Hot oil circulation pumps Mechanical seal failures API plan 62 6

[MERO DZ]

Hi All,

we currently suffer form unbelievable of mechanical seal failure recurring in hot oil circulation system. We follow a clearly defined procedure in starting up.
circulation hot oil pump equipped by MS API plan 62. the most problem noted in the first side seal which faced with process hot oil.

Any ideas what is causing the seal failure?
Is the seal plan not suitable for the service?

Your inputs will be greatly appreciated.

regards,

 

[JJPellin]

Plan 62 usually refers to a steam quench on the atmospheric side of the seal. What flush plan is used on the primary seal? What is the seal configuration?

Johnny Pellin

 

[MERO DZ]

used only quench by nitrogen gas purity 97%.
External quench mechanical seal John Crane 604 plan 62.
3NC-FB plan 62.

 

[Tmoose]

"Any ideas what is causing the seal failure?"

To start, I don't have any idea what the nature if the "failure" is.

Is this seal provided as original equipment on a purchased pump?
What does the pump manufacturer have to say?

But before calling them, I'd have detailed information about the "failure."
Is it simply leaking?
When the pump was purchased, what operating conditions were provided to the pump supplier?
If you have replaced the seal, high resolution close up pictures of the seal surfaces and the condition of the components have an important story to tell.

 

[quadtracker]

Throttle bushing may be worn and have too much clearance allowing too much fluid pressure into primary seal area from pump casing. Check pump shaft run out should not be more than .002". check pump alignment, seals don't like misalignment no more than .001". Check shaft o-ring on primary seal for correct material composition for temperature range and fluid. Check stuffing box face runout, should be square to shaft no more than .001" Check shaft diameter and shaft condition in o-ring area of seal. Shaft diameter must be in manufactured spec. for o-ring to seal tight. check manufacture specs on these tolerances as mentioned.

 

[MERO DZ]

failure seal report!!!

 

[drc3]

Hmmm, interesting, there I was hoping to find some helpful information about hot oil pump experience from other sites only to find a colleague has posted our problems here already!

Anyway, to fill in a few gaps on the background as a first time poster:

Site is in the remote desert, with no steam plant, hence the use of N2 for the quench.

Mechanical seal is a John Crane 604 with a static bellows. Although described as a single mechanical seal, it also has an ECS secondary/backup seal as part of the cartridge (described as dry running), as in the original design a disaster bushing wasn't considered adequate.

Nature of the failure is external leakage through the outboard ECS (emission control seal). Most recent failure had the ECS seal rings in pieces, but not the only failure observed historically (but I don't have all the details I'd like).

Plan 62 seal, with N2 as the quench. (There is no flush connection supplied on the gland plate) Also a plan 65A leak detection system on the quench outlet / drain to monitor primary leakage rates.

A problem I'm told we consistently have is blockage of the quench outlet/drain with black oily gunk, such that it can block the quenching flow out the drain. As oil leaks from the primary seal this can backup into the nitrogen feed line (plus leak externally).

Has anybody ever tried using an in-situ cleaning solution to dry and clean up quench outlet lines on a hot oil system???

 

[georgeverghese]

Hot oil pumps I've worked on were all fitted with either tandem or double seals, many were modifications of plan 52 ( with pressurised seal fluid reservoir).
Sounds like your hot oil is badly fouled up, and you have excluded high tubeskin temps in the WHRU or the fired heater as a cause in this report. Another reason may be reverse flow of process fluids into hot oil at one or more of the process HXs', most likely at the tube - tubesheet joints- this requires hot oil pressures to be less than process side pressure. Ideally, you'd want hot oil pressure to be higher than process side pressure, else use seal welded tube-tubesheet joints.

 

[MERO DZ]

Hi,

#drc3

You are totally right!!!,both seals are failed single seal leak through leak detection and ECS leak into external.(Excess leakage flow backs up at orifice and fills leak detector tank,External Leakage = both seals failed) see attached picture.

primary single seal are equipped with quench fluid N2 on atmospheric side plan62 and external drain with leakage detection system plan65A to monitor oil leaking.
"A problem I'm told we consistently have is blockage of the quench outlet/drain with black oily gunk, such that it can block the quenching flow out the drain. As oil leaks from the primary seal this can backup into the nitrogen feed line (plus leak externally)."what we should do to stop and fix this issue???

could please provide more details regarding the chemical cleaning solution(how & when we use it) "Has anybody ever tried using an in-situ cleaning solution to dry and clean up quench outlet lines on a hot oil system???" we never used !!!

Your support is more than welcome
Thank you

 

[FMJalink]

MERO DZ appears you have to solve something nasty.

A mechanical seal leaks from the high pressure side to the low pressure side.

With a single mechanical the hot oil will go through the seal. Solids in the hot oil will detorioate the seal surfaces and increase the leakage rate. Only real solution there is a pressurized dual seal.

With the single seal you get oil on the other side of the seal. This will have to be removed. I doubt whether Nitrogen is able to do this. Hot steam is to my opinion much better to remove the oil on the outside. You might even have a similar appliance at home for cleaning.

If there is Oxygen in the Nitrogen oxidation processes can be expected causing clogging etc.

 

[qturbo]

Will using solvent before starting up this Hot Oil Pump, help? We are considering the use of solvent, with specified residence time, before starting up the hot Oil Pump, in order to dislodge the coking debris trapped in the below and loading springs, as well as between the seal faces. We are not intending to use any aggressive solvent, just one which can do some cleaning before starting the pump.

 

[shashankTurbomachine]

Plan 23 will be good
Plan 62 is for future expansion and is provided on atmospheric side. Quench and drain connection.

Plan 62 steam quench or air cooled are options.

plan 62 comes with SAPCV normally supplied by pump manufacturer.1 no flowmeter, 1 NRV, 1 PG


A well phrased question has answers in itself!!!

 

[quadtracker]

It is possible that the hot oil is creating Coke at your high temperatures. These Coke particles coat the mechanical seal working parts. The coke particles restrict the movement of the sliding and flexing parts of the seal causing the lapped seal faces to open and leak. The oil must be cooled to stop coking. Sometimes the hot oil will damage bearings in the bearing housing due to the heat from the pump shaft conducted to the bearings and lubricating oil.

 

[quadtracker]

A cool clean oil flush into the seal chamber of the pump with a carbon throat bushing that restricts hot oil dirty oil from entering the seal chamber may help. Maintain the cool seal flushing pressure higher than the stuffing box pressure.

 

[gyaneshwarp]

Since Product is dirty, ECS is not proper selection.
My recommendation will be
Double Seal in Tandem (Inboard Seal Hard Face combination) with Plan 53 (You may choose between A'B or C in which you are comfortable)