NON-CONVENTIONAL HIGH PRECISION TECHNOLOGIES FOR INCREASING THE DURABILITY OF THE PETROLEUM INDUSTRY VALVES
cc.71-076/2007
a. Project title: NON-CONVENTIONAL HIGH PRECISION TECHNOLOGIES FOR INCREASING THE DURABILITY OF THE PETROLEUM INDUSTRY VALVES
b. Acronyms: TNIR
c. Project summary:
The valves used in the petroleum industry must comply with severe requirements (i.e. mechanical and corrosion resistance, tightness) specified by international standards. Long-term sealing resistance is the major criterion to select the materials and the surface hardening technologies. The components that affect the tightness of a valve are the valve seat and the valve slider.
The valve sealability is strongly influenced by the working conditions (i.e. corrosive and abrasive environments), that may shorten the life time of the valve. The consequences of the life time reduction are technical, economical and, more then that, environmental. The working conditions mentioned above require a hardening of the working surfaces. Due to severe technical requirments, most of the existing technologies cannot be used since they are not capable to produce high hardness of the treated surface, as requested. On the other hand, the actual technologies affect the valves base material, produce uncontrolled thickness of the deposited material and induce deformations that cannot be corrected after. Because of this, the Romanian manufacturers are sending their components (valve seat and slider) to companies abroad specialized in surface hardening, thus increasing the total costs of the components (the costs of the surface hardening are about 2/3 of the total costs).
The aim of the project “Non-conventional high precision technologies for increasing the durability of the petroleum industry valves” is to solve the existing problems of valve-components surface hardening by implementing a non-conventional technology that will be developed within this project.
The investigations proposed within this project are focused on development, improvement and application of the High Velocity Oxy-Fuel (HVOF) process. This process replaces the external heat source by the kinetic impact energy of the WC particles at supersonic speed. An additional task will be focused on identifying the adequate technologies to control the surface quality requirements as recommended by international standards (less than 0.025 µm). It must be noted that due to the high hardness of the treated surfaces very few solutions exist.
d. General objective and expected results:
The general objectives of the project are:
o The development of the surface hardening for valves components technologies using high precision HVOF method, by assuring the geometrical precision and quality according to existing regulations.
o The development of the surface working technologies in order to obtain the dimensions and tolerances as recommended by existing standards.
o Consolidation the collaboration relationship between the project partners, in order to increase the quality and the efficiency of the R&D activities occurs in these institutions;
o The efficient technology transfer between universities and their industry partners
The specific objectives of the project are:
o The manufacturing of valve components using high precision technology (WC coating and mechanical finishing) at comparable quality as the imported ones, but at lower production costs;
o The design and construction of the fixtures used to hold the valve components during WC coating and mechanical finishing;
o The development of a procedure for the WC coating process using the HVOF technology;
o The development of a procedure for mechanical finishing of the valve components after WC coating using HVOF.
e. Project coordinator institution: Petroleum-Gas University of Ploiesti, Bvd. Bucuresti, no. 39, Ploiesti, 100680, tel. 0244-573171, fax 0244 - 575847, e-mail rectorat@upg-ploiesti.ro
f. Project consortium:
Petroleum-Gas University of Ploiesti - Coordinator
Centre for Research and Eco-Metalurgical Expertise from Politehnica University of Bucharest - Partner 1
S.C. UZTEL S.A. Ploieşti (UZT) – Partner 2
S.C. CAMERON ROMANIA S.A (CAMERON ) – Partner 3
g. Contractor Authority: National Centre of Management Programs
h. Project duration: 36 months
i. Activities and responsibilities:
|
Year |
Phases/ Activities |
Categories of activities |
Project partner |
Terms |
Results |
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2007 |
Phase I. Theoretical studies and researches regarding the identification of the manufacturing and exploitation specific problems of the valves used in the petroleum industry
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15.09.2007 – 15.12.2007 |
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Activity I.1. A world wide critical review of designs, materials and technological solutions used for valve components
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Researches and development activities – A.2. Industrial research |
UPG Ploieşti |
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technological solutions to optimize the seat/gate system, with applications to the specific products of the industry partners. |
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Activity I.2. A critical review of methods and technology to obtain the surface hardening of valve components
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Researches and development activities – A.2. Industrial research |
UPG Ploieşti |
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optimal coating process for the products specific to the industry partners and the key parameters involved in this process |
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2008 |
Phase II. Laboratory researches regarding the hardface of the valve gate-seat assembly
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15.12.2007 – 15.07.2008 |
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Activity II.1. Laboratory testing of WC deposition/coating process |
Researches and development activities – A.2. Industrial research |
UPG Ploieşti |
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fixtures for surface hardening process, small scale specimens and testing procedures to quantify the quality of the results. |
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UPB-CCEEM |
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UZT |
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CAMERON |
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2009 |
Phase III. Full scale researches regarding the hardface of the valve gate-seat assembly
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15.07.2008 – 15.01.2009 |
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Activity III.1. Full scale tests of WC deposition/coating process |
Researches and development activities – A.2. Industrial research |
UPG Ploieşti |
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full scale specimens, coating properties measurements, optimizing of the coating process.
