to intersect the bore 13 the other end of the plunger bore terminates in an enlarged section 44 into which the discharge valve 21 is situated the pumping chamber 106 is defined by the space between the discharge valve 21 and the suction valve 30 the suction valve 30 is in the form of a tapered plug or core which is pressed into an opening in the liquid cylinder 109 of the pump a small hydraulic feed line 107 is provided through which high pressure hydraulic fluid may be introduced for the purpose of removing the suction valve for maintenance purposes fluid is supplied to the suction valve 30 by an inlet 43 note that the plunger moves along its own central longitudinal axis in the direction of the arrow 105 as will be explained moving parts in the suction and discharge valves also move in this direction it can be said therefore that the axes of actuation of both valves are parallel to the central axis of the plunger it should also be noted that in the case of the examples given here the valves and plunger share a common centrally located or colinear axis of symmetry this alignment of the valves is considered efficient and space saving because it allows large valve openings but also allows for a small residual volume in the pumping chamber seals 108 are provided between the suction valve 30 and the liquid cylinder 109 fig2 shows in more detail the.