[Mick McCafferty]

I would welcome opinions on configurations of Control Valve Assemblies. In most Piping books and Company standards the assembly will look similar to attachment i.e. with bypass line directly above control valve. In my experience as client piping engineer this is the common configuration modeled by Contractor(s) and presented during model review and our comment is always to demonstrate how to remove control valve which is typically by mobile crane or by slinging from overhead beam or similar with the problem being that bypass line will foul. Our maintenance people always quite rightly want a straight lift to maximize safety and reject solutions such as slinging at an angle and counterbalancing with rope or additional sling. Sometimes at grade level we can accept trolly/forklift underneath valve but this is limited by valve size and weight.

At start of every project I highlight this to Piping Leads and am assured that they will consider this in their material handling but invariably becomes a client comment during review and subject to rework. Present project (FEED) I have had it written into basis of Design and stated that bypass to be offset to allow valve removal although come model reviews I expect to have to address again.

I would welcome some feedback and if concur that I am correct why is it never addressed in literature, one of common replies by experienced pipers is that this is the way that it is always shown in books etc.

Regards.

Mick.

Attachments:

• 

Discussion

[Anton Dooley]

Hi Mick,

I agree with you, I would normally offset the bypass to ensure that the removal of the CV is not fouled by the bypass pipework – after all, one of the reasons for having a bypass is to allow maintenance on the CV.

Now – why this isn’t addressed in literature, is something I can’t answer, but I would expect that a seasoned piper would be looking at access and maintenance as part of his/her design, in much the same way as we would allow for pulling tube bundles from an exchanger, or agitator removal from a vessel.

This is one of many reasons, that a piping project requires that senior level experienced pipers are employed, rather than just cad operators.
Not everything that we do is covered by a code, standard, work instruction, manual etc … some things require the experience of a senior level piper.

Anton

[Mick McCafferty]

Hi Anton,

Thanks for the prompt reply.

My gut feeling is that designers are being discouraged to offset these bypass for a purely cost cutting exercise to save on additional fittings and related welds which I suppose on a large project will incur a not inconsiderable cost ergo why I have included it in Basis of Design in FEED so there hopefully no ambiguity during EPC.

I would like in general to see more focus on material handling within Piping discipline as I think these days it is a weak point maybe due to lack of practical experience and/or exposure to site conditions which is a result of short term profit attitude to training and mentoring.

Cheers.

Mick.

[Alan Smith]

As Anton says the main point here is that the top works of the control valve must be able to be easily removed for maimtaince. How a designer achieves that is up to him, his experience and the circunstances, not a set of rules.
In my experiece a control set with say a 4″ or smaller control valve does not need an offset by-pass as the top works are relatively light and short enough that the by-pass can be non offset while still low enough to give good access to the globe valve..
Having said that every case must be considered on it’s individual circumstances.
I certainly do not believe designers should ever be pressured to save fittings in any layout. Any one who applies that pressure is not a Lead and anyone who succumbs to that pressure is not a Designer.

As for the comment about material handling focus by Pipers Please explain

[Mick McCafferty]

Garzabla1,

I would also agree that it is normally top works of CV removed for maintenance but general philosophy we use is to treat all valves whether actuated or manual as removable for maintenance and is driven by guys who will be maintaining and operating plant. I am not advocating a set of rules in lieu of experience but only that if literature is depicting a certain configuration it should highlight pros and cons.

As for being pressurized I believe it is coming from project management which my recent experiences have been in Far East in lump sum contracts where the EPC bidders tend to come in a lot lower to secure contracts and then penny pinch. The discipline guys there work under a lot of pressure regarding costs and what a manager says goes.

As for material or mechanical handling I normally see this type of philosophy document offshore where space is constraint and configurations more complex therefore removal of all equipment including valves is addressed. How to lift it out and transport it to laydown area for removal to workshop/barge etc and this should focus designer mind on this concept. Quite a large % of comments during model review are maintenance related which I feel topic is lacking in Piping otherwise it would not come up as frequently.
As a result of this we are having a material handling philosophy prepared for current onshore project where we will list our expectations for each type of equipment so EPC is in no doubt to our requirements.

Cheers.

Mick.

[Alan Smith]

I agree with everything you say Mick, but reading between the lines I think we are talking about the difference in the way things were versus the way things are.

Twenty years ago it was expected that a Senior Piping designer would be fully conversant with all aspects of all the equipment he was connecting, including process desing, operation, maintenance and removal. In fact that same designer would have been responsible for the plant layout in the first place when maintenance, operational safety and efficiency would have been major considerations in that layout. This became even more of a challenge when the large North Sea Production Platforms began to be designed where wieght and therefore reduced maintainence space became an important design consideration.

As outsourcing to Low Cost (not High Value) Engineering centers became fashionable we started to lose that expertise replacing it with CAD operators supervised by inexperienced Engineers. With the result that poor quality design is produced by cheap labour in countries with cultural hierachy issues between designers and inexperienced engineering or project managers. Just another example of you get what you pay for, but quality always costs.

The result is that today we have (at least in Western Canada) large numbers of highly trained and experienced designers, myself included, who are unemployed partly as a result of outsourcing. The real shame is that no-one has recognised that we now represent the Highest Value and Lowest Cost engineering center in the world.

[Mick McCafferty]

Garzabla1,
I think we are both on same page and to be fair to the younger generation I would think the guys on the boards had the same thoughts about CAD. I missed out on manual draughting as was a pipefitter originally and by the time I came into this side of industry in 1997 3D was king although in my case I leave it to the designers.

Best of luck on employment front, I know its hard out there just now.

Cheers.

Mick.

[Author]

Replies