Powerex MTSD0303 - Controls

Scroll Medical & Laboratory Compressed Air Systems
Powerex • 150 Producon Drive • Harrison, OH 45030 • USA
P 1.888.769.7979 • F 513.367.3125 • www.powerexinc.com
IN907800AV • 08/2018
Page 3 of 40
The compressed air is then carried to the aer cooler. During aer
cooling, condensaon is formed and captured in the condensate trap
downstream from the aer cooler. The condensate trap collecon
bowl is piped to an automac drain system. The liquid formed is
condensed atmospheric water vapor and it may be allowable to
drain into your local sewer system. Check local regulaons for actual
requirements.
The compressor pumps are driven by three phase electric motors
acng through vee belt drives. The belts are carefully engineered
and selected for durability and reliability. When the vee belts run,
especially in the rst few hundered hours of operaon, dust is
generated as the prole of the belt wears in to match the grooves in
the drive and driven sheaves. The dust is normal and will not cause
any operang problems. If the belts are not slipping, no adjustement
of tension is necessary. If tension adjustement or belt replacement
does become necessary, the motor mount is designed to act as a slide
base tensioning systems and detailed instrucons are provided in this
manual.
Aer the condensate trap, a check valve and a ball valve is installed
in each branch of the compressor system. This valve allows an unused
branch to be closed o from the system. If the valve is ulized to allow
service to be performed, a locking cover must be installed to meet
Lock out Tag out requirements. A relief valve is installed upstream
of the ball valve, so that if the ball valve is closed and the pump is
started, the relief valve will open and prevent catastrophic pressure
rise and damage. The relief valve is not intended to allow connuous
operaon of the pump with the ball valve closed.
Compressed air systems contain electrical energy.
Remove and lock out all energy sources from the
system if any maintenance is being performed where the energy may
cause the pump or motor to operate.
Compressed air is collected and piped to the air receiver. The air
receiver has a bypass valve manifold installed for use if necessary. The
air receiver has an an-corrosion lining. Each air receiver has an ASME
safety relief valve to prevent system pressure from exceeding the
design capability of the vessel. A mechanical pressure gauge allows
visual vericaon of the system pressure. Condensaon that forms
aer the aer cooler will collect in the receiver. An automac tank
drain is installed along with a manual drain valve to remove the liquid.
Since the compressors are oilless, the liquid formed is condensed
atmospheric water vapor and it may be allowable to drain into your
local sewer system. Check local regulaons for actual requirements.
A transparent tube is installed in the lower secon of the air receiver
to allow visual vericaon that the condensate is being removed from
the vessel.
Risk of Injury or death. Do not modify the air
receiver or the ASME safety relief valve. Do not
obstruct or restrict the outlet of the ASME safety relief valve. Do not
operate the system at pressures higher than the rated pressure. Do not
perform any work on the receiver or connected components while energy
(compressed air) is present.
Compressed air from the receiver is routed to the dryer secon
where duplex desiccant dryers remove water vapor to the specied
dew point of the system. A desiccant dryer uses chemical reacons
with water vapor and the surface of the desiccant material to hold
water molecules when compressed air is owing through the bed.
The bed is then regenerated using some of the dry air in the “purge”
mode at low pressure to reverse the chemical reacon. The dryer
controls automacally cycle the beds to extract moisture from the
compressed air. Each branch of the duplex desiccant dryer system is
equipped with isolaon valves so that one dryer can be online and
in use while the other is idle. Each branch has lters and pressure
regulators as needed. Dryer inlet ltraon includes mechanical
cyclonic water droplet separaon as well as coalescing lters. Dryer
outlet ltraon prevents any desiccant dust from leaving the system.
Aer the dryers, the compressed air is connected to dew point and
CO monitors. (CO monitor is oponal for laboratory systems). The
monitors take a small amount of sample air. The dew point monitor
works with the dryer controls to minimize the amount of purge air
used to regenerate the desiccant beds. The Dew Point and CO monitor
go into alarm mode if allowable parameters are exceeded.
Controls
The disconnects and protecon devices in the Powerex control
system are for the motor branch circuits, accessory supply circuits and
for the control circuit only. The controls on the Powerex Laboratory
Open Scroll System do not include a service disconnect and circuit
protecon for the supply circuit. Selecon and installaon of these
items must be provided in compliance to local and naonal codes in
accordance with each facility’s need.
The PLC automacally alternates the lead designaon and brings
on lag pumps as needed, equalizing run me on the pumps in the
system. The touch screen HMI (Human Machine Interface) panel on
the front allows operaon and monitoring of the system. The touch
screen provides the user with displays showing the operang status
and allows the user to access features of the control system. The
control panel also allows communicaon using the BACnet® protocol.
The control panel includes Hand-O-Auto selector switches for
each pump so that a pump can be held on (or o). This can be useful
if maintenance or diagnosc procedures are being performed.
The transformer is sized for the loads imposed by the Powerex
factory controls and should not be ulized for any other purpose.
Premium control panels ulize a backup transformer with a reserve
transformer in use alarm.
Local alarms are provided for low pressure and general fault
condions. The general fault alarm includes high temperature,
reserve transformer in use, motor overload and reserve pump in use
(when specied). The wiring connecon point for the alarms is on the
terminal strip in the control panel box, with good condions being
contacts closed. (If a wire connecon is lost, the result is an alarm.)