=Paper=
{{Paper
|id=Vol-2843/shortpaper016
|storemode=property
|title=Decision Support Models and Algorithms for Remote Monitoring of the Equipment State (short paper)
|pdfUrl=https://ceur-ws.org/Vol-2843/shortpaper016.pdf
|volume=Vol-2843
|authors=Eugene Soldatov,Alexey Bogomolov
}}
==Decision Support Models and Algorithms for Remote Monitoring of the Equipment State (short paper)==
https://ceur-ws.org/Vol-2843/shortpaper016.pdf
Decision Support Models and Algorithms for Remote
Monitoring of the Equipment State*
Eugene Soldatov and Alexey Bogomolov
Saint Petersburg Fed. Res. Center of the Russian Academy of Sciences,
39, 14 line, Saint-Petersburg, 199178, Russian Federation
gniiivm-s@yandex.ru
Abstract. The article describes some problem aspects of monitoring the opera-
tional regimes of the remote equipment: stationary and transport cryogenic
tanks. A functional structure is presented that demonstrates interconnection of
programs for modeling heat and mass transfer processes, a computational mod-
ules and programs for monitoring the state of stationary and cryogenic tanks of
various types. The main advantages of using the considered models and algo-
rithms for remote monitoring and controlling are the possibilities of taking into
account the changing of different operational regimes for cryogenic equipment,
variable ambient temperature, as well as the technical condition of the screen-
vacuum superinsulation. An example of a decision support algorithm for con-
trolling operational regimes of cryogenic tanks with a volume of up to 70 cubic
meters is considered. The effectiveness of the proposed models and algorithms
is confirmed by the results of software testing according to experimental data
obtained during multimodal transportation of cryogenic products by various
types of transport.
Keywords: Remote monitoring, Decision support algorithm, Cryoproduct,
Holding time, Cryogenic tank, Liquefied natural gas.
1 Introduction
The main problem aspect need to be taken into account in monitoring and controlling
the remote cryogenic equipment is frequently changing operational regimes of sta-
tionary and transport tanks [1-3]. The more important independent factors influencing
the value of time until the end of the non-drainage storage process of the cryoproduct
are the degree of thermal stratification, the value of the heat flux through the screen-
vacuum superinsulation, and the influence of vibrations of the tank during the trans-
portation [4-6].
Lack of adequate information about the current parameters of the cryoproduct in
the tank can lead to making the incorrect decisions by the personnel responsible for
the remote control of the equipment [7-8]. The pressure increasing in the tank jointly
*
Copyright © 2021 for this paper by its authors. Use permitted under Creative Commons License Attribu-
tion 4.0 International (CC BY 4.0).
with a small product consumption can eventually lead to undesirable gas losses due to
discharge through safety valves and in the case of storage of flammable cryoproducts
(e.g. liquefied natural gas, ethylene) create explosive mixtures in air and cause fire
hazardous situations [9-15].
2 Materials and methods
2.1 About a formal statement of the problem of controlling the operational
regimes of the remote equipment
The main task in controlling the operational regimes of cryogenic tanks is to achieve
the maximum drainage free holding time, which is ensured by regulation of the pres-
sure in the gas phase ps with the help of discharge valves (Fig. 1), as well as switching
to product delivery from the gas phase, instead of delivery from the liquid phase, and
vice versa (if technically possible), at a given maximum working pressure in the tank
pmax. Therefore, as the objective function is considered drainage free holding time of
the cryoproduct τH (the holding time) [16-19].
Based on practical experience in operation of stationary and transport cryogenic
tanks [20-23], it makes sense to consider the holding time as a function of the follow-
ing independent parameters:
H f p s , p f , p vac , T0m , Al , f l , Atr , f tr max (1)
Where pf, ps – current values of pressure in, respectively, liquid and vapour phase
of the tank, T0m – current measured value of outside air temperature, pvac – pressure in
the vacuum space (optional), τH – the holding time. For transport tanks with appropri-
ate mechanical sensors can be taken into consideration amplitude Al, Atr and fre-
quency fl, ftr of, respectively, longitudinal and transverse vibrations of the tank.
Fig. 1. Control scheme of cryoproducts storage regimes (ΔTstr – temperature stratification, Lf –
level of liquid in the tank).
With such a formulation of the problem, especially given a lot of random parame-
ters, it is impractical to compile a general analytical expression for the objective func-
tion. To solve the problem of maximizing the holding time, a decision support algo-
rithm for predicting drainage free holding time of the cryoproduct was developed.
2.2 Structure of decision support system for controlling the operational
regimes of cryogenic tanks
To improve information support of operators, it is proposed to use decision support
system for controlling the operational regimes of cryogenic tanks. The functional
scheme of the considered system support system is shown in Fig. 2. The based infor-
mation for evaluation of the pressure in the vapour phase of tank and predicted hold-
ing time is the results of computational modeling, obtained in universal software
complex ANSYS Fluent. A several two-dimensional computer models were prepared
to calculate temperature and pressure fields for heat and mass transfer processes in
cryogenic tank [24-27].