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UPB-CCEEM |
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UZT |
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CAMERON |
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Activity III.2. Writing the report and technical documents for the WC coating process |
Researches and development activities – A.3. Experimental development |
UPG Ploieşti
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technical file for the valve seat and gate, coating procedures of the valve seat and valve gate and control procedure of the products quality. |
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UPB-CCEEM |
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UZT |
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CAMERON |
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2010 |
Phase IV. Laboratory and full scale researches regarding the mechanical finishing of the tungsten carbide layers
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15.01.2009 – 29.09.2010 |
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Activity IV.1. Laboratory investigations of various abrasives to be used for mechanical finishing of coated surfaces
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Researches and development activities – A.2. Industrial research |
UPG Ploieşti |
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small scale specimens and tests, specific measurements, abrasive materials |
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UZT |
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CAMERON |
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Activity IV.2. Full scale investigations of various abrasives to be used for mechanical finishing of coated surfaces |
Researches and development activities – A.2. Industrial research |
UPG Ploieşti |
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full scale specimens, specific testing, determining the optimal parameters of the process.
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UPB-CCEEM |
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UZT |
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CAMERON |
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Activity IV.3. Writing the report and technical documents for the mechanical finishing process |
Researches and development activities – A.3. Experimental development |
UPG Ploieşti |
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procedures for mechanical finishing of WC coated surfaces and control procedure of the products |
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UZT |
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CAMERON |
j. Project budget:
|
Project partner
|
Abbreviated name |
Type of the organization |
2007 |
2008 |
2009 |
2010 |
Total |
||||||
|
B |
C |
B |
C |
Buget |
Credit de angajament |
C |
B |
C |
B |
C |
|||
|
Petroleum-Gas University of Ploiesti - Coordinator
|
UPG |
UNI |
68000 |
0 |
484000 |
0 |
196800 |
0 |
0 |
65920 |
0 |
814720 |
0 |
|
Centre for Research and Eco-Metalurgical Expertise from Politehnica University of Bucharest - Partner 1
|
UPB-CCEEM |
UNI |
0 |
0 |
120000 |
0 |
120000 |
0 |
0 |
11262 |
0 |
251262 |
0 |
|
S.C.UZTEL S.A. Ploieşti – Partner 2 |
UZT |
SACD |
0 |
0 |
0 |
3000 |
0 |
0 |
11100 |
0 |
15900 |
0 |
30000 |
|
S.C. CAMERON ROMANIA S.A – Partner 3 |
CAMERON |
SACD |
0 |
0 |
0 |
3000 |
0 |
0 |
11100 |
0 |
15900 |
0 |
30000 |
|
Total project |
68000 |
0 |
68000 |
0 |
604000 |
6000 |
316800 |
0 |
22200 |
77182 |
31800 |
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k. Obtained results
PHASE I
SUMMARY
The main component which influences the valve tightness and the good operation is gate-seat assembly. The valve sealability is strongly influenced by the working conditions (i.e. corrosive and abrasive environments), that may loosen the sealability and may shorten the life time of the valve. The consequences of the life time reduction are technical, economical and, more then that, environmental. This lead to the necessity of assurance the sealability of the gate-seat assembly by hardfacing the gate-seat contact surfaces using hard materials.
