Product category:
Valve Hardware (Filters, Flow Controls, Positioners etc)
News Release from: Lee Products | Subject: APO plugs
Edited by the Engineeringtalk Editorial
Team on 29 June 2004
Plugs seal in tricky situations
Lee Products has developed a range of AFO plugs (axial force only) that are both removable, reusable and are ideal for high-pressure/high-temperature situations.
High-pressure high-temperature manifold applications, such as those occurring in the petrochemicals and offshore oil industry, typically demand metal-to-metal devices that provide a leak-tight seal and meet API specifications Miniature component specialist Lee Products has developed a range of AFO plugs (axial force only) that are both removable, reusable and are ideal for these high-pressure/high-temperature situations
This article was originally published on Engineeringtalk on 12 Mar 2001 at 8.00am (UK)
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AFO plugs feature a floating seal that self-aligns to allow for threaded holes that are not concentric with the through hole.
As a result of the plug's two-piece construction, the seal does not rotate during installation, thus preventing galling of the seat.
Also, as all the force is contained in the axial direction, the boss diameter can be smaller compared to other designs of plug.
Standard AFO plugs are manufactured from corrosion resistant 303 and 15-5 stainless steel and do not require O-rings or sealants.
They are designed to withstand pressures up to 60,000lb/in2 (4136bar) and temperatures to 315C when fitted into hard materials as well as in softer materials, such as aluminium or plastic.
The plugs are available in sizes from 0.19 to 0.75in with UNF threads; however, depending on specific application requirements, special versions can be supplied.
For example, to meet NACE standards required in the oil industry AFO plugs have recently been supplied in Monel in sizes up to 1.325in UNF threads.
These special plugs were required to withstand 15,000lb/in2 (1034bar) working pressure and 22,500lb/in2 (1551bar) proof pressure.
Current API specifications dictate that plugging devices must provide both primary and secondary seal.
The AFO plug itself is considered to be the primary seal and because they are welded in position, the welding process satisfies the secondary seal requirement.
Although the oil industry has traditionally used NPT plugs, achieving a leak-tight seal with these types of plugs can prove difficult, particularly as PTFE tape is no longer permitted.
If the NPT plugs do not seal first time, the thread often has to be recut due to the distortion caused by the tapered thread on the NPT plug.
Typical offshore oil industry applications for AFO plugs include subsea wellhead trees, tubing hangers, completion tools, slick joints and down hole tools. Request a free brochure from Lee Products ...
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