Lin­ear mo­tors re­duce an­tibi­otics in fish farms

DEMM Engineering & Manufacturing - - FOOD - by Franz Joachim Rossmann

From a global per­spec­tive, fish is the most im­por­tant source of protein for hu­man con­sump­tion. De­mand could as much as dou­ble within one or two decades. With­out aqua­cul­ture, this hunger for fish can­not be sat­is­fied.

The neg­a­tive side ef­fects of in­dus­trial aqua­cul­ture, such as high lev­els of pol­lu­tion from med­i­ca­tions, have scared off con­sumers in Europe – in par­tic­u­lar – caus­ing sales to col­lapse a few years ago.

Aqua­cul­ture fish are bred for max­i­mum pro­duc­tion, and for eco­nomic rea­sons have sig­nif­i­cantly less liv­ing space than their cousins in the wild. This makes them es­pe­cially sus­cep­ti­ble to ill­ness and par­a­sites.

The dam­age caused by an in­fes­ta­tion can quickly threaten the liveli­hood of the farmer. The epi­demic of in­fec­tious sal­mon anaemia (ISA) that broke out in 2007, for ex­am­ple, caused sal­mon pro­duc­tion in Chile to plum­met from 400,000 tonnes to just 250,000 tonnes within two years. There are many other dis­eases be­sides ISA, such as fu­run­cu­lous, that threaten fish stocks.

Many breed­ers use large amounts of pro­phy­lac­tic med­i­ca­tions, es­pe­cially an­tibi­otics. Grow­ing crit­i­cism of these side ef­fects has led to the use of med­i­ca­tions be­ing re­stricted in Europe.

Vac­ci­nat­ing fish

Nor­way in par­tic­u­lar has long en­deav­oured to solve the prob­lems faced by those in aqua­cul­ture. The coun­try, where fish is the third most im­por­tant ex­port, has al­most elim­i­nated its use of an­tibi­otics in fish farms.

At their peak in 1987, Nor­we­gian fish­eries used about 50 tonnes of an­tibi­otics a year – more than were pre­scribed for the en­tire pop­u­la­tion of Nor­way in the same time pe­riod. Their use in fish farms is now less than 100kg a year. Ninety-eight per­cent of all sal­mon farmed in there have no ex­po­sure to an­tibi­otics. This was made pos­si­ble by vac­ci­nat­ing the fish.

Typ­i­cally, sev­eral vac­cines are in­jec­tion at once. The meta­bolic rate of fish de­pends on the tem­per­a­ture, so the in­jec­tion con­tains an agent that heats up the im­mune sys­tem.

This pro­ce­dure is dif­fi­cult, be­cause up un­til now, each fish has had to be man­u­ally in­jected with the vac­cine us­ing a syringe. Con­sid­er­ing the num­ber of fish bread an­nu­ally – 1.4 mil­lion tonnes of sal­mon in aqua­cul­ture world­wide in 2010 – this pro­ce­dure has reached its lim­its.

Ma­chine builder Maskon has turned to au­to­ma­tion of the vac­ci­na­tion process. A sys­tem de­vel­oped by the com­pany, that can au­to­mat­i­cally anaes­thetise, sort, sin­gle out, and vac­ci­nate up to 20,000 fish an hour, depend­ing on the ma­chine used.

This would have pre­vi­ously re­quired four to six ex­pe­ri­enced ‘fish in­jec­tors’. The ma­chine also en­sures a sig­nif­i­cantly higher level of qual­ity of vac­ci­na­tion than hu­mans can pro­vide.

The core of the sys­tem con­sists of one ( VX-4) or two ( VX-8) vac­ci­na­tion mod­ules each equipped with four vac­ci­na­tion sta­tions. An im­age pro­cess­ing sys­tem by the Oslo com­pany Tor­di­vel first mea­sures each fish and pro­vides in­for­ma­tion to cal­cu­late the point of in­jec­tion.

The en­tire vac­ci­na­tion sta­tion is then po­si­tioned ac­cord­ingly by a lin­ear mo­tor from LinMot. This makes it pos­si­ble to hit the op­ti­mal in­jec­tion site for each fish with a pre­ci­sion of more than 98 per cent. The length of the fish, as de­ter­mined by the im­age pro­cess­ing sys­tem, is also used to cal­cu­late the depth of the in­jec­tion for each in­di­vid­ual fish.

