Bharat Petroleum Corporation Limited (BPCL) is one of the largest state-owned oil and gas companies in India, whose refinery operates 24/7. Offering an insight into the demands of petroleum refining, PLN Murthy and RC Agarawal of BPCL discuss the processes involved and what is demanded from the pump suppliers and their products.
WPI: Please give a brief background about the BPCL refinery.
PLNM: BPCL's Mahul refinery, spread over 454 acres of land at the village of Mahul and was declared open in 1955 by Dr. S Radakrishnan, vice president of India. At that time the plant was designed to refine about 2.2 MMTPA (million metric tons per annum) of crude oil. It was the largest refinery in India then. With this infrastructure, free India took the first step closer to self-reliance.
Bharat Petroleum produces a diverse range of products, from petrochemicals and solvents to aircraft fuel and specialty lubricants and markets them through its wide network of petrol stations, dealers, LPG distributors, lube shops, besides supplying fuel directly to several industries and international as well as domestic airlines.
WPI: Can you throw light on the activities in a refinery?
PLNM: In simple terms, in a refinery we refine crude oil to get a range of products, ranging from the highly volatile fuels like LPG and aviation fuel to waxes and tars. Crude oils themselves come in various grades. BPCL has had the unique distinction of refining a large, probably the largest, variety of crude oils.
Economics of the operation of a refinery demand that it must operate 24/7. The processes are complex. Hence shutting down and restarting one section also requires operations to be carried out in a definite sequence and is time-consuming. Every downtime causes loss of production, which upsets the economics.
WPI: What is the scope of pumping in a petroleum refinery?
PLNM: Pumping applications in petroleum refining can be considered to be of 3-4 major types - process pumps, custody transfer pumps, metering pumps, utility pumps. Actually, most petroleum refineries would have captive power generation also. So, pumps for power generation are an integral part of pumps in petroleum refining.
Nearly 85% of crude oil refined in refineries in India is imported. The transfer duty pumping starts from pumping crude oil from oil tankers docking at jetties, to the storage tanks in the refinery. A refinery of 12 MMT annual capacity like ours has some 2,500 pumps with drive ratings ranging from sub-10 kW to 350-450 kW.
WPI: Among the variety of pumping duties, which pumps would you describe as being critical duty pumps in a refinery?
PLNM/RCA: Column bottom pumps and feed pumps are critical duty pumps in a refinery.
WPI: Of the total number of pumps that you have, what is the proportion of imported pumps and domestic pumps?
PLNM: Almost 98% of the pumps are Indian made. We expect the pump manufacturer to ensure prompt and competent back-up service. That is best ensured by Indian manufacturers. Our experience with Indian pump manufacturers has been quite satisfactory.
WPI: How do you go about the maintenance and servicing of pumps?
PLNM: We do most of the maintenance on our own. Of course we have to have prompt supply of spares from the manufacturers. We seek their technical help also, but only in exceptional cases.
WPI: How many of your centrifugal pumps are compliant with the American Petroleum Institute (API) 610 standard?
RCA: All the centrifugal pumps in process duty service are compliant with the API 610 standard.
WPI: Apart from centrifugal pumps, which other pumps are in operation?
RCA: We have centrifugal pumps for most of the processes.
WPI: Even for fuel firing?
RCA: Yes even for fuel firing we use centrifugal pumps. We have pressurized headers and hence a continuous supply of the fuel is delivered by centrifugal pumps. Two pumps are combined in a unit, out of which one is motor driven and other is turbine driven and we normally use the turbine driven pump with the motor driven pump as standby.
WPI: We understand that normally thermal power stations use screw pumps for fuel firing and that the same would be the case with you too?
RCA: Since the production of fuel oil is done here itself, we don't have too much of storage of fuel. The storage tank is also heated with a steam coil. So the viscosity doesn't fall to those levels that a positive displacement pump will be really required.
WPI: As per our knowledge, BPCL has better capability in handling crude oils than its competitors. Is this true?
RCA: According to me 'capability' is not the right word. But yes, we may have many firsts to our credit. BPCL Is the first company to handle 61 different types of crude, making it one of the most flexible refineries in the country.
