NAERINGSPH-Nærings-phd

Pin bolts are mostly used to allow relative motions between two bodies, for instance in an excavator or a crane. Traditionally, such pin bolts have cylindrical shape and are secured against rotation by using, for example, a locking plate. To insert such cylindrical bolts without interference, the diameter of the bolt must be less than the diameter of the hole when inserted, which is typical for most heavy-duty machinery due to being low cost joining methods and therefore widely used in the industry. An improperly designed joint will not only have slack that fails to transmit forces/torques, but also cause wear and tear that lead to increased maintenance costs and reduce the service life of the whole system, including loss of human life. Slack occurs because of the bolt being smaller than the mating surface due to either contact surface wear or due to too small interference fit between the parts. The PIN joint of Bondura® Technology is an innovative solution intended to eliminate the slack at the contact surface of the pin joint of heavy-duty machinery such as in offshore installations and hoisting/lifting machinery. In this product, clamping force is induced by tightening bolts that push a conical sleeve along the pivot pin and creating a press load on the internal surface of the assembly. Compared with the conventional press or shrink fit, Bondura® PIN joint offers distribution of the load over larger contact surface and eliminates the wear problem due to ovality. This also results in an easier installation and retrieval process, and an all-over safer pin solution. However, the effect of this PIN joint requires further investigation when used in different machines and under different operation conditions. Thus, this research work is intended to document the effects on the equipment itself, on the bolts and the users? experiences, when operating various heavy-duty machines applying cylindrical bolt/expanding PIN joints. The study will focus on both customer survey, analysis, and experimental work.

Expanding pin solutions of various types and shapes have been commercially available for use in machines, cranes, and different equipment for around 30 years, but they are still not as well-known and comprehensively applied as the case in more standard cylindrical pin solutions. There are currently 2 – 4 companies on the global arena supplying such specialized pin solutions, in addition to several smaller companies supplying to their local or national marked, or to their own use in own machines. This PhD study has focused on the effects and consequences of applying expanding pin solutions in heavy machinery, and the theoretical background, research methodology, and results are presented in nine published papers. The results from the questionnaire-based survey (Specific objective (i), and RQ1 and RQ2), with corresponding discussions, were presented in Chapter 4.2.1, based on responses from stakeholders with some, or comprehensive, knowledge and experience with one or more types of expanding pin solutions. The majority, or 85 % of the respondents, stated that the economic impact of use of expanding pins compared to standard pins was important or very important for them and their clients. The results regarding the studies of traditional expanding pins (Specific objectives (ii), and (iv), and RQ3), with corresponding discussions, were presented in Chapter 4.2.2, which is based mainly on experimental tests. It could clearly be observed that when applying an expanding pin in a radial spherical plain bearing, the rotational moment needed to turn the outer ring relatively to the inner ring was considerably reduced, compared to the lowest torque value, for all values of external load. This effect happened for all torque values for the configuration with two expanding sleeves on one bearing, and for all torque values except the highest for the configuration with one expanding sleeves on one bearing. The results regarding the studies of newly developed pin solutions (Specific objectives (iii), and RQ4), with corresponding discussions, were presented in Chapter 4.2.3, which is based mainly on experimental tests. A pin solution which combined preloaded and expanding pin capabilities was investigated and showed interesting results. The axial preload was achieved by torquing a number of smaller bolts (tightening screws) instead of one bigger nut (as for normal bolt-nut systems), and the radial expanding locking was achieved as for “normal” expanding pin solutions, with axially cut sleeves. It can be concluded that the expanding pin system in general is very well appreciated by those who have experiences with it, and it has an important economic impact, both when it comes to safe handling the pins and during operation and repairs of machines and equipment. This pin solution can improve the functionality of a bearing, reduce downtime due to repairs, increase shear capacities of flanged connections, and eliminate self-loosening of bolts.

Bondura har utviklet teknologi som gjør bolter selvekspanderende slik at de passer perfekt i ledd og eliminerer risiko som oppstår ved krave om installasjonsklarering for å sikre at bolten kan fysisk føres på plass i ulike ledd. Bolten er konet i formen og det plasseres en innvendig konet hylse i hver ende av bolten. Når man så strammer til endeskruene / mutrene så påføres det aksiell kraft på hylsene slik at disse presses inn på de konete endene på bolten og ekspanderer mot kontaktflatene til den innvendige hullveggen på utstyret. Dermed fyller man hele ringrommet, eliminerer klaringene mellom bolt og utstyr, og dermed unngås slitasjeinduserende bevegelser. Hovedmålet med doktorgradstudiet er å dokumentere og kartlegge de tekniske konsekvensene på utstyr og bolt ved bruk av kil-tilnærmet ekspanderende PIN-løsninger under ulike operasjonelle formål. Vi skal se nærmere på effekten av temperatur, vibrasjoner, slitasje, korrosjon og ulike operasjonelle belastninger. Dette må kartlegges for ettersom denne kunnskapen mangler og er et hinder for videreutvikling av teknologien. Det mangler forståelse av de ulike fysiske påkjenningene som oppstår under operasjonelle forhold ved bruk av ekspanderende PIN-teknologi. Sentrale utfordringer blir hvordan man innhenter kritisk informasjon for å ivareta dokumentasjonskrav og -kvalitet. Dette er grunnen til at tidligere forskning kun gir veiledende konklusjoner. Utfordring blir å finne metoder, teknikker og modeller som tillater måling og analyse av fysiske påkjenninger i 360 graders retning under et utall av ulike operasjonelle forhold. Hvordan kan vi sørge for at dette studie vil resultere i ny kunnskap og konklusjoner som tillater utvikling av virkelighetsnære matematiske modeller som tillater videre analyse, numerisk eksperimentering og tilstandsbasert vedlikehold gjennom operasjonell overvåking?