TECHNIQUES AND EQUIPMENT FOR INFORMATIZED VERIFICATION OF THE CHAIRS WITH BALLS TIGHTNESS AT THE DRILLING PUMPS Abstract Author: PhD Eng. Aurel ZAPCIU INSTITUTUL NATIONAL DE CERCETARE DEZVOLTARE PENTRU MECANICA FINA Şos. Pantelimon nr. 6 8, sector 2, 021631, Bucureşti, ROMÂNIA E-mail: incdmf@incdmf.ro ; cefin@cefin.ro; The equipment for verifying the chair with balls tightness is based on the pressure modification in a close system formed by the chair with balls, electronic vacuum meter with pressure sensor and electro valve. To consider a tight system it must maintain a constant measured vide of 0,64 bar, for min. 3 seconds. The working cyclorama must provide the tightness measurement in 3 different positions of the ball on the chair. The chair with ball is considered of a good quality if in the 3 positions the tightness is assured. The system for verifying the chairs with balls tightness is including: system to produce the vide with filter and the afferent electro valves box for automate with programmable automate for realizing the tightness measurement cyclorama frame in modular construction from Bosch type profile 30 x 30 mm acquisition and data registration system switches, wires The economic efficiency of applying the research results are within the strategic field represented by the oil industry, of efficient valorizing of the oil resources, the work productivity in the field. The quality of the chair with balls is responsible for the productivity in the field of oil extraction, by using new materials (cms), are reduced the tenses for un programmed stops with 40 50%, thus improving the production. It is considered that the equipment development is good both for the chairs with balls made of cms producer and for the beneficiaries of these products: improve the products quality realized by eliminating the rejects possibility of export offers improve of the (?) with 20% important decrease of the pollution with oil products by improving the tightness of the chairs with balls. Content In the last decades because of the development of the field of the hard and extra hard materials had been imposed the achievement of the chairs with balls from the drilling pumps made of sintered metallic carburets, very resistant to mechanic and chemical wear. They were realized because of successful use of the finishing by the help of the materials based on synthetic diamond powders in lapping and smoothing technologies. 312
Improving the tightness of the chairs with balls made of sintered metallic carburets provide the elimination of the un programmed stops at the drilling and pumping equipments improving the output in exploiting and work productivity at the oil platforms. At the world wide level lately appears the tendency of developing some sintered materials with reduced density opposite to the conventional ones based on wolfram carburets. Above the reduced density, these materials present other improved characteristics too resistance at high temperature, resistance at corrosion and abrasive and erosive wear and made possible their use both in processes with dynamic intensive solicitations or wear in the energetic, nuclear, military, etc. field. The chairs with balls realizing these characteristics include a high content of titanium carburet. Chairs with balls are high technical constructive elements, solicited in the oil industry, both by the producers of extraction, deep pumps and by their users, mainly the oil extraction platforms. At the extraction equipments, the sintered metallic carburets (cms) are parts of a sub ensemble with functions of unique sense valve (fig.1), within the extraction pump. Fig.1 Chair with ball From the above fig. are remarkable the precision and the very high level of processing, geometrical conditions very difficult to achieve. For the tightness trial it is taken into consideration the achievement of a method and techniques corresponding to the internal and international standards because of the addressed field. The British standards taken in this field are: SR EN 1779: 2002/A1: 2004 Tightening trial. Criteria for chousing the method and the technique SR EN 13184: 2003/A1: 2004 Tightening trial. Method by pressure variation SR EN 13185: 2003/A1: 2004 Tightening trial. Method with tracer gas SR EN 1593: 2002/A1: 2004 Tightening trial. Technique by emission of bubbles. Chousing one or another of the quantity and quantity verification and measurement tightening techniques is made taking into consideration the device we want to verify concrete case. 313
Tightness is determined by measuring the gas lose rate. For a gas (air) the tightness may be convenient expressed by the pressure in specific time conditions. For tests, the tightness lose may be expressed as a flow rate in units of lose gas ( Pascali.mc3/s).in specific temperature and pressure conditions. For example a pressure lose rate of 5 x 10-4 Pa.mc/s Pa.mc./s is accepted for the compressed air in the cylinder of a compressor corresponds to a pressure variation of 5000Pa in a volume of 10 I in 24 hours or 0,5 I lost measured at atmospheric pressure. A rate of lose of10-10pa.m3/s is normal for a cardiac stimulator corresponding to lose of1 cm3 at 30 years. The following factors have the greatest importance in tightness: the gas nature and pressure the working temperature The testing gas mass is determined from any point of the application with the law of the ideal gas m pv = M RT pmv m = RT MV m = RT ( p-p V (T)) Where V free intern volume, m3 R gas universal constant, J/mol.0K P Pascali total pressure pv(t)- T) partial steam pressure, in pascali, at T temperature in in orig m uncondensed gas total mass, in kg M test gas total mass, in kg/mol T test gas temperature, in 0K M` - test gas mass, in kg. The mass lose is: (1) where sub scriptures 1,2 refer to the test gas at the beginning and at the end of the test taking into consideration the relative humidity, the water vapors may be considered behaving as an ideal gas and thus the above expression becomes: (2) 314
