Asbestos Gland Packing
Asbestos-yarn packing rings compressed into stuffing boxes to seal rotating shafts on pumps and valves.
Description
Asbestos gland packing is a specialised sealing product consisting of die-formed or hand-cut rings of braided asbestos yarn, compressed into the stuffing box or gland housing of pumps, valves, agitators, and other rotating or reciprocating equipment. The packing rings are tightened against the rotating shaft by a gland follower and adjusting nuts, creating a seal that prevents process fluid from leaking along the shaft.
Gland packing was manufactured from braided asbestos yarn, typically chrysotile, impregnated with graphite, PTFE, tallow, mineral oil, or wax lubricants. The lubricant reduced friction between the packing and the shaft, extending both packing and shaft life. Asbestos content ranges from 60 % to 95 %, with the balance being the impregnating lubricant.
From the 1910s through the late 1980s, asbestos gland packing was the universal sealing solution for rotating equipment across virtually every industry: petrochemical, power generation, water and wastewater treatment, pulp and paper, food and beverage, marine, and mining. Millions of pumps and valves worldwide were packed with asbestos gland packing.
The packing is classified as friable because it degrades during service. The rotating shaft gradually wears the inner surface of the packing rings, generating asbestos-containing dust that leaks past the gland. When the packing is removed for replacement (a routine maintenance task), the old rings may be dry, hardened, and crumbly, releasing fibres when extracted. The stuffing box must then be cleaned of residual packing material, which generates additional fibre exposure.
Gland packing replacement (repacking) was one of the most frequent maintenance tasks in industrial facilities and a significant source of cumulative asbestos exposure for pump mechanics, marine engineers, and maintenance fitters. Many asbestos disease claims in the UK and US have been brought by workers whose primary exposure was from repacking pumps and valves.
Modern gland packing materials include PTFE, expanded graphite, carbon fibre, aramid fibre, and various synthetic blends. Mechanical seals have also replaced gland packing in many applications, eliminating the need for packing altogether.
Countries where commonly found
Commercial brands
How to identify
Asbestos gland packing appears as square or round braided rings installed around the shaft inside a stuffing box. The rings are typically white, grey, or black depending on the lubricant. Graphite-impregnated packing is dark grey or black. The material has a distinctive tightly woven or braided pattern. When worn, it may be compressed, hardened, and difficult to extract. Any packing in equipment installed or last serviced before the 1990s should be tested.
Health risk & friability
This material has a risk level of 3 out of 5.
It is classified as friable, meaning asbestos fibers can be released into the air with minimal disturbance. This makes it one of the more dangerous asbestos-containing materials. Any work on or near this material should only be carried out by licensed professionals with appropriate containment measures.
What to do if you find this material
Do not attempt to remove or replace gland packing without appropriate precautions. If the equipment is functioning normally and the packing is not leaking, it can remain in place. When repacking is required, keep the area damp, use proper packing extraction tools, wear RPE and disposable coveralls, and bag all removed material for disposal as asbestos waste. Replace with non-asbestos packing or consider upgrading to a mechanical seal.
Frequently asked questions
What is the difference between gland packing and general asbestos packing?
How common is asbestos gland packing in older equipment?
Can I upgrade from gland packing to a mechanical seal?
Who is most at risk from asbestos gland packing?
Related materials
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