Great Hysys Training material

Internet is always a great place to learn. One of the interesting manual available to learn hysys especially for young engineers is:

HYSYS: an introduction to chemical engineering simulation for UTM Degree++ program

The book is written by Abd Hamid, Mohd Kamaruddin for University Technology Malaysia/
Below is the extract obtain from UTM website
Abd Hamid, Mohd Kamaruddin (2007) HYSYS: an introduction to chemical engineering simulation for UTM Degree++ program. Manual. Universiti Teknologi Malaysia. (Unpublished)

                               Click the link to download the tutorial manual.
 
 
Also click Aspen and Hysys tag  for more information.

 

Abstract

HYSYS is a powerful engineering simulation tool, has been uniquely created with respect to the program architecture, interface design, engineering capabilities, and interactive operation. The integrated steady state and dynamic modeling capabilities, where the same model can be evaluated from either perspective with full sharing of process information, represent a significant advancement in the engineering software industry. The various components that comprise HYSYS provide an extremely powerful approach to steady state modeling. At a fundamental level, the comprehensive selection of operations and property methods allows you to model a wide range of processes with confidence. Perhaps even more important is how the HYSYS approach to modeling maximizes your return on simulation time through increased process understanding. To comprehend why HYSYS is such a powerful engineering simulation tool, you need look no further than its strong thermodynamic foundation. The inherent flexibility contributed through its design, combined with the unparalleled accuracy and robustness provided by its property package calculations leads to the presentation of a more realistic model. HYSYS is widely used in universities and colleges in introductory and advanced courses especially in chemical engineering. In industry the software is used in research, development, modeling and design. HYSYS serves as the engineering platform for modeling processes from Upsteam, through Gas Processing and Cryogenic facilities, to Refining and Chemicals processes. There are several key aspects of HYSYS which have been designed specifically to maximize the engineer’s efficiency in using simulation technology. Usability and efficiency are two obvious attributes, which HYSYS has and continues to excel at. The single model concept is key not only to the individual engineer’s efficiency, but to the efficiency of an organization. Books about HYSYS are sometimes difficult to find. HYSYS has been used for research and development in universities and colleges for many years. In the last few years, however, HYSYS is being introduced to universities and colleges students as the first (and sometimes the only) computer simulator they learn. For these students there is a need for a book that teaches HYSYS assuming no prior experience in computer simulation.

Cause of thermal expansion inside cavity:

 
Cause of thermal expansion inside cavity:
For the floating type/soft seat ball valve, and liquid fluid
1) In case of temperature of fluid and atmosphere has some increasing(for example""water: 30°C"", depends on fluid), and valve not operated for the time of increasing temperature,"
2) In case of valve position is "Full Open" for the time of increasing temperature,
3) In case of valve position is ""Full Close"" for the time of increasing temperature and differential pressure between upstream and downstream is below 0.98MPa,
4) In case of operation frequency is little and ball seat is new,
The above conditions are happened more than 2subjects, fluid inside body cavity(inside pocket) is increased pressure by thermal expansion. This condition is called "Thermal Expansion Inside Cavity".
 
Thermal Expansion inside Cavity is happened other problems as followings.
1) Operation torque is increased suddenly, and happened operation problem for on-off valve and manual valve.
2)There is possibility to get damage for seal parts.
3)There is a possibility to get damage for valve body. (especially for cast iron body.)

 
In order to avoid thermal expansion in cavity:
1)Making a hole (bypass) body cavity to valve port. (For the time of increasing temperature and valve position ""Full Open"", body cavity and port is same pressure condition.) Standard Spec. for HF5 model."
2) In case of increased temperature, valve position "full open" and fluid pressurizing direction 1-way,
1. make a relief groove on ball seat at upstream side.
2. make a hole on ball face at upstream side pass to port.
3) In case of increasing tempertaure, valve position ""full close"" and fluid pressurizing direction non-fixed, valve should be used Trunnion type ball valve."


 
Reference:
http://www.hisaka.co.jp/english/valve/techDoc/techDoc08.html

Diaphragm seals in chemical/ petrochemical / offshore plant /facilities

Diaphragm seals, also known as chemical or remote seals, are used for pressure measurements when the process medium must not come in contact with pressurized parts of the measuring instrument.

Example of diaphragm seals used in measurement of dp across a filter.
Image source: http://www.aplisens.de/produkty/pdf/APRE-2200.pdf
Diaphragms are used in:

1. The medium is corrosive. Diaphragm seals protect the pressure measuring element (e.g., the interior of the Bourdon tube) against corrosive medium.
2. The medium is highly viscous and fibrous. Diaphragm seals prevent measuring problems due to dead spaces and constrictions in the bores of the measuring instrument (pressure channels, Bourdon tubes)
3. The medium has a tendency towards crystallization or polymerization. Diaphragm seals will stop the crystallization/ polymerization from reaching the measuring instrument.
4. The medium has a very high temperature. Diaphragm seals and capillaries minimize the effect of high temperatures, reducing high temperature errors in the display of the measuring instrument and averting damage due to heat exceeding the upper limits for the thermal loading of the instrument components.
5. The pressure measuring point is in an awkward position, inhibiting the installation of the measuring instrument or prohibiting the accurate reading of the display. By using a diaphragm seal and a capillary, the measuring instrument can be conveniently installed in a location where it can be easily viewed.
6. Hygienic standards require special requirements. Diaphragm seals remove dead space in the measuring instrument and fittings.
7. The medium is toxic or harmful to the environment. The design of the diaphragm seal helps prevent leakage into the environment.

