Äärik on osad, mis ühendavad kahte toru otsa, äärikuühendus on määratletud äärikuga, tihendi ja polt kolm on ühendatud eemaldatava ühenduse kombineeritud tihendusstruktuuri rühmana. Kahe ääriku vahele lisatakse tihend ja seejärel kinnitatakse poltidega. Different pressure flange, thickness is different, and the bolts they use are different, when pump and valve connect with pipe, the parts of the equipment are also made of the corresponding flange shape, also known as flange connection, usually closured bolted connection parts are also known as flanges, such as the connection of ventilation pipe, this kind of parts can be called “flange type part”, but this connection is only part of a device, such as the connection between flange and water pump, it’s not Veepumba nimetamine äärikutüübi osadena, kuid suhteliselt väike ventiil võib seda nimetada äärikutüübi osadeks.