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Alternate Energy Systems' venturi
type LPG/air mixing systems are designed around the Hallberg venturi tube. This
high-efficiency tube/nozzle combination is used in several different sizes throughout the
range of our products.
The systems
described here are intended to be used with existing LPG vaporizers, either as replacement
for LPG/air mixing systems from other manufacturers, or in the conversion from straight
LPG applications to LPG/air systems. They are simple in design, easy to integrate with
existing equipment, and require only AC 115 V 60 Hz (or AC 220/240 V 50
Hz), single phase electrical supply for
operation.
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1 Steel Skid
2 Vapor Header
3 Low Vapor Pressure Switch
4 Ball Valve
5 “Y” Type Strainer
6 Pressure Regulator
7 Pressure Gauge
8 “Static” Solenoid Valve
“Dynamic” Solenoid Valve
9 Air Intake / Check Valve
10 Venturi Nozzle
11 Venturi Tube
12 Check Valve
13 Ball Valve
14 Surge (Receiver) Tank
15 Relief Valve
16 Pressure Transmitter
17 Control Panel
18 PLC (not shown)
19 Display Unit
20 Vapor Inlet
21 Mixed Gas Outlet |
General
Description
All HVS Systems are designed to be used with an existing LPG vapor
source, such as a vaporizer, or as the replacement for less
efficient or less reliable LPG-vapor/air mixing systems. They come
complete with steel skid, vapor inlet header, venturi arrangements,
surge tank, electric/electronic controls, and all other equipment
necessary for safe and reliable operation.
All HVS systems
monitor the gas pressure in the surge tank. Smaller systems up to
two venturi arrangements use pressure switches and standard
controls. Larger systems with three or more venturi arrangements use
a pressure transmitter which is connected to an Allen-Bradley PLC.
The PLC “sequences” the venturi lines and controls all system safety
functions. The PLC also communicates with an Allen-Bradley display
(Operator Interface), indicating system pressures, Venturi status,
and any trouble conditions that may occur. The PLC may also be used
to “interlock” the HVS system with an external vaporizer.
Installations where
the mixer system is separated from an open-flame vaporizer, and
installations with electric vaporizers, require the option
“Explosion Proof Control Components”, which includes explosion proof
transmitters and solenoid valves. The control panel for mixers with
less than three venturi trains (HVS-7 to HVS-14) is installed on the
mixer skid. The control panels for all systems with PLC controls are
designed to be installed in a non-hazardous location.
Mixed Gas Pressures
of more than 12 (15) psi require the High Pressure option. High
Pressure Option includes ASME “U”-stamped surge tank.
Beginning in March
2004, all HVS Mixers are equipped with two solenoid valves per
venturi train. The “dynamic” solenoid valve opens and closes each
time a venturi train is activated to produce mixed gas. The “static”
solenoid valves opens when the mixer is started and stays open until
the mixer is stopped, or until a high-pressure alarm occurs. This
feature provides an additional level of safety and prevents the
unwanted discharge of mixed gas in case of a failure of the
“dynamic” solenoid valve.
How it
works
Using pressurized LPG vapor through a venturi
arrangement to inspirate air, the BTU content of the mixture is determined by regulating
the LPG vapor pressure. The LPG/air mixture is directly compatible and interchangeable
with natural gas, and is collected in a surge tank, which is part of the system. The
pressure in the surge tank is monitored by pressure transmitters (smaller systems use
pressure switches), and is set to the required system pressure (delivered gas pressure).
When pressure in the surge tank drops due to the outflow of gas, solenoid valves at
the inlet side of the venturi systems are activated, allowing pressurized LPG vapor from
the vaporizer to flow through the nozzle/tube combination, and thereby generating the
LPG/air mixture. When the pre-set pressure in the surge tank is again reached, the
solenoid valves are closed and the system rests until demand for gas repeats the cycle.
Stand-alone systems come complete with vapor inlet header, venturi assemblies, pressure
controls, surge tank, blow down, safety relief valve protection, high and low mix gas
safety, low propane pressure safety, and dual check valve system. Solenoid valves are
explosion proof and pressure switches and transmitters are of standard type. The entire
system is mounted on a common steel skid for easy installation.
All standard systems are manufactured to the requirements of the ASME Code, the latest
edition of NFPA #58, and are approved for Factory Mutual (FM) or Industrial Risk Insurers
(IRI) installations. The model number (HVS) of the venturi system designates
millions of BTU per hour LPG-air mixture.
Standard Models have an output pressure of 5
psi LPG/air mixture, with pressures of 4 to 8 psi obtained by factory adjustment.
Other naturally aspirated configurations are available for delivery
pressures up to 12 (15) psi. These configurations require very high
motive (LP vapor) pressure, and are not recommended for installation
in regions with low ambient temperatures. High Pressure Models with
delivery pressures up to 50 psi LPG/air mixture are also available.
These systems require compressed air for operation.
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