Guide for installation of impregnation plants for timber
1980 Edition

Overview of Scope

• The standard governs essential criteria for timber impregnation plants and related machinery.
• It does not cover mobile treatment units.
• Emphasizes harmonization with international standards and local requirements.

Water Tank Requirements (Clause 3.6.4)

• Minimum height: 6 meters
• Volume: Sufficient for one week's water supply
• Equipped with appropriate piping connections

Units and Terms

For detailed design aspects, refer to IS 401-1967 and applicable pressure vessel regulations.

Types of Pressure Plants

• Oil-based preservatives require elevated temperature treatment.
• Water-soluble preservatives are treated at ambient temperature.
• Supports Full Cell, Lowry, and Rueping processes as per IS 401-1967.

Key Components (Clause 3.3 & Fig.1)

• Pressure treatment vessel: primary chamber for preservation.
• Service tank: identical in size to open tank, with steam coils and cover.
• Storage tanks: containers for preservative chemicals, integrated with steam piping.
• Auxiliary devices: air compressor/vacuum pump, centrifugal pump, pressure and temperature recorders.

Diagrammatic Elements

Design Specifications

• Service tank must meet Clause 2.1.3(a) standards.
• Steam coils provide uniform heating.
• Stop-cocks regulate flow and drainage.
• Plant design accommodates various pressure processes and possible seasoning.

For detailed dimensions and operational parameters, consult IS 2683 clauses 2.

Design Parameters

• Working pressure: 1.4 MPa
• Safety factor: 1.9
• Reference: IS 2825-1969 (Unfired Pressure Vessels Code)

Material & Construction

• Cylinder material and design conform with IS 2825-1969.
• Steam coils and temperature instrumentation are optional (Clause 2.2.1).

Dimensions

• Length based on maximum timber length or multiples.
• Diameter dependent on timber volume per treatment batch.

Rueping Cylinder

• Operating pressure: 550 kPa
• Safety factor: 1.5
• Capacity at least 75% of treating cylinder volume
• Connections to treatment vessel, air compressor, vents, and discharge valves
• May be substituted by a high-pressure centrifugal pump (~700 kPa)

Wall Thickness Formula

[ t = \frac{P \times D}{2 \times \sigma \times \eta - P} ] Where:

• (t): wall thickness
• (P): design pressure
• (D): internal diameter
• (\sigma): allowable material stress
• (\eta): joint efficiency (usually 1)

Summary:

Material Standards

• Mixing tank: Mild steel plates compliant with IS 2825-1969 or IS 803-1976.
• Single open tank: pressed or mild steel plates as per IS 803-1976 or IS 804-1967.
• Heating coils: 25 mm bore steam pipes, shielded from direct timber contact.

Design Features

Accessories

• Steam traps, inlet/outlet piping, valves, stop-cocks
• Water tank: minimum 6 m high, capacity for one-week water needs (Clause 3.6.4)

Volume Calculation

[ V_{tank} = 2 \times V_{timber} ] Where:

• (V_{tank}): open tank volume
• (V_{timber}): timber volume per batch

Heating System Requirements (Clauses 2.1.1.4 & 2.1.2.2)

• Heating coils linked to steam lines controlled by external valves.
• Steam pipes situated at the cylinder bottom, covered by perforated steel plates.
• Live steam connections have holes spaced every 45 cm for conditioning and cleaning.
• Steam traps installed at line ends to eliminate condensate.
• Lagging insulation applied to cylinders and exposed steam pipes to reduce heat loss.

Pressure Cylinder

• Must meet general construction standards; steam coils and temperature monitoring are not mandatory.

Condenser and Boiler (Clause 2.2.6)

• Necessary for seasoning or sterilizing green timber.
• Should comply with Clauses 2.1.5 and 2.1.12 for condensers and boilers respectively.

Heat Loss Formula

[ Q = \frac{2 \pi k L (T_{steam} - T_{ambient})}{\ln(r_2/r_1)} ] Where:

• (Q): heat loss rate
• (k): thermal conductivity
• (L): pipe length
• (r_1, r_2): inner and outer radii of insulation
• (T_{steam}, T_{ambient}): respective temperatures

Tank Quantity and Capacity

• Minimum two tanks: one for creosote, one for fuel oil.
• Capacity sufficient for 4 to 6 months’ preservative stock, as agreed.

Material and Construction

• Built according to IS 2825-1969 or IS 803-1976 standards.

Accessories

• Level gauge
• Manhole with cover
• Ladders for access

Connections

• Bottom fittings for filling and connection to mixing/service tanks.