In this phase of the project were performed a world wide critical review of designs, materials and technological solutions used for valve components and a critical review of methods and technology to obtain the surface hardening of valve components.
Researches show that the working surfaces of the valve gate-seat assembly are usually hardface with cobalt base alloys (ex: STELLITE® 6, STELLITE® 12) and tungsten carbide powder in a metallic matrix (ex: 10-12% Co, 4-5% Cr, 4-6% C, rest W). From the harfacing materials used to hardface the working surfaces of the valve gate-seat assembly the tungsten carbide powders presents the maximum performance. The tungsten carbide powders can not be applied by using the welding technologies because the thickness of 0,2 mm imposed to the layers by the international standards require it to be hardface with a very small size granulation and the hardfacing technologies by using the welding process lead to their degradation. Also, when the welding technologies are used, the tungsten carbide powders are dissolute in the parent metal which considerably affects the mechanical characteristics. The welding technologies not allow to obtain the required porosity of the layer (under 1,5 %) and the non-uniform heating and cooling of the pieces lead to large deformation of the pieces and to residual tension.
The hardfacing with tungsten carbides by using the High Velocity Oxygen Fuel Process (HVOF) of the working surfaces of the valve gate-seat assembly have favorable repercussion to the mechanical and physical characteristics of the layer highlighted by: obtain a large density (low porosity) due to high energy impact of the tungsten carbide powders; high corrosion resistance due to low porosity (under 1,5 %); high wear resistance due to the tungsten carbide powders; good bond between the layer and the parent metal due to the improved adherence of the particles applied with high velocity; thickness of the layer is small (min.0,05 mm), and the level of the residual tension are very low, limiting deformation of the pieces. The hardfacing technology by using the HVOF process consists in: surface preparation of the pieces subjected to be hardface, preheating the pieces, spraying process and final heat treatment.
PHASE II
SUMMARY
In this phase of the project the experimental researches were conducted in laboratory conditions. Small scale specimens (experimental models), manufactured by materials used in valve gate-seat assembly construction, were hardfaced with tungsten carbide powders. Experimental researches aimed to put into practice and to verify the results S/T obtained after the theoretical studies made in the first phase of the project, such us: applicability of the HVOF process to hardface with tungsten carbide the materials used in valve gate-seat assembly construction.
For experimental researches were used rectangular pieces having 60 x 30 x 135 mm manufactured by steel grade AISI 410SS-75K (used in valve gate-seat assembly construction). The pieces were hardfaced with powder AMDRY 5843 (sintered tungsten carbide powder in a matrix of cobalt-chrome type WC 10Co 4Cr, having 22 ¸ 62 mm) by using de HVOF process. Experimental researches were made with the hardfacing equipment existent in the Petroleum-Gas University.
The macroscopic, metallographic analyses and the hardness measurements made to investigate the quality of deposition have resulted in a series of conclusions which confirm the applicability of HVOF process to hardface the working surfaces of the valve gate-seat assembly with tungsten carbide powders. The investigations made show the following:
- the layer is continuous across the entire pieces;
- a good bond between the layer and the parent metal is assured;
- in order to be hardface the surface of the pieces must to be very carefully clean;
- the average thickness of the layer is 0,34 mm;
- the porosity of the layer is non-uniform - a large average porosity of 6,6 % with non-uniform distribution (in the superior part of the layer porosity is 1,5 % and in the inferior part of the layer porosity is under 1,5 %);
- three phases are formed in the layer (α, β and γ) - phase α is non-altered tungsten carbide because the chemical composition consists only in tungsten and wolfram, and β and γ phases are chemical compounds on C, Cr, Co and W bases.
- the hardness of the layer is 58…61 HRC;
- the micro-hardness of the layer is 1280…1657 HV0,2.
The results of the macroscopic, metallographic analyses and the hardness measurements indicate that the tungsten carbide (AMDRY 5843) layers obtained by using the high velocity oxygen fuel process fulfill the quality conditions imposed to the valve gate hardfaced with tungsten carbide (final thickness of the layer smaller then 0,2 mm, layer porosity smaller then 1,5 % and minimum hardness of 57 HRC).
The observations and the results obtained in this phase of the project will be use to hardface the full scale specimen (functional model - real size valve gate-seat assembly) in the next phases of the project which will be completed by development of the HVOF technology applied to hardface the valve gate-seat assembly destined to the petroleum industry.