WPI: 61 types of crude?
RCA: Yes. But normally we get seven to eight types of crude annually. We have been enterprising, right from the beginning and have hence have not hesitated, when situation demanded processing different types of crude. And we have succeeded too.
WPI: It still sounds interesting that crude oil comes in such a large variety.
RCA: In fact, the variety becomes more with different mixes and combinations.
WPI: What are the end products obtained after crude processing? If our understanding is right, the end products range between two extremes i.e. aviation fuel and tar?
RCA: Yes you are right. The products range from LPG to Bitumen (tar). There are different grades in HSD (high speed diesel), petrol, various grades of fuel oils and tars.
WPI: About 2,500 pumps with drive ratings ranging from sub-10 kW to as high as 350-450 kW - do they require a power source for driving the pumps? Do you get the power from the grid or do you have captive power generation?
RCA: We have captive power generation and also an arrangement with Tat Power for any emergency back-up requirement.
WPI: What is the captive power generation capacity? And how much is the pumping load?
RCA: The captive power generation capacity is 70 MW. Out of this 15 MW is used for compressors, about 40 MW for pumps and the rest for lighting, air conditioning, etc.
WPI: You mentioned the turbine driven pumps. So would the speed be very high over there?
RCA: The speed is around 3000 rpm.
WPI: Today energy conservation is the area of focus for many organizations. What measures has BPCL taken for 'energy conservation'?
RCA: Energy conservation is very important. Whenever we plan to purchase any equipment, we initially conduct a thorough analysis of energy consumed by the equipment or a LCC analysis. Currently we are working on a continuous catalytic cracking reforming unit (CCR), where we are judiciously selecting energy efficient equipments.
WPI: In pumping problems, people speak of cavitation as one problem that is quite challenging. Do you face any such problems in your operations?
RCA: No pump would operate under cavitation. While at the designing stage of the system it is ensured that NPSHa is greater than NPSHr. This is the most important criterion to be fulfilled among other criteria. We do not face any cavitation in the normal running of our plants.
WPI: This is basically a system design problem and not a maintenance problem?
RCA: Yes, precisely. Sometimes we face problems like deposits choking the strainer. The strainer is then cleaned and put in place.
WPI: Refinery pumps have to deal with a host of volatile liquids, which may give rise to entrainment of gas inside the pumps. What are the problems likely to result from this?
RCA: Although the liquids are volatile, we maintain optimum temperature and pressure so that the liquids don't vapourise. So our pumps don't face the problem of gas entrainment which may result in cavitation.
WPI: In your total refinery output, do you produce LPG and other gases?
RCA: Yes we do. LPG is compressed to liquid and then pumped and then there are some other products lighter than LPG such as C3/C4.
WPI: Are LPGs also of different types, for example, cooking LPG, auto LPG?
RCA: Yes, very true LPGs are of different types though they have more or less the same constituents with changes in their proportion composition. We also have a product known as Bharat cutting gas which is a substitute of acetylene.
WPI: What is the difference between CNG and LPG? IS CNG also obtained from an oil refinery?
RCA: CNG comes directly from the well. It is not a product of oil refinery. LPG is obtained after refining the crude.
SLA: In pumping volatile liquids in particular, seals play a very important role, don't they?
RCA: Seals are an integral part of all the pumps. Almost 30% of the failure of pumps is due to failure of seals. We adhere to API 682 for seals and make sure that the seals that we procure are highly reliable.
WPI: Do you have any condition monitoring system installed in pumps permanently?
RCA: In our hydro-cracker unit, feed pumps and amine pumps have condition monitoring systems permanently installed. This has certainly helped us in monitoring and improving the mean time for pump maintenance.
WPI: Does condition monitoring cover both vibration monitoring and temperature monitoring, say, monitoring bearing temp?
RCA: Yes. Today there are technologies such as thermograph, where you can get a thermographic picture of the entire system, showing the temperature of different components simultaneously. But I think temperature monitoring is an issue. However, vibration monitoring often provides adequate condition monitoring.
