Exam seat no:
Project Report On “HEXAMINE”
Prepared By:Roll No:B.E Semester VIII Chemical.
Guided By:Professor & Head of Department, Chemical Engineering Department.
Chemical Engineering Department, Vishwakarma Government Engineering College, Chandkheda- 382424 2009
Vishwakarma Government Engineering College, Chandkheda-382424.
CERTIFICATE
This is to certify that Mr. , Roll no. of B.E. Semester VIIIth (Chemical) has successfully completed his project Report on “HEXAMINE”, during the academic year 2009-10.
Date of Submission:
Professor & Head of Department, Chemical Engineering Department.
Acknowledgement I would like to take this opportunity to express my sincere regards and deep sense of gratitude to my Head of the department & my guide Prof. M.G. Desai. I am thankful to my guide Prof. M.G. Desai , for not only guiding me for this project report, but also encouraging me and finding time for reading and commenting on manuscript. His encouragement kept my spirit alive and lifted my moral up to very high level of interest during the preparation of this project report. I am highly thankful of library staff and my guide for providing valuable references throughout the preparation of this project report. I would like to thank my college authorities who gave me the internet facility to get some data and other required information. I would also like to take this opportunity to thank all my friends without whom support I would not be able to complete this project report in time. Finally, my grateful acknowledgements are of those who have helped me directly or indirectly for preparing this project report.
INDEX
SR. NO 1.
CHP. NO. 1.1 1.2 1.3 1.4
2. 2.1 2.2
3. 3.1 3.2 3.3
4.
CHAPTER INTRODUCTION
6
Regulatory history Uses Health Effects Product specification
LITERATURE SURVEY
6 7 7 7 10
Properties of raw material Properties of HEXAMINE
10 11
PROCESS SELECTION AND DETAIL DESCRIPTIO
13
Process selection Process description Schematic representation of manufacturing process
13 13 15 16
MATERIAL BALANCE 4.1 4.2 4.3 4.4 4.5 4.6
5.
Material balance around Reactor -1 Material balance around Reactor -2 Filter press Material balance around Reactor -3 Spray dryer Rotary vaccum dryer
ENERGY BALANCE 5.1 5.2 5.3 5.4 5.5
6. 6.1 6.2 6.3 6.4 6.5 6.6
PAGE NO.
Energy balance around reactor – 1 Energy balance around reactor – 2 Energy balance around reactor – 3 Spray dryer Rotary vaccum dryer
16 18 20 20 21 22 23
EQUIPMENT DESIGN
23 24 26 27 27 28
Design of shell Design of head Design of jacket Design of agitator Design of flange Design of bracket support
28 31 33 34 39 45
7. 7.1 7.2 7.3 7.4 7.5 7.6
8.
INSTRUMENTATION AND PROCESS CONTROL
50
Process control Control centre Instrumentation Flow control Ratio control Alarm and safety trips and interlock
50 51 51 52 53 53 54
COST ESTIMATION 8.1 8.2 8.3 8.4 8.5 8.6 8.7
9
Purchase equipment cost Installation charge Total product cost Manufacturing cost Profitability analysis Payout period Break even point
POLLUTION CONTROL AND SAFETY ASSPECT 9.1 9.2
10.
UTILITIES
61 63 67
11.
PLANT LOCATION AND LAYOUT
70
Plant location Site selection criteria Plant layout
70 71 73 76
11.1 11.2 11.3
12.
Pollution control Material safety data sheet
54 55 56 56 59 59 59 61
REFERENCES
CHAPTER-1 INTRODUCTION
1.1 Regulatory history Hexamine is also known as hexamethylenetetramine, aminoform, crystamine, methenamine or formin. It was first prepared in 1859 by Butlerov of Russia. It is a white, crystalline powder with a slight amine odor. It is soluble in water, alcohol, and chloroform, but it is insoluble in ether. However the aqueous solutions exhibit inverse solubility, i.e., less hexamine dissolves as the temperature increases. The hydrate, C6H12N4.6H2O, can be crystallized from the aqueous solution at temperatures below 14°C. In 2000 Mexico accounted for 63% of the US imports. In 2001, 58% of imported material came from Germany while 31% came from Mexico. In 2001 two producers, Borden Chemical and Wright Chemical, served the US market. As the above table shows, capacity is much greater than demand. No longterm demand growth is expected unless a significant new end use is found. There has been growth in some smaller volume applications, (such as commercial explosives and steel pickling solutions). However the growth in these markets will not be great enough to offset the slow decline in the use of phenolic resins that contain hexamine The price of hexamine can generally be expected to track the price of methanol, which is the raw material for formaldehyde. As a rule of thumb, the realized cost of hexamine moves 1 cent for every 4 cent move in the methanol price. The price also moves one quarter of a cent for every $5/ton move in ammonia costs. Between 1995 and 2000, the price of imported hexamine dropped from $0.54/lb to $0.34/lb. 1.2 USES Hexamine is produced as a granular and free flowing powder as well as a 42.5% solution. The solution is shipped in tank trucks, railcars and drums. Solid forms are packed in bags, fiber drums and super sacks. Hexamine is sensitive to moisture. Therefore it should be stored in an atmosphere with a relative humidity below 60%. Hexamine is used in the following areas: •
Rubber Industry: Vulcanization accelerator and rubber blowing agent
•
Explosives Industry: Cyclonite (RDX), octogen (HMX), hexamethylene triperoxide amine (HMTA)
•
Synthetic Resin Industry: Liquid resin stabilizer, molding powder, carbohydrate resins, vulcanization of vinyl resins and copolymers, aniline shellac resins
•
Pharmaceutical Industry: Disinfectant (formin, urotropin, crystazol, helmitol), urinary antiseptic
•
Photographic Industry: Stabilizer for developers Organic Synthesis Industry: Additives in deodorizing powder, absorption of phosgene gas, preservation of fresh products
•
•
Metal Industry: Inhibitor against acids and hydrogen sulphide
•
Leather Industry: Conservation of furs and skins
•
Paper Industry: Surface treatment during manufacture of water repellent papers and cardboards
•
Lubricant Industry: Stabilizer for greases and oils
•
Fertilizer Industry: Anticaking agent for prilled urea
•
Other: Dyeing and artificial aging of wood, preservative for cosmetics, treatment of cholera in chickens
An estimate five (5) million pounds per year of hexamine are consumed to make commercial explosives. Hexamine demand from the phenolic resin segment has declined due to increased competition from formaldehyde free resins and other resins that offer performance advantages. The production of nitrilotriacetic acid (NTA) may be the largest application for hexamine (40 to 60 million pounds per year). However, since hexamine for this use is manufactured as a captive intermediate (in solution) this segment is usually not included in the production statistics. 1.3 Health Effects •
Acute Health Effects: Irritating to the skin and eyes on contact. Inhalation will cause irritation to the lungs and mucus membrane. Irritation to the eyes will cause watering and redness. Reddening, scaling, and itching are characteristics of skin inflammation. Follow safe industrial hygiene practices and always wear protective equipment when handling this compound.
•
Chronic Health Effects: Prolonged skin contact may produce a rash to affected area(in particular the wrist, ankles, beltline, and collar area of the neck) similar in appearance to poison ivy. Hexamine may decompose to formaldehyde in the presence of perspiration (slighly acidic pH 4-6.5). The formaldehyde is trapped in the sweat pores of the skin and then oxidized to formic acid, which is believed to be the actual agent responsible for the skin rash. (WARNING: Formaldehyde may be a potential cancer hazard).
•
Acute Health Effects: Hexamine could decompose to formaldehyde, which is a listed potential carcinogen.
1.4 Product specification
Hexamine is a heterocyclic organic compound with the formula (CH2)6N4. This white crystalline compound is highly soluble in water and polar organic solvents. It has a cage-like structure similar to adamantane. It is useful in the synthesis of other chemical compounds, e.g. plastics, pharmaceuticals, rubber additives. It sublimes in a vacuum at 280 °C.
