15 replies to this topic

[yogu77]

Hi

Any one has come across work experience with Dresser Rand Reciprocating compressor?

Ours is H2 compressor with 2 stages each for LP/HP stage. Compressing H2 from 2 barg to 150 barg

Problem:

We face the problem of oil accumulation in both LP/HP stages discharge pot (also called as pulsation pot), We are looking for source to have permenant connection from the discharge pot to drain the oil.. The risk involved is oil at high pressure.

Pls share your knowledge if you have experienced around this area..thanks

[Art Montemayor]

Yogu:

The reason that you are collecting oil in your compressor’s discharge separator is that the separator is doing its job of separating the oil.

You fail to tell us what model of Dresser Rand recip you are running. I have to guess that it is an oil lubricated model in the cylinders – but I don’t know if you are supposed to have mini-lube or full cylinder lubrication. In other words, are you using cast iron rings or do you have Teflon rings?

I’ve operated Ingersoll-Rand (now Dresser) recips on CO₂, air, Nitrogen, Nitrous Oxide, and Hydrogen – in machines of up to 3 stages. If you have an oil lubricated cylinder model machine, then you should expect (& design for) oil separation and eventual drainage. This is not a large amount of oil, but it must still be drained. Obviously you knew this, even before you bought and installed the machine. What is the reason that this is a problem now - and what kind of problem is it?

All inter-stage (& after-stage) compressor separators have to be drained of condensed liquids as well as cylinder lubricating oil (if the cylinders are oil lubricated). This is a known and accepted fact. Continuous, automatic drainers are installed on the separators to allow for automatic draining of all the trapped liquid. This is the normal and expected design. This is my knowledge and experience in this matter.

You have not stated a specific and detailed problem regarding your post. I can’t comment any further since I have given you what you asked for - my knowledge and experience.

[yogu77]

Hi Art Montemayor,

Thanks very much for your quick response

Our compressor consists of 2 sections , Low Pressure (2 stages) & HP (2 stages)

Our model is ESH2

Size: 4.25” / 3” (LP) & 3”/3.0-2.25” (HP)

Stroke: 7” (both for LP & HP)

Yes, you are right, our compressor is oil lubricated. I am not sure what type of rings we are using, I have to check with mechanical. The attached powerpoint file explains our problem here. Our compressor is in service about 6-8 months. At present we are taking shutdown for few days for every 20 or 30 days based on our rawmaterial/product demand. However, in future it’s planned to run our unit for long run.

2) Another doubt if you don’t mind, we have suction strainer at the H2 gas inlet line to compressor. As per the vendor drawing, this strainer supposed to be for initial start up only, and not for permanent service. Our compressor is in service for more than half a year. We didn’t remove the strainer yet, we thought it helps to protect the compressor parts if there is any dirt/foreign particles from the inlet gas. Is there any problem if we continue to operate with suction strainer in line?

Thanks,

Regards
Yogu

Attached Files

•  Oil_Build_Up.ppt   31KB   177 downloads

[abhi_agrawa]

yogu77,

1) Since oil is expected in the pulsation pot, suggest you should put a Level Controller to drain the pot automatically or at least install a sight glass for manual drainage. Unless you have some indication of the level in the pulsation pot, it will not be safe to drain the same when the compressor is running.

2) Operating with the suction strainer is a good idea.

abhishek

[yogu77]

Thanks Abishek...

[resmihadi]

hi Yogu77,

I have operated the same compressor for a couple years.
though its three stage , with the first suct press is 14 kg/cm^2 and disc press of third stage is 200 kg/cm^2, we operate as h2 make up comprss.
we use teflon type for rings an lubricated either.
about your problem, may you re arrange the amount of lubricant (usually in 'drops') that flows to the rings. if theres too many, it could be a problem on the disc valve and pulsation pot. but if less than the needs it could be danger for the compressor.
so, you should be carefully arrange the numbers of lubricant drops, follows the design will be best.

resmi

[yogu77]

Hi Mr Art /Abhi/Resmi ...

Just to add more info on this subject..


1. We are using Teflon rings with forced feed lubrication system. The oil accumulation observed is quite significant. I am just wondering why dresser rand didn’t design to have facility of online draining or atleast level gaue to monitor the accumulation. We are working to have some draining facility now. Thanks for all your comments.

2. 2nd thing we have noticed pressure drop in the LP 2nd stage (normal running 28 to 30 barg), droppped to 24 barg. We managed to run by increasing suction pressure little bit. We opened H2 compressor for inspection. Attached are the piston picture and you can see the white mark. As per the mechanical, H2 gas leak (escape) through the ring (between the stages) That might be the cause of pressure drop in the system..Please share your comments if any.

