Instrument Air

Macphail
27th August 2009, 23:10
Instrument Air..

Pneumatics play a very important role.
The quality is so important, the air should be dry and slightly warm, poor quality instrument air can effect operation of the ship, engine failure, cargo valve failure and more.
I feel that an over kill is important, driers and more driers, poor air means instrument failure and expensive replacement.
What is the trend on the modern ship ?.

John.

Satanic Mechanic
27th August 2009, 23:36
dry dry dry dry dry

for the love of god make sure it is dry

oddly though very recently i encountered a case where a bit of oil was encouraged on a main engine control system!!!!!

Philthechill
28th August 2009, 22:23
The automation on the ACL ship's "Atlantic Causeway" and "Atlantic Conveyor" was pneumatic with all the valves being Fisher manufacture and the automation controllers being by Moore Products Inc.(very high-quality American kit).

All well-and-good except that the ships were steam-ships with the air-compressors "sucking" all their air from an extremely humid atmosphere (both ouside the ship and also in a moisture-laden engine-room!!) with the net-result that the driers worked overtime, and not always totally successfully, as could be witnessed by the regular "p-s-s-s-s-t" from the myriad traps behind the Control Room main panel as the accumulation of water, the driers had not been able to remove, was vented.

Whereas air-driers in a "normal" environment would have more than enough time to dry-out the silica-gel, in the off-line drier, the driers on these two ships never had enough time to completely regenerate before the on-line drier automatically changed-over because of the high water content which had built-up in the on-line drier!!!

A nightmare because, as has been mentioned by John, in his "Thread-starter", (and endorsed quite emphatically by "Vambo"!!!!), dry air is an absolute must for instrumentation purposes!

Whether the more up-to-date refrigerated air-driers would have been able to cope in such a "wet" environment is a moot point-------probably not. Salaams, Phil(Hippy)

Macphail
29th August 2009, 21:48
Lubricated Pneumatic Controls…
In the early eighty’s the quality of instrument air and the implications of a poor instrument air supply were not appreciated. I joined a gas ship in winter time Le Havre , early eighty’s, all the instrument control boxes on each cargo tank dome where wide open and a fire hose was jetting water into each box, by the Cargo Engineer, this was to prevent the instrument air freezing up ?. Another dodge was to inject Methanol down the line, but then an explosive mixture was created.
The Wabco / Westinghouse controls for the Main Engine can be a problem, because of the under kill on instrument air quality, I cannot understand the logic of saving a $ during the build but paying 100 $ later on.
I ask again, what is the present day attitude to good quality Instrument Air.
Like many things, it must be warm and well lubricated.

John.

Philthechill
29th August 2009, 22:45
Lubricated Pneumatic Controls…
In the early eighty’s the quality of instrument air and the implications of a poor instrument air supply were not appreciated. I joined a gas ship in winter time Le Havre , early eighty’s, all the instrument control boxes on each cargo tank dome where wide open and a fire hose was jetting water into each box, by the Cargo Engineer, this was to prevent the instrument air freezing up ?. Another dodge was to inject Methanol down the line, but then an explosive mixture was created.
The Wabco / Westinghouse controls for the Main Engine can be a problem, because of the under kill on instrument air quality, I cannot understand the logic of saving a $ during the build but paying 100 $ later on.
I ask again, what is the present day attitude to good quality Instrument Air.
Like many things, it must be warm and well lubricated.

John.John! Your, "I cannot understand the logic of saving a $, during the build, but paying $100 later", is covered by that old chestnut, "Cost & value".

The bean-counters, as long as their ring-pieces point South, will never understand this concept! All they see is, "If you can buy something cheap, which will bring the eventual cost of the project down, then go for it!"

Then, when the cost of putting their cheapskate attitude right comes home to roost, they are long gone and, (even though the cost of putting their tightfistedness far outstrips the original costings several-fold) forgotten and they will be committing the same mistakes all over again!

"Cost & value" should be explained to every would-be bean-counter, (before they are let loose in the real world) and the understanding of this simple formula hammered into their money-driven brains until they finally realise that saving a couple of buck's, in the early day's of a project, could well cost many, many times that when it comes to rectifying their parsimony!! Salaams, Phil(Hippy)

Satanic Mechanic
30th August 2009, 08:46
Its infuriating Phil. I was about to write a spiel about it but I can already feel that vein in my temple throbbing - so for my own as well as my keyboards sake I will refrain

surfaceblow
30th August 2009, 20:06
I really haven't had a problem with Instrument Air for a very long time. This occurred about the same time that Rotary Air Compressors, automatic water traps and refrigerafilters where installed on ships that I served on. Most of the Control Air Receivers had the outlet line on the top of the tank and if the watches drained the receivers each watch we did not have a problem with the water.

When I went from Steam Ships to Motor Vessels I did find on some Vessels the Main Engine Control Air that came off the Air Start Receivers at times had both Oil and Moisture problems and of course since the vessel was UMS the receivers may have been blown down twice a day compare to six times a day or more when there were watch standers. High Pressure Reciprocating Air Compressors that liked to pump oil and moisture into the Air Receivers. On opening the Control Air Cabinet on the Main Engine I found that a lack of maintenance was the cause of untreated air was allowed to bypass the separators . After rebuilding the Control Air Cabinet the company I worked for decided to install a separate refrigerafilter for the Main Engine Controls. The company found that the parts were hard to find and cost more than the refrigeafilter.