2 replies to this topic

[drdave]

Hello,

We have three (3)high pressure plunger pumps containing 7 plungers in each pump( 2 running & 1 standby in normal) to pressurize liquid ammonia flow of 40 cu.m./hr at 16°C & 20 kg/cm2g suction pressure to 210 kg/cm2g discharge pressure round the clock for process requirement.
Recently, We have observed that discharge header of plunger pumps vibrates more than normal specified. Vibration is felt physically also alarming. It can be subsided / rduced to normal on decrease of liquid ammonia flow from 40 to 38 cu.m./hr. These pumps have been running normal since long but vibration problem started appearing recently. It makes us consider discharge side pulsation damper augmentation or restriction orifice provision.
Here, I want to know from expert forum that ;
1] Why such vibrations started appearing of late?
2] Does liquid ammonia temperature cause such phenomena? earlier NH3(Liq.) temperature was 40°C.
3] Is there any method to confirm line support efficacy & necessity ? Present discharge support gets sheared off due to vibrations.
4] Will it help to increase discharge header size by one up size ? Present flow velocity is 3.5 ~ 4 m/sec.

Let me clarify the following points to get your expert feedback :

1] There is no pulsation dampner right from the inception. It is only recently thought of in light of erratic vibrations at higher loading(i.e. 100 % load of pump,in fact.)
2] We need 45 cu.m./ hr (Max) liquid ammonia flow at 215 kg/cm2g.
3] No chance of ammonia flashing in system, as pressure is spiralling up with temperature of 28~32 °C at discharge.
4] This is procured since long(approx. 30 years span) Vendor is not contactable. Our Mechanical maintenace group is maintaining these pumps well but now vibration problems with higher load.

Thanks

DRDave

[abhi_agrawa]

Dave,
Just a wild suggestion:
See if the vibration frequency of the header is close to that of the plunger. If this is the case then vibration is due to resonance.
-abhishek

[ASH25320]

I think I can suggest something, U must have suction as well as discharge dampeners in the reciprocating pump. A verticle pot with steam jacketed top side is the ideal solution for suction side.(The ammonia vapours formed will absorb the pulsations). we have similar kind of arrangement which have reduced the vibrations considerably. in this U also must have tangential entry/exit of ammonia for effective operation.