5 replies to this topic

[StriderN]

HI!

I'm a process engineer working for an Oil & Gas Contractor Company.
In my current project, reciprocating plunger pumps are being proposed for the purpose of transfering diesel.
But as per my knowledge, plunger pumps are prone to leakages over a period of time due to the exposed packing / seals especially if the fluid is diesel.

So wanted to enquire if it is advisable to use plunger pumps as diesel transfer pumps ? and what alternative can I go for...

Thank you!

[ankur2061]

Strider,

Reciprocating plunger pumps are used for the purpose of dosing or injecting very small quantities of chemicals in pipelines and mixing equipment simply because they are best suited for this kind of service. Typical flow rates are 0.1 to 1 U.S. gpm (20 to 225 liters per hour). Some of the chemical injection services require to handle very corrosive and toxic liquids and the reputed pump manufacturers know what kind of sealing systems are required to prevent any leakage from the pumps. API 674 - "Positive Displacement Pumps - Reciprocating" has guidelines for seal systems that need to be employed for reciprocating pumps. For hazardous / toxic services and where even the smallesrt leakage of the pumped fluid is unacceptable to the atmosphere reciprocating pumps of the "Double Diaphragm" type construction are recommended

I have never heard of reciprocating plunger pumps being used for diesel service even if there is a metering service involved. What I have encountered for diesel service is, centrifugal pumps with flow control and excess flow recycle systems where diesel needs to be metered for services such as a fuel for fired heaters.

Hope this helps.

Regards,
Ankur.

[StriderN]

Thank you for the inputs. But won't the centrifugal pump cause coalescing of the diesel fuel with water (that may enter the diesel storage tank along with air, as it is an atmospheric tank)?

[ankur2061]

Low speed centrifugal pumps or progressive cavity pumps (type of screw pumps) reduce or prevent formation of oil-water (in your case diesel-water) emulsions and are coomonly recommended for applications where hydrocarbon-water emulsions are detrimental to the overall process.

Hope this helps.

Regards,
Ankur.

[Art Montemayor]

Stridern:

You ask: “(is) it is advisable to use plunger pumps as diesel transfer pumps? And what alternative can I go for...?”

Ankur’s response, in my opinion, is very correct. I also would never contemplate using a recip pump to transfer diesel fuel into an atmospheric tank. It is inherently low in capacity and is prone to leaks within the plunger packing. Additionally, why employ an inherent high pressure, low capacity pump in what is normally a low transfer pressure, high capacity service? It doesn’t make for good sense.

You further inquire: “won't the centrifugal pump cause coalescing of the diesel fuel with water (that may enter the diesel storage tank along with air)?” This also doesn’t make sense. Any pump will pump LIQUID diesel into the tank – usually through the bottom section or through a dip pipe. The fact that the tank is vented to the atmosphere has no bearing on the incoming diesel fuel. It is not until the liquid resides inside the tank that water moisture may condense and contaminate the diesel. If this happens, it is well after the pumping action is over. Conventional centrifugal pumps (API 610) would do just well and there is no need for a special progressive cavity pump.

Your problem lies not in the pumping of the diesel, but in allowing water moisture to contaminate it. Now, if you allow for SUBSTANTIAL water to contaminate the diesel and you have to pump it out of the tank, then you may need a special progressive cavity pump.

[StriderN]

Thank you for your inputs.