Advantages of diaphragm seal:

1. Longer service life of the measuring assembly;
2. Lower mounting costs
3. Elimination of maintenance.

Common error during design and installation of diaphragm seal
1)        Failure to use Low Volume Nipples:
Always use a low volume nipple with high quality threads when a nipple is required to connect the diaphragm seal to the instrument. This will help eliminate temperature induced errors and reduce the possibility of fill fluid leakage.
2)        Fill Fluid Vaporization:
The fill fluid can vaporize and destroy the diaphragm seal system if the process or ambient temperatures exceed the capabilities of the fill fluid. The potential for problems increases with high operating temperatures at low pressure ranges. Always ensure the fill fluid will work within the pressure and temperature range of the application.
3)        Improper Filling:
Overall performance of a diaphragm seal system can be dramatically affected by improper filling of the system. The diaphragm may bulge outward or the static pressure exerted by the fill fluid on the measuring instrument may induce gross measurement errors if the system is overfilled. The system may experience a lack of response or non-linear reading if the system is under filled.
4)        Improperly Sized Diaphragm:
The diaphragm seal may not be capable of driving the measuring instrument if the diaphragm is too small. There may be problems with instrument resolution while measuring small pressure changes and the system may be susceptible to temperature errors caused by contraction and expansion of the fill fluid.
5)        Slow Response Time:
Longer capillary lines were used than were necessary for the application, consideration was not given to ambient temperature effects, incorrect fill fluid was specified, or incorrect capillary internal diameter was used. Always consult vendor for assistance in determining the response time of a diaphragm seal system in an application.
6)        Unequal Capillary Lines:
Unequal capillary lines are not recommended for differential pressure instruments since the system may be susceptible to zero shifts resulting from fill fluid expansion and contraction.
 
Reference:

1. http://www.aplisens.de/produkty/pdf/APRE-2200.pdf

Proper location of level-measurement nozzle

 

DETAILED DESIGN of a vessel includes determining the proper locations for level gauge/transmitter nozzles.

Figure above shows what happens when a gauge glass is connected to a vessel containing a vapour and two liquid phases. Assume that equal amounts of a liquid with Sg = 1.0, e.g. water, and a liquid with Sg = 0.5, perhaps oil, gradually flow into the vessel. Assume further that the span of the gauge glass is four feet, beginning one foot from the bottom of the vessel.

As the level of the oil rises, it flows into the glass. As both liquids rise further, water begins to enter the bottom of the glass. This is the state shown in vessel A. Up to this point, the glass shows a true indication of the level of propane in the vessel. Once water enters the glass, the oil is cut off. A constant plug, one foot thick, floats on top of the water. Its level no longer bears any obvious relationship to the actual level in the vessel. This is state shown in vessel B. The only relationship between the vessel and the glass is that the hydrostatic pressure is the same for both at the point where the glass taps into the vessel. A gauge glass is really nothing more than a manometer.

Once the level of the oil rises above the upper tap, it flows into the glass and the two interface levels adjust to the same elevation, as shown in vessel C. The gauge will continue to read correctly as long as its lower tap is in the water and the upper tap is in propane. If either fluid is withdrawn so that the upper tap is in the vapour space, the glass will once again read falsely.

This same analysis applies to any type of level indication based on density. Remember that a DP transmitter only gives a single reading, i.e. differential pressure. Therefore only a single quantity can be inferred. If the instrument is affected by only two fluids, it can yield the correct interface level between the two. If there are more than two distinct phases within the span of the two taps, it will give a reading based on the average densities of all the fluids within its span.

Capacitance or nuclear level transmitters will give similar results in multiphase situations, based on the average dielectric or nuclear absorption constants, respectively.

Question:

How can the process controls engineer be assured that the level readings are meaningful if even a gauge glass can't be trusted?

1. Make the entire vessel out of glass. But, this isn't usually practical.
2. Every section of a gauge glass must have separate taps into the vessel so that each pair of taps has no "hidden" phase floating in between. Either that, or accept the fact that until the interface reaches its "normal" range, gauge glasses and transmitters will read falsely.
3. For proper location of externally mounted level measurement nozzles, ensure that at least one nozzle is located in the top liquid phase and at least one nozzle is located in the bottom liquid phase.

 

Reference:

1. http://www.driedger.ca/ce6_v&t/CE6_V&T.html

1. Chemicalprocessing.com , Best Practices for Level Measurement

Error in bridles level measurement

Why bridles pipe are not accurate when measuring liquid with different density. 

A simple calculation to show error in level measurement by bridles.
Pv + ρoil g H1 + ρwater g H2 = Pv + ρoil g H1* (1)
Pv + ρoil g H1 + ρwater g (H2+ Htap) = Pv + ρoil g(H1* + H2*) + ρwater g Hwater (2)
Equalizing the formula:
ρoil H2* = ρwater H2*
Clearly it is a contradiction since both oil and water density could not be the same, under same temperature and pressure.


Reference:

1. Shinskey, F. G.; Process-Control Systems, McGraw-Hill Book Company.

1. Driedger, W. C., " CONTROLLING VESSELS and TANKS"; Hydrocarbon Processing , 1995.
2. Chemicalprocessing.com , Best Practices for Level Measurement