Insulation Support Lug...

Friday, July 31, 2009

As a high temperature fluid transporter, piping shall be insulated. It can be a mineral fiber insulation, or ceramic fiber insulation, depend on the temperature characteristic. There are two type of pipe insulation, blanket type and preformed type. Each type has strenghtness and weakness. In this article, i'd like to explain about how the insulations attached on the pipe, regarding with their strenghtness and weakness.


The first type of pipe insulation is blanket type. Actually, this type can be directly attached to the pipe as long as the pipe orientation is horizontal. But, if the pipe orientation is vertical, then the pipe should be completed with insulation support lug to avoid the insulation will shagging.
It shall shop welded with the same material of the pipe. The thickness is around 1/16", so while the material is alloy, it is allowed to ignore the PWHT. Insulation support lug is needed only for a 6" NPS or larger and attached at every 6' elevation. The width is 2" and the length shall extend to reach 1" penetrating the 2nd layer of insulation. In every elevation, insulation support lug quantity are four at each quadrant of the pipe.
The alternative for this insulation lug is called Marman clamp that can be attached in field, without any welding work. This clamp will be discussed in the next article.
The second type of insulation is preformed type, while insulation support lug is not required.

Welded attachments are not correctly located...

Monday, July 20, 2009

There are various thing can happen while the pipes have already delivered in site. One of the unexpected condition is while the welded attachments are not correctly located at the definited location.
It can be caused by miss-measured or un-updated ISO dwg while in design process. The only thing we can do is just remove the welded attachments from the current position and relocate to the correct location. While they are an alloy material, of course we've got to PWHT the welding joint area.

Incorrect valve's schedule

As i've ever wrote for some incorrect things while in fabrication process, in this article, i'd like to tell you what should you do while you've got incorrect valve's schedule. For example, the supplied valve is sch.80, meanwhile the pipe is sch.160.

Valves used to be field assembled. For some reason, our site representative prefer to modify the valve then to wait the resupplied valves delivered to the site. Since the pipe is a calculated part, so it is important to not to do anything with the pipe. Don't remachining the end pipe to make it meet with valve sch. (sch.80 in this case). The first thing we've to do is make a discussion with the valve supplier.
Ussually, they will advise to built up and then machining the end valve to meet with the pipe sch. (sch.160 in this case). The other recommendation is mill back the end valve to meet the pipe sch. (sch.160 in this case).
The first option takes more resources and expensive, but we can maintain the end to end valve length. Meanwhile, the last option takes short time and a few resources, but we've to add a short spool between the modified valve and the origin pipe, since the end to end valve length isn't as the original size.
So, hopefully you can resolve all issues occur with the incorrect valves.

Thermowell cann't fitted into the pipe...

Sunday, July 19, 2009

Sometime, we are facing with unexpected condition while in shop fabrication process. It could be the specification of the supplied fittings or instruments aren't match with the required datasheet. Or, it could be we did an error while in design process, so the supplied fittings or instruments cann't be attached into the pipe. This article will explain the solution while you've got your instrument (let's say a thermowell) cann't be attached into the pipe or wrong size of the thermowell.

Prior to discuss further regarding with the wrong size thermowell, i'd like to point that bottom side of the thermowell should be shallowed as least 1/3 ID pipe. So, while the bottom side of the thermowell cann't achieve to reach 1/3 ID pipe, then it can be categorized as wrong size thermowell.
There are two conditions while you've got your wrong size thermowell. First, the thermowell has already shop welded into the pipe via the sockolet. Then, there is nothing you can do unless just plug the thermowell using threaded plug and seal welded. Then you have to have a new one thermowll and one sockolet to be attached to the pipe at the new location as far as at the upstream location.
The other condition is while the thermowell hasn't shop welded yet, so what you have to do is just machining the thermowell OD to make the bottom side of the thermowell can reach 1/3 ID pipe.
That's all we can do while we've got a wrong size thermowell, should you have any other question or comment, please don't be hesitate to fill the comment box.

