Red Jacket LPG Premier, Installation Manual, Page: 17 / 40

Introduction By-Pass
13
By-Pass
All Red Jacket submersible LPG pumps are required to be coupled to a motor containing an internal bleed (by-
pass).
The Premier pump developed maximum pressure is 1000 kPa (145 psi) differential pressure. The Premier Mid-
Flow pump developed maximum pressure is 880 kPa (127 psi) differential pressure. The Premier Hi-Flow pump
developed maximum pressure is 1220 kPa (180 psi) differential pressure. For pump technical reasons an externally
mounted by-pass is not required.
According to the “Regulations”
1
, “An LPG pump shall be provided with an overflow/relief valve to protect the
pump casing from overpressure when pumping against closed discharge. This bypass valve shall discharge into
the LPG storage tank at a predetermined set pressure selected in relation to the pump operating pressure. This
bypass valve shall be of sufficient capacity to handle the maximum flow at this pressure.” The internal bleed in the
Red Jacket LPG motor is designed according to this regulation.
When a local safety regulation requires an external by-pass this requirement must be applied. By the use of an
external by-pass the setting must be above normal pump maximum pressure as stated above. By-pass must be of
the soft-seat type without permanent bleed.
Equalization Line
The function of the equalization line is to equalize the pressure in the vapor space of the tank and the pressure of
the manifold, to overcome running dry of the submersible pump by low liquid level and to equalize the pressure
during refill of the installation.
The design of the equalization line must be so that the outside temperature has no influence on the function of the
equalization line. An internal equalization line is recommended. Note if liquid level is below internal bleed in the
motor, the amount of liquid of the internal bleed will increase the pressure in the manifold if the equalization line is
too small.
The equalization line is one of the most important parts of the installation. As described above the equalization line
needs to be as short as possible and relatively large in diameter. The lower the level of the liquid in the storage
tank the more important is the function of the equalization line.
The functionality of the equalization line can be tested very easily when the liquid level is below the internal by-pass
of the motor.
• Let the pump run against closed valve.
• Measure the differential pressure of the pump.
• If the differential pressure remains the same after 10 or 15 minutes of pump run the equalization line is working.
• If the pressure drops, the pump is cavitating, and the pump will become vapor-locked. In this case, the
equalization line is not sufficient.
31 Relief valve 1/4 Rego 3127 G
32 Storage vessel
33 Check valve 2 Rego A3186
Table 4. Recommended Material List for Horizontal Manifold with Red Jacket LPG Pump-Motor Unit (ref. Figure 3)
Item Description
Size
(inches)
Recommended
Manufacturer Type/Remark Other