Specification for technical grade Hexamine Properties
Unit
Standard
Content
%
≥ 99
Moisture
%
≤ 0.5
Ash
%
≤ 0.03
Heavy metals
%
≤ 0.001
Chloride
%
≤ 0.015
Sulphates
%
≤ 0.02
Ammonium
%
≤ 0.001
CHAPTER-2 LITERATURE SURVEY Physical and Chemical Properties
2.1 PROPERTIES OF RAW MATERIALS: 1.
Formaldehyde Solution (37 %) •
Physical State at 15° C and 1 atm:
Liquid
•
Molecular Weight:
18-30
•
Boiling Point at 1 atm:
Varies with concentration
•
Freezing Point:
Varies with concentration
•
Critical Temperature:
Not pertinent
•
Critical Pressure:
Not pertinent
•
Specific Gravity:
1.1 at 25°C (liquid)
•
Liquid Surface Tension:
Not pertinent
•
Liquid Water Interfacial Tension:
Not pertinent
•
Vapor (Gas) Specific Gravity:
Not pertinent
•
Ratio of Specific Heats of Vapor (Gas):
Not pertinent
•
Latent Heat of Vaporization:
Not pertinent
•
Heat of Combustion:
Not pertinent
•
Heat of Decomposition:
Not pertinent
•
Heat of Solution:
•
Heat of Polymerization:
Not pertinent
•
Heat of Fusion:
Currently not available
•
Limiting Value:
Currently not available
•
Reid Vapor Pressure:
0.09 psia
(est.) –9 Btu/lb = –5 cal/g = –0.2 X 105 J/kg
2. Ammonia •
Molecular Weight:
17.03
•
Boiling Point (°C):
33.35 at 760 mm Hg
•
Freezing Point (°C):
77.7
•
Decomposition Temperature (°C / °F):
450 to 500 / 842 to 932
•
Color:
Colorless
•
Critical Temperature (°C):
133.0
•
Critical Pressure (kPa / psi):
1‚425 / 1‚657
•
Specific Heat (J/kg °K) 0 °C: 100 °C: 200 °C:
2‚097.2 2‚226.2 2‚105.6
•
Solubility in Water (weight %) 0 °C : 20 °C: 25 °C: 40 °C: 60 °C:
42.8 33.1 31.8 23.4 14.1
•
Specific Gravity of Anhydrous Ammonia 40.0°C : 33.4°C : 0.00 °C : 40.0 °C :
0.690 0.682 0.639 0.580
•
Vapor Pressure:
116.6 psig at 21°C (70 °F) 7‚500 mm Hg at 25 °C
•
Vapor Density (Air = 1.0):
0.6 at 0 °C
•
Flammable Limits in Air (% by Volume) Lower Explosion Limit (LEL): 15 Upper Explosion Limit (UEL): 28
•
Autoignition Temperature (°C / °F):
•
NFPA Ratings for Storage Vessels Health : Flammability : Reactivity : 2.2 PROPERTIES OF HEXAMINE
651 / 1‚204 3 out of 4 1 out of 4 0 out of 4
Chemical name
:
Hexamethylenetetramine
Formula
:
(CH2)6N4
Molecular Weight
:
140.19
Sublimation Temperature
:
285 – 295°C
Flash Point
:
250°C
Density of solid @ 20°C
:
1.33 g/cm3
Bulk Density
:
700 to 800 g/L
Particle Size
:
700 micron Maximum
Specific Heat
:
36.5 cal/°C
Heat of Formation @ 25°C
:
28.8 kcal/mol
Heat of Combustion @ 25°C :
1,003 kcal/mol
Solubility in Water 20°C 25°C 60°C
874 g/L 867 g/L 844 g/L
: : :
pH of 10% Aqueous Solution :
8 to 9
Vapor Pressure @ 20°C
0.0035 mbar
:
CHAPTER-3 3.1 PROCESS SELECTION AND DETAIL PROCESS DESCRIPTION PROCESS 1:
Main Process Features The feed materials for the production of Hexamethylene Tetramine (Hexamine) are Formaldehyde and Ammonia. Formation and crystallization of Hexamine proceed simultaneously in the same reactor. Hexamine in crystalline form is continuously discharged from the reactor. Subsequent separation from the mother liquor and drying are sufficient for product conditioning prior to bagging. The Hexamine process delivers a pure white and crystalline product with best flow characteristics for all applications and down stream uses of Hexamine.
Brief Process Description Hexamine is produced from compressed Ammonia and Formaldehyde solution (37%). In the process, gaseous Ammonia from store fed to the compressor and compressed ammonia is bubbled in the Formaldehyde solution, which is already fed to the reactor. The reaction of Formaldehyde with Ammonia to Hexamine proceeds according to the following chemical equation: 6 CH2O +
4 NH3
(CH2)6N4
+ 6 H2O
+ 746 kJ
The formation of Hexamine takes place in the reactor. Due to the large amount of water, hexamine produced, is remain dissolved in water. Therefore from reactor it will feed to the Triple Effect Evaporator. The concentration of hexamine is increased from 26% to 60%. Then the concentrated feed is charged to the crystallizer, where hexamine crystals are formed. Hexamine in crystalline form is continuously withdrawn from the crystalliser and separated from the mother liquor by centrifugation. The mother liquor is purified in a filtration unit and returned to the Hexamine process. The separated Hexamine is dried to the desired rest moisture content in a drying unit before being bagged and packed. The Hexamine produced by this process meets highest requirements for all down stream uses. The Hexamine crystals are pure white and show best flow characteristics.
PROCESS 2: In this process, gaseous Ammonia from store and Formaldehyde process gas are directly introduced into the Hexamine reactor without intermediate condensation. The Formaldehyde process gas is generated either by a Metal Oxide Catalyst process or by
a Silver Catalyst process for the production of Formaldehyde. The formation and crystallization of Hexamine take place in the same reactor. The heat of reaction, i.e. the heat of formation of Hexamine, and the heat of solution of are directly used for the evaporation of excess water, Methanol and other condensable components accumulating in the mother liquor within the reactor. Hexamine in crystalline form is continuously withdrawn from the reactor and separated from the mother liquor by centrifugation. The mother liquor is purified in a filtration unit and returned to the Hexamine process. The separated Hexamine is dried to the desired rest moisture content in a drying unit before being bagged and packed.
CHAPTER-4 MATERIAL BALANCE:
Basis: Plant is to be designed to consume 1000-kg/batch of formaldehyde. Reactants used: • •
Formaldehyde solution (37%) Ammonia (compressed)
DATA: Components
Molecular Weight 30 17 18 140
Formaldehyde Ammonia Water Hexamine
Reaction: 6CH2O + Formaldehyde
4NH3 Ammonia
(CH2)6N4 + 6H2O Hexamine
Water
4.1 Reactor: Assuming 90% conversion of reactants into hexamine.
CH2O = 1000 Kg NH3
= 377.7 Kg
Reactor 1
For 1000 kg of formaldehyde, its solution required:
Hexamine = 700 kg
= 1000/0.37 = 2702.7 kg/batch (Aq. Formaldehyde solution)
water added: = 2702.7 - 1000 = 1702.7 kg/batch
Mole feed of formaldehyde = 1000/30 = 33.33 kmol HCHO NH3 required : 6 kmol HCHO required 4 kmol NH3 33.33 kmol HCHO required 22.22 kmol NH3 Amount of NH3 is consumed: = 22.22 * 17 = 377.77 kg/batch Total feed in reactor : HCHO solution + NH3 2702.7 + 377.77 = 3080.478 kg/batch Since the conversion is 90% Therefore, HCHO reacted = 900 kg/batch Ammonia reacted = 340 kg/batch HCHO unreacted = 100 kg/batch NH3 unreacted = 37.7 kg/batch Solubility of ammonia is 33.1% weight in water at 20ºC. Composition at Reactor outlet Hexamine produced: 6 kmol HCHO required 1 kmol Hexamine 29.99 kmol HCHO required 4.99 kmol hexamine Amount of Hexamine produced: = 4.99 * 140 = 699.76 = 700 kg/batch Water: 6 kmol of HCHO = 6 kmol of water 2.99 kmol of HCHO = 2.99 kmol of water Amount of water produced: = 29.99 * 18 = 540 kg/batch Water from HCHO solution = 1702.7 kg/batch
Total water = 2242.52 kg/batch INPUT HCHO Water NH3
KG/BATCH 1000 1702.7 377.7
TOTAL
3080.4
OUTPUT Hexamine Water (produced) Water (as reactant) HCHO NH3
KG/BATCH 700 540 1702.7 100 37.7 3080.4
4.2 TRIPPLE EFFECT EVAPORATOR:
In triple effect evaporator hexamine solution is concentrated to 60 %. Overall material balance: mf = m1 + mv1 + mv2 + mv3 Material balance of hexamine 26% hexamine entered and 60% hexamine is collected from outlet. 0.26 * 10784 = 0.6 * m1 m1 = 4673 kg Let us assume the
U1 = 2500 W/m2K U2 = 2000 W/m2K U3 = 1000 W/m2K
Ts = 150ºC = 443 K (Temp of steam to the 1st effect) Boiling point of solution in last effect = 90ºC
Overall temperature drop ∆T = 150 – 90 = 60ºC Assuming heat loads equal in all sides Q1 = Q2 = Q3 U1A1∆T1 = U2A2∆T2 = U3A3∆T3 For equal heat transfer surface U1∆T1 = U2∆T2 = U3∆T3 ∆T1 = U2/U1 ∆T2 ∆T = ∆T1 + ∆T2 + ∆T3 ∆T = ∆T1 [ 1 + U1/U2 + U1/U3 ] 60 = ∆T1 [ 1 + 1.25 + 1.25 ] ∆T1 = 12ºC Similarly, ∆T2 = 15.8ºC ∆T3 = 31.6ºC Now, T1’ = Ts - ∆T1 = 150 – 12 = 138ºC T2’ = 138 – 15.8 = 122.2ºC T3’ = 122.2 – 31.6 = 90.6ºC Now we assume that amount water evaporated in every effect is same i.e. mv1 = mv2 = mv3 = mv mf = m1 + mv1 + mv2 + mv3 mf = m1 + 3mv 10784 = 4673 + 3 mv mv = 2037 kg = mv1 = mv2 = mv3 Now, mass balance at 3rd effect mf = m3 + mv3 10784 = m3 + 2037 m3 = 8747 kg
mass balance at 2nd effect m3 = m2 + mv2 8747 = m2 + 2037 m2 = 6710 kg m1 = 4673 kg m2 = 6710 kg m3 = 8747 kg Heat transfer area required, A2 = mv1 * ƛv1/U2 * ∆T2 = 2037 * 2199.46 * 103/ 2000*15.8*3600 = 40 m2 similarly A3 = 40 m2 Evaporator outlet composition: Hexamine solution 60% + Water 40%.
