reguladores gascat

1. Minimum Configuration
Simplified Formula:
1.1. Software
1.1.1. Windows 2000 (recommended windows XP SP2)
1.1.2. Access runtime version 2000 (recommended Office Professional 2003 SP3)
1.1.3. Acrobat Reader 7 (recommended Acrobat Reader 7.0.7)
1.2. Hardware
1.2.1. Microcomputer P3 800Mhz (recommended P4 2800Mhz)
1.2.2. 256 MB RAM (recommended 512MB RAM)
1.2.3. Free 1GB HD
P
P
1
Critical Flow: > 2
Sub-Critical Flow:
P
P
1
≤
2
2
2
2Q
× Top
× Z
CV =
31.014 × P × T
Q × T
op
×
CV =
31 .014 × T
Re f
1
1
×
0,6
G
× P
2
Re f
Z
× Δ
P
2. Theory Summary
2.1. Method for calculation of the Flow Coefficient for Pressure Regulating Valves
Firstly, it is necessary to understand what we are looking for when we calculate the flow
coefficient of a pressure-regulating valve.
In practice, we are determining which is the most appropriate valve size to attend the process
operation conditions. It is important to be aware that there are several methodologies for
calculation of the Flow Coefficient:
• CV – Of American origin: This is the flow of water, at 60 ºF in American gallons per
minute, that produces a pressure fall of 1 psig through a completely open valve.
• KV – Of European origin: This is the flow of water in m 3 /h, that produces a
pressure fall of 1 kgf/cm² through a completely open valve – KV = 0,86 x CV.
• KG – This is a derivative of the method above, developed for application with gases,
with manufacturers usually presenting in their literatures these values already
standardized for natural gas – KG = 31.014 x CV.
In the 70’s the Instrument Society of America (ISA) published more precise dimensioning
formulas than the used until then, based on the Fluid Controls Institute (FCI) formulas.
These new formulas, however had some complexity, what led some manufacturers to develop
their own, more simplified, formulas which were adopted by manufacturers and designers along
the time.
Since these formulas were simplified versions, it was also adopted the practice of considering
the application of a safety factor to the final value found, in order to avoid dimensioning errors.
Where:
Q
P1
P2
T Ref
T Op
ΔP
Gas Flow (m³/h; Nm³/h; Sm³/h)
Absolute upstream pressure (kgf/cm²)
Absolute downstream pressure. (kgf/cm²)
Reference Temperature (Kelvin)
Operation Temperature (Kelvin)
P1 - P2
G Gas Specific Gravity (0,6)
Z
Compressibility Factor
CV
Flow Coefficient
For dimensioning purposes, the regulator worst operation condition is when the differential
between outlet and inlet pressures is the smallest possible, the flow is maximum and
temperature is the highest possible temperature, whilst the best condition is the opposite of
the same.
Complementary Information:
In several situations, we will observe that the information regarding process flow considers
different reference conditions, a fact that that needs further understanding. To do this, we
give, in following, the most commonly found forms of reference flow.
CNTP (Normal Temperature and Pressure Conditions) – Flow in Nm 3 /h – considers 1 atm and 0ºC
as the reference pressure and temperature.
Standard Conditions (I.S.C. English / American Standard) – Flow in Sm 3 /h – considers 14.7 psia
(1 atm) and 60ºF (≈ 15ºC) as reference pressure and temperature.
I.S.O R554 - Petrobrás Standard (presently used as the Brazilian standard) – Flow in m 3 /h @ 1
atm and 20ºC - considers 1 atm as the reference pressure and 20ºC as the reference
temperature.
Gcalc Program Manual – Page 1 of 6

2.2. Gas flow speed
Other main factor to be considered in the calculation of the pressure regulators diameters is
the “speed of gas flow”.
To move the cursor from window to window, to use the “tab” key.
Screen for a new register:
Formula:
Calculation method of the inlet and outlet ND based on speed
∅ ²= 353,7 x Q x T x Pr
V x Tr x P
Where:
∅
V
Q
T
P
T R
Pr
Nominal diameter (mm)
Speed (m/s)
Gas Flow (m³/h; Nm³/h; Sm³/h)
Gas temperature (Kelvin)
Minimum gas pressure (kgf/cm²)
Reference temperature (Kelvin)
Reference pressure (kgf/cm²)
There are values usually considered as standard speed limits for several inlet and outlet NDs of
pressure regulators, as follows:
Speed Limits at the Regulator Input (m/s)
Up to 2" 100
2.1/2" to 4" 85
6" to 8" 75
10" to 12" 60
Speed Limit at the Regulator Outlet: 150 m/s
3. Program Usage:
3.1. “Data Input Screen”
For a new register click on the "+" key.
By doing so, the data entry windows are
cleaned and become ready to be filled
out with new data.
Where:
Project: May be used as a reference for the customer name identification.
User: May be used as a reference for the application identification.
P1: Maximum and minimum upstream pressure
P2: Maximum and minimum downstream pressure
To select the calculation
units for P1 and P2, it is
enough to click in the
drop-down button next
to each item:
Gcalc Program Manual - Page 2 of 6

