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TOPIC: P&IDs Review by Piping Engineers in an EPC project

Re: P&IDs Review by Piping Engineers in an EPC project 10 years 3 months ago #5164

  • Willis
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Am I being cynical?
Have any of you guys shared these wonderful experiences?
Unfortunately I have found myself in this same boat for the last few years, with process, piping, mechanical, and structural all starting at the same time. In a situation like this, communication between the disciplines is key and when not functioning it will lead to major problems down the road.

Re: P&IDs Review by Piping Engineers in an EPC project 10 years 3 months ago #5165

  • aubajwa
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Title: Pump Suction Lines 'Flooded and Overflooded'

Morning!

Just got little bit confused with two types of pump suction lines. Pls clear:

A) What difference b/w 'Overflow Pump Suction Line'. / 'Flooded oump suction' (I feel it is normal suction line running from equipment to pump; and should be flooded; in casse if pump is not self priming?).
and Do these two lines normally present in all centrifugal pumps?

B) Process book recommends 'Overflow pump suction lines are designed for about a one foot/second velocity, unless a higher velocity is necessary to keep small solids or precipitates in suspension.' <===== What could actually they meant by 'suspending the solids' and why would they like to do so.

C)Also in attached figure what could be possible reason fo having a backflow (indicated in red) to pump discharge line again.

Thanks
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Re: P&IDs Review by Piping Engineers in an EPC project 10 years 3 months ago #5166

  • Jop
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"C)In attached figure what could be possible reason for having a back flow (indicated in red) to pump discharge line again?"

This small 20mm (3/4") line around the Check Valve is called a "Warm-up Bypass" and to understand its purpose you must understand the pump service and operational and maintenance philosophy.
I am not there and I cannot talk to your Process Engineer so I must make some assumptions based on my past experiences.

So here goes.
I think that these pumps are in a "Hot" service. This is supported by the designation of "PP" for "Personnel Protection" insulation. The fluid in this circuit is possible the type that if it is allowed to cool too much it could be difficult to start the pump.
I think these pumps normally run with one operating and one on "Stand-By". This run/stand-by would be set on a fixed time cycle. This cycle might be 24 hours or 48 hours so that each pump will see near equal use and wear. This prevents the bearings in the shut down pump from developing flat spots and going dry.

The purpose of the "Warm-up Bypass" is to allow the hot fluid being discharged from one pump to go backwards down the discharge of the stand-by pump, around the check valve and through the pump to the suction side line. It is not normal to have a valve in this small line. It is more normal to just install a restriction orifice union. The orifice would have a small fixed hole for the flow. This small flow will keep the pump case warm so if the pump "Auto" start circuit turns the pump on the pump is not "frozen" and is not damaged.

Another way this can be (and is often is) done is to just drill a small hole in the disc of the check valve.
Do it once and Do it Right

Re: P&IDs Review by Piping Engineers in an EPC project 10 years 3 months ago #5169

  • Jop
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Items A & B

"Flooded Suction"
http://www.pumpworld.com/Flooded%20Suction.htm

"Overflow Suction"
I cannot find anything on "Overflow Suction" and I have never heard of this.
Do it once and Do it Right

Re: P&IDs Review by Piping Engineers in an EPC project 10 years 3 months ago #5171

  • Jop
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The line identification is made up of six groups of numbers and or letters (400-CL-040-9114-A2AS-PP), Please define what these are and what they mean for this project.
400 - Pipe size?
CL-?
040-?
9114-?
A2AS-?
PP- Insulation Code for "Personnel Protection"?

The more I look at the P&ID for these pumps the more questions I have.
1. What is the material of the pump Suction and Discharge lines?
2. What is the flange rating for these lines?
3. What is the wall schedule for these lines.
4. What is the realistic Operating temperature for these lines (not the Design Temperature)?

We know the nominal pipe sizes for these lines 400mm (16") for the Suction and 150mm (6") for the Discharge. But we do not know why there is this large difference in the line sizes. With a Discharge line size of 150mm we can assume that the pump discharge nozzle would be likely 100mm (4") or 150mm (6") but we do not know for sure. If the discharge nozzle is in fact no larger than 150mm then the Suction nozzle would normally be 200mm (8") or 250mm (10") maximum size. Understanding that then the next question is:
5. Why is the main suction line 400mm (16")?
6. If the main suction header is in fact 400mm, then what size are the suction block valves? And do they require Gear Operators?

Next there is a big question in my mind about other piping around these pumps. The pumps are "Hot" and being pumps they have Barings, Seals and Packing Glands. All of these will fail over time and need to be replaced. To replace any of these the pump must be shut down, made safe, drained and steamed out.
7. Where is the case vent?
8. Where is case drain?
9. Where is the Base Plate drain?
10. Where are the valved 20mm (3/4") connections (on the pipe near the suction block valve and the discharge block valve). These are for Nitrogen purge to blow out the fluid in the line and for Steam to steam-out the pump and all the piping?
11. Where is the drain funnel for pump drips to the base plate drain to the Oily Water Sewer?

There is also a possible need for cooling water for the Baring cooling, the Gland cooling and possibly pedestal cooling.
12. Do these pumps have one of the API 682 Standard Pump Seal Plans?
13. If so, which one?
14. How much of the API 682 piping is furnished by the pump vendor and how much is by the Engineering Contractor?
(Look at this web site for information and examples) http://www.scribd.com/doc/2462681/API-Flushing-Plans
After you look at this you will see that Piping IS involved. If there is a cooler then piping must supply the connections to the cooling water supply and return. If there is a Bleed or vent to the Flare then piping needs to supply the connection. Piping also is responsible for making sure that other process piping does not block access to these API 682 items for maintenance.

Maintenance items:
15. If those figure "8" blinds are large and weight more than one man (or two) can lift is there going to be lifting facilities available?
16. If so what kind?
17 How much room is required for access and removal?

Do what you can on these but don't forget to take time for lunch.
Do it once and Do it Right

Re: P&IDs Review by Piping Engineers in an EPC project 10 years 2 months ago #5177

  • aubajwa
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Hi Jop,

Right, here it goes....

400 - Pipe size? <==== Yes.
CL-? <=== Low Pressure Condesate
040-? <==== Unit No
9114-? <=== Line Sequence No
A2AS-? <=== Material Spec
PP- Insulation Code for "Personnel Protection"? <=== Yes Correct

The more I look at the P&ID for these pumps the more questions I have.
1. What is the material of the pump Suction and Discharge lines? <=== Probably A2AS, i.e. CS
2. What is the flange rating for these lines? <=== 150 lb as per A2AS spec...but pump nozzle is 300 lb flange
3. What is the wall schedule for these lines. <=== STD, as pe spec
4. What is the realistic Operating temperature for these lines (not the Design Temperature)? <== Line list shows design temperature only 150 deg C.

5. Why is the main suction line 400mm (16")? <=== well I really have no idea about that. Its the process decision.
6. If the main suction header is in fact 400mm, then what size are the suction block valves? And do they require Gear Operators? <=== Seems to me of same size as of pipe. P&ID not talks about any Gear Operator stuff. ****But Pls suggest what could Gear Operator valves have impact on Piping.

Qs 7-11, I hope new REV gives some Idea. Also pls see my Email.

12. Do these pumps have one of the API 682 Standard Pump Seal Plans? <=== YES
13. If so, which one? <=== Seal Category 2 / Code BSTFN
14. How much of the API 682 piping is furnished by the pump vendor and how much is by the Engineering Contractor? <=== For this I have sent info in the Email.

I hope Jop I have answered clearly.

Thanks
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