Service Tank Details

• Material and design per applicable standards.
• Capacity equal to the treatment cylinder.
• Equipped with gauge (±10 litres accuracy), manhole, drain valve, steam coils, thermometer (up to 120°C), and antifloat devices for bogie stability.

Volume Calculation

[ V = \pi r^2 h ] Where:

• (V): volume
• (r): radius
• (h): height

Summary: At least two storage tanks are required, designed per IS codes, sized for several months of preservative storage, and fitted with necessary accessories.

Centrifugal Pumps (Clause 2.1.6.1)

• Transfer preservatives between tanks and cylinders.
• Must be capable of filling or emptying the treatment cylinder within approximately 10 minutes.
• Multiple pumps can be employed to meet capacity needs.

Hydraulic Pressure Pumps (Clause 2.1.6.3)

• Must develop 1.4 MPa pressure within 15 minutes.
• Maintain pressure continuously for 4 to 5 hours during treatment.

Rueping Cylinder (Clause 2.1.2)

• Design pressure: 550 kPa with a safety factor of 1.5.
• Capacity at least 75% of the treating cylinder.
• Can be replaced by a high-pressure centrifugal pump (~700 kPa).

Compliance

• Pumps and related equipment must adhere to Clauses 2.1.6 through 2.1.11.

Summary Table:

Condenser Specifications (Clause 2.1.5)

• Constructed from mild steel plates.
• Designed in accordance with IS 2825-1969 or IS 803-1976.
• Includes catch pot for condensate drainage.
• Features conical receivers to separate water and preservative oil.
• Positioned between vacuum pump line and goose neck.
• Equipped with interceptors to prevent vapor condensation damage.

Vacuum System

• Vacuum-pressure gauge range up to 76 cm Hg and 2.0 MPa.
• Goose neck height: 12 m; bore diameter: 50–70 mm to prevent overflow during vacuum boiling.

Air Compressor-cum-Vacuum Pump (Clause 2.1.6.2)

• Compressor mode: produces 500 kPa pressure within 10 minutes.
• Vacuum mode: achieves 60 cm Hg vacuum in 10–15 minutes.

Summary: Proper condenser and vacuum system design ensures effective condensate management and vacuum control in timber impregnation plants.

Bogies (Clause 2.1.7)

• Minimum two sets: one loading and one treatment, plus 1-2 spare bogies.
• Each bogie has four wheels.
• Equipped with low-friction ball or roller bearings lubricated with waterproof grease (for water-borne preservative plants) or specialized grease (for creosote plants).
• Steel stanchions secure timber; coupling arrangements are mandatory.
• Length tailored to timber dimensions to maximize cylinder fill.

Rail-Track (Clause 2.1.1.3)

• Narrow or metre gauge depending on cylinder dimensions.
• Extends along entire length inside the cylinder.
• Guard rails installed to prevent derailment.

Track Scale (Clause 2.1.9)

• Accuracy: ±1 kg.
• Rails match trolley gauge.
• Length sufficient for 1-2 coupled trolleys.
• Usually installed at both cylinder ends.

Summary Table:

Winch Requirements (Clause 2.1.8)

• Utilized for loading and unloading timber in treatment cylinders.
• Must have capacity matched to load requirements.
• Can be electrically or manually driven.

Supporting Equipment (Clause 2.2.5)

• Pumps, bogies, winches, track scales, water tanks, and motors must comply with Clauses 2.1.6 to 2.1.11.

Track Scale (Clause 2.1.9)

• Platform scale with ±1 kg accuracy.
• Rails matching trolley gauge.
• Length to accommodate 1-2 coupled bogies.
• Preferably two scales, one at each cylinder end.

Portable Cranes (Clause 3.6.2)

• Required for handling large timber items such as poles and sleepers.

Winch Capacity Calculation

[ \text{Capacity} = \frac{\text{Load} \times \text{Safety Factor}}{\text{Efficiency}} ]

• Safety factor: 1.5–2.0
• Efficiency: 0.8–0.9

Summary: Proper winch and auxiliary equipment ensure safe and efficient timber handling during treatment operations.

Plant Types (Clause 2.2)

• Pressure plants designed for room temperature water-soluble preservatives.
• Equipment adapted for Full Cell, Lowry, and Rueping processes as per IS 401-1967.
• Auxiliary systems allow switching among these processes.
• Additional equipment may be included for timber seasoning or conditioning such as steaming or Boulton process.