4.3 Crystallizer: M.L. = 4920 kg
Feed = 1550.57 kg
Hexamine crystals Crystalliz er
Solubility of hexamine at 100ºC = 814 g/l 1866.68 * 0.814 = 1517.3 kg Hence 1517.3 kg of hexamine remains dissolved in water. Crystals form = total hexamine – hexamine dissolved = 2800 – 1517.3 = 1282.7 kg M.L. = water + hexamine + HCHO soln + NH3 soln
= 1282.7
= 1866.68 + 1517.3 + 1080 + 455.6 = 4920 kg INPUT Hexamine Water
KG/DAY 2800 1866.68
HCHO soln NH3 soln
1080 455.6
Total
6202.28
OUTPUT Hexamine crystals Hexamine dissolved Water HCHO soln NH3 soln
KG/DAY 1282.7 1517.3 1866.68 1080 455.6 6202.28
4.4 Centrifuge:
PPT = 987.7kg Feed = 737.552kg
Centrifug e
M.L.= 1193 kg Input : Feed
= 1282.7 kg hexamine + 30% water = 1667.5 kg
Process water = 1 kg water / kg hexamine = 1282.7 kg Total feed = 2950.2 kg Output : Water = 10% water / kg hexamine = 0.1 * 1282.7 = 128.27 kg Hexamine = 1282.7 kg Total = 1411 kg Mother Lye = 1540 kg INPUT Hexamine
KG 1282.7
OUTPUT Hexamine
KG 1282.7
Water Process water
384.8 1282.7 2950.2
Water M.L.
128.27 1540 2950.97
4.5 Drier:
Feed = 1411 kg water)
Drier
Product = 1295.5 kg (1%
Water = 1 % water / kg hexamine = 0.01 * 1282.7 kg = 12.82 kg Hexamine = 1282.7 kg Water evaporated = 115.44 kg INPUT Hexamine Water
KG 1282.7 128.27 1410.97
CHAPTER-5 ENERGY BALANCE
5.1 REACTOR :
OUTPUT Hexamine Water Water evap.
KG 1282.7 12.824 115.44 1410.964
Base temp 0°C In reactor temp is 60°C to 70°C Cp for HCHO soln:
3.42 KJ / Kg K
Cp for NH3:
2.226 KJ / Kg K
Cp for Hexamine:
0.153 KJ / Kg K
Cp for water:
4.176 KJ / Kg K
HEAT INPUT = Σ m Cp Δt = m Cp Δt HCHO + m Cp Δt NH3 = (2702.7×3.42× 35+273) + (377.77×2.226×308) = 3105220.21 KJ / batch HEAT OUTPUT = m Cp Δt = m Cp Δt HCHO + m Cp ΔtWater + m Cp ΔtNH3 + m Cp Δt Hexamine = (100.3x3.43x353) + (2242.520x4.17×353) + (37.804×2.226×353) + (700x0.153x353) = 3384580.27 KJ / Batch Heat of reaction at 68ºC = 745 KJ/mol Therefore, (700/140) ×745 = 3725 KJ/batch (heat generated)
Q = HEAT OUTPUT - HEAT INPUT + Hreaction = 3384580.27 – 3105220.21 + 3725 = 283085.06 KJ / Batch
Water required for Jacket in reactor Qtotal = mCp Δt Water 283085.06 = m(4.176)[(75—40)+273] m = 220.09 Kg/batch
5.2 TRIPLE EFFECT EVAPORATOR Q = A U ∆TLMTD = 10 x 2500 x 144 = 3.6x106 W = 12.96x106 KJ/S [Note: Detailed calculations of above equipment is calculated in Chapter 4 Material Balance]
5.3 ROTARY DRYER: HEAT INPUT = Σ m Cp Δt = m Cp Δt Hexamine + m Cp Δt Water + m Cp Δt Hot air = (1282.7 x 0.153 x 353)+(128.27 x 4.176 x 353)+(1282.7 x 1.014 x 393) = 769522.25 KJ / Batch HEAT INPUT = HEAT OUTPUT 769522.25 = m Cp Δt Hexamine + m Cp Δt Water + m Cp Δt water evaporated + m Cp Δt Air 769522.25 = (1282.7 x 0.153 x T2) + (12.824 x 4.176 x T2) + (115.44 x 4.176 x T2) + (1282.7 x 1.014 x T2) 769522.25 = 2032.52 T2 T2 = 378.6 K = 105ºC
CHAPTER-6 PROCESS EQUIPMENT DESIGN 6.1 Triple Effect Evaporator Design data for the evaporator in the first effect:
•
Feed inlet
= 6706.5 kg
•
Product outlet
= 4666.68 kg
•
Water evaporated
= 2040 kg
•
Steam inlet
= 2040 kg
•
Pressure of steam
= 5 kg/cm2
•
Temperature of steam
= 150 ºC
•
Temperature inside evaporator
= 138 ºC
•
Pressure inside evaporator
= 3.46 kg/cm2
•
Heat transfer area, A
= 40 m2
•
Overall heat transfer coefficient, U
= 2500 W/m2 ºC
∆TLMTD = (150 + 138)/2 = 144 ºC Q = U A ∆TLMTD = 2500 × 40 × 144 = 14.4×106 W Tube Diameter, Do = 1 inch = 25.4mm Tube Length, L = 4 Ft = 1219.2 mm Area, A = 40 = Nt π Do L No. of tubes, Nt = 40 / (π × 0.0254 × 1.219) = 411.2 = 411 tubes Cross section area of 1 tube = π/4 × Do2 = 506.7 mm2 Cross section area of 411 tubes = 411 × 506.7 = 208253.7 mm We assume that c.s. area of tubes are 25% of the total c.s. of evaporator. Cross section area of evaporator = 208253.7/0.25 = 833014.8 mm2 Diameter of evaporator, do : π/4 × do2 = 833014.8 do = 1.029 m
Downcomer area = 25% of 833014.8 = 208253.7 mm2 Diameter of downcomer = 208253.7 × 4 / π = 514.9 mm
MECHANICAL DESIGN The required data are as following: • Internal pressure = 5 kg/cm2 • External pressure = 1.033 kg/cm2 • Poisson’s ratio = 0.3 • Modulus of Elasticity = 1.9×105 N/mm2 • Allowable stress, f = 966.5 kg/cm2 • Height of the evaporator, H = 2710 mm • Inside Diameter of the evaporator, Di = 1030 mm
6.2 DESIGN OF SHELL:
Internal design Pressure = operating pressure × 10% of operating pressure
= (5 - 1.033) × 1.1 = 4.3637 kg/cm2
External design pressure = operating pressure × 10% of operating pressure
= 1.033 kg/cm2
SHELL THICKNESS: Thickness of shell required to withstand internal pressure: ts’ = P × ri / (f × j - O.6 × P) + C.A Where, ri = inside radius of shell
P = internal design pressure f = maximum allowable stress j = joint efficiency (If we go for double welded butt joint with 10% radiography) then j = 0.85 & CA = 1.5 mm = 4.3637 × 515/ (966.5 × 0.85-0.6 × 4.3637) + 1.5 2
(f = 966.5kg/cm ) = 0.42cm ts = l.06 × ts’ =1.06 × 4.2 = 4.452 mm Let ts = 8 mm Thickness of shell required to withstand external pressure: We find thickness by graphically method Let ts = 8 mm, t = 8 - 1.5 = 6.5 mm D0 = Di + 2t – 1.5 = 1044.5 mm L/D0= 2.59 D0/t = 160.69 From graph given in illustrated of process equipment design. (Appendix - C) A=0.00014 B = 3500 Psi = 246.48 Kg/cm2 Pallow = B / (Do/t) = 1.533 Kg/cm2 Pd < Pallow, satisfied So ts= 8mm Outside Diameter of reactor D0 = Di + 2 th = 1030 + 2 (8) = 1046mm WEIGHT OF SHELL: = π (Di + tas) × ts × l × δ = π (1030 + 8) × 8 × 2710 × 8000 × 10-9
= 565.58 kg
6.3 HEAD DESIGN Top head (torispherical head is used) :
Internal design pressure = 4.3637 kg/cm2
External design pressure = 1.033 kg/cm2
Internal diameter = 1030 mm
Crown radius =1030 mm
MOC = SA - 285, grade -C (c.s. plate material)
Now Knuckle radius = 0.1 × 1030 = 103 mm Concentration factor, W = ¼ [3 + (Rc/Rk)1/2] = 1/4 [3 + (1030/103)1/2] = 1.54 Thickness of head required to withstand internal pressure: th’ = P × Rc × w/(2fj-O.2P)+C.A W = 1/4 (3+ (Rc/Rk)0.5) Rc = crown radius, ID of reactor Rk = knuckle radius, 10% of reactor W=l.54 th’ = 4.3637 × 1030 × 1.54 1(2 × 966.5 × 0.85 - 0.2 × 4.3637) + 1.5 = 5.71 mm th = 1.06 × th’ = 6.05 mm.