Piping Design (part 02)

Monday, June 29, 2009

While piping designer generate the routing in a plant, some aspect which effect to the piping performance have to be considered. A piping designer should have strong imagination about the condition in the plant while in operating process. For that, complete data as the predecessor should be available to support the designer start to create the routing.

The following items are what the piping designer should be use as their checklist.

1. Pipe specification, such as nominal pipe size (NPS), pipe's schedule, design temperature, and also the material specification.
2. Connection type for the opposite piping, is that weld connection, flange connection, or threaded connection. If weld connection, NPS under 2.5" should be in socket weld connection. For NPS above 2.5" should be in butt weld connection.
3. Still related with item#2 above, the designer should consider while there is a discrepancies with the pipe's wall thickness. ASME B16.25 should be refered to design how should the end of pipe to be machined.
4. Field weld connection should be considered due to the accessible of the spool of pipe to be installed in site. For example while the pipe penetrate a structural wall and fitted with expansion bellows. Then, a field weld connection should be provided to allow the expansion bellows installed in the penetration section.
5. Field weld connection also important to be provided, to allow adjusting the alignment of a very long spool of pipe in field.
6. To do the routing, the piping designer has to make sure that there isn't any clashes with other objects in field. The insulation thickness should be considered also as the outer size of pipes.
7. For piping with high thermal movement, it should be provided with expansion path. Although there are pipe supports that will guide the movement.
8. The designer has to make sure for the availability space for maintenance process. For example, the space to dismantle a strainer cover, as a strainer ussually installed to face the ground.
9. If there are valves or instruments those are installed on the piping, they should be accessible for operating and maintenance.
10. The routing should be placed much closer with any structural steel, to allow the pipe supports can be attached on the structural.
11. A transition material for a connection between high alloy pipe (P91 grade) with carbon steel pipe (SA-106) should be added, ussualy by using low alloy pipe (P22 grade).
12. Any welded attachment as a guidance of part of the supports should be shown in the isometric drawing clearly, completed with the coordinate location.

By considering the above items, any problem that usually comes while in erection stage can be avoided. The next part of this article will discuss about mechanically aspect in design process.

Piping Design (part 01)

First of all, i'd like to make a clear understanding in determining between pipeline and piping. Pipeline has long distance in transporting fluids, it can be a hundreds miles away from the upstream to downstream. Meanwhile, piping just to transport the fluids in a short distance within the plant area. Pipeline used to be has large bore of nominal pipe size, above 20". meanwhile piping has smaller bore of nominal pipe size, under 18".
Now we've understood the main discrepancies between pipeline and piping, since i'd like to discuss about the design process for piping only, in the next paragraph.

Many aspects should be considered while design a piping system. As we've discussed in previous article, regarding the discrepancy between pipeline and piping. So, in this article we talk about piping design consideration, instead of pipeline. Although the items to be considered are mostly same, but i'd like to focus in piping.
In design stage, there are three main aspect which cover the overall detail aspects. The first aspect is related with the piping system's performance to transport the fluids. Based on "Inspeksi Teknik-Buku3" wrote by Sri Widharto, the parameters should be considered are as follow :

* Design temperature, is the temperature of pipe's material which is simulated in the most critical condition. In this case, critical condition means a condition that demand the maximum specification of the piping's material, including it's fittings. I divide the piping for two condition, un-insulated and insulated.

1. For un-insulated piping system, if the fluid temperature <>= 100 deg F (38 deg C), then the piping system's temperature (including the valves, flat face flange, welded joint fittings, and other components which have equal rating with the pipe's wall thickness, may not less then 95% of fluid's temperature. For flange's temperature (unless flat face flange) may not less then 90% of fluid's temperature. And for the fastener's temperature may not less then 80% of fluid's temperature.
2. For an insulated piping system, the piping system's temperature is designed to be equal with the fluid's temperature. Unless, based on previous experienced operation that make the design temperature should be considered to follow the existing data.

