warm up for chemical process pump

[sunloco]

who can explain clearly warm up for chemical process pump? In many case like pumping Aromatic Hydrocarbon need warm up before start? any one knows ? why need warm up ? how to warm up ?the piping or capacity ,temperature ?

 

[StoneCold]

You have to be more specific if you want more information. What kind of pump is it? Centrifugal? How much fluid are you pumping (gpm or m3/hr)? What is the process temperature? With this information people can understand more about what you are doing and then give you a better response.

Regards
Stonecold

 

[MJCronin]

sunloco...

You must be very specific..

Large, multi-stage, high pressure pumps, like those used as boiler feed pumps in power plants require slow heatup. Steam turbine driven pumps will require heat-up

Small, single stage pumps, typically do not

As a general rule, larger, long-horizontal axis rotating machinery requires a slow warm-up.

My opinion only...

-MJC

 

[sshep]

sunloco,

Where centrifugal process pumps are spared for reliability, the warm-up is usually achieved by allowing a small recirculation (so as not to counter rotate) of the running pump backwards through the standby pump. A restriction orifice is often sized to limit the flow. In cases of remote start, like BFW pumps, the recirculation is always lined up so that the pumps are always ready for start.

As mentioned above, more detail of your system will allow the forum to better suggest a proceedure applicable to your situation.

 

[epoisses]

The reason could also be process related. Sunloco mentioned aromatics - e.g. benzene has a melting point of 6 deg C, you will want to warm up your benzene pump before you start it in the middle of the winter.

 

[dcasto]

Think about the reverse too. In our cryogenic plants we have too cool down the pump before we put it on line, otherwise the cryogenic fluid flashes and vaporlocks the pump immeadiately.

 

[reena1957]

Dear sunloco,
Every mechanical equipment undergoes a thermal expansion on heating snd so does a pumps shaft, impellers,etc. So in case you case you are pumping any hot fluid, the spare pump to be made immediately available for stsrting, requires to be at the same temperature as the running pump. Otherwise, the differential expansion of the shafe and impellers may leasd to rubbing of the rotating impeller/seals on the stationary parts and cause damage to the equipment. Now that we are clear about this, the methods of warming up the non-ritating spare pumps are already mentioned by others. Normally it is one of the follwing:
1. Allow the hot liquid from the dicharge header to flow through the spare pump either through a bypass line ( with or without restriction orifice) around the discharge and NRV into the pump and back to suction header through the normally open suction valve. Simple back flushing.
2. Keep the the suction valve of spare pump closed and connect the dicharge of running pump to the downstream of spare pumps suction valve. Connect the spare pumps dicharge (upstream of discharge valve back) back to the suction of running pump( after ensuring all the gas/air is vented out) or to a lower pressure source like column bottom. Like a figure 8.
This second method is used in vacuum service to avoid losing suction of running pump in case the spare pump has a leaky seal or has come back fresh from manitenanace and is at atomospheric pressure.
Hope I have been able to make it clear.
Best wishes

 

[sunloco]

Thanks above all.

I specify the system.
the pump is API BB2 type for PX project,BB2 is centrifugal pump between bearing and two stages, medium is Aromatic hydrocarbon, normal temperature is 279? degree,specific gravity is 0.61,pump capacity is 2340m3/hr,diff.head is 191m.
now my understand is that warm-up is necessary before pump start,alway there are a spare pump,then warm up flows is from running pump discharge(usually restriction orifice used) lined to suction of spare pump through spare pump discharge back to running pump?

 

[reena1957]

Dear sunloco,
If you follow my scheme 1 above(provided there is no vacuum), you have to provide a simple 1 inch(or smaller) bypass line with a gate valve around the NRV and Dicharge valve of spare pump and keep the pump suction valve open. The circulation will take place. Restriction orifice is optional . You can throttle the valve on the bypass line instead of restriction orifice. You have to provide this for both pumps since you do not know which is going to be spare pump.
Best wishes

 

[sunloco]

one more question,what capacity is used for warm up ?and whether the capacity will impact the running pump's performance? what temperature shall be reached through warm up?

 

[sunloco]

sorry for my many question. I also want to know how to warm up for the running pump before it start(for spare pump can be warmed up by the running pump).

 

[SeanB]

Another method of providing a warm up bypass is to use a drilled check valve. I have had clients where this was their preference.

 

[epoisses]

@sunloco
Come on, these questions are so generic, how can anyone give a specific answer? What type of pump exactly in what service are you talking about? Re how to warm up, this is usually done with a steam lance if no permanent facilities are in place.

 

[epoisses]

@sunloco
On 2nd thoughts I understand that we're not being very helpful.

Let me try something else. I take it you are a young engineer. (I have 10 yrs of experience and would still call myself a young eng, but anyway). You are in your office staring at Eng-Tips looking for solutions. I guess that is generally a good thing to do. Except in cases like this. Take your coveralls and your hard hat. Go out in the plant and catch an operator. Ask him which pumps he warms up and why and how and how long. Ask him to show you. Ask him what happened that time when he forgot to warm it up. Ask him also to start it. Look at what valves he opens and in what order and look at when exactly he starts the pump. Put your hand (gloves on, of course) on a couple of pumps and see at what temperature they run. That will teach you more than a thousand words!

 

[pumpking]

Dont forget to mention thermal shock on mechanical seal faces or mag drive pump bearings - warm up and down is required to ensure this doesnt occur, or else the faces or bearings will fracture requiring replacement !!

 

[sunloco]

thanks to all, Epoisses ,thanks for your kind suggestion.