Val-Matic 6-8 Combination Air Valve (Single Housing Type) - Manual (Page 3)

2
2. As air accumulates in the piping system
and enters the valve, the round float
drops and the orifice button breaks
contact with the small orifice.
Accumulated air will vent through the
small outlet in the valve cover while the
system is under pressure. As all of the
air is vented, the round float rises again
and closes the orifice button.
3. When the piping system is drained, both
floats will drop and allow air to rapidly
reenter the piping system through both
the air/vacuum and air release orifices.
INSTALLATION
The installation of the valve is important for its
proper operation. Valves must be installed at
the system high points in the vertical position
with the inlet down. For pipeline service, a vault
with freeze protection, adequate screened
venting, and drainage should be provided.
During closure, some fluid discharge will occur
so vent lines should extend to an open drain
area in plant service. A shutoff valve should be
installed below the valve in the event servicing is
required.
Flanges should be mated with flat-faced pipe
flanges equipped with resilient gaskets. Flange
bolts should be lubricated and lightly turned until
all gaps are eliminated. The tightening of the
bolts should then be done in graduated steps
using the crossover tightening method. 3/4”
bolts require a torque of 40-150 ft-lbs. 7/8” bolts
(model 258C) require a torque of 45-205 ft-lbs.
If leakage occurs, allow gaskets to absorb fluid
and check torque and leakage in 24 hours. Do
not exceed bolt rating or crush gasket more than
50% of its thickness.
VALVE CONSTRUCTION
The standard Combination Air Valve body and
cover are cast iron. See specific Materials List
submitted for the order if other than standard
cast iron construction. The internal metal
components are stainless steel. The orifice
button and seat are resilient Buna-N. The
general details of construction are illustrated in
Figure 2. The body (1) is flanged for connection
to the pipeline. The air/vacuum seat (4) is
retained by retaining screws (8) in the cover (2).
The air release seat (4A) is threaded into the
cover (2) and sealed with the adjustable orifice
button (11), which has a threaded post for
attachment to the orifice button arm (22).