Where n is the moli number The flow rate becomes Vs = n. R. T p m, cu n = M (3) where t is the test time the flow rate, expressed as loss percentage (mass, pressure) (4) According to the above expressed the mass tightness loses may be expressed as pressure loses. The standard describes the techniques determining the flow rates along the edge of an isolated part under different pressures. Techniques are based on evaluation the gas mass change from the tested part. Changing the part volume (because of the temperature and pressure changes during the test) should be taken into consideration. Even so, in some industrial applications this variation is so small that it could be ignored. Thus the big part, the main part of this standard considers the volume as being a constant during the test. The ideal gas equation determines the relation between mass, pressure, temperature and gas volume included in the inside free volume of the part. In certain circumstances one or more variable may be constant thus changing the mass may be, deduced by monitoring the pressure or the pressure change the temperature within the tested part. The chair with bolls tightness test will be made at the ambient temperature, the temperature variation will be ignored. To test the tightness using the tracer gas method is rather difficult to apply because of the high expenses connected to the necessary devices, mainly the sensible device for the gas teaser (mass spectrometer) placing it on the opposite side of the controlled part edges. Because the tightness must be measured in 3-4 positions of the ball on its chair, it must be rotated this means that the access to the ball should be free. The tightness test using the emission with bubbles method is considered more a qualitative trial having the same disadvantages as the method with teaser gas method; the part is in immersion in the test liquid. This method difficult to be used because of the need of verification the tightness of the ball in different positions. Studying the verification method of the chair with balls it is noted that the easiest method to be used is the pressure variation method. In usual test conditions the temperature difference during test is ignored because of the short vacuum maintaining time thus temperature is considered constant. 315
The used gas is the air which in the provided purification conditions may be assimilated/compared with the ideal gas thus we may apply the thermodynamic calculation formulas. The pressure difference to the chair - balls ensemble do not provide deformations that may affect the parts shape and contribute to the wrong interpretation of the results. The installation for verifying the tightness of the chair with balls is based on the pressure modification in a closed system formed by the chair with balls, the electronic vacuum meter with pressure sensor and electro valve. To be considered tight to system must maintain constant a measured vide of 0,64 bars, for min. 3 seconds. These parameters pressure and time respect the American standards in the field API 11 AX, used by the most important oil equipments producer COOPER CAMERON, standard adopted by PCC Sterom SA Campina, one of the users of the installation verifying the tightness. The accomplishment of the working cyclorama/timetable is made with a programmable automate and data recording is made with paper belt. The timetable must provide the tightness measurement in 3 different positions of the ball on the chair. The chair with balls is considered admitted from the qualitative point of view if in the 3 positions the tightness is provided. Technical characteristics: the system must provide tightness to a vide of 0,64 bars vide maintaining time 3 seconds automation with programmable automate vide measurement with electronic vacuum meter data record on paper belt. The system for the chair with balls verification (fig. 2.1) is composed of: system of producing the vide with the afferent electro valves and electronic vacuum meter (1) automation box with programmable automate for providing the tightness measurement timetable with acquisition and data recording system (2) modular designed frame made of profile type Bosch 30 x 30 mm. (3) When starting the system the electro valves are in normal closed position. In the first phase/stage is opened the isolation electro valve (4) and starts the vacuum pump (6 fig. 3). When the required vacuum is achieved 0,64 bari, the vacuum sensor from the vacuum meter control the closure (4) and the opening of the electro valve (3) by the programmable automate from the automation box. After 3 seconds temporization the pressure on the vacuum meter id red and is recorded on the paper belt. It is opened (4) and the ball is rotated on the chair in another position. Thus are processed 3 different positions of the ball and if during the 3 measurements the pressure is not modified, it is considered that the chair with ball provides the tightness. 316
1 2 3 Fig.2. Installation for the chair with balls verification For a good visibility the vacuum meter is fixed on the base plate near the verified chair with balls (fig. 3) 1 2 3 4 5 6 Fig. 3 1- connecting piece between the vacuum path with vacuum 317
meter and the chair with ball 2- hard wire made of pvc 3- electro valve for air 4- electro valve for isolation 5- filter 6- vacuum pump type RL2 capacity 35 I/min, engine 0,16 Kw, supply 220 V Electro valves are normal closed type, acting by magnet type solenoid with answering time 10 ms. 1 2 Fig. 4 The base plate with the chair with balls and electronic vacuum meter 1. ensemble chair with balls 2. electronic vacuum meter with ball type DP2, measured pressure 0-100 kpa and connecting thread with vacuum inside 1/8``, supply 12 Vcc. Technical characteristics of the installation Constructive characteristics of the verified parts: material: cms, sorts for the parts wear (G30; NG15); dimensional range: Ø 19,05 Ø 42,88 mm; execution precission: tolerances: ± 0,015 mm round deviation: 0,250 1,000 µm surface quality: Ra < 0,025 10-3 mm. 318
Characteristics of the technological parameters for verification: verification vacuum at tightness 0,64 bari vacuum maintaining time 3 seconds, the ball is verified in min. 3 positions Constructive characteristics of the product: Mechanical characteristics: Vacuum achievement: with the vacuum pump capacity 35 I/min., for a vacuum of 15 microns (0,020 mbar) Mechatronic characteristics: To control the vacuum: vacuum sensor with measurement precision 0,1% electronic vacuum meter with display for temporization programmable automate controlling electro valves 1 2 3 4 Fig. 5 Inside of the automation box 1. registering device type TRM10C for data registration on paper belt 2. fuses 3. programmable automate 4. electronic relay 319
CONCLUSIONS The equipment achievement for verifying the chair with balls tightness from the oil extraction pumps may be used for verifying the tightness of different closed inside arias using the same soft. The economic efficiency of applying the research results are of strategic interest represented by the oil industry, by efficient use the oil resources, by the work efficiency in this field. This device is unique, it was achieved by using the top technique, it eliminates the operator intervention in reading and interpreting the results. Bibliography SR EN 1779: 2002/A1: 2004 Tightening trial. Criteria for chousing the method and the technique SR EN 13184: 2003/A1: 2004 Tightening trial. Method by pressure variation SR EN 13185: 2003/A1: 2004 Tightening trial. Method with tracer gas SR EN 1593: 2002/A1: 2004 Tightening trial. Technique by emission of bubbles. RS/18.08.2008 320