Packings for Pumps and Valves – Graphite, PTFE, Aramid
Special sealing elements for pumps and valves. Graphite, PTFE, Aramid, and glass braids for rotary and linear motion.
GraphitePTFEAramid
Principle and Application
A packing cord is a special sealing element manufactured by braiding or knitting various technical materials. Its primary function is to ensure reliable sealing in equipment with rotating or linear moving parts, such as pump shafts, valves, or mixers. The sealing principle relies on radial compression of the cord, filling the space between the static and moving parts of the equipment.
The braid structure is key to the cord's functionality – a diagonal braid ensures even pressure distribution, while braid density affects extrusion resistance.
Material Variants
Graphite: Excellent for high-temperature applications up to 650 °C (in inert atmosphere) due to thermal conductivity and self-lubricating properties.
PTFE: Ensures exceptional chemical resistance and low friction coefficient. Temperature limit up to 280 °C.
Aramid (Kevlar): Provides extraordinary mechanical strength and extrusion resistance. Withstands pressures up to 250 bar.
Glass Fibers: Economical solution for less demanding applications.
Installation and Maintenance
1
Thoroughly clean the space and check the shaft condition.
2
Accurately measure the length (usually a 45° angle cut).
3
Insert rings with joints rotated by 90°.
4
Tighten evenly (first to the stop, then slightly loosen).
5
Operational Tip: Slight leakage is desirable in some applications to ensure lubrication and cooling of the cord.
How to Choose Correctly?
Sealed Medium: Chemicals require PTFE, steam requires graphite, abrasive media require aramid fibers.
Operating Temperature: Regular temperature cycles can cause degradation.
Pressure Conditions: Vacuum has different requirements than high positive pressure.
Peripheral Shaft Speed: For speeds above 10 m/s, only special composite cords are suitable.
Warning: Graphite cords may cause galvanic corrosion in some stainless steel shafts.
Technical Specifications
MaterialExp. Graphite
Temp [°C]-200 to +650
Pressure [bar]100-250
pH Range0 – 14
ApplicationSteam, Hot Water, Chemicals
MaterialPure PTFE
Temp [°C]-200 to +280
Pressure [bar]20-80
pH Range0 – 14
ApplicationAggressive Chemistry, Food
MaterialAramid / Kevlar
Temp [°C]-100 to +280
Pressure [bar]up to 250
pH Range2 – 12
ApplicationAbrasive Media, Sludge
MaterialPTFE / Graphite
Temp [°C]-200 to +280
Pressure [bar]up to 100
pH Range0 – 14
ApplicationPumps, High Peripheral Speeds
| Material | Temp [°C] | Pressure [bar] | pH Range | Application |
|---|---|---|---|---|
| Exp. Graphite | -200 to +650 | 100-250 | 0 – 14 | Steam, Hot Water, Chemicals |
| Pure PTFE | -200 to +280 | 20-80 | 0 – 14 | Aggressive Chemistry, Food |
| Aramid / Kevlar | -100 to +280 | up to 250 | 2 – 12 | Abrasive Media, Sludge |
| PTFE / Graphite | -200 to +280 | up to 100 | 0 – 14 | Pumps, High Peripheral Speeds |