Self-Priming Operation; Safety Relief Valve - Working Principle; Sound; General Performance - Johnson Pump TG GS2-25 Instruction Manual

3.2.1

Self-priming operation

TopGear pumps are self-priming when sufficient liquid is present in the pump to fill up the
clearances and the dead spaces between the teeth. (For self-priming operation see also section
3.18.6.2 Piping).
3.2.2 Safety relief valve – Working principle
The positive displacement principle requires the installation of a safety relief valve
protecting the pump against overpressure. It can be installed on the pump or in the installation.
This safety relief valve limits the differential pressure (∆p) between suction and discharge, not the
maximum pressure within the installation.
For example, as media cannot escape when
the discharge side of the pump is obstructed,
an over-pressure may cause severe damage to
the pump.
The safety relief valve provides an escape
path, rerouting the media back to the suction
side when reaching a specified pressure level.
• The safety relief valve protects the pump against over-pressure only in one flow direction.
The safety relief valve will not provide protection against over-pressure when the pump rotates
in the opposite direction. When the pump is used in both directions, a double safety relief valve
is required.
• An open safety relief valve indicates that the installation is not functioning properly. The pump
must be shut down at once. Find and solve the problem before restarting the pump.
• When the safety relief valve is not installed on the pump, other protections against over-
pressure have to be provided.
• Note! Do not use the safety relief valve as a flow regulator. The liquid will circulate only through
the pump and will heat up quickly.
Contact your local supplier if a flow regulator is required.
3.3

Sound

TopGear pumps are rotary displacement pumps. Because of the contact between internal parts
(rotor/idler), pressure variations etc. they produce more noise than for example centrifugal pumps.
Also the sound coming from drive and installation must be taken into consideration.
As the sound level at the operating area may exceed 85 dB(A), ear protection must be worn.
See also section 3.7 Sound level.
3.4

General performance

Important!
The pump is calculated for the liquid transport as described in the quotation. Contact your local
supplier if one or several application parameters change.
Liquids not suitable for the pump can cause damages to the pump unit and imply risk of personal
injury.
Correct application requires that consideration be given to all of the following:
Product name, concentration and density. Product viscosity, product particles (size, hardness,
concentration, shape), product purity, product temperature, inlet and outlet pressure, RPM, etc.
A.0500.501 – IM-TGGS/05.01 EN (03/2013) 15