Flowserve Seal Support Reservoir - Manual (Page 2)

Introduction
This manual covers the installation and operation of Flowserve Seal Support
Systems for dual unpressurized (API Plan 52/ANSI Plan 7352) and dual
pressurized seals (API Plan 53A, 53B, 53C/ANSI Plan 7353). The following
instructions describe the appropriate system, buffer/barrier fluids, installation,
start-up and maintenance.
Reservoir
The standard supply tank is designed in accordance with ASME Code Section VIII,
Division 1. All tanks are welded in accordance with ASME Code Section IX. Tanks
include inlet, outlet, vent and fill, along with mounting lugs as minimum connection.
Sealing System Description
Supply tank assemblies can be used as reservoirs for dual seal designs. The
sealing system produced is defined as being either a thermal convection system
or a forced circulation system.
Support System Descriptions
API Plan 53A, 53B, 53C/ANSI Plan 7353A for dual pressurized seals
An API Plan 53A/ANSI 7353A is a pressurized dual seal system which is used
in services where no process leakage to atmosphere is tolerated. The system
consists of dual mechanical seals with a barrier fluid between them. The barrier
fluid in the supply tank is pressurized to a higher pressure than the seal chamber,
normally 15 to 25 psig (1 to 1.7 bar). Primary (inboard) seal leakage will be barrier
fluid into the product. A small amount of leakage is customary.
An API Plan 53A/ANSI Plan 7353A is usually chosen over an API Plan 52/ ANSI
Plan 7352 for dirty, abrasive or polymerizing products which would either damage
the seal faces or cause problems with the barrier fluid system if an API Plan 52/
ANSI Plan 7352 is used. There are two disadvantages to an API Plan 53A/ANSI
Plan 7353A which must be considered. First, there will always be some leakage
of barrier fluid into the product. Normally, this leakage will be minute, and the
leakage rate can be monitored via the level gauges or other instrumentation.
However, the product must be able to accommodate a small amount of contami-
nation from the barrier fluid. Secondly, an API Plan 53A/ANSI Plan 7353A system
is dependent on having the supply tank pressure maintained at the proper level.
If the supply tank pressure drops, seal leakage direction will be reversed and the
barrier fluid will be contaminated with the process fluid.
An Induced Circulation System is essentially the same as the thermal convec-
tion system, except for the addition of a circulating device in the seal cavity which
provides for positive flow in the system. The addition of the circulating device
provides for positive flow of barrier/buffer fluid shown in Figure 1. Because supply
tanks provide for poor radiation and convection of heat to the atmosphere, it is
common to add cooling coils inside the reservoir as a means of removing heat.
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