Taking into consideration that in the next phase of the project will be hardface full scale specimen was necessary to design and to construction some installations and devices which complete the HVOF equipment.
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α |
b |
g |
PHASE III
SUMMARY
In this phase of the project were hardface, in the industrial conditions, the full scale specimen (functional model - real size valve gate-seat assembly) by using the process established, to be suitable to hardface the working surfaces of the valve gate-seat assembly, in the Activity I.2. and confirmed by the experimental researches made in the Activity II.1
The experimental researches were made on groups formed by three full scale specimens gate type 2 1/16 7-1 and seat type 2 1/16 7-1. The pieces were manufactured by steel grade AISI 4130. The working surfaces of the valve gate-seat assembly were hardfaced with powder type AMDRY 5843 (sintered tungsten carbide powder in a matrix of cobalt-chrome type WC 10Co 4Cr, having 22 ¸ 62 mm) by using the HVOF gun type 2700DJH, move controlled by the industrial robot type FANUC M-16iB/20.
From the macroscopic, metallographic analyses and hardness measurements made in order to investigate the quality of depositions a lot o conclusions were results, such us:
- the thickness of layer is 545-597 microns, with an average of 567 microns, for seat specimen and 423-461 microns, with an average of 444 microns, for gate specimen;
- the diffusion layer was not observed;
- the layers are uniforms from the point of view of dimensions;
- the porosity of the layer is divided on size classes - under 90 % from pores have areas under 50mm2 (1229 pores for seat specimen and 1272 pores for gate specimen);
- the micro hardness measurement made on the seat specimen indicate 2795 – 2905 mHV100 and the measurement made on the gate specimen indicate1979 – 2815 mHV100;
- at some specimens, was observed a separation of the layer from the parent metal and its cracking in the traverse direction under an angle of 450; this is attribute to the presence of tension in the layer induced in the moment of mechanical finishing of the metallographic sample or induce due to the differences between the contraction coefficients of the layer and the parent metal; the next phases of the project is dedicated to investigate the mechanical finishing of the layer in order to prevent the separation of the layer from the parent metal and its cracking and to prevent the apparition of residual tension.
- the layer consists in polygonal particles of tungsten carbides in a matrix solid solution of Cr-Co.
The observations and the results obtained in this phase of the project allowed to develop and to prepare, in project phase, the following technical documentation regarding the hardfacing technology of valve gate-seat assembly with tungsten carbide by using the HVOF process:
- specifications for valve gate hardfacing (manufactured by steel grade AISI 4130 and AISI 410) with tungsten carbide by using the HVOF process;
- specifications for valve seat hardfacing (manufactured by steel grade AISI 4130 and AISI 410) with tungsten carbide by using the HVOF process;
- operational procedures to control the quality of the hardface layer of the valve gate manufactured from steel grade AISI 4130 and AISI 410;
- operational procedures to control the quality of the hardface layer of the valve seat manufactured from steel grade AISI 4130 and AISI 410;
- operational procedures to hardface the valve gate manufactured from steel grade AISI 4130 and AISI 410;
- operational procedures to hardface the valve seat manufactured from steel grade AISI 4130 and AISI 410;
- operational procedures to control the non-conformity of the product type valve gate made from steel grade AISI 4130 and AISI 410;
- operational procedures to control the non-conformity of the product type valve seat made from steel grade AISI 4130 and AISI 410.
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l. Description/presentation of different events proceeded to the project: -
m. Links to different interested web pages for visitors: -
n. Project manager contact: Prof. PhD.eng. ULMANU VLAD, Petroleum-Gas University of Ploiesti, Department of Manufacturing Technologies and Industrial Management, tel. 0244/575292, fax 0244/57584, e-mail vulmanu@upg-ploiesti.ro
o. Final results of the project.
o development of a non-conventional high-precision technology for WC coating that will assure the mechanical characteristics needed for the working conditions;
o development of a technology to re-work the hardened surfaces (with high hardness) in order to better control the thickness of the deposited WC;
o manufacturing of the valve components (seat and slider) using the above technologies at comparable characteristics with those produced by other companies, but at lower production costs;
o Technology transfer between universities and the two industry partners.