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.