Attached Files

•  Piston.JPG   352.19KB   94 downloads

[Art Montemayor]

Yogu:

My comments on this post are as follows –

I assume you are an engineer and as such can understand what I have written in my prior post. There are many things about this thread that are causing mistakes, confusion and an inability to add positive value and help to your present situation. This is unfortunate because what you are facing is a relatively easy problem to resolve.

Although you now have furnished additional data, it is by no means complete, detailed, or accurate. Please refer to the Workbook that I will attach to this post later (when I get the time to generate it) for an example of what data is required in order to discuss your reciprocating compressor problem intelligently with us and with others.

I consider this a very important and critical problem facing your company (& you) because it threatens your production rate and your economic success. This problem should have the highest of priorities within your production department. Why it has taken this long (2 weeks) to get at least some needed data is something I don’t understand. We intend to be of as much help to you as we can but we need all the basic data and details that we can get. I have faced these types of problems in many past opportunities and resolved each one successfully - within days. We cannot be of help if we have a lack of details and inaccurate information.

You state that you are compressing hydrogen from 2 barg to 150 barg in 2 stages of compression using a Dresser Rand ESH2 model compressor. You further stated that the compressor consists of 2 sections, Low Pressure (2 stages) & HP (2 stages) and that the Size is 4.25” / 3” (LP) & 3”/3.0-2.25” (HP) with a 7” Stroke (both for LP & HP). This information can’t be correct as written. You require a minimum of 3 compression stages for the compression ratio that you state (151/3 = 50). Also, what do you mean by “sections”? The “sizes” that you quote also don’t make sense. The ESH machine is a basic, one-throw, in-tandem compressor. It can be 1, 2, or 3 stages of compression. The size of the machine is noted as 1st stage diameter x 2nd stage diameter x 3rd stage diameter x the stroke (@ the rpm). Other data that is normally given is the action (single or double-acting) of each piston, oil-lubrication or non-lube on the cylinders, the suction & discharge pressure of each stage, the gas capacity of the 1st stage, the connected horsepower, and whether there are any side-streams of gas entering any of the stages. There is no “Low” and “HP” side on one machine; the machine has various stages of compression and the pressure is increased in a progressive manner as the stages increase. Your sizing information is very confusing and, as such, tells us nothing except that this is a relatively very small capacity machine (although it probably plays an imporant role in your processing needs). The picture of the piston you have submitted verifies that this is a small machine.

How old is the machine? Please furnish all the information stamped on the compressor’s name plate, including the serial number. I presume this compressor is electric motor driven, through a V-belt drive. It is customary for Dresser Rand – like all other compressor manufacturers – to have their machines “packaged” (skid-mounted & assembled with coolers, piping, driver, controls, etc.) by a “Packager” company. Where did you purchase your compressor? I think you are located in Singapore, although you don’t reveal any useful information on your personal profile information. If you purchased this machine recently from Dresser Rand India Pvt. Ltd. Then you can refer to their description at:

http://www.techbizindia.com/virtual_exhibition/pdf/Dresser_Rand.pdf

A process/compressor audit is available as a customer service by them and you should be contacting them already. Dresser Rand is a serious, established, and recognized manufacturer who stands by their products. They can be of immediate help locally if you use them. Here, I am presuming that you bought the compressor recently as new equipment (& not “used”) and that the machine carries the usual Dresser Rand warranty and service.

Now you have revealed that you indeed do have Teflon rings installed in the machine (in all stages?) as I had suspected from the beginning. If you have oil-lubricated cylinders, then you must have what is called “mini-lube”. This is an oil-lubrication system to the cylinders that is measured in miniscule quantities. Depending on the diameter of the cylinder in question, the oil lubrication rate to that cylinder can be ½ to 3 drops of oil per minute. It is just enough oil to keep the Teflon rider band and piston rings riding on a thin film of oil and barely touching the cylinder liner. Teflon, as such, does not require any lubrication. Mini-lube is applied to reduce the potential of Teflon wear and give more life to the rider bands and rings while forming a more positive seal between the ring and the cylinder liner. You definitely should not be having any oil separation problems – and much less any Teflon ring problems. Something is definitely wrong in the manner your machine has been packaged or in the manner you are operating it. You have failed to tell us the oil lubrication rate you are imposing on the machine and I suspect that you are exceeding the recommendations of Dresser Rand. That is why you must make contact with your local D-R representative and advise them of your problems and obtain their recommendations.