Thickness of head required to withstand external pressure (By analytical method): th’ = Pe × Rc × W/(2fj-O.2P) + C.A
w = 1/4 (3+ (Rc/Rk)0.5) Rc = crown radius, i.D of reactor Rk = knuckle radius, 10% of reactor Pc =1.67 × 1.033 = 1.725 kg/cm2 W= 1.54 th’ = 1.725 × 1.54 × 1030 /(2 × 966.5 × 0.85 - 0.2 × 1.725) + 1.5 = 3.16 mm th = 1.06 × th’ =3.35 mm Here we take the thickness for top head is ts = 6mm Head diameter D0 = 1030 + 2 × 6 = 1042 mm SF = 3 × th or 1.5 inch which ever is greater. = 1.5 × 25.4 = 38.1 mm,
iCr = 10% ID of reactor,
Blank diameter = OD + OD/24 + th + 2SF + 2/3 × iCr = 1042 + 1042/24 + 6 + 2 × 38.1 + 2/3 × 103 = 1236.3 mm Weight of Head = (π /4) × (blank diameter) × th × δ = (π /4) × (1.23632 × 0.008 × 7800) = 74.9 = 75 Kg Height of head OA = th + b + SF b = Re – [(Re - Ri)2 – (i.D/2 - Ri)2]0.5 = 1030 - [(1030 - 103)2 - (1030/2 - 103)2]0.5 = 199.58 mm = 200mm
6.4 DESIGN OF FLANGE:
Gasket material = asbestos composition Internal design pressure = 1.133 Kgf/cm2 Gasket factor m = 2.75 Minimum design seating stress y = 251.77 kg/cm2 Flange material = SA 240 Grade S type 304 Maximum allowable stress of flange material at design temp = 1020.7 kgf/cm2 Maximum allowable stress of f1ange material at atm. temp = 1257.9 kgf/cm2 Maximum allowable stress of bolting material at design temp = 816.5 kgf/cm2 Maximum allowable stress of bolting material at atm. temp = 1020.7 kgf/crn2
GASKET WIDTH: do/di = [y-Pm]/[y-p(m-1)] ___________________(a) where, do = outside diameter of gasket di = inside diameter of gasket Internal diameter of flange = O.D of shell di= 1.046 meter Put the value in Eq-(a) then do/di = 1.023, do = 1.07m minimum gasket width = (do-di)/2 = (1.07 – 1.046) /2 = 0.014 m Hence minimum gasket width N =14 mm Basic gasket seating width bo = N/2 =7mm = 0.275” > 0.25” Effective gasket seating width b = (bo)0.5/2
= 1.323 mm Mean diameter of gasket G = (1.07+1.046) / 2 = 1.058 m BOLT DESIGN: Load due to design pressure, (operating pressure) H= (π/4) ×G2×P = π/4 × (1058)2 × (1.133/100) = 9960.7 kgf Load to keep joint tight under operation Hp = π × G×2b×mxp = π × 1058 × 2 × 1.323 × 2.75 × 1.133 = 27402.36 kgf Total operating load, W1 = H + Hp = 9960.7+27402.36 = 37363.06 kgf Load to seat gasket under bolting up condition, W2= π ×G × b × y = π× 1058 × 1.323 × 251.77/100 = 11071.32 kgf Bolt area required at operating condition Am1 = W1 / fb = 37363.06/816.5 = 45.76 cm2 Bolt area required at bolting up condition Am2 = W2 / fa = 11071.32/ 1020.7 = 10.846 cm2
Root area of bolt = 0.302” x 2.5422 = 1.9483 cm2 Amax. = 45.76 cm2 So no. of bolts required. = Am / 1 .9483 = 45.76/1.9483 = 23.48 Use 24 nos. of bolts Bolt circle diameter is, C = B + 2(g1+ R) B = ID of shell = 1.03 m g1 = 1.5 × thickness of shell = 1.5 x 8 = 12 mm R = (do-Do)/2 + dbh/2 + th
(dbh=22mm, assume)
(1070—1046)/2 + 22/2 + 8 = 31 mm C= 1030 + 2 (12+ 31) = 1116 mm Bolt spacing = πC / n = π 1116/ 24 = 146.084mm = 146 mm Bs is not in range of 45 to 75 mm so take n = no. of bolts = 50 Bs = 70 mm Thickness of flange t mm, Bs = 2db + 6 × tmin / (m+0.5) 70 = 2×22 + 6×tmin / (2.75 + 0.5) tmin = 14.083 mm Check of gasket width. Ab actual = 50 × 1.9483
= 97.415 cm2 Min gasket width = (Ab×fba) / (2πyG) = (97.415 × 1020.7) / (2×π×251.77×105.8) = 0.594 cm criteria for selection of flange 1. t -= 14.08 mm < 15.875 mm 2. B/t = 73.13 mm < 320 mm 3. P = 1.133 kg/cm2 Conditions are satisfied hence loose flange can be used. Bending moment calculation. For bolting up condition. Design bolt load W = (Ab+Am)fa/2 W = (97.415+45.76) ×1020.7/2 = 73069.36 kgf hG = ½ (C-G) = ½ (1116-1058) = 29 mm Bending moment created in flange material at bolting-up condition Ma = WhG = 2119 kgfm Bending moment for operating condition Mo = MD + MG + MT Where MD = HD hD HD = hydrostatic force acting on inside area of flange HD = π/4 B2 P = π/4 (10302) × (1.133/100) = 9440.48 kgf
hD = (C-B)/2 = (1116-1030)/2 = 43 mm MD = 9440.48×43 = 405.94 kgf MG = HG × hG HG = Wm1- π/4 G2P = 37363.06 – 993.07 HG = 36369.99 kgf hG = (C-G)/2 = (1116-1058)/2 = 29 mm MG = 1054.7 kgfm MT = HT × hT HT = π/4 G2 P - π/4 B2 P HT = 52024.54 hT = (2C – B - G )/2 = 72 mm MT = 3745.76 kgfm MO = 405.94+1054.7+3745.76 = 5206.4 kgfm Ma . Ffo/Ffa = 2119 × 1020.7/1257.9 = 1719.42 kgfm < MO Mmax = MO = 5206.4 kgfm Thickness of flange. tf = ((YMmaxCF)/fB)^0.5 + C.A.+ M.A.
here, C.A. = corrosion allowance and M.A. = mechanical allowance Assuming that CF = 1 For SS-304 C.A. = 0 K=
= (O.D. of flange)/(ID of flange)
= 1186/1030 = 1.15 (k2log10K/(k2-1))
Y= Y = 25.579 tf = 11.56 cm. tf = 115.6+5
(adding 5mm machining allowance)
actual bolt spacing Bs=
C/n
= π× 2626/24 = 146 mm Bolt pitch correction factor = CF = (Bs/(2d+t))0.5 = (146/(2×19.05+115.6))0.5 = 0.974 (CF)1/2 = 0.987 tf = 0.987 × 115.6 = 114 mm
CHAPTER:7 INSTRUMENTATION AND PROCESS CONTROL Instrumentation and process control deal with the measurement and control of physical conditions required for mass production of high iuality products. Instrumentation and process control ensures high output and uniform quality of
products and to ensure that least amourt of raw material are used. Physical science have been used to argument over sense of temperature, viscosity, pressure and color, we arc incapable of sensing within narrow slits, dillerence in temperature, speed, color or light intensity. It produces mechanical aids that never get tired, seldom get into trouble but are accurate and sensitive in response for long period of time while also eliminating the elements of human errors. The primary objective of the designer when specifying instrumentation and control schemes are: A. Safe plant operation: o To keep the process variable within safe operating limits. o To dictate dangerous situation as they develop and provide alarm automatic shut down system. o To provide interlock and alarms to prevent dangerous operating system. B. Production Rate: To achieve the desired product output. C. Product Quality: To maintain the product composition within, the specified quaiity standards. D. Cost: To operate at lowest production cost commensurate with the objective but sometimes it may be better strategy to produce a better quality at a higher cost. E. In a typical chemical plant, these objectives arc achieved by combination of automatic control, manual monitoring and laboratory analysis.
7.1 Process Control: Automatic process control and instrumentation are considered the mechanical brains, and never of modern chemical processing. Automation is the must as it reduces labor and improves feasibility of the product plant operation; the process and other units are sensitive to temperature, pressure, and flow rate. I lcnce these variables are as follows: The reaction vessel is the heart of the plant operation. Its performance determines product quality and its efficiency is a major contributing factor to the total plant production. For temperature control cascade loop is used. The controlling variable is jacket heating oil steam, which is allowed to adjust a jet point of a secondary loop; whose response to change is rapid. Reaction temperature controller varies set point of jacket temperature control ioop. The advantage of this loop is that a change in supply is corrected for in sleeve loop and does not upset master controllers.
7.2 Control centre: Since all devices are controlled from a control center, it becomes the brain of process plant; it is designed for comfortable working conditions. It consists of a control board and data logging system. Instruments are mounted closely together to centralize working area, and central room is small in size, thus giving a good location. The room must he air conditioned and free from flammable and toxic gases, green door is used as it is pleasing and restful comfortable working surface, locate control panels lhr’opcrating functionality.
7.3 Instrumentation: Selection installation maintenance and operations of an instrumentation system are of great importance to the company. Adequate effective instrumentation provides one way to increase quality control, while maintaining or reducing prices ir the face of higher cost of material supplied and labour. We will describe here the instrumentation system for temperature, pressure, and levels and flow rate measuremems. We have to select instrument which satisfy both our perfect technical and economy.
