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History of Jars

The mechanical success of cable tool drilling has greatly depended on a device called jars, invented by a spring pole driller, William Morris, in the salt well days of the 1830's. Little is known about Morris except for his invention and that he listed Kanawha County (now in West Virginia) as his address. Morris patented this unique tool in 1841 for artesian well drilling. Later, using jars, the cable tool system was able to efficiently meet the demands of drilling wells for oil.

The jars were improved over time, especially at the hands of the oil drillers, and reached the most useful and workable design by the 1870's, due to another patent in 1868 by Edward Guillod of Titusville, Pennsylvania, which addressed the use of steel on the jars' surfaces that were subject to the greatest wear. Many years later, in the 1930's, very strong steel alloy jars were made.

A set of jars consisted of two interlocking links which could telescope. In 1880 they had a play of about 13 inches such that the upper link could be lifted 13 inches before the lower link was engaged. This engagement occurred when the cross-heads came together.Today, there are two primary types, hydraulic and mechanical jars. While their respective designs are quite different, their operation is similar. Energy is stored in the drillstring and suddenly released by the jar when it fires. Jars can be designed to strike up, down, or both. In the case of jarring up above a stuck bottomhole assembly, the driller slowly pulls up on the drillstring but the BHA does not move. Since the top of the drillstring is moving up, this means that the drillstring itself is stretching and storing energy. When the jars reach their firing point, they suddenly allow one section of the jar to move axially relative to a second, being pulled up rapidly in much the same way that one end of a stretched spring moves when released. After a few inches of movement, this moving section slams into a steel shoulder, imparting an impact load.

In addition to the mechanical and hydraulic versions, jars are classified as drilling jars or fishing jars. The operation of the two types is similar, and both deliver approximately the same impact blow, but the drilling jar is built such that it can better withstand the rotary and vibrational loading associated with drilling. Jars are designed to be reset by simple string manipulation and are capable of repeated operation or firing before being recovered from the well. Jarring effectiveness is determined by how rapidly you can impact weight into the jars. When jarring without a compounder or accelerator you rely only on pipe stretch to lift the drill collars upwards after the jar releases to create the upwards impact in the jar. This accelerated upward movement will often be reduced by the friction of the working string along the sides of the well bore, reducing the speed of upwards movement of the drill collars which impact into the jar. At shallow depths jar impact is not achieved because of lack of pipe stretch in the working string.

When pipe stretch alone cannot provide enough energy to free a fish, compounders or accelerators are used. Compounders or accelerators are energized when you over pull on the working string and compress a compressible fluid through a few feet of stroke distance and at the same time activate the fishing jar. When the fishing jar releases the stored energy in the compounder/acclerator lifts the drill collars upwards at a high rate of speed creating a high impact in the jar.

System Dynamics of Jars

Jars rely on the principle of stretching a pipe to build elastic potential energy such that when the jar trips it relies on the masses of the drill pipe and collars to gain velocity and subsequently strike the anvil section of jar. This impact results in a force, or blow, which is converted into energy.

History of Power Swivel Development
by Larry Keast, P.E., Founder and CEO
Venturetech Corporation International


This brief history is written from my experience since 1980, from researching Gulf Publishing's Composite Catalogs, and from stories told to me. Until Venturetech's XK power swivels, the only real player in this business was Bowen, although there were others along the way. There have also been a few non-engineering companies building poorly-designed equipment and even direct Bowen copies, and there have been fabrication packagers who buy a Bowen swivel and put it on their own power unit. In this history, I have only included power swivels designed and built by engineering-based manufacturing companies.

1948 - The first power swivels appeared in the Composite Catalog. Baash-Ross and Homco each had a full page, and the S.R. Bowen Company offered one introductory sentence with no photo or other information. The largest of these first power swivels were rated up to 2000 ft-lbs torque, 40 tons capacity, and 31 rpm. Engines were up to 12 HP, and gear and vane-type hydraulic pumps and motors operated around 1000 psi.

1950 - S.R. Bowen Company added a full catalog sheet on their very similar "powered swivel".

About 1960, Baash-Ross was bought by Joy Manufacturing and in 1962 they introduced their 65 ton and 100 ton power swivels. Then about 1980, Baash-Ross introduced well-engineered upgrades of these models, calling them the PS-85 and PS-130. They only made them until Varco bought Baash-Ross and discontinued these swivels altogether in the early 90's. We continue providing parts for these swivels.

