4-9
Installation and Operation Manual
X-TMF-5860E-MFM-eng
Part Number: 541B106AAG
November, 2008
Brooks
®
Model 5860E
Section 4 Maintenance
4-6 Restrictor Sizing
The restrictor assembly is a ranging device for the sensor portion of the
flowmeter. It creates a pressure drop which is linear with flow rate. This
diverts a sample quantity of the process gas flow through the sensor. Each
restrictor maintains the ratio of sensor flow to restrictor flow, however the
total flow through each restrictor is different. Different restrictors (micron
porosity and active area) have different pressure drops and produce
meters with different full scale flow rates. For a discussion of the
interaction of the various parts of the meter, you are urged to review
Section 3-1 (Theory of Operation).
If the restrictor assembly has been contaminated with foreign matter, the
pressure drop vs. flow characteristics will be altered and it must be cleaned
or replaced. It may also be necessary to replace the restrictor assembly
when the mass flowmeter is to be calibrated to a new full scale flow rate.
Restrictor assembly replacement should be performed only by trained
personnel. The tools required for the removal/replacement procedure are
as follows:
Appropriate size wrench for the removal of the inlet process connec-
tion.
Restrictor removal tool (contained in service tool kit P/N S-778-D-017-
AAA)
Restrictor O-ring, refer to the spare parts Section 5, for the correct part
number.
Restrictors
The Model 5860E Series Mass Flowmeters use three types of restrictor
assemblies depending on full scale flowrate and expected service
conditions.
1. Porous sintered metal for air equivalent flow rates up to and including
9.5 slpm. The porosity ranges from 1-40 microns. This type of
assembly is least expensive and should be used when the gas
stream will not contain any particulate matter.
2. Sintered wire mesh for air equivalent flow rates above 3.5 slpm.
These restrictor assemblies are made from a cylinder of sintered
wire mesh and are easily cleaned if they become contaminated in
service.
3. Anti-Clog Laminar Flow Element (ACLFE). This type of restrictor
assembly is used for air equivalent flow rates less than 3.4 slpm the
ACLFE is much more tolerant to particulate contamination than the
sintered metal assembly. This is especially important when handling
semiconductor gases that tend to precipitate particles. The ACLFE
will also improve accuracy when operating at very low pressures.
Sizing
All Model 5860E Series restrictor assemblies are factory adjusted to
provide a 115 mm water column pressure drop for a specific flow rate. This
corresponds to the desired full scale flow rate. A list of restrictor
assemblies used in the Model 5860E Series Mass Flowmeters is shown in
Table 4-4.