7.3.1 Instrumentation for temperature: In our plant teiupciature is oi the prime importance and it should be strictly maintained a the required level. For this purpose, we have &li if erent types of expansion thermometers as 1) Mercury in glass thermometer 2) Bimetallic thermometer 3) Pressure spring thermometer 4) Pneumatic balance thermometer
7.3.2 Instrumentation for pressure Measurement: Pressure is one of the most important factors in our process industry. For pressure measurement we ave liquid column manometers such as U — tube manometer, enlarged leg manometers, inclined tube manometer and well manometer. Beside from this pressure spring gauge bellows pressure elements, melallic and non —metallic diaphragm pressure elements and differential pressure meters. We select pressure spring thermometer and especially bourdoii pressure gauge. it is simple in
construction and without any Conipi ication in oper it covers wind range of pressure scale most system-handling vapour or gas ; the method of control will depend on the process.
7.1.3 For level indication: It is all-important to maintain the specified level in all storage tank and reaction vessels. The level to be maintained depends upon quantities to be processed and design specifications. For generally float end tube liquid level gauge float and shaft liquid level unit and hydraulic remote transmission units are used. For the level measurements in open vessels bubble system and diaphragm box system are widely used. Level measurements in the pressure vessel liquid differential pressure manometer, liquid scale with manometer and displacement float liquid level gauge are used. For the measurement of flow, venturei meter, orifice meter, head flow meter, pitot tube area flow meter such as rotameter and some quantity meters are used most widely. In many equipment, where an interface exists between two phases some me of maintaining the interface the required level must be provided. This may be incorporated in the design of the equipment as is usually done for the decanter or by automatic control of the flow to the equipment.
7.4 Flow control: Flow control is usually assGciated with inventory control in a storage tank or other equipment; there must be a reservoir to take up the change in flow rates. To provide flaw control as a compressor pump running at a fixed speed and supplying near constant volume output by a pass control be used.
7.5 Ratio Control: Ratio control can be used when it is deckled to maintain two Ilows at a constant ratio. For e.g. reactor feeds and distillation column reflux.
7.6 Alarm and safety trips and interlock:
Alarms are used to alert operations of serious and potentially hazardous deviations in process conditions. Key instruments arc fitted with switches and relays to operate audible and visual alarm on the control panels, lack ol’ response by the operator is likely to land on the rapid development of a hazardous situation, the instrument would be fitted with a tirp system to take action utomatically to prevent the hazard, such as shutting down pumps, closing valves, operating energy. The basic components of an automatic trip system are: A sensor to monitor the control variable and provide an output signal when a present value is exceeded instrument. A link to transfer the signal to the actuator usually consisting of a system ‘of pneumatic or electric relays. An actuator to carry out required action, close or open valve or switch offmonitor.
CHAPTER-8
Cost Estimation Cost estimation mainly consists of three parts: 1. TOTAL CAPITAL INVESTMENT
2. TOTAL PRODUCTION COST 3. PROFITABILITY TOTAL CAPITAL INVESTMENT
FIXED
CAPITAL
INVESTMENT
WORKING CAPITAL (10% OF FCI)
DIRECT COST INDIRECT COST 1. Purchased equipment
1. Engg. And supervision
2. Purchased equip. installation
2. Construction expanse
3. Instrument & control
3. Contractor’s fees
4. Piping installation
4. Contingency
5. Electrical installation 6. Building installation 7. Yard improvement 8. Service facilities 9. land
•
SUMMARY OF PURCHASED EQUIPMENT & ITS COST:
SR. NO
EQUIPMENT
NO. OF EQUIPMENT
COST IN $
COST IN Rs.
1.
Reactor
1
32,400
14,90,400
2.
Triple effect evaporator
1
494,100
2,27,29,060
3.
Crystallizer
1
46,800
21,52,800
4.
Centrifuge
1
12,900
5,93,400
5.
Drier
1
155,900
71,71,400
6.
Filter bag
1
19,700
9,06,200
7.
Agitator
1
4,000
1,84,000
8.
Storage tank
4
104,400
48,02,400
9.
Pump
4
22,500
10,35,000
10.
Compressor
1
69,600
32,01,600
TOTAL
-------
868,340
4,42,66,260
All the equipments cost are taken from the internet http://www.matche.com/EquipCost/index.htm Now, 1$ = 46 Indian Rupees Therefore, Total Purchased Equipment Cost =Rs. 4, 42, 66, 260 --------------- (A) 8.1 CALCULATION OF FIXED CAPITAL INVESTMENT (FCI): For calculating fixed capital investment we have to calculate (A) Direct Cost (B) Indirect Cost
A. CALCULATION OF DIRECT COST: 1. PURCHASED EQUIPMENT COST: The cost of purchased equipment is the basis for estimating fixed capital investment.
The most accurate method for determining purchased equipment cost is to obtain quotation from fabricators or suppliers. The second best method is to obtain cost values from the file of past purchased record. From above the total purchased equipment cost is found to be Rs. 4, 42, 66, 260 ----------------------------------------(A) The total purchased equipment cost is always 15 to 40% of fixed capital investment. For our convenience we take it as 22% of fixed capital investment. As we know purchased equipment cost we can calculate estimated fixed capital investment. Therefore Estimated fixed capital investment = 4, 42, 66, 260 0.22 = Rs. 20,12,10,272.70 So, The estimated fixed capital investment = Rs. 20, 12, 10,272.70. 2. PURCHASED EQUIPMENT INSTALLATION: The installation of equipment involves cost for labor, foundation, support, platform, construction expense & other factors directly related to the erection of purchased equipment. Purchased equipment installation is always 6-14% of fixed capital investment. For our convenience we take it as 9% of fixed capital investment. Therefore, Cost of purchased equipment installation = 0.09*20,12,10,272.70 = Rs. 1,81,08,924.55 -------------- (B)
3. INSTRUMENTATION & CONTROL: Instrument costs, installation cost constitute the major portion of capital investment required for instrumentation. Total instrumentation cost depends on the amount of controller required. This cost is always 2-8% of fixed capital investment. For our convenience we take it as 6% of fixed capital investment. Therefore, Cost of instrumentation & control = 0.06 * 20,12,10,272.70 = Rs. 1,20,72,616.36 ---------------(C)
4. PIPING: The cost of piping covers labor, valve, fitting, pipe, support & other item involved in erection of all piping used in the process. This cost is always 3-20% of fixed capital investment. But For our convenience we take it as 10% of fixed capital investment. Therefore, Cost of piping
= 0.1 * 20,12,10,272.70 =Rs. 2,01,21,027.27 ---------------- (D)
5. ELECTRICAL INSTALLATION: The costs for electrical installation consist primarily of installation, labor & material for power & lighting. The electrical installation consists mainly of four major components namely power wiring, lighting, transformation & service & instrument & control wiring. This cost is always2-10 % of fixed capital investment. But For our convenience we take it as 7% of fixed capital investment. Therefore, Cost of electrical installation
= 0.07 * 20,12,10,272.70 = Rs. 1,40,84,719.09 ---------- (E)
6. BULIDING INSTALLATION: The cost for building including services consists of expense for labor, material & supply involved in the erection of all building connected with the plant. In this cost of plumbing, heating, lighting, ventilation & similar services are included. This cost is always 3-18 % of fixed capital investment. But For our convenience we take it as 11% of fixed capital investment. Therefore, Cost of building installation
= 0.11 * 20,12,10,272.70 = Rs. 2,21,33,130 ----------- (F)
7. YARD IMPROVEMENT: Cost of fencing, grading, roads, sidewalk, railroad siding, landscaping & similar item constitute the portion of yard improvement. This cost is always 2-5 % of fixed capital investment. For our convenience we take it as 4% of fixed capital investment. Therefore, Cost of yard improvement
= 0.04 * 20,12,10,272.70 = Rs. 80,48,411 ------------ (G)
8. SERVICE FACILITIES:
Utilities for supplying steam, water, power, compressed air & fuel lies in the service facilities. Waste disposal, fire protection & miscellaneous service item such as first aid & cafeteria equipment are included in this. This cost is always 8-20 % of fixed capital investment. But For our convenience we take it as 9% of fixed capital investment. Therefore, Cost of service facility
= 0.09 * 20,12,10,272.70 = Rs. 1,81,08,924.54 ------------- (H)
9. LAND: The cost of land & the accompanying surveys & fees depends on the location of property & may vary by cost factor. This cost is always 1-2 % of fixed capital investment. For our convenience we take it as 2% of fixed capital investment. Therefore, Cost of land = 0.02 * 20,12,10,272.70 = Rs. 40,24,205 ----------------- (I) Now, Direct Cost = (A) + (B) + (C) + (D) + (E) + (F) + (G) + (H) + (I) = Rs. 16, 09, 68, 218 ------------------------- (A#) B. CALCULATION OF INDIRECT COST:
