9. Make certain that the diagnostics seal at the top of the eccentric box flange and the HPV
feed port o-ring at the bottom of the flange are in place (refer to Figure 4).
10. Insert the pump head onto the eccentric box using the locating pins as a guide.
11. Some compression of the piston return spring will be required in order to start the pump
head retaining bolts after which the bolts can be tightened to complete installation of the
head. Spring compression will be minimized with the eccentric in the retracted position and
the stroke setting at 100%.
12. Reinstall the diaphragm and reagent head.
13. Reinstall the eccentric box drain plug and fill with PULSAlube 7H hydraulic oil.
14. Re-prime the pump.
7.5 HYDRAULIC BYPASS VALVE (HBV)
Figure 20
All PULSAR pumps incorporate a Hydraulic Bypass Valve which is an adjustable spring-loaded
valve ported into the hydraulic cavity of the pump head. The valve is designed to protect the
pump against excessive hydraulic pressure and will not limit or regulate system pressure. The
valve is factory-adjusted for pressure as originally specified, or at 10% above the rated pump
pressure.
The HBV is located at the top of the pump head and any discharge, indicating over
pressurization, is visible at the outer diagnostics port. To adjust the valve, remove the valve’s
plastic cover, loosen the locknut, and turn the adjustment screw clockwise (as seen facing the
screw) to increase the bypass pressure and counterclockwise to decrease it. The locking nut
must be tightened after adjustment.
Pump damage may occur during a system upset, if the hydraulic bypass pressure is set higher
than 10% over the design pressure of the pump. Conversely, if the setting is too low the valve
will operate on each discharge stroke. This results in decreased pumping capacity and will
eventually affect the efficiency of the valve.
To check the hydraulic bypass pressure setting, install a gauge and a regulating valve in the
pump discharge line. The gauge must be between the pump and valve. For convenience,
locate the two as close to the pump as possible. With the pump operating at maximum stroke
length, gradually increase the discharge pressure and observe when the HBV starts to operate.
The cracking pressure of the valve must be at least as high as the maximum pressure of the
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