Who is it that you describe as “the mechanical”? You have said that you don’t know what type of piston rings you had in the machine but that this person did. Is this an engineer or a technician / mechanic? Are you dealing with experienced, knowledgeable personnel? You are obviously feeding excessive oil to the cylinders and that gives cause for concern on the part of the quality of operators that you have. The quality of the piston picture you submitted is very bad. The lighting is not conducive to reveal the piston ring damage or type. The “white mark” tells little or nothing about the failure.

Your ESH machine is described in the following website:

http://www.dresser-rand.com/recip/eq/esh.asp

If you indeed do have pulsation drums installed on the suction and discharge of each of the stages on your machine, you have a basically good packaged design. However, do not implement what abhi_agrawa is recommending. You don’t need a level gauge to detect oil in the pulsation drums. Oil should not be collected there normally – if it is a sound and good design. Contrary to the recommendation, hydrogen can be safely purged from the pulsation drum at intervals to reveal its oil drains out. The level gauge is a potential hazard in that if it is broken, a dangerous fire or explosion can occur. The manual intermittent draining of the pulsation drum is not a hazard when the compressor is running. If you are compressing hydrogen, it should be classed as a very clean and solids-free gas stream. You should not need or employ a strainer on the suction of the 1st stage. Now, if you are working with a dirty gas then you are going to inherit worse problems – such as valve and ring damage. I would make sure the gas is properly cleaned and meets the criterion for entering the reciprocating machine.

What resmihadi is recommending regarding the amount of oil lubrication to each cylinder is exactly what I have stated. However, it is inaccurate to state “but if less than the needs it could be danger for the compressor”. Reciprocating compressors with Teflon rings and rider bands are designed and fabricated to operate without any oil. I have operated such machines for many years – without any problems. I have also specified and applied mini-lube machines with the same Teflon construction. The latter has been done because of client requests. Both have operated with the expected success. What is important for your machine is that you follow the detailed and specific instruction issued by Dresser Rand regarding the design and application of your machine. That is why I keep asking you to tell us if you have a new machine purchased from a D-R representative and with the usual D-R warranties and service availability. The fact that you knew nothing about your piston rings and that you have not described your machine accurately tells me that you are not experienced with reciprocating compressors and their characteristics. Before you attempt to make any repairs or modifications to this machine, I would obtain the services of an experienced, knowledgeable engineer who not only knows this type of machine, but who will work directly with the packager and Dresser Rand as well.

I will attach the workbook I promised to this post as soon as I can.

[Art Montemayor]

Yogu:

Attached find the Workbook I promished you. Please note that I am showing 4 stages of compression. I still don't know the diameters of each stage. The stroke (which I assume is 7") is common to all cylinders since the ESH model is an in-tandem design.

For such a small machine, I cannot imagine how the packager was able to install two pulsation drums on each cylinder. Yours must be a very, very crowded skid or installation.

If you have a new machine, I strongly advise you not to tamper with the basic design. Do not install any glass level gauges. Your pulsation drums should be running dry - especially the suction side. As I said, you have to be feeding excessive lubrication oil to the cylinders. That is the only way the oil can get into the pulsation drums. You must consult with your Dresser Rand manufacturer and let them know what is happening. This is not normal and you could ruin the machine if you fill any compression cylinder with oil. You have already taken out one of the pistons, so you should tell the manufacturer what you have found. Refer to the factory-supplied operating manual to find the prescribed quantity of oil lubrication drops to feed to each of the compresion cylinders. You must follow the manufacturer's instructions or you will forfeit the warranty.

If you can, fill in any information about the compressor on the schematic drawing I have supplied.
 Reciprocating_Compressor_Schematic.xls   1.75MB   337 downloads

[yogu77]

Mr Art,

Did you receive my previous email? May I know your personal email, to send you the name plate details.. I afraid to share those details in the forum. Hope you understand. Thanks

Yogu.

[yogu77]

Dear Mr Art

I am writing you after a long time. I believe you have our compressor details. Ours is 4 stage reciprocating compressor, in which 1st & 2nd stages are being driven by one motor and 3rd & 4th stages by another motor. In general for stopping a compressor, is it a normal procedure to unload the compressor stages and stop the motor OR we can stop the compressor when it is fully loaded and depressurize the gas inside after the compressor is shut down?

When the compressor is tripped due to some emergency (when it is fully loaded), will it cause any problems to the compressor internals?

