English to Danish Tech/Engineering Mechanics / Mech Engineering part exchange of an old machine for a new one

Teksten er en del af et salgsbrev fra et firma, som lever af at opkøbe brugte maskiner af firmaer, som har taget dem af kunder som en del af betaling for en ny maskine. På engelsk kalder man det en 'part exchange' - hvad kalder man det på dansk?

Her er et par paragraffer:
"If you have a customer wanting to part exchange an old macine for a new one and it is sgetting in the way of your deal, we can help."

"We currently help the majoirty of the new machine tool sales companies in the UK selling new machines with their part exchanges and we are looking to expand our customer base. We help by offering to buy the used machine, which is being given in part exchange."

Part exchange - brugt maskine til delvis betaling? Depositum? Udbetaling mod køb af ny maskine? Er der et fast udtryk på dansk for det engelske 'part exchange'?

Tak!!