20120531085214634.pdf

SIEMENS Technical Information

1. Information about possibly incorrectly Level control measurement

Level control measurement in pressurized tanks, using Differential Pressure measurement with temperature correction, produces an error in the measurement transducer level value. The resulting measurement error (< 3%) can mean that protection triggering is not carried out. This is particularly a concern where protection triggering should be activated near the measurement limits (95%). The measuring fault occurs as a result of incorrect assumptions about the density in the comparison column in the cold water condition. The measurement transducer may be calibrated for a temperature in the reference column of 4 Celsius (corresponds to a density of 1.000 kg/m3) and in application the correction calculation of e.g. 50 Celsius (corresponds to a density of 988 kg/m3) was carried out. Affected are: SPPA-T3000 corrections block LEVEL and F_CLEVEL SPPA-T2000 corrections block K_HOEHE All Level control measurement (e.g. drum, feed water tanks, pre-heater) can be affected. Please, check and correct the adjustments of the measurement transducers in accordance with the enclosed description. To avoid disturbances in the working sequence, the corrective action should either be carried out during an outage or suitable precautions must be taken.

Level_Info-CorrectiveGuidance.doc 1/5 2012-04-27 Release 1.1 E F IE


2. Corrective guidance manual for Level correction calculation

2.1. Transducer adjustment Following inputs have to be known:

Distance between the upper and the lower nozzle (H) Distance between the lower nozzle and the measurement range beginning (UM) Distance between the lower nozzle and the measurement range end (OM) Distance are to be provided in metric units (meter)

H OM Tank or Container UM 0

In addition following values need to be determined:

Temperature of the reference water column (TEMP), usually 50C within buildings, 40C for open air

Gravity (g), usually 9.81 m/s2, respectively the on location depending value.



The density RHO of water at 1 bar absolute and the chosen temperature TEMP of the correction water column has to be determined TEMP RHO 40 C 992,2 kg/m350 C 988,0 kg/m3 If other correction water column temperature is used, the water density can be found in water-steam table. The measurement range calculation of differential pressure based level measurement is carried out as follow (density of water at 100 C and 1 bar = 958,63 kg/m, density steam at 100 C and 1 bar = 0,59 kg/m ) po = (RHO-958,63 kg/m3) * H * g / 100 pu = (RHO-0,59 kg/m3) * H * g / 100 With po: Differential pressure while water filled up to upper nozzle in mbar pu: Differential pressure with empty tank in mbar If the measurement range is identical to the upper nozzle, therefore OM = H and the measurement range beginning is the lower nozzle, UM=0 one is ready now. . The measurement range of the pressure transmitter has to be adjusted to po to pu. This corresponds to one uncorrected level of 0 (zero) up to H. This measurement range has to be entered into the corresponding function block of control system software as (uncorrected) measurement range of the level. If other measurement ranges have been chosen, calculate the corresponding measurement range of differential pressures as follow: pOM = OM / H * (po - pu) + pu pUM = UM / H * (po - pu) + pu With pOM: Differential pressure with tank filled up to measurement upper limit pUM: Differential pressure with tank filled up to measurement lower limit The measurement range of the pressure transmitter can be adjusted from pUM to pOM (in mbar). This corresponds to an uncorrected level from UM to OM. The changes should, compared with the old values, not be larger then max. +3% at pOM and -3% for pUM. We recommend to re-check the adjustments if larger difference exists. The level entries corresponding to the measurement range have to be checked and corrected if necessary at the corresponding software component of the control system. The corresponding constituents are listed in the following table:

- T3000 non Failsafe SIM Hardware-Proxy - T3000 non Failsafe FUM FUM_ASMON - T3000-Failsafe: F-CH_AI - T2000 non Failsafe: GA - T2000 APF (Failsafe): FA



If Failsafe measurement must be changed, the country specific certification authority should be informed as necessary. If measurements have to be checked by routine proof tests, the corresponding documentation has to be updated. Generally, it has to be taken into account that the documentation (e.g. calibration protocols) has to be updated on the correct values. Example calculation: H = 10,55 m The nozzle correspondent to measurement range of (UM = 0 m, OM = 10,55 m). g = 9,81 m/s2. The temperature of the reference water column TEMP = 50 C. Resulting into RHO = 988,0 kg/m3 po = (988,0 kg/m3-958,63 kg/m3) * 10,55 m * 9,81 m/s2 / 100 = 30 mbar pu = (988,0 kg/m3-0,59 kg/m3) * 10,55 m * 9,81 m/s2 / 100 = 1022 mbar

2.2. The settings of the corrections calculator:

a) in SPPA-T3000 Function block LEVEL, F_CLEVEL Parameter name in T3000 Adjusted value TEMP TEMP (e.g. 50C) T_REF TEMP EN_T 1 (binary) DISTANCE H UL H LL 0 (Null)

b) in SPPA-T2000 Function block K_HOEHE Parameter name in T2000 Adjusted value T TEMP (z. B. 50C) TEMPMESS 1 (binary) STABST H in cm STABSMA 0



This document is confidential to Siemens AG (Siemens). Your acceptance of it is an acknowledgment of a confidential relationship between you and Siemens. It is to be used solely by you for the purpose for which it is furnished. Neither this document nor any information contained in it or obtained from it is to be used otherwise, or transmitted or disclosed to any third party or in whole or in part without the prior written authorization of Siemens.

The information, recommendations and descriptions in this document are based on Siemens experience and judgment, but SHOULD NOT BE CONSIDERED AS ALL-INCLUSIVE OR COVERING ALL CONTINGENCIES. If there are any questions regarding its contents, or if further information is required, Siemens should be consulted.

NO WARRANTIES, EXPRESSED OR IMPLIED, WHETHER OF FITNESS FOR PURPOSE OR MERCHANTABILITY, FROM COURSE OF DEALING OR USAGE OF TRADE, AS TO THE COMPLETENESS, USEFULNESS, ADEQUACY, OR ACCURACY THEREOF, OR OTHERWISE, ARE MADE REGARDING THE INFORMATION, RECOMMENDATIONS, OR DESCRIPTIONS CONTAINED IN THIS DOCUMENT. Any obligation or liability of Siemens shall be solely if and to the extent set forth in existing contracts, if any, and nothing in this DOCUMENT shall be deemed or construed to give rise to any additional obligation or liability of Siemens. In no event will Siemens or its affiliates, or any of their respective contractors, subcontractors or suppliers be liable whether in contract, tort (including negligence), strict liability or otherwise for any special, indirect, incidental, or consequential damage or loss whatsoever, damage to or loss of use of equipment, plant, or power system; cost or capital; loss of profits or revenues; cost of replacement power; additional expenses in the use of existing power facilities; or claims against the user by its customers, for, arising out of or resulting from the information, recommendations, or descriptions contained in this document


1. Information about possibly incorrectly Level control measurement2. Corrective guidance manual for Level correction calculation2.1. Transducer adjustment2.2. The settings of the corrections calculator:

20120531085214634.pdf

Documents