Thanks,

Regards
Yogu

[Art Montemayor]

Yogu:

I'm on my way to a meeting, so I don't have much time to dedicate to this response.

Under no conditions should a reciprocating compressor be stopped while under load - in other words, a reciprocating compressor has to be totally unloaded before attempting to stop the machine. I realize that the designer/fabricator should be the expert on this specific subject rather than I, but I have been specifying, purchasing, installing, and operating a lot of reciprocating compressors through the years and I have never heard of any fabricator that would accept to have his/her machine stopped without first totally unloading the machine.

Please take this advice seriously. A lot of serious damage and harm can occur if you stop the machine under load!

[yogu77]

Dear Mr Art

We sincerely thank you for your response to this query and for the previous posts. Sorry for not replying so fast.

Our 1st and 2nd stage compressors have air operated unloader valves and for 3rd and 4th stage we didn’t have. There is a automatic recirculation valve (on/off) between 2nd and 4th stage. 1st/2nd stages are loaded by air operated unloader valves and 3rd/4th stages are loaded by closing the recirculation valve during the startup.

Our current practice of shutdown is we unload 1st/2nd stages (together) first and after 3 minutes 3rd/4th stages will be unloaded automatically by opening the recirculation valve to 2nd stage. But when the valve opens, high pressure gas (150 barg) flow towards low pressure stage, either the motor will trip due to high pressure or PSV will pop up. So we throttled the manual block vales upstream and downstream of the recirculation valve to prevent the motor from tripping or psv pop up. Then we manually stop both motors. What is the usual practice of unloading high pressure compressors and to where? Are we doing the correct method? Our operating pressure is 150 barg, so at what pressure can we comfortably say the compressor has been unloaded fully (< 50 barg?) so that we can stop the compressor?

Our initial operating notes during commissioning states that we can stop the compressor in loaded condition. Even though we are not practicing that, we confused and thats why I have asked you the query of whether we can stop the compressor in loaded condition. Thanks very much for clarifying that.

Yogu

[yogu77]

Dear Mr Art

Did you see my previous post? I still have some queries regarding compressor unloading.

Our 1st and 2nd stage compressors have air operated unloader valves and for 3rd and 4th stage we didn’t have. There is a automatic recirculation valve (on/off) between 2nd and 4th stage. 1st/2nd stages are loaded by air operated unloader valves and 3rd/4th stages are loaded by closing the recirculation valve during the startup.

Our current practice of shutdown is we unload 1st/2nd stages (together) first and after 3 minutes 3rd/4th stages will be unloaded automatically by opening the recirculation valve to 2nd stage. But when the valve opens, high pressure gas (150 barg) flow towards low pressure stage, either the motor will trip due to high pressure or PSV will pop up. So we throttled the manual block vales upstream and downstream of the recirculation valve to prevent the motor from tripping or psv pop up. Then we manually stop both motors. What is the usual practice of unloading high pressure compressors and to where? Are we doing the correct method? Our operating pressure is 150 barg, so at what pressure can we comfortably say the compressor has been unloaded fully (< 50 barg?) so that we can stop the compressor?

Our initial operating notes during commissioning states that we can stop the compressor in loaded condition. Even though we are not practicing that, we confused and thats why I have asked you the query of whether we can stop the compressor in loaded condition. Thanks very much for clarifying that.

Yogu

[Art Montemayor]

Yogu:

Eight months later, I am still sad you continue to have serious compressor problems and mis-understandings with what I consider to be a simple compressor application. You will recall that I stated: "Although you now have furnished additional data, it is by no means complete, detailed, or accurate. "

I think you actually have two compressors, connected in series. You have not stated to the contrary. You also have not furnished a schematic drawing or diagram showing the compressors, the different stages, intercoolers, or separators. I have supplied you with a drawing schematic and I was hoping that you would take the time to edit it or correct it where I had to assume certain information. I also asked for pressures, temperatures, and scope of work.

I am presently not at my home but spending holiday time with my grandchildren in Tucson, Arizona. I will not be home until two week from now. In the meantime, if you are able to invest some of your time and effort in trying to resolve your problem by supplying me with what I have requested, I would appreciate it. It would make a correct and logical resolution of your problem much more simpler and easier to explain and apply in the field.

Also, please respond or comment to all the previous comments and recommendations that I furnished you.

Expect your reply soon.

[yogu77]

Dear Mr Art

I have already shared the info about the compressor details on your personal email and I have got reply from you quite some time before. Many thanks for that reply.

I started the query again regarding the shutdown philosophy of the compressor. Sorry for the inconvenience caused.

Yogu