Talk:Pigging

Netherlocks/Interlocks cleanup
Is it me, or is the section on interlocks unlike most other wikipedia articles (IE internal references and/or citations), with it's excessive sales-pitch references to netherlocks who are clearly just trying to sell/garner PR on their product rather than actually contributing. Where is the evidence that, to back up the claim, which I quote "valve interlocks, which is nowadays adopted by all global oil and gas operating companies." - what, *all* of them? Even the small ones? The article is also not a stand-alone editable section, given the header, pigbacking on the "Safety considerations". Could someone well versed in wikipedia editing clean up the excessive - and unhelpful (linking to a page that says "Netherlocks has developed process interlocking solutions for various applications such as pressure relief valves" does not tell me how they work or what they look like - a sales pitch, rather than learning) external links in this section? Thanks. 80.43.238.201 (talk) 01:45, 7 March 2015 (UTC)

Merger with Pipeline inspection gauge
Pigging is a standard required practice for cleaning pipes. Inspection gauges are different and distinct from pigging. It might make more sense to link inspection gauge as a part of smart pigging as these are used to determine dents in pipelines. KB —Preceding unsigned comment added by 142.59.143.221 (talk) 14:10, 10 April 2008 (UTC)

Pigging has a wider meaning: It is used for pipeline inspection as well as for pipeline cleaning. Merging it with "Pipeline inspection gauge" would limit it to pipeline inspection only. --BonGoggle (talk) 08:17, 7 April 2008 (UTC)

Seems like these articles would better serve the reader as one. Thoughts? Sag6 (talk) 13:42, 5 January 2008 (UTC)

They need to be merged and the Pipeline inspection gauge article needs to go away. Mrmcgibby (talk) 14:56, 8 April 2008 (UTC)

merged or not, PIG is a universal term and includes "smart" pigs (inspection, gaging) as well as "dumb" pigs (cleaning, separation, etc). PIGs can be a air-filled plastic ball or a half-million-dollar magnetic-flux leakage (MFL) inspection tool. They're all PIGs.

I also took the liberty to add appropriate text and links to 2 of the major types of smart pigs: MFL and EMAT. Ken (talk) 16:32, 5 December 2008 (UTC)

-Just a note about terminology: "dumb" pigs are normally called "utility" pigs. After having thought about this subject for some years in a major Oil Company, I would probably support the idea of merging the two subjects of utility and inspection pigs under one article but, after a general common introduction, discuss them in dedicated chapters: they are intertwined but different technical disciplines.--Adilullo (talk) 03:50, 30 December 2008 (UTC)

God help us: Backing up to the "Pipeline inspection gauge" - the term is incorrect. The gauging plate is attached to a pig identified as a "Gauging Plate Pig". The gauging plate can only find a dent if it happens to stop or lodge at the dented area (in which case, I hope you have installed a tracking transmitter on the pig), otherwise the gauging plate simply comes in at the receiver end of the line and is found damaged - there is no resonable conclusion drawn from the bending the infers "dent". The gauging plate is just pron to bending from a partially closed valve, a check valve clapper, going around a bend in the pipe that is either to sharp of a bend for the length of the pig used to carry the gauging plate or the speed of the pig was to fast the the gauging plate struck the side of the bend while attempting to traverse the bend. The only use of the gauging plate pig is found "if the plate comes in undamaged" then then is no obstruction in the line (qualify this as to the point of) reducing the diameter to a point the gauging plate is damaged. Most of the gauging plates used are far to small in diameter to give any useful information at all. Better to spend your time and money on running a caliper (geometry) pig. This tool will size the dented area - assure you the pipe is either dented or the bends are sharp radius and it keeps track of the distance traveled, as well as giving the distance location of the obstruction. Newer versions of the caliper pig will provide o'clock orientation of the suspect dent - know if the dent is on the top side of the line or the bottom of the line enables one to determine if the dent is potential third party damage or simple rock denting caused during the construction of the line. Top of the line denting can be seen down to .5 percent of pipe diameter (and should be looked at down to this size; bottom of the line "dent" damage is generally not considered a problem unless is larger than 2 percent of the pipe diameter. Ovality found in a pipeline is generally not looked at or relieved unless it is at least 5 percent of the pipeline diameter. "Pipeline Inspection Gauge" should be dropped (as a term assoicated with pigging).  Mr. Kit Dual  —Preceding unsigned comment added by 71.153.179.62 (talk) 03:07, 5 January 2009 (UTC)

agreed, gage plates are pretty useless, I believe the major reason for their use is customer (pipeline operator) insistence. I know we argued against them often, always to no avail (never argue with a paying customer). But they are cheap, and therefore, customers like them. If there was construction near the line and you had a good prior history, at least it could tell you if significant damage was done. But that's about it.

