SOME ASPECTS OF PRACTICAL BALANCING RIGID ROTORS IN OWN SUPPORTS

The balancing of rotors of fans, pumps, smoke exhausters, blowers (with a capacity of 50...500 kW, with a rotational speed of 950...3000 rpm) in their own supports is carried out most often at industrial enterprises. The effectiveness of this operation is ensured by the implementation of a number of rules, confirmed by practical experience. Some stages of balancing of rotors are considered in the work. A preliminary examination of the mechanism provides an accurate diagnosis and an informed decision for balancing. Correct determination of the angle of installation of the test cargo at various places of installation of the vibration and photo sensor allows reducing the level of vibration and additional loads on the elements of the mechanism during the test run. Controlling the values of the dynamic coefficient of influence during the balancing process allows you to control the change in the stiffness of the base, loosening of threaded connections, which are often the cause of unsuccessful balancing. The above provisions are confirmed by the results of research and practical application.

New Triaxial Connection Safety Factor for Tubular Design

Summary The American Petroleum Institute (API) equation for internal leak of API connections is uniaxial because it ignores axial force and external backup pressure. The ISO 13679 (2002) standard for qualification of premium connections is biaxial at best. It includes tension/compression but ignores backup pressure for both internal and external leak tests. For tubular design, this paper introduces a new fully triaxial safety factor for threaded connections with dependence on thread shear and hydrostatic pressure. Triaxial hydrostatic behavior is modeled with the mean normal stress, and thread shear behavior is modeled with the shear component of the von Mises stress. A leak line for use like the pipe body ellipse is proposed for quick leak assessment. Leak ratings and correlation with finite element analysis (FEA) results are presented for an example case of a 7-in.35-ppf N80 long-thread-casing (LTC) connection. The new triaxial safety factor with two connection constants applies to all types of threaded connections, including tubing, casing, and drillpipe, so long as the two constants are evaluated with appropriate but simple physical tests.

BIOMECHANICAL JUSTIFICATION FOR EXTERNAL FIXATION OF THE PELVIS USING RODS WITH DIFFERENT THREAD HANDS

Background. External fixation devices (EFD) have found wide application in pelvic fractures treating, but it is not always that strength characteristics of these devices make it possible to realize early rehabilitation. Objective. the biomechanical justification for external pelvic osteosynthesis with use of rods having different thread hands on the basis of analysis of the stress-strain state (SSS) of the “EFD – pelvis” system and an experimental study of the strength of threaded connections of different rods and the pelvic bone under the effect of alternate cyclic loads. Materials and Methods. Was analyzed the SSS of the “EFD – pelvis” system verified in an experimental study of the strength of threaded connections of different rods and the pelvic bone under the effect of alternate cyclic loads. Results. Standing on a single basis in the AVF rods with the same thread, there are torques directed in different directions: on the right - clockwise (screwing in), on the left - counterclockwise (screwing out).A change in the thread direction does not lead to change in the moment values, but directions of the action of the moments of force for the left rod will correspond to the direction of its screwing both in the left- and right-sided one-support position. Conclusions. Bar-connected rods with a differently directed thread create a reciprocally interlocking structure, which counteracts self-unscrewing. Such a structure significantly increases the strength of connection of an EFD with the pelvic bone and creates conditions for an effective use of the early rehabilitation of patients with pelvic fractures.

New Triaxial Connection Safety Factor for Tubular Design

The API equation for internal leak of API connections is uniaxial since it ignores axial force and external backup pressure. ISO 13679 for qualification of premium connections is biaxial at best. It includes tension/compression but ignores backup pressure for both internal and external leak tests. For tubular design, this paper introduces a new fully triaxial safety factor for threaded connections with dependence on thread shear and hydrostatic pressure. Hydrostatic behavior is modelled with the Mean Normal Stress, and thread shear behavior is modelled with the shear component of the von Mises Stress. A Leak Line for use like the pipe body ellipse is proposed for quick leak assessment. Leak ratings are presented for an example case of 7-in. 35-ppf N80 LTC. The new triaxial safety factor with two connection constants applies to all types of threaded connections, including tubing, casing, and drill pipe, so long as the two constants are evaluated with appropriate but simple physical tests.

Analiza wpływu dodatku wodoru do gazu ziemnego na szczelność połączeń mechanicznych wybranych elementów sieci i instalacji gazowych

One of the ways to use electrical energy obtained from renewable energy sources is hydrogen production, which produces only energy and water vapour when burned. Adding hydrogen to natural gas and burning it will lower carbon dioxide emission, making this fuel more eco-friendly. Hydrogen added to natural gas can be transported using gas transmission pipelines and can then be provided to industrial and individual consumers via a distribution pipeline network. Due to the much lower density of hydrogen compared to natural gas, it is especially important to maintain the tightness of mechanical connections of network elements and gas installations. This publication presents the results of research carried out at the Oil and Gas Institute-National Research Institute on the influence that adding hydrogen to natural gas has on the tightness of connections of selected elements of gas installations and networks. According to the developed methodology, tests were performed on selected elements of gas networks and gas installations, in which joints were made using differing methods and using various sealing materials. In the case of steel pipes used in gas installations in buildings, joined by means of threaded connections with tightness obtained on the thread, the test samples were prepared with the use of linen hemp with sealing paste, Teflon tapes and threads, and anaerobic adhesives. Samples made of copper pipes were joined with press fittings. Other installation elements - such as flexible hoses, both extensible and non-extensible, and metal hose assemblies - were attached by means of threaded connections with tightness obtained beyond the thread; the sealing material was NBR rubber gaskets and klingerite. The gas network elements were connected by means of threaded connections with hemp and sealing paste, flare fittings, and steel and polyethylene flanges (sealing with a flat gasket made of NBR and klingerite). PE/Steel connectors where also tested. The tests included tightness tests of the prepared samples with the use of methane, and then a mix of 85% methane and 15% hydrogen. The tests on samples with simulated leaks were also performed. Based on the tests and the analysis of the results, it was found that adding the hydrogen to the methane did not cause leaks in the joined elements. In addition, it was found that in the case of leaks appearing in elements of installations or gas networks, the methane-hydrogen mixture flows out faster than methane alone, and in closed rooms this may result in the lower explosion limit being reached in a shorter time.