Dew Point; Dew Point Adjustment - Sigma HRD Serie Manual De Instrucciones

• Turn on the power switch located on the control
enclosure. Depending on the position of the
switching valve and specified operating pres-
sure, one of the vessels will depressurize, or
both vessels will remain pressurized for up to
90 seconds, then one will depressurize.
• Operate the dryer for three cycles to verify sat-
isfactory operation. The dryer cycle is 10 min-
utes with each vessel onstream for five minutes.
8. For HRD-EM Series dryers:
• Turn on power switch on electrical box.
• When power switch is turned on "power on"
light will light. Both vessels will remain at
pressure for up to 60 seconds, then one will
depressurize and the green "Variable Purge"
light will light.
• The LCD display will show in sequence:
DELTECH ENGINEERING, L.P., COPYRIGHT
INLET TEMP. 99° ENERGY SAVINGS = 80%
NO MALFUNCTIONS EXIST
FIRST CYCLE OF OPERATION
USING DEFAULT VALUES
During the next five minutes, the microcom-
puter will check itself for any malfunctions.
The dryer will operate in a fixed-cycle mode,
using 15% purge, during start-up.
At the end of this period, dryer operation will
be computer-controlled, the "Variable Purge
Mode" light will be on and the microcomputer
will automatically control purge rate to match
the dryer load.
The LCD display will show:
INLET TEMP XX ENERGY SAVINGS = XX%
NO MALFUNCTION EXISTS
If there is low or no demand for compressed
air, the dryer will go into the standby mode.
(See Compu-Purge Control section.)
The LCD display will show:
NO LOAD ON DRYER
IN STANDBY MODE: SAVING PURGE AIR
• Turn alarm silencer switch on front of electrical
box to "ON."
9. Slowly open the outlet shutoff valve.
10. Close customer-supplied bypass valve.
1-10
1988...1991

Dew Point

The pressure dew point of the outlet air is controlled
by the amount of purge air used for reactivation. Purge
airflow is continuous and is adjustable within a set
range. The dew point can be manually adjusted ±20
degrees (depending on operating conditions) using the
purge adjustment valve. Closing the valve will result
in a higher dew point. Opening the valve will result in
a lower dew point. Dryer installation and start-up must
be completed before the purge valve is adjusted.
For applications requiring dew points outside this
range, contact your local distributor.

Dew Point Adjustment

After your dryer has been installed and the start-up
procedure completed, adjust the dryer for a –40°F dew
point as follows.
1. Determine air pressure (psig) at the dryer inlet.
2. Refer to Table 3. For your model and inlet air
pressure, determine the inlet airflow and average
purge rate (% of inlet air) required to produce a
–40°F dew point.
3. Calculate the required purge flow (scfm):
Purge Flow = Purge Rate x Inlet Flow
4. Refer to the purge flow calibration graph shipped
with the dryer. On the graph, locate the average
purge airflow (calculated in Step 3) and the corre-
sponding purge adjustment valve setting (psig).
5. Manually adjust the purge adjustment valve at the
top of the dryer until the correct setting is indi-
cated on the gauge. For dryers 55 thru 160 , adjust
the purge as follows:
DANGER
Do not remove the petcock base from the
shuttle valve.
• Unscrew and remove the petcock wing from the
petcock base on the shuttle valve at the top of
the dryer (see
Figure 5).
• Insert a -inch
3
16
allen wrench
through the pet-
cock base to the
set screw.
• Adjust the set
screw until the
pressure on the
purge gauge cor-
HRD and HRD-EM Series (Bulletin 378)
Figure 5
Cutaway of Shuttle Valve