However in the term Pipeline Inspection Gauge/Gage, gage plates are but one type of gauge used and the colloquial/general-use term includes caliper as well as MFL, ultrasonic, et al "gauges". Ken (talk) 19:04, 6 January 2009 (UTC)


 * Merger is completed. However, it needs expert attention and extensive cleanup. Beagel (talk) 08:01, 15 August 2009 (UTC)

Etymology of "pig"
What is the evidence that the etymology of the word "pig" is "Pigs get their name from the squealing sound they make while traveling through a pipeline."? Mrmcgibby 21:50, 25 July 2005 (UTC)
 * I didn't add it to the article, but I heard that's where the name comes from on a Modern Marvels episode on the History Channel. I don't know if their source was reliable. However, this pigging company also relates the story. I've also found sources that say the original pigs squealed. I'll add it back in and if anyone objects, they can remove it and say why here. -- Kjkolb 03:03, 13 December 2005 (UTC)
 * Please cite whatever reliable reference you can find before putting it back. I've removed it for now. Mrmcgibby 20:04, 16 December 2005 (UTC)
 * Here's a cite from a magazine. -- Kjkolb 04:00, 18 December 2005 (UTC)

The etymology of "pig" seems more likely to be an acronym of "Pipeline Inspection Gauge". Sag6 (talk) 13:42, 5 January 2008 (UTC)

I just spent two weeks working in natural gas processing and interstate pipeline operations. When I asked them if the pigs "squealed" every one I asked responded "no" and that likely the only sound to be heard was a "thump" sound when they passed by a pipe weld. —Preceding unsigned comment added by Paniti (talk • contribs) 17:38, 19 July 2008 (UTC)

- The name did originally come from the squealing sound, made by a separation (or poly) pigs. Yes, they did squeal, but only a cetain type of pig squeals and more modern materials seem to have reduced the squealing. Other types of PIGs (inspection, gaging, cleaning, etc) do not squeal except in certain conditions (frozen wheel bearings would be one). People in the industry invented "Pipeline Inspection Gage" afterward as a bit more business-like name which could also fit with the very commonly used (by then) PIG name. I worked as an engineer for a specific company involved in designing, building and using smart pigs. Ken (talk) 16:04, 5 December 2008 (UTC)

I added a source for the squeling sound, hope its a good source also for the whole site here is another potential overview refrence that could help http://www.ppsa-online.com/about-pigs.php Vonabisz (talk) 12:36, 19 October 2010 (UTC)

Interupting flow?
You say that the pig doesn't interupt production flow. I am afraid that this is not the case! Production flow must be stopped for the pigging run to take place. A slug of fluid is fired behind the pig to push it along but there is no production whilst this is being done. Just thought I'd clear that up.
 * I'm afraid you're simply wrong. Perhaps this is true for the pigging runs that you've done, but 99% of the runs we do are done in the pipeline product. Mrmcgibby 20:04, 16 December 2005 (UTC)

Yes pigging runs are done in the pipeline product but you will not be running production flow through them. For the simple reason that a pig is essentially a loose plug. You simply cannot run production flows while pigging. The slug that is pushed behind it may well be the product too but production flow is lost. Ask any major operator.
 * I just did ask a major operator. They're quite confused by your statement.  Are you talking about a specific type of pigging?  We do inline inspection of oil, gas, and other lines and most of our runs are done with production flow in the line.  That is to say, the product in the line is being used for whatever purpose it would normally be used for when the line is not being pigged.  Perhaps we differ on the definition of "production flow"? Mrmcgibby 19:22, 6 January 2006 (UTC)  (P.S. Please sign your entries with ~ )

I have some experience with pigs. They are used with different purposes in different processes: Brindis 21:52, 26 January 2006 (UTC)
 * Pigs used in lube oil or painting blending: they are used to clean the pipes to avoid cross-contamination, and to empty the pipes into the product tanks (or sometimes to send a component back to its tank). Usually pigging is done at the beginning and at the end of each batch, but sometimes it is done in the midst of a batch, eg when producing a premix that will be used as an intermediate component.
 * Pigs used in oil and gas pipelines: they are used to clean the pipes but also there are "smart pigs" used to measure things like pipe thickness along the pipeline(photo here ). They usually do not interrupt production, though some product can be lost when the pig is extracted. They can also be used to separate different products in a multiproduct pipeline.

