Characterisation of friction and lubrication regimes in premium tubular connections

Abstract

A friction test rig has been developed to carry out repeated sliding friction tests for premium tubular connections. The test rig enables accurate measurement of friction in various contact regimes which are relevant to the threaded connections between tubular components. Higher load tests can simulate the contact in metal-to-metal seals under very high contact pressures by using perpendicular pin-on-pin tests. The contact in the thread loading flank under intermediate pressures can be simulated by using larger radius coupon-on-coupon tests. The measured coefficient of friction is well correlated with a lubrication parameter combining lubricant film thickness and initial surface roughness.

A Simplified Model of Surface Burnishing and Friction in Repeated Make-Up Process of Premium Tubular Connections

“…The results indicated that with asreceived surfaces the initial CoF reduced rapidly in magnitude during the first stroke and then stabilised in subsequent test cycles. This was coincident with a rapid drop in the surface roughness of the initially shot-peened surface, as reported in (6). This trend is similar to that observed in the cold drawing of shot-blasted stainless steel strips studied by Le et al (13).…”

“…To maintain working pressures it is important that the connections are fully sealed by applying the correct torque during the make-up process so that sufficient pre-load is applied to the metal-to-metal seal at the shoulder. This has been investigated in a previous paper by the authors (6). The make-up torque T can be related to the coefficient of friction (CoF) at the interacting surfaces by the well-established equation for power screw mechanisms, eqn (1), which combines a torque component generated by the friction on the loading flank of threads with that generated by contact between the components at the shoulder ( …”

“…10 for a sliding speed of 3-15mm/s. Experimental measurements were taken from two separate tests with ceramic peened surface against plated surfaces under a load which increased linearly to 500 N as described previously (6). Surface measurements were taken after each stroke of sliding.…”

“…A much smaller cross-cylinder friction test rig was developed by the authors to simulate the contact regimes on the threads of a tubular connection (6) and is illustrated in Fig. 3.…”

Tribological properties of nanoclay reinforced polyimide nanocomposite coatings for alloy steels

“…The suspension was deposited on chromium steel substrate and then dried and cured by thermal imidization in oven. The tribological properties of the nanocomposites were examined using a cross‐cylinder sliding test rig developed by the author and his collaborators …”