Other than Bowen, Baash-Ross, Homco, and King were the only power swivels under 250 tons designed and built in engineering-based manufacturing companies. They never competed effectively with Bowen after 1970, whose leadership was due to much more aggressive sales and marketing than the others.

In 1964, Bowen introduced the 85 ton S-2 and the 120 ton S-3. These models employed early Vickers piston-type hydraulic motors which were limited to 3000 psi and had to be bolted on from the inside of the gearbox before swivel assembly.


In the 1970's, after not offering a swivel for years, Homco developed their own ingenious power swivels, but they were too expensive and too large to be practical. They never got off the ground, and after a few years, Homco started buying Bowens for use in their service operations.


King Oil Tools has been known since the 50's for their complete line of water well and workover swivels, not power swivels. King introduced 90 and 130 ton power swivels in the late 70's, and some have been sold through the years, but they were never a major competitor.

In 1972, Bowen Introduced the S-2.5 and in 1973, the S-3.5. The load ratings remained the same as the previous S-2 and S-3, and the appearance was almost the same, but the gearing and main body were redesigned for higher torques. To increase torque, they used the new Sundstrand 5000 psi piston-type closed loop hydraulics including variable displacement pumps. High pressure piston equipment was new to the oilfield at the time, and gear and vane-type pumps and motors were still limited to 2500 psi. It's important to note that the oilfield didn't understand that the new high pressure piston equipment was extremely dirt sensitive.

So the Bowen 2.5 and 3.5 have been around more than 30 years - so long that their model numbers became generic, a fine thing for Bowen. As a result, people incorrectly refer to other brands of power swivels by Bowen model numbers, and our customers ask if we make a 2.5 or 3.5. We explain those are Bowen's model numbers and our XK-90 and XK-150 swivels are quite different, although they compete directly.

Typical of big companies growing by merger and acquisition, when IRI bought Bowen in the 1990's, some marketing guru or committee made the ill-informed decision to change model numbers. That would have been a great idea in the beginning, before the 2.5 and 3.5 became generic. The goal was to give all their power swivels consistent model numbers reflecting the tonnage rating. So the S-2.5 was renamed S-85 for 85 tons, and the S-3.5 renamed S-120 for 120 tons. As part of this renaming exercise, they changed their power units, using later model engines, pumps, some lower cost components, and a poorly designed triple power hose reel destined for long term problems. The swivel heads remained unchanged. The world still refers to the 2.5 and 3.5, and we have even heard field people refer to the 4.5, logically thinking it meant Bowen's 250 ton, which it never did.

Then when National-Oilwell bought IRI in 2000, they even deleted the Bowen name from their advertising, a name which had earned a respected reputation around the world. Mr. Bowen must have rolled over in his grave.

This has all been very confusing, customers in the field don't understand, and no doubt most National-Oilwell people don't know this history.

Our only business is power swivels, and for many years, we have made replacement parts for Bowen, Baash-Ross, and other brands no longer in production. Everyday, we ship replacement parts worldwide. But as a creative design engineer and inventor, I never wanted to copy the whole Bowen machines, because that would be an insult to my creativity and to Mr. Bowen's hard work building his company. I suppose I'm a bit unusual since the oilfield is filled with companies copying the originator's products. It's all legal after the patents run out, and they probably make more money than we do, but I just wouldn't have any fun. I'm sure the original Bowen design engineers would approve of our work, and it's not that their designs were bad, just different; and they didn't have today's hydraulic components to work with.

We have been successful because power swivels are the only product line we have focused on for 25 years. All the other manufacturing companies were much larger and had many product lines unrelated to power swivels which diluted their attention.

Finally, I'm an old hot rodder and motorhead, and I love cars, trucks, and engines. When I discovered this power swivel business niche had diesel engines, technical hydraulics, and remote pneumatic controls, it was very interesting to me, looked like fun, and seemed like something I could do with excellence. That has proven to be the case, and I'm grateful. I'm also grateful to have a great team of people who love this equipment as much as I do. We enjoy working together to build first class machinery for our customers and we look forward to continued development.



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