-I have designed smart pigs for 5 years now. I can tell you that we do not interupt the production / flow of the lines we inspect. Even in gas we do not use a slug to "push", and the product in the line is not effected in any way. We may ask for reduced / increased flow rates, but we do not ask for a slug of non-production fluid. MMMBOB 17:50, 29 January 2007 (UTC)

-and likewise my experience (4 years in design, mfg and deployment) aggrees with MMMBOB. The movement of the product is what moves the pig. In many cases the flow rate of the product is controlled very carefully as the speed of the pig is extremely important to the reliability of the data (especially true in Magnetic Flux inspection). The sealing surfaces of the pigs are designed to allow some bypass when needed; as a rule the pig moves a bit slower than the material due to this bypass. Some bypass actually makes the pig's speed easier to control. Since pigs sometimes get stuck, some bypass is needed to prevent totally plugging the line. Ken (talk) 16:12, 5 December 2008 (UTC)

-With respect to pigging in the oil industry, of which I have direct experience within a major Oil Company, what Mrmcgibby and MMMBOB say has been quite often true, i.e. pigging does not imply production/flow stops. But there are some circumstances when production may have to be significantly reduced, temporarily stopped or completely stopped during the pigging operation. I provide a few practical examples, just for clarity: In conclusion, pigging has many different purposes and a wide applicability so that an absolute statement about production stop may be misleading. What is important is that most pigging operations may be carried out by pushing the pig with the produced fluid (possibly at a limited flowrate) and only in specific contexts a complete production stop is required.--Adilullo (talk) 03:32, 30 December 2008 (UTC)
 * cleaning operations of gas lines with a gas velocity higher than that acceptable for a cleaning pig (which is normally in the range 0.5 - 2.5 m/s, or so) may imply a significant production reduction (e.g. from 10 m/s to 2 m/s);
 * cleaning operations carried out with support from suspending fluids (e.g. gels or solvents) and, possibly, multiple pigs, require flow interruption during gel/fluid injection in the line, even if the final driving fluid is the product itself;
 * a complete production stop may be required, for example, when the fluid pressure available from the producing system is not sufficient to push the pig from the launching to the receiving trap, so that the driving fluid needs to be introduced artificially. In that case, the higher pressure of the driving fluid may "kill" the production system during the pigging operation.

-It would be worth adding a paragraph on PIG speed control via bypass? —Preceding unsigned comment added by Jerryludlow (talk • contribs) 16:26, 4 May 2011 (UTC)

GPS?
I've got real heartburn with this part:

"Modern pigging systems are highly sophisticated sets of equipment that consist of a standard 5-6 finned pig with an intelligent transmitter that has a global positioning system fixed on it to tell the exact location of the pig inside the pipeline while it is on the move. Along with the GPS positioner there are a host of other instruments like the internal camera that takes live video of the pipe condition inside while the pig is moving, the thickness gauge that constantly measures the thickness of the wall of the pipe as the pig moves. "

>GPS will not work from within a pipeline as GPS requires line of site/signal to work, unless something is severely lacking in my knowledge. I'll give it a few days for comments and then I'll rewrite it towards how I know the ones I used worked. Ken (talk) 22:29, 17 December 2008 (UTC)

nevermind, I've decided to re-write it. If you disagree with what I've written, talk to me here. Ken (talk) 18:11, 18 December 2008 (UTC)

>In my experience too, GPS does not work within a pipeline. Pig tracking systems (i.e. methods to monitor the position of the pig from outside the line) work on different principles, all based on the detection the presence of the pig in a specific location of the pipeline where a sensor has been installed (different types are available). Instead, internal position in intelligent pigs is normally measured by an odometer, i.e. one or more wheels that roll while the pig is sliding and an electronic system to measure their turns. As far as I know, I would discard any mention to GPS systems.--Adilullo (talk) 03:40, 30 December 2008 (UTC)

"As far as I know, I would discard any mention to GPS systems.." >that's probably a very good idea....Ken (talk) 01:41, 31 December 2008 (UTC)

The use of GPS and pigs works in this general manner: The pig is outfitted with an Inertial Navigation System (INS). There is a correlation between the INS package and above ground collected data at Global Point Stations (GPS). GPS points are taken at various locations along the length of the pipeline; these points must be taken at some point that is recognizable by the pig (such as valves, bends in the pipe etc..). Once a pig run has been obtained, the GPS collection points are entered onto the pig data stream at the appropriate locations. The INS package plots all turns and distance of the pig travel; once the GPS points are entered at the correct locations and aligned with the INS data the programming routine used with the INS package can "Predict" further GPS locations along the pigs travel. An "as-built" map of the pipeline can be created from the combination of entered correction point GPS and the INS predictions; the more GPS points collected - the better the mapping. Hope this helps - Mr. Kit Dual —Preceding unsigned comment added by Mr. Kit Dual (talk • contribs) 02:14, 5 January 2009 (UTC)

yes, your explanation fairly well matches the re-write I did of that section. The re-write I did mostly served to correct the impression that the pig communicated directly via GPS, which it can't and doesn't. Unfortuately, accurate mapping is a necessary service as many pipelines weren't mapped very well when built. It is often disconcerting to the general public to realize that the exact route of the pipeline isn't as precisely known as would normally be thought. Ken (talk) 18:54, 6 January 2009 (UTC)


