RAP-1 & RAP-3 Regulated Air Vacuum Pumps0 pages

Product Specifications

The air vacuum pumps are ideal for
collecting sampling media onto
filters, or pulling airborne gases
through active sampling systems, for
radiological detection applications.

RAP-1 & RAP-3
Regulated Air Vacuum Pumps

Model RAP-3

Model RAP-1

• Regulated airflow
• Durable construction
• Portable system
• Adjustable flow rate

RAP-1
The Model RAP-1 is a compact, portable
system containing an oilless vacuum pump,
motor and airflow regulator. The Thermo
Scientific airflow regulator is designed to
maintain a constant pressure drop across
an in-line orifice by controlling a variable
bypass valve into the pump. The orifice is
adjustable, permitting flow rate adjustment
from near zero up to the maximum pump
flow capacity. This flow control system
permits the pump to operate at a minimum
pressure drop at all times which provides
cooler pump operation to extend the
lifetime.
Some RAP-1 operating curves are
shown on the backside. The top line is the
pump operating curve. The curves below
the pump operating curve show how the
sample inlet flow varies with intake
vacuum for two different regulated
settings.
After the regulator is set at a particular
inlet flow the sample flow rate follows a
similar curve, decreasing as intake vacuum
increases.

RAP-3
The Model RAP-3 consists of a diaphragm
vacuum pump with regulator for use with
air monitors or samplers where a nearly
constant airflow is desirable. Airflow into
the controlled air inlet passes through a
variable orifice, causing a pressure drop
across that orifice. Each side of the orifice
is vented to one side of the regulator
diaphragm so the diaphragm is positioned
by the pressure drop across the orifice
and, therefore, by the flow.
Attached to the regulator diaphragm is a
bypass valve. When the pressure drop
across the orifice exceeds the spring
pressure on the diaphragm, the bypass
valve will start opening. Air will then flow
into the bypass inlet and out to the pump.
Thus, the bypass flow is varied by the
diaphragm to hold the controlled flow
constant. This system allows the pump to
move a maximum amount of air at minimum head pressure at all times. The pump,
therefore, runs cooler and has a longer
lifetime.
It should be noted that when pressure
varies, at a constant rate, the flow through
an orifice varies approximately as the
square root of the ratio of the absolute
pressure. Thus, if paper loading causes a
pressure drop to one-half of the original,
the flow, referred to atmosphere, will
decrease to 0.7 of the original. The orifice
is adjustable, allowing flow rate
adjustment from near zero up to the
maximum capacity of the pump.