Engineering Values Computation

SRPC - Clamart Page 77 of 113 Part Number : EP490380-AC

Property of Schlumberger - Do not disclose, use or reproduce without written approval from Schlumberger. Propriété de Schlumberger - Ne pas exposer, utiliser ou copier sans l'autorisation expresse de Schlumberger

SPECIFICATION USER MANUAL & PROTOCOL to SUBSEA PERMANENT GAUGE INTERFACE SYSTEM

Prepared by R.Zeyssolff Des. Engineer R.Zeyssolff Records Artec

Date prepared 06/29/04 Mfg. Engineer S.Cherchali Project Manager S.Osmani

6.8.13 Engineering values (or Physical Unit) computation (for PQG & Sapphire type of gauges)

In order to provide Engineering Values (EV) to the final clients, specific computation must be done. There are two possibilities:

• at surface (in topside PC) with third party computation (according to the explanations given later on), • or directly inside the SLIC/ESLIC interface.

This computation is automatically done inside the SLIC/ESLIC interface as soon as the coefficients belonging to the gauges are stored inside the interface. In this case, EV are provided in Psia for pressure and DegC for temperature. Computation uses Gauge’s coefficients that can be stored in the Interface (when Engineering values have to be retrieved directly from interface) or in the surface PC (when Engineering values are computed in the topside PC). Each gauge is delivered with its own coefficients set. It cannot be used for an other gauge. Description how to convert the raw data acquired by the SLIC/ESLIC to Engineering Values (EV) also called Physical Units is given below. The computation of any kind of measure is based on a calibration coefficients matrix and a computation model. The model depends on the gauge type.

Gauge type : xPQG Digital gauge with QUARTZ sensor DPG-PS Digital gauge with SAPPHIRE sensor DPG-TA Digital gauge with 2 SAPPHIRE sensors






6.8.14 Computation model

The following computation model is used according to the gauge type and the measure to compute :

Gauge Type Pressure Temperature PQG & EPQG P = f(Fp, Ft) T = f(Ft) DPG-PS P = f(Fp, Ft) T = f(Ft,Fp) DPG-TA P = f(Fp, Ft) T = f(Ft,Fp)

Where : P -> Pressure in Psia T -> Temperature in DegC Fp -> Internal Pressure Value also called Pressure frequency Ft -> Internal Temperature Value also called Temperature frequency f -> Transfer function

6.8.15 Coefficient Matrix

The maximum size of a coefficient matrix is 6x6. The coefficient issued from the coefficient file appears as follow :

(sign).xxxxxxxxxxxxE(sign)xx

where : x is a digit [0 - 9] sign is + or -

6.8.16 Computation equations

The gauges provide the pressure and temperature Raw data. The pressure and temperature frequencies (Fp), (Ft), must

be calculated in the surface system by scaling the gauge Raw data according to the following formula. The computation should be made in 3 steps.






Step 1: (Raw Data to Frequencies)

kHz

kHz

where: is the Temperature Frequency in kHz also called Internal Temperature value

is the Pressure Frequency in kHz also called Internal Pressure value

* = R x 1000 (R in KHz)

* = C1/256

* = C2

* = N

* Computed from the digitizer parameters (R, C1, C2, N) sent by the gauge. For PQG & EPQG, the typical values are: n = 8, Coeff1 = 0.750, Coeff2 = 1, Fref = 7.2 MHz. (when normal mode on 7.2Mhz crystal) n = 8, Coeff1 = 0.625, Coeff2 = 1, Fref = 6.0 MHz. (when working on 6Mhz default crystal, in this case, raw data may become “0”). For NPQG, the typical values are: n = 8, Coeff1 = 0.750, Coeff2 = 1, Fref = 7.2 MHz. (when normal mode on 7.2Mhz crystal) n = 8, Coeff1 = 0.625, Coeff2 = 1, Fref = 6.0 MHz. (when working on 6Mhz default crystal, in this case, raw data may become “0”).






In other words : Frequencies (or Internal Data values) = Raw_data * GAIN The table below shows the gain values for each measure and each gauge.

GAIN Table

GAUGE Pressure Temperature PQG & EPQG 4.47035*10-6 4.47035*10-6

NPQG DPG-PS 1 1 DPG-TA 1 1






• Step 2 : Convert the Frequencies (or Internal Data values) to Physical Unit (also called Engineering Values (EV)) in Psia and DegC by applying the coefficient matrix and the computation model. The matrix columns are numbered from 0 to 5 and the matrix lines are labeled from G to L as shown in the calibration data sheet (coefficient paper file).

