Innovative vibration damping on truck-mounted concrete pumps with strain sensors

The trend on truck-mount­ed con­crete pumps is for greater reach with less weight. Tech­ni­cal advances at Schwing are cur­rent­ly mak­ing it one of the mar­ket lead­ers in this field. In order to raise oper­a­tor com­fort lev­els on truck-mount­ed con­crete pumps with large booms, the com­pa­ny has launched an inno­v­a­tive vibra­tion damp­ing sys­tem. Schwing, in part­ner­ship with Baumer Elec­tric AG, has devel­oped a new strain sen­sor with an IP69K pro­tec­tion rat­ing and an excep­tion­al­ly broad mea­sur­ing range to pro­vide pre­cise sig­nal­ing of deflec­tions as they occur in the boom.
Since its for­ma­tion in the 1930s, the Ger­man group of com­pa­nies has been design­ing, con­struct­ing and sell­ing pumps, machines and plant equip­ment for the pro­duc­tion, trans­port and repro­cess­ing of con­crete: batch­ing plants, truck-mix­ers, sta­tion­ary and truck-mount­ed con­crete pumps as well as recy­cling plants. Whether con­cret­ing a swim­ming pool in the front gar­den of a fam­i­ly home or real­iz­ing pres­ti­gious pub­lic projects such as the One World Trade Cen­ter in New York, USA, or the third Bosporus bridge in Turkey, the machines and plant are deployed wher­ev­er con­crete is used to pro­vide per­ma­nent sta­bil­i­ty. With six man­u­fac­tur­ing sites and sub­sidiaries or rep­re­sen­ta­tives in more than 100 coun­tries, the com­pa­ny pro­vides effi­cient, reli­able and long-term solu­tions through­out the world. Exten­sive in-house pro­duc­tion capac­i­ty for core com­po­nents guar­an­tees strict inspec­tion process­es and high prod­uct quality.
Truck-mount­ed con­crete pumps of var­i­ous sizes and types are man­u­fac­tured at sites in Herne (Ger­many), Chen­nai (India), and Sao Paulo (Brazil). The mod­els with the longest plac­ing booms are man­u­fac­tured at the SCHWING Group’s Ger­man head­quar­ters. With a new boom dri­ve con­cept, high-strength steel, less weight, and more oper­a­tor com­fort, they are Schwing’s answer to the mar­ket’s increas­ing demands in terms of eco­nom­ics, ecol­o­gy and ergonomics.

Tough construction site conditions

Mod­ern plac­ing booms have a reach of almost 65 meters. With high­ly effi­cient twin cylin­der pis­ton pumps and a pres­sure of up to 85 bar, they pump con­crete at up to 164 m³ per hour. This obvi­ous­ly caus­es vibra­tions in the boom. In order to be able to offer end users improved oper­a­tor com­fort at the end hose, Schwing has devel­oped an inno­v­a­tive vibra­tion damp­ing con­cept which has includ­ed a com­plete revi­sion of the hydraulic ele­ments. A pre­ci­sion trans­duc­er was required which could pick up the elon­ga­tions from the sig­nal boom caused by move­ment of the whole plac­ing boom, and which would then trans­mit the com­mand vari­ables for the vibra­tion damp­ing. A force sen­sor would have to be mechan­i­cal­ly built into the direct flow of forces from the arm and then exact­ly matched to the machine geom­e­try. It was pos­si­ble to sig­nif­i­cant­ly reduce the devel­op­ment effort by absorb­ing the move­ment over the elon­ga­tion. The effect of a force always pro­duces elon­ga­tions in a mechan­i­cal struc­ture. These elon­ga­tions depend on the geom­e­try of the struc­ture to be mea­sured and the mod­u­lus of elasticity.

Customer-specific solution

“We devel­oped a cus­tomer-spe­cif­ic, inno­v­a­tive strain sen­sor in close col­lab­o­ra­tion with Baumer Elec­tric AG which com­fort­ably over­comes all the chal­lenges,” explains Rein­er Vierkot­ten, Senior Engi­neer Con­trol Sys­tems at SCHWING GmbH. “The new high-strength steels we have used allow the mechan­i­cal stress­es and elon­ga­tions to take place in high­er areas than in pre­vi­ous­ly used mate­ri­als. Con­ven­tion­al strain sen­sors can­not oper­ate in these areas.”
A com­plete­ly new set of sen­sor mechan­ics was devel­oped using FEM sim­u­la­tions with a mea­sur­ing range of ±2000 µm/m. The easy-to-mount sen­sor with long-term seal func­tions per­fect­ly in mul­ti-shift oper­a­tion in spite of the tough con­di­tions on build­ing sites. It is cal­i­brat­ed at the fac­to­ry which speeds up instal­la­tion and any pos­si­ble replace­ment work. The new sen­sor, with its on-board elec­tron­ics, sup­plies a high-res­o­lu­tion dig­i­tal CANopen sig­nal direct­ly to the truck-mount­ed con­crete pump’s con­trol system.
Com­pared to force sen­sors, which have to be pre­cise­ly adjust­ed to the machine geom­e­try, the strain sen­sor can be eas­i­ly mount­ed at the opti­mum posi­tion with just two bolts. This does not affect the struc­ture of the machine, save times in devel­op­ment and makes mount­ing easy. The robust design of the sen­sor makes it imper­vi­ous to shocks, impacts, and oth­er mechan­i­cal influ­ences and is there­fore ide­al for use in the con­struc­tion envi­ron­ment. At the same time, it is very gen­tle, reacts quick­ly, and can accu­rate­ly detect even the slight­est elon­ga­tion or com­pres­sion. It is resis­tant to wind and weath­er due to its a cor­ro­sion-resis­tant hous­ing. With a cer­tifi­cat­ed pro­tec­tion class of IP69K, its seal is absolute­ly guar­an­teed and can be cleaned with high-pres­sure or steam clean­ing systems.
“We are very pleased with our col­lab­o­ra­tion,” con­firms Vierkot­ten. “The inno­v­a­tive damp­ing sys­tem is also avail­able for the lat­est S 65 SXF truck-mount­ed con­crete pump from SCHWING which was launched at the begin­ning of 2018 at the World of Con­crete trade fair in Las Vegas. Fol­low­ing com­pre­hen­sive pro­to­type test­ing and opti­miza­tion dur­ing the devel­op­ment phas­es, the new DST55R strain sen­sor was suc­cess­ful­ly put into vol­ume pro­duc­tion by Baumer. We can imag­ine using Baumer sen­sors for future projects on our truck-mount­ed con­crete pumps.”