Main­te­nance Mat­ters

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Hy­draulic cylin­ders are re­quired to op­er­ate in a va­ri­ety of ap­pli­ca­tions and en­vi­ron­men­tal con­di­tions, in­clud­ing ex­po­sure to abra­sives, de­bris and both high and low tem­per­a­tures SKF of­fer a com­pre­hen­sive range of fluid power seals made from high qual­ity ma­te­ri­als and with op­ti­mised seal de­signs to meet ap­pli­ca­tion re­quire­ments. Rig­or­ous test­ing in some of the harsh­est en­vi­ron­ments demon­strates why SKF is a mar­ket leader in hy­draulic seals.

The SKF hy­draulic seal range cov­ers all the ma­jor seal­ing com­po­nents in light to heavy duty cylin­ders, with each seal type being de­signed and man­u­fac­tured to SKF’s high­est qual­ity stan­dards.

SKF wiper seals (also known as scraper, ex­cluder or dust seal) are ex­cel­lent at pre­vent­ing con­tam­i­na­tion and ex­ter­nal de­bris from en­ter­ing the cylin­der as­sem­bly. The wiper seal is fit­ted to the ex­ter­nal side of the cylin­der head. The out­side static seal­ing of the SKF wiper within the re­cess of the cylin­der head is im­por­tant to avoid con­tam­i­na­tion en­ter­ing the cylin­der .

Wiper Seal fea­tures:

• Wide range of pro­files, sizes and ma­te­ri­als for a wide va­ri­ety of op­er­at­ing con­di­tions and ap­pli­ca­tions. • Press-in and snap- on wipers. • Sin­gle act­ing and dou­ble act­ing wipers.

The SKF pis­ton seal range main­tains the seal­ing con­tact in a slid­ing mo­tion be­tween the pis­ton and the cylin­der bore. Pres­sure act­ing on the pis­ton seal to ex­tend or re­tract the rod can be in ex­cess of 400 bar (5800 psi) re­sult­ing in the seal con­tact force in­creas­ing dra­mat­i­cally, there­fore the sur­face prop­er­ties of the pis­ton seal are crit­i­cal.

SKF Pis­ton Seal fea­tures:

• Sin­gle and dou­ble act­ing seals. • Wide range of pro­files, sizes and ma­te­ri­als for a wide va­ri­ety of op­er­at­ing con­di­tions and ap­pli­ca­tions. • Low fric­tion de­sign. • Op­ti­mised com­pat­i­bil­ity with op­er­at­ing flu­ids.

In ad­di­tion to the seal­ing func­tion of the rod and buf­fer seals, rod seals are de­signed to pro­vide a thin lu­bri­ca­tion film on the pis­ton rod that lu­bri­cates them­selves and the wiper seal. Ex­ter­nal forces act­ing on the rod can cause pres­sure peaks cre­at­ing the risk of gap ex­tru­sion which can be avoided for rod and buf­fer seals by us­ing SKF anti- ex­tru­sion rings.

SKF Rod and Buf­fer Seal fea­tures:

• Rod seals pro­vide a thin lu­bri­ca­tion film that lu­bri­cates them­selves as well as the wiper seals and in­hibits cor­ro­sion of the pis­ton rod sur­face. • In­te­grated anti-ex­tru­sion ring de­signs. • Op­ti­mised wear re­sis­tance. • Wide range of pro­files, sizes and ma­te­ri­als for a wide va­ri­ety of op­er­at­ing con­di­tions and ap­pli­ca­tions.

Seal ma­te­ri­als play a ma­jor role in the per­for­mance and ser­vice life of hy­draulic seals. Gen­er­ally, hy­draulic seals are ex­posed to a va­ri­ety of ap­pli­ca­tion and work­ing con­di­tions, such as a wide tem­per­a­ture range, con­tact with var­i­ous hy­draulic flu­ids and the out­side en­vi­ron­ment, as well as high pres­sure and con­tact forces. An ap­pro­pri­ate seal ma­te­rial must be se­lected to achieve a rea­son­able ser­vice life and ser­vice in­ter­vals. A wide va­ri­ety of hy­draulic seal ma­te­ri­als from four ma­jor poly­meric ma­te­rial groups is avail­able from SKF: • Ther­mo­plas­tic elas­tomers, such as poly-ure­thane ( TPU) and ther­mo­plas­tic ether- ester block copoly­mers ( TPC). • Rub­bers, such as ni­trile (NBR) and hy­dro­genated ni­trile rub­ber (HNBR), fluoro­car­bon rub­bers (FKM, FPM). • Polyte­traflu­o­rethy­lene (PTFE) and its com­pounds. • Rigid ther­mo­plas­tics and ther­mosets and their com­pos­ites.

The ben­e­fits of us­ing the SKF Hy­draulic Seal range in­clude:

• Im­proved seal­ing per­for­mance. • Ex­tended sys­tem ser­vice life. • In­creased pro­duc­tiv­ity. • Re­duced main­te­nance costs. • In­creased mean time be­tween fail­ures (MTBF). • Op­ti­mised de­sign and de­vel­op­ment of fluid seal­ing sys­tems for cus­tom ap­pli­ca­tions.

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