* Design pressure, is the pressure which may not less then a combined pressure from internal and external pressure in maximum and or minimum temperature which may occur in operating condition. A design pressure have to be able to throw out an over pressure that could be occur while in operating condition. Over pressure caused by a fluctuative pressure, incorrect operating, or even failure of equipment's function. Therefore, a pressure relieving device always installed in a piping system.

That is all i can describe about design process for piping system which is related with it's performance. We are going to have a long discussion regarding with design process related with the piping routing and mechanically consideration, in the next part of this article

What are they, actually.....

Many people realize for something just by see it, touch it, or just heard from someone else. They can describe it only by what they have known. Let us talk about pipe. With this method in understanding, it can be various opinion in determining the pipe, since every people have their own imagination.

It's important to refer from something that already agreed to be used universally.Based on ASME B31.1-2007, "pipe is a tube with round cross section conforming to the dimensional requirements for nominal pipe size". Regarding with pipe size, you can see it in ASME B36.10M table 1 and ASME B36.19M table 1. There are some discrepancies between pipe and tube, such as tubes are specified by its outside diameter, meanwhile pipes by its nominal diameter. Pipes are used to transport any fluids, meanwhile tubes are used in a process industry or plant, mostly. Therefore, there is a finned tube to have an expanded area in heat transfering.
Pipes are produced up to large diameter, meanwhile tubes are produced in a small bore. Range of size for pipes are from 1/2" up to 60", meanwhile tubes are from 1/2" up to 8".
Generally there are two kinds of pipe, based on how they're manufactured. The first type is a seamless pipe, and the other is a seam pipe or welded pipe.Welded pipe itself, consist of longitudinal seam pipe and spiral welded pipe.
Seamless pipe mean that there is not any welding process in manufacturing the pipe, the pipe are produced from a hot round solid steel billet. A steel round bar then penetrated to the hot round solid steel billet, make it expand become a seamless pipe.
Welded pipes are produced from a plain plate which rolled and then welded on the edge of joint.
Pipe are specified in based on its material, wall thickness, and its nominal diameter. Some example for carbon steel material for pipe are as follow :

* A-53 Gr.A and Gr.B is the standard material defined by ASTM for both of seamless pipe and welded pipe.
* A-106 Gr.A and Gr.B, produced for seamless pipe.
* A-333 Gr.1, this one used for working temperature under 1 degree Celcius or minus 50 degree Fahrenheit.
* A-335-P1, categorized to alloy pipe. Used to working temperature between 414 to 468 deg Celcius or between 776 to 875 deg Fahrenheit.
* A-335-P22, also categorized to alloy pipe, with range of working temperature between 539 to 593 deg Celcius or equal with 1001 to 1100 deg Fahrenheit. Ussualy, used as transition material between high alloy(P91) to carbon steel.

There are still other materials specification those cann't be mentioned in this article. But if you curious to learn more, you can find them in ASME IID.

History of pipe...

It has been many years people in this world using pipeline to convey any fluids to their definite place. Where it's began is unclear yet, but the trusted source tell that it was Romans and Persians who found the idea in conveying water to other faraway place, called aqueducts. Meanwhile, it was bamboo which was used to convey water, in China, some time ago. In that time, pipeline only used to support irrigation and also for citizens consumable. However, they were succes in maintaining the pressure, so the water can be delivered to the required elevation. In it's development, people start to produce stronger pipe using cast-iron, in 18th BC. Then in 19th BC, pipe material were developed into steel, producing in various size. This improvement, allowing pipe to convey natural gas and oil. The main reason why people at that time did a research in pipe's material development is they need pipe which able to convey any various characteristic of fluid. Hot fluid, high presure fluid, corroded fluid, etc. That is why, now we can just choose what kind of pipe that is suitable to be installed in our systems, based on what should be conveyed.