CAUT

Recently I have come across three Hidrau benches with a noise problem when adjusting up or down. All are in piano teaching studios and get a lot of use. The noise is best described as a metallic scraping sound. All three of these benches also have worn bench top coverings that are flaking off in fine particles. I believe it is possible that some fine particles from the worn top have found their way into the pneumatic system thus creating the scraping sound. One of these benches is particularly loud. I contacted Hidrau and was told they have not heard of this problem.

Hidrau does acknowledge the worn top problem and will sell a new top if the customer wishes. For now, all three benches have fitted covers over the top. They believe that the recent upswing in deteriorating bench tops is due to the use of antibacterial solutions used during the pandemic. 

Has anyone observed this scraping noise and if so, were you able to eliminate the noise? Hidrau suggested I try a little bit of WD-40 Specialist White Lithium Spray. I am a bit concerned about using this spray but may try it is no other good solution comes along.

WD-40 Specialist Protective White Lithium Grease Spray with SMART STRAW SPRAYS 2 WAYS, 10 OZ 

We have hundreds of these benches at Juilliard. I've been applying TFL-50 wet between the posts, and that has helped keep them returning (up) when they got slow or stopped returning. We haven't had scraping noises though. The other spot where TFL50 helps is where the adjustment lever pivots under the seat. This frees the lever to return readily.

Thank you David and Mario. I will try one or the other lubricant when I have the opportunity.

I would be careful about mcLube444 in this application. Its solvent is extremely aggressive and might eat the seal on the pneumatic cartridge. But I have no idea how it all looks inside and whether the seal is vulnerable, just that spraying a lubricant helps.