1. ENGINEERING &SUPERVISION: The cost of construction design & engineering, drafting, purchasing, accounting, construction & cost engineering, travel, reproductions are included in this cost. This cost is always 4-21 % of fixed capital investment. For our convenience we take it as 12% of fixed capital investment. Therefore, Engineering & supervision cost = 0.12 * 20,12,10,272.70 = Rs. 2,41,45,232.72 -------- (A) 2. CONSTRUCTION EXPENSE: This includes temporary construction & operation, construction tool & rental office, home office at construction site etc. This cost is always 4-16 % of fixed capital investment. For our convenience we take it as 13% of fixed capital investment. Therefore, Construction expense
= 0.13 * 20,12,10,272.70 = Rs. 2,61,57,335.45 ----------- (B)
3. CONTRACTOR’S FEES:
The contractor’s fee varies for different situation but it is always 2-6 % of fixed capital investment. For our convenience we take it as 3% of fixed capital investment. Therefore, Contractor’s fees
= 0.03 * 20,12,10,272.70 = Rs. 60,36,308.181 ------------ (C)
4. CONTINGENCIES: A contingency factor is usually included in an estimate of capital investment to compensate for unpredictable events such as storms, floods, strikes, price change, small design change etc. This is always 5-15 % of fixed capital investment. For our convenience we take it as 5% of fixed capital investment. Therefore, Contingencies Now, Total indirect cost
= 0.05 * 20,12,10,272.70 = Rs. 1,00,60,513.64 --------------- (D) = (A) + (B) +(C) + (D) = Rs. 6, 63, 99, 390 ------------------ (B#)
Therefore, Fixed Capital Investment = Direct Cost + Indirect Cost = (A#) + (B#) = Rs. 22, 73, 67, 607.8 8.2 CALCULATION OF TOTAL CAPITAL INVESTMENT (TCI): TCI = FCI + WORKING CAPITAL ---------- (1#) Working Capital is always 10% of TCI. Therefore equation (1#) become, TCI = FCI + 0.1 TCI 0.9 TCI = 22, 73, 67, 607.8 Therefore, TCI = Rs. 25, 26, 30, 675.3. 9
CALCULATION OF TOTAL PRODUCT COST:
RAW MATERIAL COST FOR 1.3 TPD OF Hexamine PRODUCTIONS: Total working days in a year = 300 days Raw Material
Rs/Kg
Rs/Annum
Formaldehyde (37% solution) Ammonia (gas) Water Total
15
1,80,00,000
28 0.06
1,26,93,072 15,840 3,07,08,912
All chemical’s price data taken from the internet http://www.sunivo.com. A. CALCULATION OF DIRECT PRODUCT COST:
1. RAW MATERIAL COST: The amount of raw material which must be supplied per unit time can be determined from process material balance & from that we can find raw material cost required per annum. The raw material cost for our product is Rs. 3,07,08,912 ---------- (a) The raw material cost is always 10 -50% of total product cost. For our convenience we take it as 49% of total product cost. Therefore, Estimated total product cost = Raw material cost / 0.49 = 3,07,08,912 / 0.49 = Rs 6,26,71,249 2. OPERATING LABOR COST: In general, operating labor cost is divided into skilled & unskilled labor. It is most commonly 10 -50% of total product cost. For our convenience we take it as 10% of total product cost. Therefore, Operating labor cost
= 0.10 * 6,26,71,249 = Rs. 62,67,124.9--------- (b)
3. UTILITIES: The cost for utilities such as steam, electricity, process & cooling water, compressed air varies depending on the amount of consumption. As a rough approximation it is always 10-20% of total product cost. For our convenience we take it as 10% of total product cost. Therefore, Utility cost
= 0.10 * 6,26,71,249 = Rs. 62,67,124.9------------- (c)
4. MAINTENANCE & REPAIRS:
A considerable amount of expense is necessary for maintenance & repair if a plant is to be kept in efficient operating condition. As a rough approximation this is always 6% of Fixed Capital Investment Therefore, Maintenance & repair cost
= 0.06 * 20,12,10,272.70 = Rs. 1,20,72,616.36 ------- (d)
5. OPERATING SUPPLIES: In any manufacturing operation, many miscellaneous supplies are needed to keep the process functioning efficiently & it is not included in the raw material cost. It is always 15% of maintenance & repair cost. Therefore, Operating supplies cost
= 0.15 * 1,20,72,616.36 = Rs. 18,10,892.45 ----------- (e)
6. LABORATORY CHARGES: The cost of laboratory test for control of operation & for product quality is covered in this cost. For quick estimates, this is always 10-20% of operating labor cost. For our convenience we take it as 10% of operating labor cost. Therefore, Laboratory charges
= 0.10 * 62,67,124.9 = Rs. 6,26,712.49-------- (f)
7. PATENTS & ROYALTIES: Many manufacturing processes are covered by patents & it may be necessary to pay a set amount for patent right or royalty based on the amount of material produced. For rough approximation this is 0-6% of total product cost. For our convenience we take it as 1% of total product cost. Therefore, Patent & royalty cost Therefore, Direct product cost
= 0.01 * 6,26,71,249 = Rs. 6,26,712.5---------- (g) = (a) + (b) + (c) + (d) + (e) + (f) + (g) = Rs. 5,83,80,095.61 ------------------ (C#)
B. CALCULATION OF FIXED CHARGES:
1. DEPRECIATION:
Equipment, building & other material object comprising a manufacturing plant require an initial investment which must be written off as a manufacturing expense. This is called as depreciation. This is always 10% of fixed capital investment. Therefore, Depreciation
= 0.1 * 22, 73, 67, 607.8 = Rs. 2, 27, 36, 760.78 ---------- (h)
2. LOCAL TAXES: The magnitude of local property taxes depends on the particular locality of the plant & regional laws. This is always 2-4% of fixed capital investment. For our convenience we take it as 2% of fixed capital investment. Therefore, Local taxes
= 0.02 * 22, 73, 67, 607.8 = Rs. 45,47,352.156--------- (i)
3. INSURANCE: Insurance rate depends on the type of process being carried out in the manufacturing operation & on the extent of available protection facilities. It is always 1% of fixed capital investment. Therefore, Insurance
= 0.01 * 22, 73, 67, 607.8 = Rs. 22,73,676.078 ----------- (j)
Therefore Fixed charges
= (h) + (i) + (j) = Rs. 2,95,57,789.01 ---- (D#)
C. CALCULATION OF PLANT OVERHEAD COST: The expenditure required for routine plant services are included in plant overhead cost. This is always 50- 70% of total expense of operating labor cost. For our convenience we take it as a 50% of operating labor cost. Therefore, Plant overhead cost
Therefore, Manufacturing cost
= 0.50 * 62,67,124.9 = Rs. 31,33,562.45 -------------- (E#)
= (C#) + (D#) + (E#) = Rs. 9,10,71,447 -------- (F#)
D. CALCULATION OF GENERAL EXPENSES:
1. ADMINISTRATIVE COST: The expenses connected with top management or administrative activities are necessary to include if economic analysis is to be done. This is always 20-30% of total expense of operating labor cost. So we take it as 20% of operating labor cost. Therefore, Administrative cost
= 0.20 * 62,67,124.9 = Rs 12,53,424.98 ---------- (k)
2. DISTRIBUTION & MARKETING COST: Distribution & marketing cost vary widely for different types of plant depending on the type of material being produced, plant location & lay out etc. For rough approximation this is 2-20% of total product cost. For our convenience we take it as 2% of total product cost. Therefore, Distribution & marketing cost
= 0.02 * 6,26,71,249 = Rs. 12,53,425 ---------- (l)
3. RESEARCH AND DEVELOPMENT: This includes salaries & wages for all personnel directly connected with this type of work. In chemical industry this cost amount is about 1% of total product cost. Therefore, Research & development cost
= 0.01 * 6,26,71,249 = Rs. 6,26,712.49 ----- (m)
4. INTEREST: Interest is considered to be compensation paid for the use of borrowed capital. For rough approximation this is 0-10% of total product cost. For our convenience we take it as 1% of total product cost. Therefore, Interest
Therefore, General expenses
= 0.01 * 6,26,71,249 = Rs. 6,26,712.49 ----- (n)
= (k) + (l) + (m) + (n) = Rs. 37,60,275 ------- (G#)
Therefore, Total product cost
= Manufacturing cost + General expenses = (F#) + (G#) = Rs. 9,48,31,722 --------- (H#).
8.4 CALCULATION OF PROFIT: Hexamine production/ day = 1.3 TPD Therefore, Hexamine production/annum = 1.3 * 300 = 390 TPA Selling price of 1 kg of Hexamine = Rs. 300 Therefore, Sales income from Hexamine
= 390,000 * 300 = Rs. 11,70,00,000 --------- (I#)
Now, Gross profit
= total sales income – total product cost = (I#) – (H#) = Rs. 2,21,68,278 ---------------- (J#) Now, total income tax is equal to 35% Therefore, Total income tax
Therefore, Net profit
Now, Rate of return
Now, Payback period:
= 0.35 * Gross profit = 0.35 * 2,21,68,278 = Rs. 77,58,897.3-------------- (K#) = Gross profit – Income tax = (J#) – (K#) = Rs 1,44,09,380.7 = (Net profit/Total capital investment) = (1,44,09,380.7/25, 26, 30, 675.3) * 100 = 5.70% depreciable fixed capital investment Net profit per year + depreciation per year = 25, 26, 30, 675.3/(1,44,09,380.7+ 2, 27, 36, 760.78)
Payback period = 6.8 years Turn over ratio = Gross Annual Sales
F.C.I = 40, 80, 00,000 22, 73, 67, 607.8 Turn over ratio = 1.8 8.4 BREAK EVEN POINT CALCULATION (n): F.C. + (DPC/kg) n = sell price* n Break Even Point ‘n’ (B.E.P.) = F.C* 100/ (sell price – DPC/Kg) Here, F.C. (Fixed Cost) = Fixed Charges + Overhead + General Expenses = 2,95,57,789.01 + 31,33,562.45 + 37,60,275 = Rs. 3,64,51,626.5 D.P.C. /kg = Rs. /kg 150 Sell Price = Rs. /kg 300 n = 243010.8433 kg/year = 243 ton/year = 0.81 ton/day = 62.31 % Thus, from the above Break Even Point it is required that the plant must produce 0.81 ton/day for no loss and no profit conditions. That is the plant must regularly run at an efficiency of n = 62.31 %.
