Part -1:
1. The figure below shows two sample points in a process line.
(a) What is the nature of the process fluid?
(b) What are the objectives of the two sample points and in what way do the samples reaching the instruments differ?
(c) Could the effectiveness of the second sample probe be improved and if so how?
(d) What additional feature would be necessary for the second sample line and why?
Before deciding on a pump to supply a sample, what information must be collected and why?
(a) For what purposes is it important to obtain a rapid response to changes in process stream composition and what methods are used, when designing a sample system, to achieve this?
(b) In the same situations as in (a) above, it is also essential to provide analyser systems which do not break down and which maintain their calibration.
What steps should be taken when designing the sampling system and the installation generally in order to ensure this?
Part -2:
1. (a) Basic physical properties (e.g. density, refractive index and thermal conductivity) can sometimes be useful for analysing the composition of a fluid. In what circumstances can this be done?
2. (a) A measure of refractive index can be used to determine changes in composition of a fluid. Define what is meant by refractive index, and give the relationship between the incident and refracted rays.
(b) A ray of light passes through a material of refractive index 1.5 and then meets material of refractive index 1.3. What is the angle of refraction at the interface between the two materials when the angle of incidence is:
(i) 30°
(ii) 65°?
(c) It is sometimes necessary to measure the refractive index of a fluid which does not transmit light well, or has gas or solids entrained. Describe a method which can be used.
3. (a) On an existing plant, the manager decides that he must know the density of the liquid flowing in part of it; he wishes to use the measurement as a guide to the composition of the liquid. For economic reasons, the plant cannot be shut down. What possibilities are open to him, and what measurements other than density would have to be made; why would they be required and how would the measurements be done?
A diagram of the relevant part of the plant is as shown in FIGURE 2. The density required is of the reactor products; it is not possible to get at the point where it enters the storage tank to draw off a sample.
(b) The level of the contents of a vessel are often measured by using a torque tube with the displacer in an external tube which has its top connection above the maximum level and its lower connection near the bottom. A similar instrument can be used to measure density. FIGURE 3 shows an installation for level. Why would it not be satisfactory for density measurement? If you wished to use this type of instrument how would you install it to give satisfactory measurement?
4. (a) Below is a diagram of a rotating disc viscometer (FIGURE 4). Explain its operations and limitations as to use. If, in a similar works situation, it is necessary to make measurements on a non-Newtonian liquid, what would be a better instrument to use and why?
(b) It is intended to automate the operation of an Ostwald capillary viscometer as shown below (FIGURE 5).It must be automatically fed with a sample, and then the sample viscosity measured at three different shear rates. What additional equipment would be required? Sketch a typical installation and set out the operational steps.
Part -3:. (a) (i) What is the relative humidity of a gas at the temperature at
which dew starts to form? Explain your answer.
(ii) What would be the R.N. if the temperature were lowered a further 10°C? Explain your answer.
(b) (i) Why is a Peltier effect cooler used in dew-point measuring instruments?
(ii) What is the effect of dust deposits on the mirror in dew-point instruments? What means can be provided to compensate for this effect?
(c) What precautions would have to be taken when measuring free water in a liquid? How would the measurement be made?
2. (a) Power stations are often sited near the coast, which allows them to use sea water for cooling in the condensers at the outlets from their turbines. What analysis measurement would be particularly important in this situation and why? How could the measurement be made?
(b) What methods are used to achieve low levels of corrosion by oxygen in boiler feed water? What measurements are essential to ensure that this is done satisfactorily, and what types of measurement could be used?
d) A process vessel has to be shut down in order to do some internal maintenance involving welding. Assuming that it had contained flammable material and that it had been scavenged by a flow of nitrogen followed by air, what measurements would have to be made in order to ensure that the work could proceed safely? Mention any special precautions that would have to be taken.
(e) In a large boiler with several burners, why is it desirable to balance burner performance? What analytical measurements are helpful?
3. Based on your experience, choose an analysis carried out at your workplace. Explain:
(i) what the analysis is
(ii) why the analysis is required
(iii) the method used, together with diagram/description of equipment and process
Part -4:
1. (a) Explain what is meant by 'the law of intermediate metals' relating to temperature measurement using thermocouples.
(b) With the aid of sketches give two industrial situations to which the law in (a) is applicable.
2. A long length of compensating cable is joined as shown in FIGURE 3. The conductors are not touching directly and the connection is made via the connectors themselves. What effect (if any) will the connection have on the accuracy of the system? Give reasons for your answer.
3. (a) With the aid of a sketch describe the construction and principle of operation of a total radiation pyrometer.
(b) Explain how the following parameters affect the total amount of radiation which is emitted from a hot object :
(i) object temperature
(ii) object surface area.
(c) Explain why the emissivity of a black body is equal to I.
Academic requirements:
• Your work should be submitted in the formats outlined for each question in the assignment