BLOG: NIP DEWATERING and felt caliper

Back in the 1980’s the performance of press felts was mainly judged by looking at the sheet; nobody really knew what was happening inside the felt once it was running. With the introduction of nip dewatering the felt designers needed more information.

A thick, bulky press felt is not a good thing. At least, not when you are running with nip dewatering. In this blog post I tell a bit more about the relation between nip dewatering and Feltest.


Nip dewatering and felt Caliper


The Caliper Profiler was Feltest’s first product ever. Actually, it was the spark that started the founding of Feltest as a company!

Back in the 1980’s my father, Nick Lensvelt, was a felt application engineer for one of the world’s leading Paper Machine Clothing manufacturers in Europe. In those old days the performance of press felts was judged only by looking at the sheet. After installation, felt properties were no longer measured or monitored; nobody really knew what was happening once the felt was running.


The introduction of nip dewatering

It were also the days that grooved press rolls were introduced: the introduction of nip dewatering! With nip dewatering a new question arose: why do felts have a startup or break-in period? My father has a very analytical background and not only wanted to see WHAT happened with the felt, but he also wanted to understand WHY. The only tools available, the Scanpro© Jetmem and the vacuum level on the Uhle box, where not giving him the information he needed to solve this puzzle.


The first in measuring felt thickness on the fly

He designed an instrument that could accurately measure the thickness of a running felt. With its pistol-like handgrip it drew quite a bit of attention.



With the new information the instrument supplied, it became very clear that the mid-nip caliper is an extremely important felt property. Thinner felts with an optimized base weave had less flow resistance in the mid-nip and once the water was out of the nip, rewetting was no longer an issue. These findings resulted in thinner felts that generated more nip dewatering, less contamination, shorter break-in periods and higher sheet dryness. The productivity of paper machines with nip dewatering increased considerably!


In the early nineties Nick Lensvelt accepted a position with another PMC manufacturer. This new company had no intention to start manufacturing measuring gear as well, so it was agreed that Nick Lensvelt would manufacture it himself and the PMC manufacturer would buy it from him. With his experience from the first model, Nick started sketching an improved version and asked me to do the engineering work. My father and I still had to think of a name for our new established company. I didn’t lose much sleep over that: the instrument is developed for a “felt test”, but then a bit more stylish, so “FelTest” is what it became!


measuring felt


1992: the first Feltest Caliper Gauge

In 1992 we supplied the first instrument to this European PMC supplier and, as they say, the rest is history. Nowadays Feltest has sold hundreds of pieces of the classic Caliper Gauge and today’s Caliper Profiler all over the world. Nick Lensvelt’s bright idea, back in the eighties, for sure contributed to the success of the concept of nip dewatering felts. It enabled him and many other felt application engineers over the world to study the effect of felt compaction and to differentiate compaction from contamination (for more details on this, check out the whitepapers or watch my Papercon presentation).


The Caliper Profiler as foundation of quality measurement today

For me personally, designing the caliper gauge in 1992 was the start of successful cooperation with my dad that lasted over a decade until he retired. It was the start Feltest Equipment BV, today offering a wide range of innovative handheld products to satisfied customers in over 70 countries.


It is Feltest’s mission to drive innovation in Paper Machine Clothing to the benefit of papermakers and PMC suppliers. The measuring gear of  Feltest enables papermakers to make fact based decisions on their Machine Clothing and to get the best possible performance of their press felts and forming fabrics!


This makes the Caliper Profiler for sure the first Product if you want to increase nip dewatering, reduce the break-in period or save on felt washing agents.



Keep on innovating!


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