Chapter 9 Material Safety Data Sheet Hexamine MSDS
Section 1: Chemical Product and Company Identification Product Name: Methenamine Catalog Codes: SLM4459, SLM3688 CAS#: 100-97-0 RTECS: MN4725000 TSCA: TSCA 8(b) inventory: Methenamine CI#: Not available. Synonym: Hexamine; Hexamethylenetetramine Chemical Name: Methenamine Chemical Formula: C6H12N4 Section 2: Composition and Information on Ingredients Composition: Name CAS # % by Weight Methenamine 100-97-0 100 Toxicological Data on Ingredients: Methenamine: ORAL (LD50): Acute: 569 mg/kg [Mouse]. Section 3: Hazards Identification Potential Acute Health Effects: Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Potential Chronic Health Effects: CARCINOGENIC EFFECTS: Not available. MUTAGENIC EFFECTS: Mutagenic for bacteria and/or yeast. TERATOGENIC EFFECTS: Not available. DEVELOPMENTAL TOXICITY: Not available. Repeated or prolonged exposure is not known to aggravate medical condition. Section 4: First Aid Measures Eye Contact: Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Cold water may be used. Get medical attention. Skin Contact: In case of contact, immediately flush skin with plenty of water. Cover the irritated skin with an emollient. Remove contaminated clothing and shoes. Cold water may be used. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention. Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention. Inhalation:
If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention. Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek medical attention. Ingestion: Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. If large quantities of this material are swallowed, call a physician immediately. Loosen tight clothing such as a collar, tie, belt or waistband. Serious Ingestion: Not available. Section 5: Fire and Explosion Data Flammability of the Product: Auto-Ignition Temperature: Flash Points: Flammable Limits: Products of Combustion:
Flammable. Not available. CLOSED CUP: 250°C (482°F). Not available. These products are carbon oxides (CO, CO2), nitrogen oxides (NO, NO2...).
Fire Hazards in Presence of Various Substances: Slightly flammable to flammable in presence of open flames and sparks, of heat. Nonflammable in presence of shocks. Explosion Hazards in Presence of Various Substances: Risks of explosion of the product in presence of mechanical impact: Not available. Risks of explosion of the product in presence of static discharge: Not available. Fire Fighting Media and Instructions: Flammable solid. SMALL FIRE: Use DRY chemical powder. LARGE FIRE: Use water spray or fog. Cool containing vessels with water jet in order to prevent pressure build-up, autoignition or explosion. Special Remarks on Fire Hazards: Not available. Special Remarks on Explosion Hazards: Explosive reaction with acetic acid + acetic anhydride + ammonium nitrate + nitric acid, 1-bromopenta borane(9) above 90 C, iodoform (at 178 C), iodine (at 138 C). Section 6: Accidental Release Measures Small Spill: Use appropriate tools to put the spilled solid in a convenient waste disposal container. Large Spill: Flammable solid.
Stop leak if without risk. Do not touch spilled material. Use water spray curtain to divert vapor drift. Prevent entry into sewers, basements or confined areas; dike if needed. Eliminate all ignition sources. Call for assistance on disposal. Section 7: Handling and Storage Precautions: Keep locked up. Keep away from heat. Keep away from sources of ignition. Ground all equipment containing material. Do not ingest. Do not breathe dust. Wear suitable protective clothing. In case of insufficient ventilation, wear suitable respiratory equipment. If ingested, seek medical advice immediately and show the container or the label. Avoid contact with skin and eyes. Keep away from incompatibles such as oxidizing agents. Storage: Keep container in a cool, well-ventilated area. Keep container tightly closed and sealed until ready for use. Avoid all possible sources of ignition (spark or flame). Do not store above 25°C (77°F). Section 8: Exposure Controls/Personal Protection Engineering Controls: Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit. Personal Protection: Splash goggles. Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent. Gloves. Personal Protection in Case of a Large Spill: Splash goggles. Full suit. Dust respirator. Boots. Gloves. A self contained breathing apparatus should be used to avoid inhalation of the product. Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product. Exposure Limits: Not available. Section 9: Physical and Chemical Properties Physical state and appearance: Solid. (Crystals solid. crystalline powder.) Odor: Odorless. Taste: Not available. Molecular Weight: 140.19 g/mole Color: White. pH (1% soln/water): Not available. Boiling Point: Not available. Melting Point: Sublimation temperature: 280°C (536°F) [Lewis, R.T., Hawley's Condensed Chemical Dictionary] 263 C [Merck Index]
Critical Temperature: Specific Gravity: Vapor Pressure: Vapor Density: Volatility: Odor Threshold: Water/Oil Dist. Coeff.: Ionicity (in Water): Dispersion Properties:
Not available. 1.331 @ -5 C (23 F) (Water = 1) Not applicable. 4.9 (Air = 1) Not available. Not available. Not available. Not available. See solubility in water.
Solubility: Soluble in cold water. Insoluble in diethyl ether. Soluble in chloroform. Soluble in alcohol. Section 10: Stability and Reactivity Data Stability: The product is stable. Instability Temperature: Not available. Conditions of Instability: Heat, incompatible materials Incompatibility with various substances: Reactive with oxidizing agents. Corrosivity: Non-corrosive in presence of glass. Special Remarks on Reactivity: Reacts violently with Na2O2. Decomposes when in prolonged contact with strong acids and concentratred solutions of organic acids. Special Remarks on Corrosivity: Not available. Polymerization: Will not occur. Section 11: Toxicological Information Routes of Entry: Inhalation. Ingestion. Toxicity to Animals: Acute oral toxicity (LD50): 569 mg/kg [Mouse]. Chronic Effects on Humans: MUTAGENIC EFFECTS: Mutagenic for bacteria and/or yeast. Other Toxic Effects on Humans: Hazardous in case of skin contact (irritant), of ingestion, of inhalation. Special Remarks on Toxicity to Animals: Not available. Special Remarks on Chronic Effects on Humans: May cause cancer (tumorigenic) based on animal data. May affect genetic material (mutagenic). Special Remarks on other Toxic Effects on Humans: Acute Potential Health Effects: Skin: Causes skin irritation. Eyes: Causes eye irritation.
Inhalation: Causes respiratory tract and mucous membrane irritation. May affect urinary system, and metabolism. Ingestion: Causes gastrointestinal tract irritation/distress with nausea, abdominal pain, vomiting. May affect the urinary system (bladder, kidneys), behavior (excitement, muscle contraction, spasticity, tremor). Section 12: Ecological Information Ecotoxicity: Not available. BOD5 and COD: Not available. Products of Biodegradation: Possibly hazardous short term degradation products are not likely. However, long term degradation products may arise. Toxicity of the Products of Biodegradation: The products of degradation are less toxic than the product itself. Special Remarks on the Products of Biodegradation: Not available. Section 13: Disposal Considerations Waste Disposal: Waste must be disposed of in accordance with federal, state and local environmental control regulations. Section 14: Transport Information DOT Classification: CLASS 4.1: Flammable solid. Identification: Hexamethylenetetramine UNNA: 1328 PG: III Special Provisions for Transport: Not available.
CHAPTER- 10 UTILITIES (A)
Utility Requirement
(B)
Labour Requirement
1. Utilities The work utilities is now generally used for the ancillary service needed in operation. These services will normally be supplied form a central site facility. The utilities requi ed include. 1. Water 2. Electricity 3. Steam requirement for process heating 4. Storage & movement of raw materials/products 5. Fire protection 6. Maintenance facilities 7. Plant sewer system and waste disposal
Water: Water is vital for any plant following types of water used for the plant.
Cooling water: Natural and forced draft cooling towers are generally used to provide the cooling water required on site. Water cay bt deacon form a river, lake of form wells. Some treatment is necessary for once through system to prevent scale f small quantity of surface active agents is added to the water. So it increases the solubility of the salt in the water by preventing. Prevented by adding corrosion inhibitors such as, chromate or surfaces acidic phosphates.
Dematerialized Water: Dematerialized water form which all the minerals have been removed by ionexchange, is used when pure water is needed for process use and as boiler feed water. Fire water:
Requirement for fire water are intermittent and assumed that other services will be shunt if necessary to provide sufficient water capacity. The fire water lop system should be so designed that breakdown at a specific hydrant does nto put the entire system out of operation. Provision should be made for emergency connection of the fire water system into the large reservoir of water. Sea water and brackish water is often used if plant is located at the coastal area. Sanitary water: It must be free disease causing bacteria and potable Treated water is chlorinated to destroy bacteria. Sanitary water systems are operated at 20-30 psi. An elevated water storage tank is installed to ensure uninterrupted flow of water. Utility water: Utility water is used for miscellaneous washing operations such as cleaning an operating area. It should be free form sediments. Notices should be put to wan personnel not to drive this. Electricity: The power required for motor drivers, righting and general use, may be generated on site, but usual it is purchased form the local supply company. In our plant main air blower is the high power consuming equipment. As in our plant large quantity of excess is available, we produce power in plant itself by using steam turbine. Actually electricity is one of the by-products of our company. The voltage at which the supply is taken will depend on the demand. In this case three phases 415V is used for general industrial purpose and 210V single phase for lighting and other low l)0 requirments. Steam: The steam for process heating is usually generated in waste heat boilers using the most economic fuel available. In our plant we produce steam in Reboiler-I&II Steam is used for power generation In power plant.
