System Setup; Fluid And Air Connections; Inlet Check Valves; Balancing The System - Graco 2K Ultra-Lite Series Instructions-Parts List Manual

Fluid and Air Connections

1/4 npt(f) Fluid Inlets
There are three fluid inlets on the A-side and three
fluid inlets on the B-side. The fluid inlets are located
on the front, side, and back of the valve to permit
various mounting and hose configurations.
1/8 npt(f) Air Inlets
The machine mount valves and the electric switch
hand-held valves have an "open" port and "close" port,
which are operated by a remote 4-way air control
valve.
The air switch hand-held valves have a single air inlet.
This valve also has an internal 4-way spool which
operates the air piston.
See Accessories, page 27, to order air control valves
and tubing.

Inlet Check Valves

Inlet check valves are recommended on the fluid inlets
where viscosity allows. An inlet check valve prevents
back-flow or crossover when the mixer is plugged or
one fluid is much lighter in viscosity than the other.
When required, a high crack pressure check valve is
installed to maintain back-pressure on low viscosity
fluids.
See Accessories, page 27, for a list of check valves.

Balancing the System

A proportioner is used to feed the two-component
dispense valve. The system must be pressure bal-
anced to avoid "lead-lag" ratio errors when starting and
stopping the flow.
Balancing is done by hose sizing, inlet check restric-
tion, and nose piece restrictors. A properly balanced
system has near equal back-pressure on the gauges
when flowing without a mixer installed.
The 2K-UL valve is supplied with 1/8 I.D. and 3/64 I.D.
restrictors (32 and 33) which can be installed in the
nose piece to help balance the system. A special nose
piece outlet that accepts a wide variety of restrictors
with filter screens is available. See application kits
manual 311230.
See Accessories, page 27, for a list of restrictive
catalyst injectors.

System Setup

Selecting Hoses

Hoses between your proportioner and the 2K-UL valve
should be selected carefully. Many factors effect hose
selection.
1. Fluid Compatibility: Fluid must not degrade the
2. Pressure Rating: Be sure hoses have a working
3. Compressibility: Hoses, especially nylon paint
4. Internal Diameter: Small I.D.'s create higher
5. Length: Hoses normally are kept as short as

System Start-up

When initially loading the fluids through the system,
leave the mixer off until both fluids flow freely from the
nose piece without any air. This prevents cross con-
tamination from having fluid on one side pushing back
up the other side.
core material or end fittings of the hose. Nylon or
PTFE cores are commonly used for chemical
compatibility. If your fluid is moisture sensitive you
should use PTFE or Moisture-Lok hoses.
pressure rating above the pressure capability of
the system.
hoses, expand with an increase in pressure. A
pressure change in the system may cause a
volume change, which can appear as a ratio error
with wide mix ratios. Compressible hoses absorb
pressure spikes which is helpful to the operator
during an application, such as trying to lay a bead.
back pressures, lower flows, and small retained
volume. Typically hose I.D.'s are selected for:
a. System Pressure Balance. "A" pressure drop
vs. "B" pressure drop.
b. Volume Balance. A:B volume ratio vs. Hose
retained volume.
c. Flexibility and weight for operator or robot.
d. Overall Pressure Drop. Pressure drop should
be minimum possible within the above guide-
lines.
practical to minimize pressure drop and compress-
ible volume. 10 ft (3.1 m) is recommended for
reciprocating pump systems.
309000 11