam throughout their stroke (approximately 90% of the stroke) and the steam does not get expanded by the cutoff of the admission valves. Thus, the diagram from the indicator would resemble two slightly deformed rectangles and is typically not a usable diagram.

Engine diagrams are used to determine the horsepower and efficiency of the steam engine, where the area traced divided by the length of stroke will yield the MEP (mean effective pressure) of the steam for the HP formula [ PLAN/33000] where P = MEP, LA = the engine constant {length of stroke times cross-sectional area of cylinder}, and N = strokes per minute.

For Duplex, triplex and simplex pumps the MEP = the admission steam pressure for this reason. For double acting pumps and engines both the head end and crank end must be calculated and combined.

HP = PLAN + PLA'N / 33000 where LA' = the crank end engine (or pump) constant. [ with area A' (subtract the cross-sectional area of the piston rod).]