Pressure computation Model P = f(Fp, Ft)

P = G + H * Fp + I * Fp2 + J * Fp3 + K * Fp4 + L * Fp5.

where : G = G0 + G1 * Ft + G2 * Ft2 + G3 * Ft3 + G4 * Ft4 + G5 * Ft5.

H = H0 + H1 * Ft + H2 * Ft2 + H3 * Ft3 + H4 * Ft4 + H5 * Ft5.

I = I0 + I1 * Ft + I2 * Ft2 + I3 * Ft3 + I4 * Ft4 + I5 * Ft5.

J = J0 + J1 * Ft + J2 * Ft2 + J3 * Ft3 + J4 * Ft4 + J5 * Ft5.

K = K0 + K1 * Ft + K2 * Ft2 + K3 * Ft3 + K4 * Ft4 + K5 * Ft5.

L = L0 + L1 * Ft + L2 * Ft2 + L3 * Ft3 + L4 * Ft4 + L5 * Ft5.

Fp -> Internal pressure value also called Pressure frequency Ft -> Internal temperature value also called Temperature frequency Gx to Lx -> Calibration coefficients (Ref. to the calibration data sheet) P -> Pressure in Psia Temperature computation Model T = f(Ft) T = T1 + T2 * Ft + T3 * Ft2 + T4 * Ft3 + T5 * Ft4 + T6 * Ft5.

where : Ft -> Internal temperature value also called Temperature frequency Tx -> Calibration coefficients (Ref. to calibration data sheet) T -> Temperature in DegC






Model T = f(Ft,Fp)

T = G + H * Ft + I * Ft2 + J * Ft3 + K * Ft4 + L * Ft5.

where : G = G0 + G1 * Fp + G2 * Fp2 + G3 * Fp3 + G4 * Fp4 + G5 * Fp5.

H = H0 + H1 * Fp + H2 * Fp2 + H3 * Fp3 + H4 * Fp4 + H5 * Fp5.

I = I0 + I1 * Fp + I2 * Fp2 + I3 * Fp3 + I4 * Fp4 + I5 * Fp5.

J = J0 + J1 * Fp + J2 * Fp2 + J3 * Fp3 + J4 * Fp4 + J5 * Fp5.

K = K0 + K1 * Fp + K2 * Fp2 + K3 * Fp3 + K4 * Fp4 + K5 * Fp5.

L = L0 + L1 * Fp + L2 * Fp2 + L3 * Fp3 + L4 * Fp4 + L5 * Fp5.

where : Fp Internal pressure value (after applying the Gain) also called Pressure frequency Ft Internal temperature value (after applying the Gain) also called Temperature frequency Gx to Lx Calibration coefficients (Ref. to calibration data sheet) T Temperature in DegC Computation example (xPQG type):

Example: Reading “Raw data” (Praw & Traw) at Modbus Register 2411 to 2414: (using PGSB box and P&T buttons at position 4).

Modbus register Value (Hex) Value (H or Dec) 2411 74 2412 0DA7

740DA7H 7605671Dec

2413 93 2414 A06D

93A06DH 9674861Dec

“Raw data Pressure”: 00740DA7H = 7605671 Dec

Knowing gain = 4.47035*10-6

Internal value (Pressure Frequency) computation:

Fp = 4,47035E-06 * Praw = 34.000 kHz Knowing P = G + H*Fp + I*Fp2 + J*Fp3 + K*Fp4 + L*Fp5 and G = G0 + G1*Fp +…






H = H0 +… ….

With example coefficients: G = - 1.09251638... E+04

H = + 4.8351... E+02 I = - 2.991... E-01 J = + 9.01... E-04 K = 0 L = 0 Gives: P = 5203.83 PsiA “Raw data Temperature”: 0093A06D H = 9674861 Dec

Using the Gain: Ft = 4,47035E-06 * Traw = 43,250 kHz Knowing T = T1 + T2*Ft + T3*Ft2 + T4*Ft3 + T5*Ft4 + T6*Ft5

With example coefficients:

T1 = + 2.954… E+02 T2 = - 9.755… E+00 T3 = + 2.843… E-01 T4 = - 6.121… E-03 T5 = + 4.032… E-05 T6 = 0 Gives: T =51.153 Deg.C

SRPC - Clamart 4 of 113 Part Number : EP490380-AC





Step 3 : Converts the Physical Unit (Psia and DegC) to other client unit system. For each measure : Measure (client unit) = Measure (from step2) * UNIT_GAIN + UNIT_OFFSET. Some examples of conversion constants are shown in the table presented below:

Unit UNIT_GAIN UNIT_OFFSET Bar 0.06894757 0

Kg/cm2 0.07030697 0 KPa 6.894757 0

Deg F 1.8 32.0

Engineering Values Computation

Documents

Transcript of Engineering Values Computation