JÄGER Busi­ness Blog

Seal­ing tech­nol­o­gy: Sev­en tips for
ana­lyz­ing the frame­work conditions

03.11.2021   |   Bas­t­ian Wondratschek 

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Seals are often con­sid­ered a means to an end in design. Yet the design and selec­tion of rub­ber or plas­tic seals can be high­ly com­plex. There are a lot of fac­tors that affect the per­for­mance and life of a seal, and if it is designed incor­rect­ly, it will fail soon­er or lat­er. Under cer­tain cir­cum­stances, this can dam­age the machine or sys­tem in which the seal is installed.

To pre­vent this, it makes sense to take a detailed look at the gen­er­al con­di­tions before select­ing or devel­op­ing a seal. The fol­low­ing sev­en ques­tions will help you with this analysis:

1. What are the pre­vail­ing oper­at­ing temperatures?

The oper­at­ing tem­per­a­ture is one of the most impor­tant gen­er­al con­di­tions in seal­ing tech­nol­o­gy. If a com­po­nent is oper­at­ed out­side its opti­mum tem­per­a­ture range, its phys­i­cal prop­er­ties may change. This applies to both down­ward and upward deviations.

The tem­per­a­tures to which a seal is exposed depend on sev­er­al fac­tors, e. g. the ambi­ent tem­per­a­ture. Here, the room or out­side tem­per­a­ture plays a role, but also the con­di­tions inside a machine or sys­tem. For exam­ple, the tem­per­a­tures inside an engine are dif­fer­ent from those out­side the vehi­cle. The tem­per­a­tures of the media with which the seal comes into con­tact should also be tak­en into account. For exam­ple, a pipe that trans­ports water vapor can become very hot, regard­less of its location.

There is also the ques­tion of tem­per­a­ture fluc­tu­a­tions. Is the tem­per­a­ture con­stant or do peaks occur? Espe­cial­ly fre­quent changes between hot and cold can dam­age a seal in the long run.

2. Which sub­stances does the seal come into con­tact with?

The chem­i­cal resis­tance of a seal depends on the mate­ri­als with which it comes into con­tact. On the one hand, the sub­stances that have a per­ma­nent effect on the seal must be tak­en into account (as a rule, these are also the sub­stances against which the seal is to be sealed), for exam­ple acids, bases, gaso­line or sol­vents. On the oth­er hand, design­ers should also con­sid­er sub­stances with which the seal only comes into con­tact tem­porar­i­ly, such as clean­ing agents or disinfectants.

It is also impor­tant to note that the con­tact media can influ­ence the tem­per­a­tures to which the seal is exposed. For exam­ple, if a machine is reg­u­lar­ly cleaned with hot steam, all its com­po­nents must be resis­tant to heat and steam, even if this is not rel­e­vant throughout.

3. What kind of mechan­i­cal stress­es act on the seal?

With regard to the mechan­i­cal prop­er­ties of a seal, it is impor­tant whether it is sub­ject­ed to sta­t­ic or dynam­ic stress­es. For exam­ple, a flat seal at rest must meet dif­fer­ent cri­te­ria than a bel­lows seal that is con­stant­ly in motion. The inten­si­ty of the stress should also be tak­en into account in the design con­sid­er­a­tions. For exam­ple, does the seal have to with­stand slight move­ments or is it exposed to strong vibra­tions? This will affect the seal mate­r­i­al, as well as the opti­mum shape of the component.

4. Is the seal intend­ed for out­door use?

Machines that are oper­at­ed out­doors are exposed to UV radi­a­tion dur­ing the day and often to ozone pol­lu­tion in the sum­mer months. Both of these fac­tors neg­a­tive­ly impact the life of many rub­ber and plas­tic com­pounds. There­fore, if the seal is intend­ed for out­door use, care should be tak­en when select­ing the mate­r­i­al to ensure that it is resis­tant to UV light and ozone.

5. Is it a vis­i­ble part?

If a seal is locat­ed inside a machine or sys­tem, its appear­ance is usu­al­ly sec­ondary. How­ev­er, if it is a vis­i­ble part, aes­thet­ic fac­tors may become rel­e­vant depend­ing on the appli­ca­tion. This includes, but is not lim­it­ed to, gap dimen­sions, dis­col­oration, and visu­al effects result­ing from the man­u­fac­tur­ing method. Here are some exam­ples of unsight­ly features:

All these are pure­ly opti­cal fac­tors that have no prac­ti­cal effect on the func­tion of the seal. Nev­er­the­less, they should be tak­en into account in the design, because the aes­thet­ics of a machine or sys­tem can be quite rel­e­vant. This applies in par­tic­u­lar to objects that are seen by customers. 

Water­jet cutting

6. Are cer­tain cer­ti­fi­ca­tions or approvals relevant?

Seals used in the med­ical and food indus­tries in par­tic­u­lar must meet strict require­ments, cer­ti­fi­ca­tions and qual­i­ty stan­dards. This pri­mar­i­ly affects the choice of mate­ri­als. Under no cir­cum­stances may a seal release harm­ful sub­stances to food or med­i­cines, regard­less of the envi­ron­men­tal fac­tors. In some sce­nar­ios, it makes sense to man­u­fac­ture seals from detectable mate­ri­als so that detached par­ti­cles can be iden­ti­fied and removed more eas­i­ly if necessary.

7. What quan­ti­ties are needed?

The planned quan­ti­ties of a seal are pri­mar­i­ly rel­e­vant to the type of pro­duc­tion. In the case of small pro­duc­tion quan­ti­ties, it makes sense to cut the mold­ed parts by plot­ter or water­jet. If the quan­ti­ties increase, on the oth­er hand, tool-based process­es (e.g. punch­ing) make more sense. The break-even point depends on geom­e­try and mate­r­i­al and must be deter­mined indi­vid­u­al­ly. How­ev­er, the envis­aged quan­ti­ties should be tak­en into account ear­ly on in the prod­uct devel­op­ment process so that the seal can be designed to meet pro­duc­tion requirements.

Con­clu­sion

The devel­op­ment and selec­tion of a seal is much more com­plex than it appears. Many fac­tors play a role, from the ambi­ent tem­per­a­ture to mechan­i­cal stress­es and pre­scribed cer­ti­fi­ca­tions to the appear­ance of the com­po­nent. All these aspects must be tak­en into account when select­ing or devel­op­ing a seal. It is there­fore impor­tant to car­ry out a detailed analy­sis of the frame­work con­di­tions at the beginning.

Whitepa­per:
Secure the Start of Production 

Learn which fac­tors influ­ence your SOP! 

Author: Bas­t­ian Wondratschek

Bas­t­ian Won­dratschek has been part of Jäger’s sales team since 2019. The trained whole­sale and for­eign trade mer­chant orig­i­nal­ly comes from the steel indus­try. As a sales rep­re­sen­ta­tive he is respon­si­ble for cus­tomer ser­vice at our Stuttgart location. 

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