 * Surveying does not have to be done with GPS. It looks like there is misunderstanding in the field about GPS, GIS and 'surveyed location'.  However in theory a pig in an above ground plastic pipe with a gas could theoretically use GPS for the position location though it seems like a fringe case and needs to be specifically described.
 * Idyllic press (talk) 23:44, 30 April 2016 (UTC)

New work
There has been work done in the past that used capacitive sensor technology to detect defects in polyethylene pipes for natural gas that can be added and should help the article more. Most of the topics talks about magnetic flux which is more for metal pipe, but very little in the article talks about any plastic pipeline. This test was conducted by NETL a DOE entity. Website containing the article. http://www.netl.doe.gov/technologies/oil-gas/publications/td/dtrs56-benchmark_report_final.pdf Pages in reference are C35 (PDF Page starting at 185)--Guilio 2008 (talk) 12:23, 8 April 2010 (UTC)

Typo -  In the antepenultimate sentence of the very last paragraph this appears: ... propogated outware through the pipes all. Obviously needs correction.76.218.103.232 (talk) 18:35, 4 January 2011 (UTC) 76.218.103.232 (talk) 18:37, 4 January 2011 (UTC)

Gate valves?
The article says pigs don't work with butterfly valves but do work with ball valves. What about gate valves?

When fully open, it appears a gate valve should not block the flow path, though the gate guide channels might cause pig snagging, and also the guide channels apparently can't be cleaned by a pig. (?)

DMahalko (talk) 04:52, 2 January 2011 (UTC)


 * As long as the valve is full-diameter and not restricting the diameteric circle of the pig, it should work. Functions of the pig such as cleaning and inspection can not be done in ancillary areas such as gate guides, etc. However since those areas are normally more replaceable than the basic pipe itself, this isn't a huge concern. Also consider that inspection technologies such as MFL are calibrated for the particular wall thickness of the pipeline and become fairly useless at inspecting valve bodies due to their much-increased thickness. Ken (talk) 19:49, 15 May 2012 (UTC)


 * I added reduced port valves as an obstruction, mentioned in the NTSB Report on the Carlsbad gas pipeline accident of 2012 that killed 12 people. Pipelineexaminer (talk)

About Types of Pigs
Don't you think it is appropriate to add a detailed description of each type of pigs are required here? Kir360 (talk) 17:19, 8 February 2012 (UTC)

Safety Considerations
I added a blurb about the "flying pig" incident in Grand Prairie, TX, in October 2010. Pipelineexaminer (talk) —Preceding undated comment added 01:28, 10 June 2012 (UTC)

Bent pipe shape distortion, and minimum bend radius to prevent leakage or pig jamming?
So, bent pipes are typically not uniformly circular but slightly oval in shape, and the non-circularity can get really severe in tightly bent pipe.

Also a pig -MUST- be more than a simple flat disc for it to stay concentric in the pipe. It must apparently use two discs connected with a rod, or at least a disc with a long rod sticking out of center of the disc.

Either case appears to limit the pipe bend radius, to be very large and sweeping for a pig to:
 * seal itself around the non-circular deformed pipe wall in the bend
 * not jam the rod-body of the pig against the walls in the bend, between the disc-ends of the pig.

DMahalko (talk) 06:18, 10 February 2012 (UTC)


 * A proper pipeline bend/curve is circular in cross section, not oval. But there are lots of 'non-proper' bends out there.... The pig I worked with (smart pigs) used disks connected by spacers. The spacers were the electronics and such. The diameter of the spacers were smaller than the diameters of the disks. The diameters of the disks, spacers and the length between them determines the minimum radius that the pig can traverse. In very small diameter pigs, the electronics must be spread out along several sections due to space limitations. Each section has a swivel joint to allow further bending of the entire tool. The largest tools are usually in 2 sections, 1 for the sensors and electronics, the other for the batteries. Ken (talk) 14:42, 24 September 2013 (UTC)

Scraping / scrapers
Might be worth stating that the alternative names (especially when working with muslim clients) for pigging and PIG are scraping and scraper Naindj (talk) 16:37, 19 June 2012 (UTC)

Dairy farms
Back in the 1970's the milking systems on dairy farms used sponge pigs to clean out the pipe work after each milking session (typically twice a day). I'm not sure if this is the case these days or if other means have been developed.

Idyllic press (talk) 23:49, 30 April 2016 (UTC)