Flow:
Temp:
SG:
Minimum and maximum flow operation
To select the units for
flow calculation, it is
enough to click the
drop-down button next to
the item:
Minimum and maximum fluid temperature, always in ºC.
Gas density in relation to air.
Select the operation
fluid (gas). If the gas is
not in the options,
type the known value in
the window aside.
3.2. Results
With the operation data correctly filled out, we shall perform the calculation.
By clicking the "Calculate" key we will obtain
the “Cv condition" (operational capacity), the
operational condition if Critic or Sub-Critic,
and the “Recommended Cv”.
Calculations Screen:
BasePressure:
Reference Pressure, selecting units. This value is a fix value.
Compressibility: Compressibility factor. If not informed, the value considered will be “1”.
When specifying values, be careful not to mistake minimum and maximum
columns, or the calculation will present an error warning.
Position: This item refers to the regulators’ assembly system, which can be
"Monitor_Regulator" or "Regulator". "Monitor_Regulator" refers to two series
mounted regulators, with the monitor being the stand-by regulator, while the regulator
operates the system.
Capacity Factor%:This is the factor that determines the maximum used capacity of the
regulator. The recommended factor is between 10% and 90%.
Example: Cv condition = 3.27
Capacity Factor % = 80
Recommended Cv = 4,09
Gcalc Program Manual - Page 3 of 6

3.3. Regulators’ Selection
Model: To select the regulator model to be used, it is enough to click on the drop-down button
beside each item (monitor and/or regulator). In the presented relation, there is a preselection
of applicable regulators and Recommended CVs.
3.3. Reports
To visualize the results click the button
“View and print”, and a screen will show
a report with all the results.
The first displays consist of the project information, with operational data.
The third picture presents calculations and flow conditions, and should be analyzed, if the value
of "Cv Condition min" is below 5% of Cv Reg, with the regulator operating for a long time in this
condition, it will probably be led to the regulator having oscillation problems.
Note: The designer shall be capable of analyzing the operation conditions considered in
dimensioning and adapt them to the calculations obtained values to selected the
regulator for such conditions.
When the “Monitor_Regulador” is selected to Position, the equipment “Capacity Utility (%CV)”,
will only present a value after selection of “Regulator” & “Model”.
Note: For presentation of the selected equipment catalog, double click the selected equipment.
Notes: In case you need to add some comment/note, use the “Notes” field. Click within the
field and type all of the information that you want to be printed in the report.
Gcalc Program Manual - Page 4 of 6

Visualization Screen for printing
Outflow speed:
The report also informs the gas
drainage speeds at inlet and outlet
connections of the regulators.
In case of poor dimensioning, the
values will be substituted by a note
informing that the ND is not
applicable, and that the diameter
should be increase. Item 2.2 of this
manual informs the recommended
drainage speed limits.
Another important factor that
shall be analyzed is the gas
drainage through the trim, in case
of the note appearing, according
to the fig. at left, which requires
a trim increase. The use of the
regulator in these conditions may
cause excessive wear of the
regulator internals, which can
produce excessive noise and/or
vibration.
3.4. Page Configuration
The initial menu offers the page
configuration possibility to adjust the
report to your conditions.
Furthermore, it has the print
command, e-mail sending, and
publishing in Microsoft Office Word.
Gcalc Program Manual - Page 5 of 6

Visualization Screen in Word
4. Troubleshooting:
4.1. I cannot open the application. Windows does not recognize the file. What shall I
do?
Check if your computer has installed at least the Microsoft Office Professional 2000,
Access 2000 or Access Runtime.
Note: Access Runtime is a free "viewer" of .mdb files and can be copied from the
Microsoft site. The application installation file already includes Access Runtime. To install,
locate the installation directory of GCalc and click on the file (\ACCRT \ ACCESSRT.MSI).
4.2. I do not visualize the products’ catalogs. What shall I do?
Check if the computer has Adobe Acrobat Reader installed.
4.3. When opening the Access application it issues an error warning and closes the
application. What shall I do?
Update for to the last version or install the last Professional Office
Microsoft Service Pack, Access or Access Runtime packs. Service Packs are
corrections timely made available in the Microsoft site to correct flaws and mistakes
in the mentioned programs.
Note: For better performance and use of all resources, always keep Windows updated
and the application Access corresponding to their last Service Packs.
3.5. Other Commands:
This command allows the program to be closed.
Gcalc Program Manual - Page 6 of 6