Differential pressure

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Dif­fer­en­tial pres­sure is al­so re­ferred to as pres­sure dif­fer­ence. The dif­fer­en­tial pres­sure is the dif­fer­ence in the pres­sure curve be­tween two pre­vi­ous­ly de­fined mea­sur­ing points in a sys­tem. The for­mu­la sym­bol for dif­fer­en­tial pres­sure is ∆p and the unit of mea­sure­ment is giv­en in mega­pas­cals (mPa).

Types of pressure

Dif­fer­en­tial pres­sure is one of the three main types of pres­sure that are measured:

  • Ab­solute pressure
  • Dif­fer­en­tial pressure
  • Gauge pres­sure

Calculation of the differential pressure (∆p)

∆p = p1 – p2

How is the differential pressure measured in practice?

Spe­cial mea­sur­ing de­vices are used to mea­sure the dif­fer­en­tial pres­sure. These are equipped with pres­sure sen­sors or manome­ters and give the op­er­a­tor the in­fo when one of these two sit­u­a­tions occurs:

  • The pres­sure at the sec­ond mea­sur­ing point is low­er than the val­ue at the first mea­sur­ing point. In this con­text we speak of pres­sure loss.
  • The pres­sure at the sec­ond mea­sur­ing point is high­er than the val­ue at the first mea­sur­ing point. In this con­text we speak of pres­sure increase.

The gauge does not out­put dif­fer­en­tial pres­sure if the pres­sure at both mea­sur­ing points has re­mained constant. 

Examples of applications in which the differential pressure is collected:

For ex­am­ple, the dif­fer­en­tial pres­sure val­ue pro­vides in­for­ma­tion about the dif­fer­ence be­tween the pres­sure at the in­let and the pres­sure at the out­let of a tool, heat ex­chang­er, pump or fil­ter. A drop in pres­sure is a pos­si­ble warn­ing that there may be a hole or break in the sys­tem. An in­crease in dif­fer­en­tial pres­sure may in­di­cate that there is ad­di­tion­al re­sis­tance in the sys­tem, such as de­bris that builds up over time. 

Unplanned differential pressure

Dif­fer­en­tial pres­sure is an im­por­tant in­di­ca­tor for mea­sur­ing flow re­sis­tance. The un­in­tend­ed in­crease or de­crease of pres­sure in an op­er­at­ing sys­tem has dire con­se­quences on the per­for­mance of the en­tire process. To earn this, faults should ide­al­ly be no­ticed di­rect­ly and elim­i­na­tion should be ini­ti­at­ed. To iden­ti­fy pres­sure dif­fer­ences di­rect­ly, so-called da­ta log­gers are used. They con­tin­u­ous­ly record the pres­sure val­ues at two mea­sur­ing points and en­able ret­ro­spec­tive sift­ing over a large pe­ri­od of time.

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