Maximum duration per unit time

Man-hour (or man-days) is the measure that is convenient for cost estimators but planning the real work we use different measures.

We determine what crew shall be used (the number of people of different specialities and the number of machines of different kind), the workloads of different crew participants (% of work time required that may be different for different crew members) and activity duration (or volume of work in physical units and crew productivity - in this case duration is calculated). Then the number of planned man-hours and machine-hours is calculated for each crew member and for activity.

Total man-hours do not supply us with required information on crew composition.

Total man-hours may lead to erroneous results when resource leveling is required.

Managers do not think in man-hours assigning people and machines to do some work, they assign quantities. And they are right.

It is not a question of the magnitude of a certain project. Man-hour is a universal and common unit and it is more specific when used properly. While Man-Day is more confusing as you need to define exactly how many hours per day, otherwise, it can always be assumed that you mean 24 hours per day. In my opinion, it is important to consider that units of scope like: m3; m2; Lm, Ea; Kg, Tons etc. must be considered discrete in the first place. And so as Man and Hour.

In mega Construction it is usually man-day.

In Manufacturing it is in man-hour.

While using the term "Practically", perhaps have room for errors, it doesn't mean that it is in error per se. Likewise, when using the unit "Man-Hour" may have room for errors, then you must consider using it practically into which may mean discretely in order to avoid errors. Men or manpower maybe paid per hour, but I guess never paid in minutes. On the other hand, men or manpower maybe used partially in terms of percentage of hours and effort, but can never be divided literally. Oh, what am I trying say? It is always in error if you see fractions and or decimals when using Man-Hour unit.

It is in error to say - When you were using the unit Man-Hr, practically, it should always be whole number(s) i.e. OneMan/OneHour. 

• In your calculations you can consider minutes or fractions of hours but never fraction of labor resources even if using partial workloads.

You shall distinguish between renewable resource quantity, consumable resource quantity, workload, effort, production rate and volume of work.

1. For renewable resources such as equipment and labor resource quantity is always discrete even if using partial workloads. Software that does not distinguish between resource quantity, workload and effort can yield wrong resource leveling.
2. Non-labor and consumable resources such as materials in some cases quantity can be non-discrete in other cases must be discrete. It should be modeled on a case by case. Just select the option that applies; discrete or non-discrete.
   1. Materials such as sand can be defined using discrete units, sometimes lower than 1, it can be only 0.5 cm of sand are required for some activity.
   2. Materials such as water closet must be defined using discrete units, consumption will be done in discrete units.
3. Workload can be defined as a %; needless to say % is not a whole number.
4. Effort can be in fraction of hours. If it takes 20 minutes to do some work then it takes 0.333 hours. In case of labor resources effort is usually defined as man-hour. In case of equipment effort is defined as hours of equipment use.
5. Production rate per hour can be expressed in fractions, if it takes 3 hours to install a unit then production rate per hour is 0.333 unis/hour.
6. Volume of work might be expressed in non-discrete units. Stripping of topsoil can be defined in acres; usually the amount comes out to be fractional. 

When you were using the unit Man-Hr, practically, it should always be whole number(s) i.e. OneMan/OneHour. When you get fractions or decimals (as a result of a computation, whether or not using a machine),then it would mean that perhaps you have considered minutes in your calculations and or you have considered half or perhaps 25% of a Man. It's very easy to spot errors especially when its obvious.

In turnaround and shutdown jobs it is not uncommon for many activities to be of short duration while spanning several shifts. Because activities will move fast and prompt response is necessary updating at minimum will be on daily basis if not after every shift. To manually adjust all activities considering their shifts in production rates and execution time can be a monumental task. A good model should take care of such adjustments at a single click of the mouse.

To split activities into separate tasks (one for every shift) will not make it as you do not know in advance what will be the work done by each team as the distribution of work shifts among teams with different production rates.

To get it right you will have to iterate the calculations until you match each activity start considering how predecessor duration impact every activity.  Calculation of a single activity iteration takes time, imagine iterating everything until everything matches, it is not a practical approach.  Why not let the computer consider all relationships at a single click? 

OOPS forgot to add a row for activity duration per day. Because the overlap of teams activity duration rolls up to 26.32 hours, this is easy! 

The need for shifts in construction jobs pale in comparison with the need for shifts in turnaround and shutdown jobs.

You cannot go wrong with math. So if you are not sure about the results when calculating with machines, you can always do it manually. And obviously the example given are all wrong.

• Different shifts, each with different resource quantity and production rates are common. More common that shifts with exactly same number of work hours per day and same production rates.

You can try yourself a simple scenario, so simple it consist of a single activity.

Activity 1A 400 cm rock excavation

1 ea Resource 1 production/resource 10 cm/hr and works Monday 10 hrs, Tuesday 10 hrs and Wednesday 8 hrs/day

2ea Resource 2 (as a team) production/team 30 cm/hour and works on Wednesday 8 hrs, Thursday 8 hrs and Friday 10 hrs/day

If activity starts on Monday it will take 26.32 hours to perform the assigned volume of work.

If activity starts on Wednesday it will take 11.20 hours to perform the assigned volume of work.

Of course it will work the same irregardless of the number of activities and or resources. It all depends on how you model it in the first place. If you started wrong then so as the results.

Try to model it in a sample project and see for yourself and kindly give feedback to us. One thing for sure, the software will just distribute equally resources quantities and units against your defined "planning unit". I suggest you use Hours as planning unit and or duration as well, as you got two 9-hour shifts. And make sure that calendars were properly defined and assigned for each shift respectively. And of course granulate your activities, to avoid overlapping as this may create over allocation of resources.

then there is your answer 8 

90 and 72 Respectively.

Day Crew = 9hrs x 10 labor = 90hrs/day

Night Crew = 9hrs x 8 labor = 72hrs/day

Zoltan

Nobody is working 18 hours per day:

both the day-timers and the night-timers are working on a 8 hour shift, there are 10 day-timers and 8 night-timers;

the working day amplitude is 18 hours, not the maximum units per time;

Adab should create 2 calendars, or 2 calendar shifts, one for the day time, the other for the night time

Alexandre

Maximum duration per unit time? H/D - Do you mean hours/day? I don't really understand but maximum would be 24 hours per day, beyond that would be another day. Like "Tomorrow" always coming but never arrives. I guess this is the problem when you are not sure of what "Planning Unit" to use. I think consistency is the key, as perhaps you can never use several planning unit for one project. So if you use hours as planning unit, then use it all the way. When you mix it with Days, then there would be fractions: i.e. Time/Time. I guess this only works for calendars and not for units of Scope and or Resources.

you are working 18 hours per day hence 1 man day is 18 hours  

Adab,

I assume you are working on 8 hour shifts, either day or night

Solution 1:

day-time helpers and night-time helpers are two different resources; you should enter 80 h/d for day-time and 64 h/d for night-time

Solution 2: day-time helpers and night-time helpers are one unique resource; you should enter 80 h/d and make sure you assign only 64 h/d at night.

Zoltan,

I agree with Vladimir, where does your figure 18 come from ?

Alexandre

Zoltan, please explain.

In Spider Project we would enter 10 helpers in the first shift and 8 in the second shift. Shifts would have their own calendars with 9 hours work day but with different work time. Everything as in the real life.

Adab wrote about 18 hours per day work calendar and you suggest to plan for 18 helpers. It means that all 18 helpers work for 18 hours per day. This is certainly not right or I just don't understand how P6 calculate project schedules.

18