Introduction
Type Dosaodor-D is a computerized odorant injection
system for natural gas using patented solenoid
injector technology that eliminates the need for
plunger pumps.
The solenoid injectors provide odorant injection
accuracy to be maintained over the entire flow range
of the system, approaching infinite turn down.
Automatic calibration during operation adjusts for any
changes in mechanical components and also detects
failures for alarming. Report by exception alarming is
a configurable option.
The system can also be configured to use
redundant injectors and/or an emergency backup or
bypass absorption system.
Real time and historical data can be read locally or
remotely by a laptop computer using ROCLINK 800
configuration software or remotely using third party
SCADA products utilizing ROC or Modbus protocol.
ROCLINK 800 software is available for complete
configuration and operation of the system including:
• Display of real time and historical data
• Configuration of alarms
• Archival of historical data
Benefits
• Uniform distribution of odorant due to frequent
smaller injections and enhanced absorption from
the wick insertion.
• High turndown ratio. For example, one specific
configuration would evenly distribute odorant at
flow rates from 2000 to 1,200,000 SCFH / 53.6 to
32,160 Nm
3
/h without mechanical adjustment.
• Automatic calibration of injection system during
normal operation ensuring consistent odorization.
• Environmentally friendly with no venting of gas or
odorant while operating.
• Extremely low maintenance cost.
• Variety of redundancy and backup options for
reliable odorization.
• User friendly configuration software.
• Standard and scalable hardware platform that
supports additional station I/O for AGA flow
calculations and PID control algorithms.
Operation
The Type Dosaodor-D odorant injection system
operates on the basic principle of a fixed differential
pressure and orifice used to measure a non-
compressible fluid.
Fixed differential pressure is maintained using double
cut regulation by fixed differential pressure regulators
(Type SA/2 regulators) which reference P
2
and reduce
the inlet pressure of a regulating station to P
2
+ ∆P.
∆P
min
= 8.7 psi / 0.60 bar, ∆P
max
= 21.7 psi / 1.5 bar
(an alternate high-pressure source can be used). This
pressure loading of the odorant calibration cylinder
filled with odorant is used to inject liquid odorant into
the downstream pipeline through an on/off valve (the
fixed orifice
1
) with a known flow coefficient that is
controlled by the automated system. The objective of
the automated control system is to maintain an injection
rate specified by the user which is proportional to the
gas flow. Accuracy of injection is accomplished utilizing
relatively small injections which are automatically
resized over a wide range dependent upon variations
in the gas flow. This results in a turn down ratio for
the system that can exceed 500:1 (the addition of a
simple bypass system utilizing the odorant storage
tank can allow the turn down ratio to approach infinity).
An odorant calibration cylinder with a fixed volume is
utilized to recalibrate the injection valve flow coefficient
each time the odorant calibration cylinder is refilled.
During the refill cycle the pressure used for injection is
relieved into the downstream pipeline which eliminates
venting of gas to atmosphere or an expansion tank.
Liquid odorant refill of the odorant calibration cylinder
is typically accomplished by using all or some part of
the P
2
+ ∆P pressure to load the odorant storage tank
thus pushing the liquid out of the tank and into the
odorant calibration cylinder, ∆P = 8.7 to 21.7 psi /
0.60 to 1.5 bar.
Since the unit uses only pressure for injection there
are few moving parts in the system resulting in very
little maintenance. Relatively low cost options for both
automated and emergency redundancy for odorization
are also available.
The gas flow rate is obtained through either a
corrected gas volume pulse input or an instantaneous
flow rate analog input (4 to 20 mA) signal. The gas
1. Although the valve orifice is fixed for a specific application the valve can be adjusted manually to accommodate flow rates as small as 2 MSCFH to over 33,000 MSCFH with one injector.
3
Type Dosaodor-D
