Emerson Rosemount 1199 User Manual

2.5 Specifying the right solution for vacuum
applications
2.5.1 Vacuum application overview
When a vessel is operating in a vacuum (negative gauge pressure), it is important to
specify the correct transmitter remote seal system to measure level accurately and
reliably. Failure to do so can result in output drift or complete system failure. The
combination of high process temperature and vacuum process pressure conditions
creates additional requirements when specifying the transmitter remote seal system.
2.5.2 Vacuum applications
There are three primary transmitter-seal system components necessary to successfully
specify vacuum application solutions:
• Seal system construction
• Fill fluid selection
• Transmitter mounting position
2.5.3
Seal system construction for vacuum applications
Emerson offers welded-repairable or all-welded vacuum system construction styles on
diaphragm seal assembles.
The all-welded vacuum construction was designed specifically for vacuum applications. In
this construction, the sensor module gaskets are removed and a disk is welded over the
sensor isolators. This eliminates the possibility of air being drawn into the seal system in
deep vacuum conditions. This premium design is strongly suggested for vacuum pressures
below 6 psia (310 mmHga).
2.5.4
Transmitter mounting position
Mounting the pressure transmitter at or below the bottom vessel tap is an important
factor to ensure a stable measurement with vacuum applications. The static pressure limit
for a differential pressure transmitter is 0.5 psia (25 mmHgA), which ensures the
transmitter sensor module fill fluid remains within the liquid phase of the vapor pressure
curve.
If the vessel static limit is below 0.5 psia, mounting the transmitter below the bottom tap
provides a capillary fill fluid head pressure on the module. A general rule is to always
mount the transmitter approximately 3 ft. (1 m) below the bottom tap of the vessel.
Remote Seal Systems Reference Manual
May 2020 00809-0100-4002
14 Rosemount DP Level

Emerson Rosemount 1199 Specifications

General

Brand	Emerson
Model	Rosemount 1199
Category	Transmitter
Language	English