Reliability prediction of the hottest full hydraul

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Reliability prediction of full hydraulic drilling rig design

Abstract This paper introduces the method of using fuzzy mathematics to predict the reliability of mechanical products and components in the process of new product development

key words: reliability prediction drilling rig chuck

in the drilling rig system, drilling equipment can be divided into power head, drilling rig, mud pump and drilling tower. Drilling rig is the most important equipment for drilling work, which completes the drilling process and tripping process. Due to the different purposes, uses and drilling methods of drilling, the types of drilling rigs are diversified. Full hydraulic rotary jet drilling rig is mainly used in underground engineering construction, which integrates rotary jet and drilling, and completes rotary jet while drilling. The drill is mainly composed of hydraulic system, power head, chuck, lifting mechanism, rotary spray mechanism, walking mechanism, etc., forming a series system. Chuck is an important part, which completes the main processes such as plus and minus pressure drilling, lifting and dropping drilling tools, and strong pulling. There are usually two types of mechanical chuck: normally closed type and normally open type. We use normally closed type, which is mainly composed of chuck shell, piston, Belleville spring, circlip, slip, slip seat and other parts. Among them, the slip is severely worn, and the reliability of chuck components is estimated by using slip, a vulnerable part

1 principle of reliability prediction

1.1 determine the set of factors that affect fuzzy evaluation

technical level, importance, complexity, environmental conditions

1.2 determine the fuzzy membership of each factor

membership refers to reflecting the position and role of each factor in the comprehensive score. It will directly affect the fuzzy evaluation value

1.3 establish a fuzzy relationship matrix

the evaluation set of each factor is recorded as bi= (BI1, Bi2, Bi3, Bi4, Bi5)

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each evaluation has a relative membership, which can be regarded as the standard value of each grade

s= (S1, S2, S3, S4, S5)

the greater the relative membership, the lower the reliability of the unit and the greater the failure rate. There are many methods to determine the degree of membership. Here, the method of expert scoring is used to determine the degree of membership (Table 1)

Table 1 factor evaluation grade table

high technical level, generally low

important degree, generally low

low complexity, generally high

good environmental conditions, generally bad

combined with each single factor evaluation, a fuzzy relationship matrix R from factor set to evaluation set can be obtained, Record as ri= (ri1, ri2, ri3, ri4, ri5)

1.4 determine the unit comprehensive evaluation score

according to the fuzzy transformation principle, the fuzzy comprehensive evaluation model can be obtained

B=a。 R=(B1,B2,B3,B4,B5)C=B。 St

1.5 system reliability prediction

let the life of mechanical parts be treated as an exponential distribution, and the failure rate of each unit in the system be taken as a constant. (in the preliminary design stage, due to the lack of reliability data, we often idealize and simplify some conditions)

the system is generally composed of units in series (assuming that each unit is independent of each other and the downstream demand of the soft bubble is 444000 tons, and the working time is the same). The system reliability K is equal to the product of the reliability of each unit, that is, k=k1k2k3... Kn (ki= it has broad application prospects in the fields of human-computer interaction system, electronic skin, human motion monitoring system, etc.) e- λ I, λ I= λ。 CI) where, λ I is the unit failure rate, λ Is the failure rate of a known unit, and CI is the comprehensive scoring coefficient of the ith unit

2 specific application in chuck design

the slips in the chuck are vulnerable parts, and the structure of the slips is basically mature. We use the reliability of the slips to predict the reliability of the chuck, so as to predict the reliability of the drilling rig

according to the factor evaluation grade table, first list the fuzzy relationship matrix as follows:

the membership degree is taken as a= (


comprehensive evaluation score (0.450. ( t=0.24

K=e- Σλ I=e-5 λ K=0.89

system reliability C refers to the partial reliability value of the chuck. In order to simplify the calculation, this component takes five main parts: slip, slip seat, Belleville spring, snap ring and piston. The failure rate and comprehensive score of slip parts are taken as the standard for calculation. The failure rate of the five parts is taken as 10% with the slip as the reference. The calculation shows that the reliability of chuck can reach 89%

3 conclusion

due to the limitation of space, this paper only explains the calculation of chuck part, but provides a method for the reliability calculation of the whole machine. In the preliminary design stage of the product, the key to using fuzzy prediction method in the absence of reliability data is to establish the relationship between the reliability of the unit to be predicted and the reliability of the known unit. Although it only provides approximate estimates under ideal conditions, it provides reliability feedback for designers


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