Storage & Movement of Raw Materials & Product: The process contains liquid raw material and products for storage area & n a floor. The CS is highly corrosive storage tank is located away form main plant storage tank is properly lined to prevent any hazard. For the movement of liquid pipe lined arc required. Pipelines are provided with flow meters to measure the flow rate. Maintenance Facilities:
Maintenance facilities are provided to ensure efficient working of equipment. The expensive units must be maintained by a knowledge mechanic as outlined by the manufacture. The most efficient filtration system available for breathing air is employed. .lf laboratory contain chromatography, it should be properly set-up. One more item deserving mention is to blow down cylinders fI while compressing air and inspecting annually with an inner scrape for water and rust. So converter should be checked at frequent time periods, its construction and performance should match with the standards set—up. Fire Protection: Acid handling line must be leak proof. If acid is present in atmosphere, hazard may occur which can become a source of Accordion. Therefore, acid handling line should be lea proof. Maintenance work is required for keeping it as leak proof. Plant Sewer System and Waste Disposal: Preliminary sources of sewage and waste in the plant are; • Sanitary Waste • Process Drain • Surface Drainage The plant sewer system is designed to conduct these wastes to the disposal system without becoming clogged with solids. Plant Roadways: Plant roadways are designed to permit easy access to all points of plant for mobile servicing equipment, trucks and fire fighting equipment.
CHAPTER- 11 11.1 PLANT LOCATION The geographical location of the final plant can have stron influence on the success of the industrial venture. Considerable care imist he exercised in selecting the plant site,
and many different factors must be considered. Primarily the plant must be located where. the minimum cost of production and distribution can be obtained but, other lactors such as room for expansion and safe living conditions for plant operation as well as the surrounding community are also important. The location of the plant can also have a crucial effect on the profitability of a project. The choice of the final site should first be based on a complete survey of the ad and disadvantages of various geographical areas and ultimately, on the advantages and disadvantages of the available real estate. The various principal factors that must be considered while selecting a suitable plant site, are briefly discussed in this section. The factors to be considered are: 1. Raw material availability. 2. Location (with respect to the marketing area.) 3. Availability of suitable land. 4. Transport facilities. 5. Availability of fabors. 6. Availability of utilities (Water, Electricity). 7. Environmental impact and effluent disposal. 8. Local community considerations. 9. Climate. 10. Political strategic considerations. 11. Taxations and legal restrictions
11.2 SITE SELECTION CRITERIA Location: The location of markets or intermediate distribution centers affects the cost of pioduct distribution and time required for shipping. Proximity to the major markets is an
important consideration in the selection of the plant site, because thc buyer usually l advantageous to purchase from near-by sources. In case of sulfuric acid plant, the major consumers are fi industries and hence the plant should be erected in close proximity to those units. Availability Of Suitable Land: The characteristics of the land at the proposed plant site should be examined carefully. The topography of the tract of lami structure must be considered, since either or both may have a pronounced effect on the construction costs. The cost of the land is important, as well as local building costs and living conditions. Future changes may make it desirable or necessary to expand the plant facilities. The land should be ideally flat, well drained and have load-bearing characteristics. A full site evaluation should be made to determine the need for piling or other special foundations. Transport The transport of materials and products to and from plant will be an overriding consideration in site selection. If practicable, a site should be selected so that it is close to at least two major forms of transport: road, rail, waterway or a seaport. Road transport is being increasingly used, and is suitable for local distribution from a central warehouse. Rail transport will be ch for the long- distance transport. If possible the plant site should have access to all three types of’ transportation. There is usually need for convenient rail and air transportation facilities between the plant and the main company head quarters, and the effective transportation facilities for the plant personnel are necessary. Availabi of Labors: Labors will be needed for construction of the plant and its operation. Skilled construction workers will usually be brought in from outside the site, but there should be an adequate pool of unskilled labors available locally and labors suitable for training to operate the plant. Skilled tradesmen will be needed for plant maintenance. Local trade union customs and restrictive practices will have to be considered when assessing the availability and suitability .of the labors for recruitment and training.
Availability of Utilities: The word “utilities” is generally used for the ancillary services needed in the operation of any production process. ‘Ihese services will normally be supplied from a central facility and includes Water, Fuel and Electricity, which are briefly described as follows: Water: -
The water is required for large industrial as well as general purposes, starting with water for cooling, washing, steam generation and as a raw material in the production of sulfuric acid. The plant therefore must be located where a dependable water supply is available namely lakes, rivers, wells, seas. If the water supply shows seasonal fluctuations, it’s desirable to construct a reservoir or to drill several standby wells. The temperattire, mineral content, slit a sand content, bacteriological content, and cost for supply and purification treatment must also be considered when choosing a water supply. Demineralized water, from which all the minerals hav been removed is used where pure water is needed l tIle process use, in boiler feed. Natural and forced draft cooling towers are generally used to provide the cooling water required on site. Electricity: Power and steam requirements are high in most industrial plants and fuel is ordinarily required to supply these utilities. Power, fuel and steam are required for running the various equipments like generators, motors, turbines, plant lightings and general use and thus be considered, as one major factor is choice of olant site. Environmental impact and Effluent Disposal: Facalities must be provided for the effective disposal of the effluent without any public nuisance. In choosing a plant site, the permissible tolerance levels for various effluents should be considered and attention should be given to potential requiren’euts for additional waste treatment facilities. As all industrial processes produce waste products, full consideration must be given to the difficulties and coat of their disposal. The disposal of’ toxic and harmful effluents will be covered by local regulations, and the appropriate authorities must be consulted during the initial site survey to determine the standards that must be met. Local Community Considerations: The proposed plant must fit in with and be acceptable to the local community. Full consideration must be given to the safe location of the plant so that it does not impose a significant additional risk to the community. Climate Adverse climatic conditions at site will increase costs. Extremes of low temperatures will require the provision of additional insulation and special heating for equipment and piping. Similarly, excessive humidity and hot temperatures pose serious problems and must be co:isidered for selecting a site for the plant. Stronger structures will be needed at locations subject to high wind loads or earthquakes. Political And Strategic Considerations: Capital grants, lax conccsstoils, and other inducements are olten given by governments to direct new investment to preferred locations; such as areas of high
unemployment. The availability of such grants can he the overriding consideration in site selection. Taxation And Legal Restrictions: State and local tax rates on property income, unemployment insurance, and similar items vary from one location to another. Similarly, local regulations on zoning, building codes, nuisance aspects and others facilities can have a major influence on the final choice of the plant site. Conclusion: Considering the above factors the plant should be •
Located near the refinery for getting propylene.
•
It should have a near the sea because of discharging a lot of brine solution or should be near the chior/alkali plant.
11.3 PLANT LAYOUT :After the flow process diagrams are completed and before detailed piping, structural and electrical design can begin, the layout of process units in a plant and the equipment within these process unit must be planned. This layout can play an important part in determining construction and manufacturing costs, and thus must be planned carefully with attention being given to future problems that may arise. Thus the economic construction and efficient operation of a process nit will depend on how well the plant and equipment specified on the process flow sheet is laid out. The principal factors that are considered are listed below: 1. Economic considerations: construction and operating costs. 2. Process requirements. 3. Convenience of operation. 4. Convenience of maintenance. 5. Health and Safety considerations. 6. Future plant expansion. 7. Modular construction. 8. Waste disposal requirements
Costs:
Adopting a layout that gives the shortest run of co pipe between equipment, and least amount of structural steel work can minimize the coat of construction. However, this will not necessarily be the best arrangement for operation and maintenance. Process Requirements: An example of the need to take into account process consideration is the need to elevate the base of columns to provide the necessary net positive suction head to a pump. Convenience of Operation: Equipment that needs to have frequent attention should be located convenient to the control room. Valves, sample points, and instruments should be located at convenient positions and heights. Sufficient working space and headroom must he provided to allow easy access to equipment. Convenience of Maintenance: Heat exchangers need to be sited so that the tube bundles can he easily withdrawn for cleaning and tube replacement. Vessels that require frequent replacement of catalyst or packing should be located on the out side of buildings. Equipment that requires (hsmanhling for maintenance, such as compressors and large pumps, should be places under cover. health and Safety Considerations: Blast walls may be needed to isolate potentially hazardous equipment, and confine the effects of an explosion. At least two escape routes for operators must be provided from each level in process buildings. Future Plant Expansion: — Equipment should be located so that it can be conveniently tied in with any future expansion of the process. Space should be left on pipe alleys for future needs, and service pipes over-sized to allow for future requirements.
Modular Construction: In recent years there has been a move to assemble sections of plant at the plant manufacturer’s site. These modules will include the equipment, structural steel, piping and instrumentation. The modules are then transported to the plant site, by road or sea. The advantages of modular construction are: 1. Improved quality control.
2. Reduced construction cost. 3. Less need for skilled labors on site. The disadvantages of modular construction arc: 1. Higher design costs & more structural stem work. 2.More flanged constructions & possible problems with assembly, on site.
