Check valve installation procedure 1

[gustorf]

Dear All,
We all know that check valves should be installed at least 3 x DN behind the discharge of pumps, not on 90° ellbows, at least 2 x DN before any downstream valve, etc.
This is common engineers knowledge, but where in the literature is this written?

 

[pennpiper]

Where did you see or hear that?

After more than 45 years in the piping business I have never heard of such a rule.
I say it is bunk.

I put in a lot of top discharge pumps where the piping after the discharge nozzle was a flange, a reducer a flange and then the check valve.

Please tell us all where you saw this.

 

[stanier]

Many check valve manufacturers have in their literature a requirement for 5-6D between pump discharge and check valve. In fact Velan recommend 10D.

The reason is that there can be turbulence from the pump that increases the wear of a check valve and lead to its failure.

There was an ASTM standard that covered this topic.

 

[pennpiper]

gustorf (Mechanical)

At this point you have gotten two different opinions. These two opinions are at the opposite end of the scale.
So what do you do?
Well I suggest that you buy "Process Plant Layout and Piping Design" by Ed Bausbacher and Roger Hunt.
You can find it on Amazon(dot)com
Chapter 8 (page 181) covers pumps and pump piping very well. Read it and then go out to a Refinery or Chemical plant and look at all the pump installations. If you can take pictures do so. If you cannot take pictures make a sketch of all or as many as you can and get the service and design conditions (pressure & temperature). Then take a few dimensions.
Decide for your self what is right.

 

[pennpiper]

stanier (Mechanical)
You are indeed a prolific contributer to the "ENG-TIPS Forum" and with out going through all 124 of the threads you have started or the 1,139 replies to other people's question or even the 93 replies you made to your own threads I must accept that you are knowledgeable about what you speak.

However, on this subject I think you may be mixing up the Hydraulic Institute recommendations for pump suction piping for an end suction pump.

If Velan has such criteria I cannot find it and I cannot fine it in any other valve vendor's technical literature.

If "ASTM" addresses this subject please furnish the number of the Standard. Also if ASTM is "American Society for Testing and Materials" why are they addressing check valve installation position relative to a pump discharge?

I also checked with a colleague (35 year piper) and we are in agreement that you are confused and giving wrong information to gustorf .

 

[insult2injury]

Pump discharge pressure and flow fluctuations, turbulence, etc. can cause increased wear on the check valve. Most valve manufacturers will recommend long lengths between piping components. While this is good practice, it is not necessarily required as the manufacturers will agree. In most applications, the process conditions are not severe enough to cause a noticeable difference in valve life and maintenance. By following the piping guidelines mentioned, no valve should fail prematurely due to improper layout. My advice is...if you can accomodate it, do so...otherwise ask the manufacturer to take a look at your specific application (not all vendors will agree to do this however).

I2I

 

[stanier]

Pennpiper,

Rather than dig up statistics on my postings perhaps a search of Eng-tips on this subject would be better time spent. Here is the ASTM reference

http://www.eng-tips.com/viewthread.cfm?qid=32499&page=61

I also suggest reading of test work by Delft laboratories and texts by Professor ARD Thorley.

I have seen this requirement quoted in company standards and in manufacturers' literiture else I would not have mentioned it. As recently as yesterday I was reading the Velan literature provided to me by a valve company other than Velan.

This is not necessarily a question addressed by a "piper" but more for a mechanical engineer in the business for 42 years.

 

[stanier]

ASTM should read ASME.

Also Velan article can be found at

http://www.valvediagnostics.com/installation/check.htm

Isnt Google wonderfully quick!

 

[stanier]

Here is another reference. Tyco want 10-20D upstream and 5D downstream of this particular rubber flap type check valve.

http://www.tycoflowcontrol-pc.com/ld/F87LIM_5_04.pdf

 

[gustorf]

Dear pennpiper and insulttoinjury,
Thanks for the input. Beeing in the check valve business just for 17 years, there is still a lot to learn.
I will check out the process plant layout book but couldn't find any info in Prof. Thorley's book.

Our company produces nozzle check valves which in fact CAN be installed in all above mentioned critical installations. I am just looking for an independant written practice to convince engineers about proper installation.

Conventional check valves suffer from turbulences and flow rates too low to keep them 100% open. Nozzle check valves need just about 1 to 1,5 m/s water velocity for stable fully open position and streamline the turbulances by their design.

Dear Stanier, thanks as always.

 

[TBP]

If conventional check valves are correctly sized (as in NOT line sized, but smaller) they work just fine. What happens, for example, is that people just put 4" check valves in 4" lines. That check valve likely won't see enough flow to drive it full-open and hold it there. It'll flap like a flag in the wind, and wear out long before it should.

If the line is sized correctly (as in not oversized), the proper conventional check valve will very likely be one pipe size smaller - a 3" in this case.

Crane's Tech Paper No. 410 has a section on this.

 

[cheaterbar]

This is from Velan service Manual for Check valves.It mentions 10 pipe diameters.

All piston and ball check valves should be installed
in a horizontal pipe run with the cover up, and the
angle of incline of the line should be no more than
45° from horizontal. Also, the roll angle of the valve
cover should be no more than 45° from side to side
(Figure 2.5D). For vertical flow condition, please
consult the Velan Customer Service Department.
Swing check valves should be installed in an
horizontal, inclined or vertical position. The roll
angle of the valve cover should be no more than
45° from side to side (Figure 2.5C).
NOTE: All check valves should be installed at
least ten pipe diameters away from upstream
pumps, elbows, fittings or equipment. If closer
installation is required, please consult the
Velan Customer Service Department.
WARNING: Soft-seated piston and swing
check valves should not be welded into the
pipeline with the soft-seated disc in the valve.
The disc must be removed and reinstalled after
the valve is welded into the pipeline.