Introduction; Basic Design; Basic Principle; Model Types - PAC Alcor JFTOT II Manual

1. INTRODUCTION

1.1 BASIC DESIGN

The JFTOT is a fully integrated bench top instrument
that provides everything needed to safety study the
thermal oxidation of any petroleum based liquid fuel.
The instrument is normally used in a batch mode
where a fuel sample is held in a reservoir and
pumped across a heated metal surface to a second
reservoir. In addition, it incorporates a special filter to
continuously trap deposits while simultaneously
monitoring the buildup by measuring differential
pressure across the test filter.
Pumping of the sample can be likened to that of a
large syringe; the sample is moved through the
system by the action of a piston which pushes the
sample from the reservoir. The movement of the
piston is controlled by a drive screw which is turned
very slowly by a gear reduced, controlled speed
motor. Flow of the liquid is restricted by a mechanical
pressure regulator which, once set, maintains the
relatively high pressure necessary to keep the heated
sample in liquid state, typically 3.45 MPa (500 psig).
Upstream of the pressure regulator is a special
sample trap called the water reservoir. This device,
initially filled with water, gives certain advantages.
First, it is a repository for the spent sample often
containing particulate matter or condensables that
may have passed through the filter. Second, it allows
the regulator valve to only have contact with water
which means the regulator will work predictably
regardless of the fuel properties. Finally, since water
is the only effluent of the system, the water reservoir
makes the system inherently safe regardless of the
fuel being tested.

1.2 BASIC PRINCIPLE

Since the JFTOT II is computer controlled, most of
the operations are automatic. There are a few
manual steps needed in preparing for a test, such as,
assembling the hardware, aerating the sample and
bleeding air from the system. With these exceptions,
the JFTOT is operated by entering parameters and
JFTOT II Operation Manual Rev. C
other test setup data into the computer. The JFTOT
stores this information and uses it whenever that
particular test is called for. This setup simplifies
operation when performing the same test.

1.3 MODEL TYPES

There are two models of JFTOT using the positive
syringe pump: Model 230 with one ∆P measuring
transducer and Model 240 with two ∆P transducers.
The Model 230 has been designed to perform ASTM
D3241 where differential pressure across a small
filter is one of the test criteria. This filter is placed in
the flow stream in such a way that reaction products
formed by the heating process and not deposited on
the heater tube will be caught downstream by this
test filter.
The Model 240 is designed with an additional differ-
ential pressure measure for deposits that may form
late in the process. In other words, temperature
induced reactions may cause certain precursors to
form that in themselves do not form a filter blocking
particle. However, these precursors may react with
other materials present to form significant insoluble
products or particles. Given sufficient time these
particles can cause ∆P across a test filter. They are
of interest because they could do this in a real fuel
system. The time reactor after-chamber and differ-
ential pressure measure offered in the Model 240
permits this additional mode of determining presence
of thermally induced insoluble components in fuels.
The Model 230 JFTOTs can be upgraded to Model
240 specifications. Contact ALCOR Petroleum
Instruments for details.
1.4 OPTIONAL OPERATION OF TIME
REACTOR SYSTEM
In this manual, operation of the Model 240 with the
time reactor system is described. When this optional
operating mode is not being used, a plug can be
installed into the fitting on the wall of the cabinet
where the ∆P output of the time reactor system is
normally attached.
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