Kev tsim tawv yog qhov chaw nyob hauv qab ntawm kev tsim kho tawv uas siv kev tsim kho, feem ntau siv hauv kev lag luam nyob hauv huab cua, dej noo, thiab kev lag luam kheej. Hauv huab cua, qhov kev tsim kho yog qhov chaw uas muab cov khoom thermoplastic mus rau hauv, ua kom sov, sib npaug, thiab ntxuav siab. Qhov chaw tseem ceeb tshaj plaws yog ib qhov rooj twj uas muaj qhov rooj twj zoo tshaj plaws uas tsis tu ncua. Qhov twj muaj qhov twj sib txawv—ntawm qhov pib, qhov ruaj khov, thiab qhov muaj peev xwm—kom pab tau zoo hauv kev siv khoom los ntawm tus cwj pwm mus rau hauv thawj yam khoom, thiab tshuaj xyuas qhov siab uas tsum tau rau lub thawj yam khoom. Kev tsim kho tau muaj ntau yam sib txawv, feem ntau siv qhov twj. Lub twj tsim kho yog qhov feem ntau tshaj plaws, muaj zog thiab zoo tshaj plaws hauv ntau yam kev siv tawv lossis kev siv khoom. Lub twj tsim kho ob, uas tuaj yeem rov qab los yog rov qab, muaj kev sib piv zoo dua, kev tshuaj xyuas, thiab kev tshuaj xyuas, ua rau nws zoo tshaj plaws rau kev sib sau nrog ntau yam khoom, kev tsim kho PVC, lossis kev siv khoom uas muaj kev nyuaj siab lossis muaj khoom ntxiv. Qhov kev ua haujlwm ntawm lub twj tsim kho yog qhov twj, L/D (nruab nrab rau qhov twj), zog tso tawm, thiab qhov kev tshuaj xyuas kom muaj qhov sov zoo, muaj qhov siab zoo, uas yog qhov tseem ceeb tshaj plaws rau kev tsim kho zoo.