Fig. 2. Decision support system for controlling the operational regimes of cryogenic tanks.
A database of the main parameters of the simulation results is being accumulated,
as new data on the geometric and operational characteristics of stationary and trans-
port tanks (including tank containers), thermodynamic components (including mix-
tures) are accumulated. From this information, upon request from the computing
module, an array of values of tank gas pressure and holding time data is formed, from
the elements of which the required value of the predicted drainage free holding time is
subsequently determined (Fig. 3).
Remote control center accumulates information from the tanks: data on the pres-
sure and level of the liquid product, technical condition of the thermal insulation, the
current storage regime (stationary or transport), the predicted holding time.
3 Results
3.1 Decision support algorithm for predicting the holding time
Fig. 3. Decision support algorithm for predicting the holding time.
The algorithm described in this subsection allows one to consider stationary and
transport cryogenic tanks for various purposes with a volume of up to 70 m3.
Optionally having a current value of the vacuum pressure pvac obtained from the
mechanical vibration sensors, the calculation of the additional heat gain due to the gas
in the inter-tank space may be written as follows:
k 1 18,2 pvac m
Qgas
T0 Tc Fc (2)
k 1 T0
Where Fc – the evaluated area of the cold wall of the tank, Tc – the temperature of
the cold wall of the tank, µ – molecular weight of the cryogenic product, k – adiabatic
Poisson's ratio, α – the energy accommodation coefficient. The evaluated heat gain
through the superinsulation Qins is calculated as follows:
T0m Tc
Qins Qdb Qgas (3)
T0 Tc
Where T0=293 К (0 °C) – normal temperature, Qdb – the returned value of the heat
gain through the superinsulation of the tank from the main database.
For a stationary mode the data array of time τH,i and storage pressure pj correspond-
ing to the previously calculated heat flow is loaded into the computing module. If the
obtained value of τH turns out to be less than the specified value of the critical pres-
sure τcr, the system generates and sends an emergency message to the remote control
center.
3.2 Typical information picture and operator’s decisions
Based on current tank-state information picture (Fig. 4), the operator responsible for
remote monitoring of the state of cryogenic tanks can make decisions for:
─ sending a message to the technical gases logistics service about the need to refuel
the tank (when the liquid level drops below 30%, if the tank is used in stationary
storage mode);
─ informing the responsible person when changing the status to "ATTENTION" (the
status changes if the value of holding time becomes less than 24 hours);
─ immediately informing the person responsible for the good condition and safe op-
eration of the tank and special services (if necessary) in case of an emergency mes-
sage (the pressure in the tank exceeds 1,15 of maximum, there is no vacuum in the
heat-insulating cavity, the liquid level exceeds 98 %, etc. ).
Fig. 4. The example of information picture on the state of a cryogenic tank on the operator’s
display of remote control center.
3.3 Computational results and software testing by empirical data
For analyzing the correspondence between the calculated and passport values of the
holding time, some experimental data concerning storage of cryogenic products (ni-
trogen, argon, liquefied natural gas and ethylene) in multimodal transport units
(40 000 litres volume ISO-containers) were considered (Fig. 5).
Fig. 5. Evaluated and experimental long-term storage parameters of cryogenic products in a
multimodal ISO-container (40 000 litres volume).
4 Discussion
For the consideration, the total holding time for one multimodal transport unit was
evaluated. The holding time from the initial minimum pressure to the maximum al-
lowed pressure 0.7 MPa was considered .
As shown in comparison diagram (Fig. 5), the evaluated and experimental values
of the holding time turn out to be significantly lower than the maximum theoretical
values (passport theoretical holding time values) for ISO-containers. The results of
the calculations of the operational parameters differ from the experimental values by
no more than 3 ... 5 %, which makes it advisable to predict the safe holding time
based on the results of computational modeling.
5 Conclusion
The research describes some features of estimation the key characteristics of station-
ary and transport cryogenic tanks, namely: the time of drainage free holding time and
level of liquid – for various regimes of storage.
The advantages of the decision support system for monitoring the state of station-
ary tanks, cisterns and ISO-containers were presented. An algorithm for calculating
the non-drainage holding time makes it possible to predict both stationary and trans-
port operational values, which allows to make timely operational decisions on storage
and transportation regimes of remote cryogenic equipment. Validation results on the
non-drainage holding time by empirical data, obtained in the process of multimodal
transportation of cryoproducts, showed that the calculated data differ from the empiri-
cal values by no more than 5 %. The introduction of the proposed monitoring system
for a specific fleet of stationary and transport cryogenic tanks will significantly in-
crease the safety of operation by ensuring technological processes without venting
flammable gases into the atmosphere.
6 Acknowledgments
The study was carried out with state support from leading scientific schools Russian
Federation, grant No. NSh-2553.2020.8.
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