6 replies to this topic

[vikramltv]

Dear Experts

I need to have some knowledge about distinguishing and selecting between simplex, duplex, triplex( single or double acting) reciprocating pumps
Can some one throw some light upon this.
For example selecting a simplex pump of larger cylinder vs duplex pump or relatively small cylinders.

Edited by ankur2061, 17 December 2012 - 02:37 PM.

[S.AHMAD]

Selection is based on the life cycle cost or the cheapest offer with free training etc.

[vikramltv]

Means its hard to decide for a junior engineer...

[ankur2061]

vikramltv,

If you can get hold of a copy of API 674, it will provide you the guidelines you are looking for. Besides the distinction between simplex, duplex and triplex pumps I had written a company standard for a middle-east O&G company wherein I had given guidelines for selection and operation of Reciprocating and Controlled volume pumps using various references. I am reproducing the same for your benefit:

General guidelines for proper selection and operation of Positive Displacement - Reciprocating and Controlled volume pumps

Reciprocating / Controlled volume pumps are capable of handling very low flows (<1 gpm) and are typically used for chemical injection duties in oil and gas installations.
a. Reciprocating pumps should comply with API 674.
b. Metering (or controlled volume) pumps should comply with API 675.
c. Type of controlled volume pump shall be specified in the project specific “SOR”. As a general guideline the following may be specified:
c.1 Packed Plunger Pumps: These are generally recommended for discharge pressures above 5000 psia.
c.2 Diaphragm pumps are generally recommended for pressures up to 5000 psia and temperatures up to 150°C.
Double Diaphragm Pumps of the sandwich type construction are generally recommended.
Double Diaphragm pumps should be used when:
a. Dilution of the product flow by hydraulic oil is not acceptable.
b. Pumped fluid is extremely hazardous and/or toxic.
c. Process leakage to the atmosphere is unacceptable
d. Process fluid must not come in contact with air
Packed plunger pumps should not be used for the above conditions.
d. Capacity adjustment (Reference API 675)
d.1 Pump capacity shall be adjusted by changing the actual or effective stroke length or the pump stroking speed.
d.2 The pump shall be capable of accepting manual or automatic capacity stroke control, either factory mounted or by field conversion.
d.3 Integral pump devices used to vary capacity either manually or automatically shall be provided with visual indication of capacity setting, shown as a percentage of the nameplate rated flow. Manual control shall include a locking device to positively retain the capacity setting.
d.4 The direction of movement to increase or decrease pump flow shall be clearly marked. All adjustment means and indicators shall be easily accessible with the pump installed.
e. Full flow pressure relief shall be provided at the pump discharge upstream of any isolating valve. Where the nature of the fluid would make relief valves unreliable, rupture discs should be used either alone or in conjunction with relief valves.
f. When specified, the vendor shall furnish pulsation suppression devices to be located at the pump suction and/or discharge connections. The following are three basic types of pulsation suppression devices:
f.1 Volume bottles without internals.
f.2 Pulsation dampeners using a gas-filled chamber isolated from the pumped fluid by a piston or elastomeric diaphragm.
f.3 Pulsation filters and attenuators, including proprietary commercial designs based on acoustical suppression techniques.
Reference is made to API 675 for the above.

Hope this helps.

Regards,
Ankur.

Edited by ankur2061, 17 December 2012 - 07:28 AM.

[kkala]

..I need to have some knowledge about distinguishing and selecting between simplex, duplex, triplex( single or double acting) reciprocating pumps. Can some one throw some light upon this. For example selecting a simplex pump of larger cylinder vs duplex pump or relatively small cylinders.

Without having specific knowledge, I hope following notes can be useful, as understood from references (α) and (β).
(α) Perry, Chemical Engineers' handbook, Positive-Displacement pumps, p. 10-31 to 10-33 in 7th edition (1977).
(β) I Karassik, W Krutzsch, W Fraser, J Messina, "Pump Handbook" (MgGraw-Hill 1976), p. 10-258 and 9-91 to 9-94.
See also http://answers.yahoo.com/question/index?qid=20070221125257AAsDejs and mentioned web references.
1. We speak about piston-type pumps, since plunger pumps are always single acting (α). Piston pumps develop discharge pressures up to 2000 psig. Suitable for low-abrasion mixtures (e.g. coal slurries) with solid sizes limited to 8 mesh or lower, (β).
2. Piston pump flow is pulsating, with a variation (roughly) of +220% to -100% of the average flow for a simplex single acting pump. This variation gets +60% to -100% for a simplex double acting pump. Improvement is much more in multicylinder pumps, for instance a triplex pump (single or double acting) will have a flow variation of +1.8% to - 16.9% (α). Perry's table 10-9 has more data, assumed to concern reciprocating pumps without pulsation dampeners (no clarification on it).
3. In case of not diligent design, pulsations (combined with resonance) can produce excessive vibrations and noise, even on triplex pumps (β).
4. I think an alternative can be less cylinders and external pulsation dampeners, http://turbolab.tamu.edu/proc/pumpproc/P10/P1025-39.pdf, http://www.cheresources.com/invision/topic/16218-pulsation-dampener-requirement. If no advice is received on the most suitable alternative, a way out could be to let vendor decide in its proposal; you have to specify acceptable flow variation before this.

Edited by kkala, 17 December 2012 - 01:59 PM.

[manchester]

Dear Experts

I need to have some knowledge about distinguishing and selecting between simplex, duplex, triplex( single or double acting) reciprocating pumps
Can some one throw some light upon this.
For example selecting a simplex pump of larger cylinder vs duplex pump or relatively small cylinders.

vikramltv,

One of the consideration is NPSHA. In my previous project, I have to chose even quintuplex, because I have to provide sufficient NPSHA for my pump. The system consist of a column and a pump. I have limitation on column height since I work in brownfield, hence my NPSHA also limited.

As you know, suction head of a reciprocating pump is also a function of acceleration head. Quintuplex will result in less acceleration head compare to that simplex, duplex and triplex. Hence, at that time, I choose quintuplex so that my NPSHA is big enough. Otherwise, if I choose simplex or duplex or triplex, my NPSHA is very low and I will be difficult to find appropriate pump.

The other consideration you may have is vibration. This is crucial especially if you work on an offshore platform, where such vibration may lead to plant shutdown or platform structure failure. Vibration of quintuplex is still big, but much less than simplex and duplex or triplex.

The last, of course money. Quintuplex is expensive than simplex, duplex and triplex. But if the money is not an issue, you better to use quintuplex

Hope it helps

Edited by manchester, 18 December 2012 - 02:21 AM.

[vikramltv]

Thanks to all for valuable inputs..