Project for SIGMA
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8/3/2019 Project for SIGMA
Working and Design Parameters of Mechanical Seals
Basic concept of Mechanical Seals:
Mechanical seal, the one and only effective solution for eliminating leakage purpose, is providedto all the pumps which are dealing with the fluids having hazardous chemical properties
especially for the chemical industries as well as all the industries which are dealing with the fluidthat may be dangerous to mankind and also pollute the surrounding environment. It can be used
in compressors, pumps, agitators, reactors, air-craft, steamers, helicopters etc. In short,mechanical seals are used in all the rotating equipments which are dealing with the fluids.
We had done our project at Sumika Seals Pvt. Ltd. which is manufacturer of mechanical seals. Itis very difficult to design a seal which works at high temperature and pressure with proper
environment control and to maintain the seal at sufficient temperature and pressure to eliminatecrystallization problem. Another problem of maintaining the seal under sufficient fluid while
working and selection of such seals materials which are made for the unidentified workingfluids such as byproduct fluids. Due to above problems, the seal doesnt performing the requiredfunctions and in some cases it might be failed which ultimately affect the functioning of the
pump and increase the maintenance and set-up time for re-installing the seals. So the basic aimof our project is to provide a full-proof solutions and finding the techniques to eliminate such
types of failures and increase the efficiency and productivity also reduce the set-up and waitingtime for modification and changing of mechanical seal. Today many companies, dealing with the
mechanical seals are having the same stated problems and they are also facing many moreproblems other than stated as above.
Detail Description of problem:
The main problems were raised in the company are:
(1) Design problem of seal in special lube system: It is difficult to design a seal at high
temperature and high pressure with proper environment control. In special lube system, gasket ofgear pump was failed due to some design problems and so high temperature and high pressure oil
leaked which might cause serious injury to the working people.(2) Crystallization at low temperature: To find sealing solution for the fluid pumps at the pressure between 17 to 19 Kgf/cm
2and having nature of crystallized below
150oC.Crystallization occurs in the mechanical seals during the working condition due to
chemical properties of the fluid. To maintain the mechanical seal above greater than 150oC is the
headache for all the industries.(3) Dry running: This problem arises while working of the mechanical seal with the pump under
certain conditions .In this, crushing of the seal faces at the time of working of the pump takesplace which leads to mechanical seal failure. At the time of working the pump level falls below
the required level and due to that at the suction side of the pump, seal faces crushes due to lackof fluid.
8/3/2019 Project for SIGMA
(4) Material selection: Wrong material was chosen for the mechanical seal which would beselected for the working fluid as the fluid identity is totally hidden for the company as well as
customer also, in case of mixing the number of fluids in a container. For example: Ammoniaplant, Sulphuric acid plant.
Expected outcome of problem:
(1) Design problem of seal in special lube system:
y Due to design problem raised in the system, which was clearance between casing andgears of pump was increased due to gasket, we suggested to the company that change thedesign of the gasket or change the design of the casing so that pressure oil would not be
accumulate between the seal casing and gasket.
y The heater which was previously fitted outside the siphon pot nearer to the gear pumpthat should be inside the siphon pot so that oil would consume maximum heat in the
siphon pot so less chances of heating too much at the nearest parts of gear pump so thatwe could increase the pump life and eventually the seal would be safe by applying this
solution.(2) Crystallization at low temperature:
y By providing the proper fluid having the specified configurations with proper viscosity, pressure and maintaining the adequate atmospheric temperature, clogging problem willbe eliminated and crystals will not be generated so the mechanical seals will functioning
appropriately with the pumps as required.
y While testing we suggest to the company that, they should maintain the speed, providingthe sufficient and proper lubrication to the seal faces and jacket must be provided as perAPI standards. Thus, after applying these conditions we can save the mechanical seal and
also the life of the mechanical seal will become more.(3) Dry running:
y By providing the adequate amount of fluid in the casing of the pump and also fill theseals with adequate amount of fluid with which we have to work.y Maintaining proper and sufficient amount of lubrications and cooling, grease and fill the
oil cup up to certain limits so that we can protect the mechanical seal.
y If well provide proper API (American Petroleum Institute) plans to the mechanical seals,dry running can be avoided.
y A good way to overcome this problem is to run a recirculation line, which will keep theseal chamber flooded and pressurized around the seal and avoid heat build-up.
y A recirculation line will circulate heat out of the seal chamber. Another way to overcomethis problem is- use a double seal with good lubrication and compatibility Characteristics.Also, pressurize the barrier fluid at least one atmosphere (15 psi 1 bar) greater than seal
chamber pressure.(4) Material Selection:
y We suggest to the company that they should prepare different charts for materialselections for different fluids.
y Before making the mechanical seal, we have to analyze the material for a specific fluid asmaterial selection is directly dependent on the working fluids. For example, SS-316 cantbe used in sulphuric acid. By choosing the right material for the mechanical seal having
the right working fluid.
8/3/2019 Project for SIGMA
y We suggest to the company that first send the material which was supplied by thesupplier to the material testing laboratory and then start the making of the mechanical
seal so that total time consumed by the final seal would be less.
y If the mechanical seal was rejected due to improper material then the work done behindthe making of mechanical seal would be wasted and so to save the overall cost and
increase the productivity the company should have to decide the seal material for theworking fluid.
y The production of the chemical byproducts should be less and should not be harmful andalso shouldnt have any negative property that may cause of mechanical seal failure.
Thus by providing the steps as stated above we have increased the life of mechanical seal as well
as increase the efficiency of the system which ultimately leads to the productivity of thecompany.
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