A sen­sor on the nee­dle then mon­i­tors the in­jec­tion process and the vac­cine dosage for each fish. As a re­sult, the mor­tal­ity rate is less than 0.02 per­cent.

The re­quire­ments for the in­jec­tion sta­tion drives are high for this ap­pli­ca­tion. In par­tic­u­lar, they need to com­ply with the hy­giene re­quire­ments of the food prod­ucts in­dus­try.

The stain­less steel mo­tors in the P01-

37x120F-HP-SSC se­ries from LinMot op­ti­mally meet this re­quire­ment. They are made en­tirely of stain­less steel (1.4404/316) and are char­ac­ter­ized by their high pro­tec­tion class of IP69K. Gas­kets were elim­i­nated from the mo­tor de­sign, and all con­nec­tions are welded. The mo­tors are also fully pot­ted to pre­vent con­den­sa­tion form­ing.

Thanks to these fea­tures and the closed, easy-to-clean stain­less steel sur­face, the INOX mo­tors are ideal for use in ma­chin­ery and equip­ment that pro­cesses food prod­ucts or phar­ma­ceu­ti­cal goods.

The com­pact form fac­tor of the lin­ear mo­tors, which have no pro­trud­ing parts or gear­boxes, ap­pealed to the de­sign­ers at Maskon.

An eval­u­a­tion by Maskon of lin­ear mo­tors on the mar­ket de­ter­mined that only the stain­less steel ones from LinMot could pro­vide the dy­nam­ics, pre­ci­sion, the pro­tec­tion class, and com­pact form fac­tor re­quired by the vac­ci­na­tion ma­chine.

This ap­plies as well to the LinMot sta­tor model PS0137x120F-HP-SSC-R used in the vac­ci­na­tion unit, with an outer di­am­e­ter of 48mm and length of 296mm. When used to­gether with the ap­pro­pri­ate slider, it is able to ap­ply a con­stant force of up to 210N over the en­tire range of its stroke. In the stan­dard prod­uct line, LinMot slid­ers are avail­able for strokes from 75 to 680mm.

A high-clear­ance vari­ant, PL01-19x350/260, with a stroke of 120mm was selected for the vac­ci­na­tion unit. The mo­tor is con­trolled by a B1100-VFHC servo in­verter, also from LinMot, that is de­signed for in­te­grat­ing the lin­ear mo­tors into sys­tems with a mas­ter axis con­troller.

The force or speed of the mo­tors is set by the mas­ter po­si­tion con­troller via an ana­logue dif­fer­en­tial sig­nal of ±10V. Ei­ther the in­ter­nal LinMot mea­sure­ment sys­tem or a high-pre­ci­sion ex­ter­nal mea­sure­ment sys­tem can be used for feed­back.

Sim­ple po­si­tion­ing con­trols can ac­tu­ate the E1100-VF con­troller with step­per mo­tor or direc­tional pulse sig­nals. For test­ing and com­mis­sion­ing, the VF con­troller can also be op­er­ated in point-to-point mode, with four freely pro­gram­mable end po­si­tions.

In ad­di­tion to the INOX mo­tors the LinMot range also in­cludes vari­ants with max­i­mum force rat­ings of up to 496 (max­i­mum stroke of 980mm) or 888N (max­i­mum stroke of 860mm). All stain­less steel mo­tors are also avail­able with ATEX cer­ti­fi­ca­tion. Dif­fer­ent bear­ing types for var­i­ous op­er­at­ing modes (dif­fer­ent stroke lengths) round out the of­fer­ings.

Au­to­ma­tion us­ing LinMot mo­tors en­ables aqua­cul­tured fish to be vac­ci­nated across the board for the first time, elim­i­nat­ing the pro­phy­lac­tic use of an­tibi­otics. Un­de­sir­able side ef­fects, such as pol­lu­tion of the oceans with med­i­ca­tion residues, the de­vel­op­ment of re­sis­tances, and reser­va­tions against the use aqua­cul­ture can be re­duced to an ab­so­lute min­i­mum.

demm.co.nz/read­eren­quiry #D140316

The VX-8 from Maskon that vac­ci­nates up to 20,000 young fish an hour.

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