Pump Seal for Asphalt Service

When my desk lamp bulb burns out, I do not try to invent a replacement bulb, or design one or construct one. I buy one for some 50 cents and problem solved. Similar with your asphalt pumping. Consult Viking Pumps. They are long years specialists in asphalt pumping with tons of experience and excellent products. They will have the best and most professional solution to your asphalt pumping dilemma, seal and all. This is what our Industrial Engineers would do in your place.

Pray tell what is the difference between an API 32 and API 52 seal? OPs need to furnish relevant information, rather than making people look stuff up.

Second, words like firstly/secondly/thirdly are bogus. Even if the OED includes them, it needs to be overruled--Editor Crankshaft.

Tornado,

There are many API seal plans (21 or so), and the best way to find the difference is to look them up in API 682 or on any seal OEM site.

Simply put, Plan 32 is a single seal with a seal flush from an external source. The flush is directed into the seal chamber and is at a pressure higher than the seal chamber pressure. The reasons for using this plan are: heat removal, keep out process liquid and solids and to increase seal chamber pressure. Can be used for paper and pulp, high temperature products, polymerizing or oxidising products.

The main problem that the OP will have using this in Asphalt service is that the flush is lost into the product (contamination), this can affect the product and is wasteful (expensive) in some case. It can be used in this service.

Plan 52 incorporates a dual seal with a non-pressurised barrier fluid. It is used to provide a backup seal to the primary seal, zero (low) emissions and does not contaminate the pumped product. It is used mainly with high vapour pressure fluids (which asphalt is not). It can not be used in Asphalt service. In asphalt service the small leakage from the product side seal will soon solidify in the buffer fluid system.

Another poster suggested plan 54, this is an externally pressurised barrier system and requires a separate external system so probably not suitable, though it would work.

Plan 53 would be acceptable if Plan 32 is not suitable. This is a double seal with a pressurised barrier fluid system. Amongst other things it is very suitable for dirty and abrasive fluids and or polymerizing products. As the barrier liquid is at a higher pressure than the pumped liquid, there is a very small leakage across the seal faces of barrier fluid to product. Though expensive initially this would probably be the most reliable seal plan for this service.

Excellent answer, it satisfies my curiosity and should be helpful to the OP. His supervisor might not be so thrilled, though!

If Asphalt contamination is not acceptable, how Plan 53 is acceptable? Since Barrier flow is at higher pressure seal fluid may go into product. Moreover Plan 62 is mandatory for asphalt to keep asphalt in liquid state. If we use plan 53, how plan 62 can be implemented? So as per my opinion the best seal selection is Plan 02 and 62.

Note that Category 2 or Category 3 seals shall be used.

What is the temperature of the fluid?

API 32 is much cheaper than API 52 since the later is duel seal. In plan 52, since the fluid is asphalt, if the inner seal leaks, sooner the outer seal chamber will get solidified with asphalt, despite some tracing around there even. Consider Plan 54 if you can provide hot pressurized external barrier fluid.

If plan 32 works, noting like that.

You can also look for API plan 01 or 11 with 61 or 62. Moreover if your turbine is low rated then you can use mechanical governors.

Perhaps, you should look at Graphalloy for seals.

You might want to check out the Flowserve GTSP double bellows type seal. Since you must steam trace asphalt service pumps you could use the steam as your buffer medium. I seem to recall that many eons ago the basic method was using packing with steam as a buffer in the middle flowing into product and weeping outwards. The water in the asphalt was minimal and usually created no problem. Keeping the asphalt from leaking outward and coking up at the stuffing box face was definitely undesirable.

Spinco, steam is not a good barrier fluid for a double mechanical seal, lubricity is pretty poor. However your recollection is correct, for packing and for single mechanical seals, steam is used as a quench medium to keep oxygen away and thus prevent coking of the leakage at the atmospheric side of the seal. I also agree that Flowserve (amongst many others) is a reputable seal supplier with experience of sealing hot products.

Why I do basically agree with you that the use of steam might not provide as good lubricity to the seal faces as we might more commonly want, this particular seal design by Flowserve does specifically recommend the use of dry steam or nitrogen as a buffer. It has a somewhat unique face design, a wave instead of flat parallel faces, and has tungsten carbide against t-c instead of utilizing faces of different hardnesses as is more typical. The use of bellows instead of springs might be a consideration as to applying a uniform pressure for face loading but only minimally. The use of bellows for high temperature services was really just becoming more popular when I left that field in the 70's.

This seal probably costs more than the whole pump did in my day.

Apologies, I did not look closely enough at the seal designation that you gave in your post. Lubricity is not a problem with this seal as it is in fact a non-contact dry running gas seal. The wavy face technology allows the seal to "lift off" so there is no contact between seat and face, but rather a very small gap. They use them (various guys make similar ones though with different face geometry) quite successfully for very hot products.

Pressure of the steam or inert gas must be guaranteed for reliable running as well as for safety reasons - ingress of air etc. Any asphalt between the faces would, I guess, be fatal to the seal.

This design/type of seal could very well be used for this duty.

My question at this point might be a bit naive, but it looks as though you are trying to pump asphalt, which should be kept warm/hot, but not be allowed to migrate into the barrier fluid space of the pump seal. (You wouldn't want it to congeal in there and gum up the works.) What would prevent you from finding a high-temperature oil to use as the barrier fluid? I might be wrong, but I would guess that there would be some oils like this that could be maintained at say 10 psi above the pump discharge pressure. If so, a small barrier-to-pumpage leak could mix a dab of compatible oil into the asphalt; whereas a small barrier-to-atmosphere leak could be drained to a pan. I'm just brainstorming here, so feel free to pick this idea apart. I doubt that it is bullet-proof, but does it not make sense? Eugene R. Walker 03 Mar 2010.

That is a very good suggestion and point in fact was a very common way of handling asphalt like services and similar hot, heavy products. The main problem is having a compatible fluid handy at the necessary pressures. Once did a plant where there was a myriad of pumps all requiring double seals, all being heat traced and where we had to set up a separate system to heat up and supply the medium, provide a reservoir with heater for the fluid and had its own pumping system with returns to the reservoir.

That system with the returns was also heat traced as were the supply filters and the gear pumps used. In most cases the buffer fluid has to have a fairly high flash point since you didn't want it to flash into a vapor when it crossed into the pump yet had to be something which wouldn't gum up or coke up at the stuffing box. Some services actually would have a steam line at the outside of the seal to prevent it from depositing near the interface and drained it away to a collection point.

API Plan 53 and 54 as per The Prof's post are what you are describing. Both seal faces of the double seal system see only the barrier fluid not the asphalt.

The Plan 32 of the OP just introduces a flush into the seal chamber at a higher pressure than the seal chamber pressure in order to accomplish the same thing. The seal faces only ever see the flush liquid, not the asphalt.

The Gas seal suggested by Spinco does the same thing, the seal faces see only the gas/steam, not the asphalt.

Basically you do not even try to seal asphalt, you seal a liquid of your choice at a temperature of your choice in order to keep the asphalt in the pump.