Open Tank Plants (Clause 3)

• Simpler design without pressure application.
• Suitable for water-soluble preservatives at room temperature.

Summary Table:

For detailed dimensions and process parameters, see IS 401-1967.

Design Requirements (Clause 3.1)

• Constructed of pressed or mild steel plates per IS 803-1976 or IS 804-1967.
• Rectangular shape with length based on maximum timber size.
• Tank volume approximately twice the timber volume per batch.
• Vertical angle irons welded inside long walls; cross bars prevent timber flotation.

Heating and Accessories

• Steam coils with bore ≥ 25 mm positioned 5 cm above tank base.
• Heating raises preservative and timber temperature to 95°C within roughly one hour.
• Top cover made from 0.8 mm galvanized iron sheet in removable sections.
• Includes steam traps, inlet/outlet piping, valves, and stop-cocks.

Service Tank (Clause 3.3)

• Equal in size to open tank, fitted with steam coils and cover.
• Meets Clause 2.1.3(a) specifications.

Volume Calculation

[ V_{tank} = 2 \times V_{timber} ] Where:

• (V_{tank}): volume of preservative tank
• (V_{timber}): timber volume per charge

Line Diagram Elements (Figs. 1 & 2)

• Treatment tanks with steam coils
• Drainage pit
• Storage tank
• Centrifugal pump
• Multiple stop-cocks for flow control

Summary: Open tank designs conforming to IS 2683 ensure effective non-pressure timber treatment.

Service Tank

• Built per IS 2825-1969 or IS 803-1976 standards.
• Capacity matches the treatment cylinder.
• Equipped with accurate gauges, manhole, drain valve, steam coils with controls, thermometer (up to 120°C), and anti-float devices for bogie stability.

Mixing Tank

• Made of mild steel plates per IS 2825 or IS 803.
• Capacity at least one-quarter that of the service tank.
• Cylindrical shape preferred.

Storage Tanks

• At least two tanks for creosote and fuel oil.
• Designed as per IS 2825 or IS 803.
• Sized for 4 to 6 months’ preservative stock.
• Accessories include level gauges, manholes, ladders, and bottom connections.

Open Tank

• Rectangular shape made of pressed or mild steel plates.
• Volume roughly twice the timber volume per charge.
• Equipped with steam traps, valves, piping, and sectional galvanized iron sheet cover.
• Heating coils of 25 mm bore located 5 cm above bottom to heat to 95°C in one hour.

Design Notes

• Open tank volume formula: (V_{tank} = 2 \times V_{timber charge})
• Steam coils provide uniform heating while protecting timber.

Summary Table: Tank types, materials, capacities, shapes, and accessory details as per IS 2683.

Configuration (Clauses 3.2, 3.2.1)

• Two identical open tanks positioned side-by-side.
• Connected by a broad pipe with a stop cock at two-thirds tank height for transferring heated preservative.
• Each tank equipped with steam coils at the base.
• Wide drainage pipe with stop cock at two-thirds height for rapid emptying to underground pit.
• Service tank equal in size to open tanks, with steam coils and cover.

Operation

1. Load timber into Tank A and fill with hot preservative.
2. Open stop cock to transfer hot preservative to Tank B.
3. Simultaneously fill Tank A with cold preservative from storage.
4. Drain preservative from Tank A to pit as timber cools.
5. Alternate cycles between tanks for continuous operation.

Design Considerations

• Mixing tank capacity at least one-quarter of service tank capacity.
• Tanks fabricated from mild steel plates per IS 2825 or IS 803.
• Cylindrical shape preferred for mixing tanks.

Diagram

Visual flow of hot preservative transfer, heating, drainage, and storage.

Stop Cock Positions

This system enhances heating and cooling efficiency in timber treatment.

Water Tank (Clause 3.6)

• Minimum height of 6 meters.
• Capacity to supply at least one week's water demand.
• Equipped with necessary piping connections.

Instrumentation (Clause 1.4)

• Safety valve adjustable to 1.4 MPa.
• Stop-cock and piping for hydraulic pump operations.
• Air compressor and vacuum pump combined unit.
• Thermometer capable of measuring up to 150°C.

Equipment Compliance (Clause 2.2.5)

• Pumps, bogies, winches, track scales, water tanks, and motors must meet specifications in Clauses 2.1.6 to 2.1.11.

Summary Table:

Notes

• Water tank size depends on daily consumption multiplied by seven.
• Safety valve ensures operational safety.
• Equipment must comply with relevant IS codes for pressure vessels and tanks.