MAC/MTT-OPS-1
26 FEB 2019
SECTION 2
System Description
2-22
Hydraulic Spray Head
A two piece aluminum valve
body, hydraulic cylinder and
adjustable ring mounted to a
water supply header pipe. The
upper portion of the valve
body contains a hydraulic
cylinder that receives hydraulic pressure from the
system solenoid control box as commanded by
the cab control switch. When the hydraulic
cylinder on the upper portion of the valve body is
pressurized, the cylinder extends to contact the
guide disk and seal the opening on the lower
portion of the valve and stop water flow.
When the cab control system is OFF and the water
pump is OFF the upper valve body incorporates a
spring to apply pressure to the guide disk to seal
the opening on the lower portion of the valve and
stop flow. When the spray head switch is turned
on, hydraulic pressure retracts the hydraulic
cylinder and pressurized water from the header
pipe will unseat the guide disk and water will flow
from the lower portion of valve.
Spray Head Adjustable Rings
The adjustable ring is used to control fan width
and water flow. The ring may be loosened and
rotated to expose more or less of the lower valve
opening to control water fan width from 15°
(narrow fan width) to 90° (full fan width). The ring
also may be used rotated to a fine spray (1/4” slot
height) or heavy spray (3/8” slot height) as shown
below to increase or decrease overall water flow.
The greater the opening, the greater the water
flow.
Solenoid Control Box
The control box assembly is mounted to the
forward bulkhead or top skin of the MTT. The
assembly contains pneumatic or hydraulic
solenoid valves that direct pneumatic or hydraulic
pressure to the spray head as commanded by the
cab control box. The solenoids receive pneumatic
pressure from the vehicle or hydraulic pressure
from water pump oil circuit and 24 VDC power
from the cab control box.
DUMP BAR
The dump bar is a pipe suspended below the main
spray bar at the rear of the water tank that has 1
row (pressure dump bar) or 2 rows (gravity dump
bar) of 3/8 inch holes drilled in the bottom. This
bar may pressurized from the water pump or
gravity fed from the sump of the tank. A
hydraulically operated butterfly valve controls the
water supply to the dump bar. The BFV is
controlled electrically from the cab control box
and is actuated by a hydraulic cylinder. The
actuators receive hydraulic pressure from the
solenoid control box assembly. Dump bars can be
either gravity or pressure fed.
Fine Spray (1/4” slot height)
Heavy Spray (3/8” slot height)
Pneumatic
Hydraulic
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