WPI: Please comment on the recent advances in the pump technology for refineries.
RCA: There has been a lot of technology upgradation in our refinery. We have upgraded the standard of procurement. For example, we insist on API 610 latest edition and it is a must. We also try to achieve a trade-off between reliability and energy efficiency. However, reliability scores over efficiency as ours is a 24-7 operation. Variable speed drives (VSD) are being used for energy efficiency. But VSDs are still in their nascent stage in India.
Actually most of the problem with the energy efficiency aspect is at the design stage itself. Pumps are designed with 'x' energy efficiency but on running, they are found to be '0.8x' efficient. So there is a difference of 20% between design and actual run. But this 20% difference can be eliminated by making some changes post-production; for example by trimming the impeller to the optimum, etc.
WPI: Do you have TDC standards also for pumps as there are for valves? As per my knowledge, TDC norms are very stringent.
RCA: For pumps we insist only on API standards. And we wish to see more and more Indian manufacturers capable of supplying pumps with API standards.
WPI: Would there be applications where compliance to API standards would not be necessary and would not be cost effective?
RCA: Yes API-compliant pumps are costlier. But we have better reliability and it pays in the long run to have a reliable pump.
WPI: Can you comment on the load of the piping system, which as pump has to bear and is specified in API standards?
RCA: Pipe loads to come on the pumps and a pump should be capable of handling the pipe load. Also, alignments can get disturbed during running. This can result in piping loads on pumps. We have found that some pumps will run without any noise at all. You may be standing besides it and yet you will never come to know that the pump is running. It is very silent.
WPI: According to API 610, a pump must have four wearing rings?
RCA: Wearing ring at the front, impeller and casing is a must. Whether to provide a back wearing ring is an issue and of course it depends upon the capability of the bearing to take up the thrust. The balancing hole should also be designed appropriately so that the load on the bearings is minimized.
WPI: For sales and sealing systems, what is the common plan followed in the refinery?
RCA: Plan 11 and Plan 52 for an unpressurised seal chamber are followed. We also have some Plan 53B installations. 53B requires manual interventions The pressure is to be raised every month. But if you see practically, the pressure falls every one or two weeks. So there is increased intervention.
WPI: What is the proportion of imported crude and crude from Bombay High?
RCA: Imported crude accounts for 70% and the rest is procured from Bombay High. Our reliance on Bombay High is decreasing by time, as less and less is available from this source.
WPI: Any more plans for modernization/expansion?
RCA: The BPCL refinery started in 1955 initially with a capacity of 2 MMT. In the past 25 years we have had massive expansions. Today we have modern facilities which help achieve our objective to reduce source emission, improve the product quality to EURO IV standard apart from enhancing the crude processing capability of refinery to 12 MMTPA. We are coming up with a CCR project.
WPI: Please comment on the oil sludge. Howe is it tackled?
RCA: Cleaning tanks by removing oil sludge is really difficult. Though the percentage of sludge in crude is negligible, the amount of crude that is processed is immense. Hence the sludge keeps on depositing over the years. There are two major issues-the sludge is highly flammable and where to dispose the sludge also needs planning. Moreover the tank outage period cannot be very long as our operations cannot be allowed to suffer on account of tank outages. Hence technologies like sludge processing are used for the removal of sludge.
WPI: is waste disposal also an issue?
RCA: We have our own effluent treatment system and we dispose only clear water in the sea.
WPI: How would you rate BPCL Mahul Refinery vis-à-vis other petroleum PSUs and private players like Reliance?
PLNM: For everyone here at Bharat Petroleum's Mumbai Refinery (BPMRs), it is a matter of great pride to be working with one of the most versatile refineries in India that excels in quality, technology, industrial relations, safety, environmental friendliness and operating cost. We can say it with pride that our refinery uses a latest microprocessor based Digital distributed control system (DDCS) and has been accredited with ISO 9002 (Quality Management System), ISO-1400 Environment Management and also OHSAS. The refinery laboratory has also been accredited with the unique distinction of a quality certification from NABL for 'Quality Assurance Laboratory'.
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